zakura-client-backend 0.1.0-rc2

//! # Utilities for Zcash wallet construction
//!
//! This module defines a set of APIs for wallet data persistence, and provides a suite of methods
//! based upon these APIs that can be used to implement a fully functional Zcash wallet. At
//! present, the interfaces provided here are built primarily around the use of a source of
//! [`CompactBlock`] data such as the Zcash Light Client Protocol as defined in
//! [ZIP 307](https://zips.z.cash/zip-0307) but they may be generalized to full-block use cases in
//! the future.
//!
//! ## Important Concepts
//!
//! There are several important operations that a Zcash wallet must perform that distinguish Zcash
//! wallet design from wallets for other cryptocurrencies.
//!
//! * Viewing Keys: Wallets based upon this module are built around the capabilities of Zcash
//!   [`UnifiedFullViewingKey`]s; the wallet backend provides no facilities for the storage
//!   of spending keys, and spending keys must be provided by the caller (or delegated to external
//!   devices via the provided [`pczt`] functionality) in order to perform transaction creation
//!   operations.
//! * Blockchain Scanning: A Zcash wallet must download and trial-decrypt each transaction on the
//!   Zcash blockchain using one or more Viewing Keys in order to find new shielded transaction
//!   outputs (generally termed "notes") belonging to the wallet. The primary entrypoint for this
//!   functionality is the [`scan_cached_blocks`] method. See the [`chain`] module for additional
//!   details.
//! * Witness Updates: In order to spend a shielded note, the wallet must be able to compute the
//!   Merkle path to that note in the global note commitment tree. When [`scan_cached_blocks`] is
//!   used to process a range of blocks, the note commitment tree is updated with the note
//!   commitments for the blocks in that range.
//! * Transaction Construction: The [`wallet`] module provides functions for creating Zcash
//!   transactions that spend funds belonging to the wallet. Input selection for transaction
//!   construction is performed automatically. When spending funds received at transparent
//!   addresses, the caller is required to explicitly specify the set of addresses from which to
//!   spend funds, in order to prevent inadvertent commingling of funds received at different
//!   addresses; allowing such commingling would enable chain observers to identify those
//!   addresses as belonging to the same user.
//!
//! ## Core Traits
//!
//! The utility functions described above depend upon four important traits defined in this
//! module, which between them encompass the data storage requirements of a light wallet.
//! The relevant traits are [`InputSource`], [`WalletRead`], [`WalletWrite`], and
//! [`WalletCommitmentTrees`]. A complete implementation of the data storage layer for a wallet
//! will include an implementation of all four of these traits. See the [`zcash_client_sqlite`]
//! crate for a complete example of the implementation of these traits.
//!
//! ## Accounts
//!
//! The operation of the [`InputSource`], [`WalletRead`] and [`WalletWrite`] traits is built around
//! the concept of a wallet having one or more accounts, with a unique `AccountId` for each
//! account.
//!
//! An account identifier corresponds to at most a single [`UnifiedSpendingKey`]'s worth of spend
//! authority, with the received and spent notes of that account tracked via the corresponding
//! [`UnifiedFullViewingKey`]. Both received notes and change spendable by that spending authority
//! (both the external and internal parts of that key, as defined by
//! [ZIP 316](https://zips.z.cash/zip-0316)) will be interpreted as belonging to that account.
//!
//! [`CompactBlock`]: crate::proto::compact_formats::CompactBlock
//! [`scan_cached_blocks`]: crate::data_api::chain::scan_cached_blocks
//! [`zcash_client_sqlite`]: https://docs.rs/zcash_client_sqlite
//! [`TransactionRequest`]: crate::zip321::TransactionRequest
//! [`propose_shielding`]: crate::data_api::wallet::propose_shielding
//! [`pczt`]: https://docs.rs/pczt

use nonempty::NonEmpty;
use secrecy::SecretVec;
use std::{
    collections::{HashMap, HashSet},
    fmt::{self, Debug},
    hash::Hash,
    io,
    num::{NonZeroU32, TryFromIntError},
};

use incrementalmerkletree::{Retention, frontier::Frontier};
use shardtree::{ShardTree, error::ShardTreeError, store::ShardStore};

use zcash_keys::{
    address::{Address, UnifiedAddress},
    keys::{
        UnifiedAddressRequest, UnifiedFullViewingKey, UnifiedIncomingViewingKey, UnifiedSpendingKey,
    },
};
use zcash_primitives::{block::BlockHash, transaction::Transaction};
use zcash_protocol::{
    PoolType, ShieldedPool, TxId,
    consensus::{self, BlockHeight, TxIndex},
    memo::{Memo, MemoBytes},
    value::{BalanceError, Zatoshis},
};
use zip32::{DiversifierIndex, fingerprint::SeedFingerprint};

use self::{
    chain::{ChainState, CommitmentTreeRoot},
    scanning::{ScanPriority, ScanRange},
};
use crate::{
    data_api::{
        error::RewindError,
        wallet::{ConfirmationsPolicy, TargetHeight, input_selection::LockFilter},
    },
    decrypt::DecryptedOutput,
    proto::service::TreeState,
    wallet::{Note, NoteId, ReceivedNote, Recipient, WalletTransparentOutput, WalletTx},
};

#[cfg(feature = "transparent-inputs")]
use {
    crate::{fees::StandardFeeRule, wallet::TransparentAddressMetadata},
    getset::{CopyGetters, Getters},
    std::time::SystemTime,
    transparent::{address::TransparentAddress, bundle::OutPoint, keys::TransparentKeyScope},
};

#[cfg(all(
    feature = "transparent-inputs",
    any(test, feature = "test-dependencies")
))]
use {std::ops::Range, transparent::keys::NonHardenedChildIndex};

#[cfg(feature = "zcashd-compat")]
use zcash_keys::keys::zcashd;

#[cfg(feature = "test-dependencies")]
use ambassador::delegatable_trait;

#[cfg(any(test, feature = "test-dependencies"))]
use zcash_protocol::consensus::NetworkUpgrade;

pub mod anchor_retention;
pub mod chain;
pub mod defaults;
pub mod error;
pub mod ll;
pub mod locking;
pub use locking::OutputLockStore;
#[cfg(feature = "test-dependencies")]
pub use locking::ambassador_impl_OutputLockStore;
pub mod scanning;
pub mod wallet;
#[cfg(feature = "orchard")]
pub mod zip318;

#[cfg(any(test, feature = "test-dependencies"))]
pub mod testing;

/// The origin of a transparent address within a wallet.
#[cfg(feature = "transparent-inputs")]
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum TransparentKeyOrigin {
    /// The address was imported standalone (no HD derivation scope).
    Imported,
    /// The address was derived from the account's HD key tree.
    Derived { scope: TransparentKeyScope },
}

/// A mapping from transparent addresses to their key origin and balance.
#[cfg(feature = "transparent-inputs")]
pub type TransparentBalances = HashMap<TransparentAddress, (TransparentKeyOrigin, Balance)>;

/// The height of subtree roots in the Sapling note commitment tree.
///
/// This conforms to the structure of subtree data returned by
/// `lightwalletd` when using the `GetSubtreeRoots` GRPC call.
pub const SAPLING_SHARD_HEIGHT: u8 = sapling::NOTE_COMMITMENT_TREE_DEPTH / 2;

/// The height of subtree roots in the Orchard note commitment tree.
///
/// This conforms to the structure of subtree data returned by
/// `lightwalletd` when using the `GetSubtreeRoots` GRPC call.
#[cfg(feature = "orchard")]
pub const ORCHARD_SHARD_HEIGHT: u8 = { orchard::NOTE_COMMITMENT_TREE_DEPTH as u8 } / 2;

/// The height of subtree roots in the Ironwood note commitment tree.
///
/// This conforms to the structure of subtree data returned by
/// `lightwalletd` when using the `GetSubtreeRoots` GRPC call.
#[cfg(feature = "orchard")]
pub const IRONWOOD_SHARD_HEIGHT: u8 = { orchard::NOTE_COMMITMENT_TREE_DEPTH as u8 } / 2;

/// An enumeration of constraints that can be applied when querying for nullifiers for notes
/// belonging to the wallet.
pub enum NullifierQuery {
    Unspent,
    All,
}

/// An intent of representing spendable value to reach a certain targeted
/// amount.
///
/// `AtLeast(Zatoshis)` refers to the amount of `Zatoshis` that can cover
/// at minimum the given zatoshis that is conformed by the sum of spendable notes.
///
///
/// Discussion: why not just use ``Zatoshis``?
///
/// the `Zatoshis` value isn't enough to explain intent when seeking to match a
/// given a given amount. Is the value expressed in `Zatoshis` the ceiling value
/// or the minimum value of a given spend intent? How would you express that the
/// value spend intent is "as much as possible" without knowing the value upfront?
#[derive(Debug, Clone, Copy)]
pub enum TargetValue {
    AtLeast(Zatoshis),
    AllFunds(MaxSpendMode),
}

/// Specifies how an TargetValue::AllFunds should be evaluated
#[derive(Debug, Clone, Copy)]
pub enum MaxSpendMode {
    /// `MaxSpendable` will target to spend all _currently_ spendable funds where it
    /// could be the case that the wallet has received other funds that are not
    /// confirmed and therefore not spendable yet and the caller evaluates that as
    /// an acceptable scenario.
    MaxSpendable,
    /// `Everything` will target to spend **all funds** and will fail if there are
    /// unspendable funds in the wallet or if the wallet is not yet synced.
    Everything,
}
/// Balance information for a value within a single pool in an account.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Balance {
    spendable_value: Zatoshis,
    locked_value: Zatoshis,
    change_pending_confirmation: Zatoshis,
    value_pending_spendability: Zatoshis,
    uneconomic_value: Zatoshis,
}

impl Balance {
    /// The [`Balance`] value having zero values for all its fields.
    pub const ZERO: Self = Self {
        spendable_value: Zatoshis::ZERO,
        locked_value: Zatoshis::ZERO,
        change_pending_confirmation: Zatoshis::ZERO,
        value_pending_spendability: Zatoshis::ZERO,
        uneconomic_value: Zatoshis::ZERO,
    };

    fn check_total_adding(&self, value: Zatoshis) -> Result<Zatoshis, BalanceError> {
        (self.spendable_value
            + self.locked_value
            + self.change_pending_confirmation
            + self.value_pending_spendability
            + value)
            .ok_or(BalanceError::Overflow)
    }

    /// Returns the value in the account that may currently be spent; it is possible to compute
    /// witnesses for all the notes that comprise this value, and all of this value is confirmed to
    /// the required confirmation depth.
    pub fn spendable_value(&self) -> Zatoshis {
        self.spendable_value
    }

    /// Returns the value in the account that is currently "locked".
    ///
    /// The outputs that comprise this balance are seen by the wallet as being committed to be
    /// spent by a transaction proposal or PCZT.
    pub fn locked_value(&self) -> Zatoshis {
        self.locked_value
    }

    /// Adds the specified value to the spendable total, checking for overflow.
    pub fn add_spendable_value(&mut self, value: Zatoshis) -> Result<(), BalanceError> {
        self.check_total_adding(value)?;
        self.spendable_value = (self.spendable_value + value).unwrap();
        Ok(())
    }

    /// Adds the specified value to the locked total, checking for overflow.
    pub fn add_locked_value(&mut self, value: Zatoshis) -> Result<(), BalanceError> {
        self.check_total_adding(value)?;
        self.locked_value = (self.locked_value + value).unwrap();
        Ok(())
    }

    /// Returns the value in the account of shielded change notes that do not yet have sufficient
    /// confirmations to be spendable.
    pub fn change_pending_confirmation(&self) -> Zatoshis {
        self.change_pending_confirmation
    }

    /// Adds the specified value to the pending change total, checking for overflow.
    pub fn add_pending_change_value(&mut self, value: Zatoshis) -> Result<(), BalanceError> {
        self.check_total_adding(value)?;
        self.change_pending_confirmation = (self.change_pending_confirmation + value).unwrap();
        Ok(())
    }

    /// Returns the value in the account of all remaining received notes that either do not have
    /// sufficient confirmations to be spendable, or for which witnesses cannot yet be constructed
    /// without additional scanning.
    pub fn value_pending_spendability(&self) -> Zatoshis {
        self.value_pending_spendability
    }

    /// Adds the specified value to the pending spendable total, checking for overflow.
    pub fn add_pending_spendable_value(&mut self, value: Zatoshis) -> Result<(), BalanceError> {
        self.check_total_adding(value)?;
        self.value_pending_spendability = (self.value_pending_spendability + value).unwrap();
        Ok(())
    }

    /// Returns the value in the account of notes that have value less than or equal to the marginal
    /// fee, and consequently cannot be spent except as a grace input.
    pub fn uneconomic_value(&self) -> Zatoshis {
        self.uneconomic_value
    }

    /// Adds the specified value to the uneconomic value total, checking for overflow.
    pub fn add_uneconomic_value(&mut self, value: Zatoshis) -> Result<(), BalanceError> {
        self.uneconomic_value = (self.uneconomic_value + value).ok_or(BalanceError::Overflow)?;
        Ok(())
    }

    /// Returns the total value of funds represented by this [`Balance`].
    pub fn total(&self) -> Zatoshis {
        (self.spendable_value
            + self.locked_value
            + self.change_pending_confirmation
            + self.value_pending_spendability)
            .expect("Balance cannot overflow MAX_MONEY")
    }
}

impl core::ops::Add<Balance> for Balance {
    type Output = Result<Balance, BalanceError>;

    fn add(self, rhs: Balance) -> Self::Output {
        let result = Balance {
            spendable_value: (self.spendable_value + rhs.spendable_value)
                .ok_or(BalanceError::Overflow)?,
            locked_value: (self.locked_value + rhs.locked_value).ok_or(BalanceError::Overflow)?,
            change_pending_confirmation: (self.change_pending_confirmation
                + rhs.change_pending_confirmation)
                .ok_or(BalanceError::Overflow)?,
            value_pending_spendability: (self.value_pending_spendability
                + rhs.value_pending_spendability)
                .ok_or(BalanceError::Overflow)?,
            uneconomic_value: (self.uneconomic_value + rhs.uneconomic_value)
                .ok_or(BalanceError::Overflow)?,
        };

        result.check_total_adding(Zatoshis::ZERO)?;

        Ok(result)
    }
}

/// Balance information for a single account. The sum of this struct's fields is the total balance
/// of the wallet.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct AccountBalance {
    sapling_balance: Balance,
    orchard_balance: Balance,
    ironwood_balance: Balance,
    unshielded_regular_balance: Balance,
    unshielded_coinbase_balance: Balance,
}

impl AccountBalance {
    /// The [`Balance`] value having zero values for all its fields.
    pub const ZERO: Self = Self {
        sapling_balance: Balance::ZERO,
        orchard_balance: Balance::ZERO,
        ironwood_balance: Balance::ZERO,
        unshielded_regular_balance: Balance::ZERO,
        unshielded_coinbase_balance: Balance::ZERO,
    };

    fn check_total(&self) -> Result<Zatoshis, BalanceError> {
        (self.sapling_balance.total()
            + self.orchard_balance.total()
            + self.ironwood_balance.total()
            + self.unshielded_regular_balance.total()
            + self.unshielded_coinbase_balance.total())
        .ok_or(BalanceError::Overflow)
    }

    /// Returns the [`Balance`] of Sapling funds in the account.
    pub fn sapling_balance(&self) -> &Balance {
        &self.sapling_balance
    }

    /// Provides a mutable reference to the [`Balance`] of Sapling funds in the account
    /// to the specified callback, checking invariants after the callback's action has been
    /// evaluated.
    pub fn with_sapling_balance_mut<A, E: From<BalanceError>>(
        &mut self,
        f: impl FnOnce(&mut Balance) -> Result<A, E>,
    ) -> Result<A, E> {
        let result = f(&mut self.sapling_balance)?;
        self.check_total()?;
        Ok(result)
    }

    /// Returns the [`Balance`] of Orchard funds in the account.
    pub fn orchard_balance(&self) -> &Balance {
        &self.orchard_balance
    }

    /// Provides a mutable reference to the [`Balance`] of Orchard funds in the account
    /// to the specified callback, checking invariants after the callback's action has been
    /// evaluated.
    pub fn with_orchard_balance_mut<A, E: From<BalanceError>>(
        &mut self,
        f: impl FnOnce(&mut Balance) -> Result<A, E>,
    ) -> Result<A, E> {
        let result = f(&mut self.orchard_balance)?;
        self.check_total()?;
        Ok(result)
    }

    /// Returns the [`Balance`] of Ironwood funds in the account.
    pub fn ironwood_balance(&self) -> &Balance {
        &self.ironwood_balance
    }

    /// Provides a mutable reference to the [`Balance`] of Ironwood funds in the account
    /// to the specified callback, checking invariants after the callback's action has been
    /// evaluated.
    pub fn with_ironwood_balance_mut<A, E: From<BalanceError>>(
        &mut self,
        f: impl FnOnce(&mut Balance) -> Result<A, E>,
    ) -> Result<A, E> {
        let result = f(&mut self.ironwood_balance)?;
        self.check_total()?;
        Ok(result)
    }

    /// Returns the total value of unspent transparent transaction outputs belonging to the wallet.
    #[deprecated(
        note = "this function is deprecated. Please use [`AccountBalance::unshielded_regular_balance`] and [`AccountBalance::unshielded_coinbase_balance`] instead."
    )]
    pub fn unshielded(&self) -> Zatoshis {
        (self.unshielded_regular_balance.total() + self.unshielded_coinbase_balance.total())
            .expect("Account balance cannot overflow MAX_MONEY")
    }

    /// Returns the combined [`Balance`] of unshielded funds in the account, computed as the sum
    /// of the [`unshielded_regular_balance`] and the [`unshielded_coinbase_balance`].
    ///
    /// The [`spendable_value`] field of the returned [`Balance`] contains funds that may be spent
    /// in a shielding transaction: transparent funds that satisfy the wallet's confirmation
    /// policy, including coinbase funds that have reached maturity. The
    /// [`value_pending_spendability`] field contains transparent funds that are not yet
    /// spendable: funds that do not yet have the number of confirmations required by the
    /// wallet's confirmation policy, and coinbase funds that have not yet reached maturity. The
    /// [`change_pending_confirmation`] field is currently always zero, because this crate does
    /// not yet distinguish transparent change from other transparent value awaiting
    /// confirmation.
    ///
    /// [`unshielded_regular_balance`]: AccountBalance::unshielded_regular_balance
    /// [`unshielded_coinbase_balance`]: AccountBalance::unshielded_coinbase_balance
    /// [`spendable_value`]: Balance::spendable_value
    /// [`change_pending_confirmation`]: Balance::change_pending_confirmation
    /// [`value_pending_spendability`]: Balance::value_pending_spendability
    pub fn unshielded_balance(&self) -> Balance {
        (self.unshielded_regular_balance + self.unshielded_coinbase_balance)
            .expect("Account balance cannot overflow MAX_MONEY")
    }

    /// Returns the [`Balance`] of regular (non-coinbase) transparent funds in the account.
    ///
    /// Transparent outputs whose containing transaction's index within its block is unknown are
    /// classified as regular (non-coinbase) funds, consistent with the treatment described for
    /// `CoinbaseFilter`.
    pub fn unshielded_regular_balance(&self) -> &Balance {
        &self.unshielded_regular_balance
    }

    /// Provides a mutable reference to the [`Balance`] of regular (non-coinbase) transparent
    /// funds in the account to the specified callback, checking invariants after the callback's
    /// action has been evaluated.
    pub fn with_unshielded_regular_balance_mut<A, E: From<BalanceError>>(
        &mut self,
        f: impl FnOnce(&mut Balance) -> Result<A, E>,
    ) -> Result<A, E> {
        let result = f(&mut self.unshielded_regular_balance)?;
        self.check_total()?;
        Ok(result)
    }

    /// Returns the [`Balance`] of funds in coinbase transparent outputs belonging to the
    /// account.
    ///
    /// Coinbase outputs may only be spent by shielding them, and only once they have reached
    /// coinbase maturity; immature coinbase funds are reported in the
    /// [`value_pending_spendability`] field of the returned [`Balance`]. Outputs whose
    /// containing transaction's index within its block is unknown are conservatively classified
    /// as regular (non-coinbase) funds and do not contribute to this balance; see
    /// `CoinbaseFilter`.
    ///
    /// [`value_pending_spendability`]: Balance::value_pending_spendability
    pub fn unshielded_coinbase_balance(&self) -> &Balance {
        &self.unshielded_coinbase_balance
    }

    /// Provides a mutable reference to the [`Balance`] of transparent coinbase funds in the
    /// account to the specified callback, checking invariants after the callback's action has
    /// been evaluated.
    pub fn with_unshielded_coinbase_balance_mut<A, E: From<BalanceError>>(
        &mut self,
        f: impl FnOnce(&mut Balance) -> Result<A, E>,
    ) -> Result<A, E> {
        let result = f(&mut self.unshielded_coinbase_balance)?;
        self.check_total()?;
        Ok(result)
    }

    /// Returns the total value of economically relevant notes and UTXOs belonging to the account.
    pub fn total(&self) -> Zatoshis {
        (self.sapling_balance.total()
            + self.orchard_balance.total()
            + self.ironwood_balance.total()
            + self.unshielded_regular_balance.total()
            + self.unshielded_coinbase_balance.total())
        .expect("Account balance cannot overflow MAX_MONEY")
    }

    /// Returns the total value of shielded (Sapling, Orchard, and Ironwood) funds that may
    /// immediately be spent.
    pub fn spendable_value(&self) -> Zatoshis {
        (self.sapling_balance.spendable_value
            + self.orchard_balance.spendable_value
            + self.ironwood_balance.spendable_value)
            .expect("Account balance cannot overflow MAX_MONEY")
    }

    /// Returns the total value of notes and UTXOs that are locked, having been committed to
    /// an in-flight transaction proposal or PCZT.
    pub fn locked_value(&self) -> Zatoshis {
        (self.sapling_balance.locked_value()
            + self.orchard_balance.locked_value()
            + self.ironwood_balance.locked_value()
            + self.unshielded_regular_balance.locked_value()
            + self.unshielded_coinbase_balance.locked_value())
        .expect("Account balance cannot overflow MAX_MONEY")
    }

    /// Returns the total value of change and/or shielding transaction outputs that are awaiting
    /// sufficient confirmations for spendability.
    pub fn change_pending_confirmation(&self) -> Zatoshis {
        (self.sapling_balance.change_pending_confirmation
            + self.orchard_balance.change_pending_confirmation
            + self.ironwood_balance.change_pending_confirmation)
            .expect("Account balance cannot overflow MAX_MONEY")
    }

    /// Returns the value of shielded funds that are not yet spendable because additional scanning
    /// is required before it will be possible to derive witnesses for the associated notes.
    pub fn value_pending_spendability(&self) -> Zatoshis {
        (self.sapling_balance.value_pending_spendability
            + self.orchard_balance.value_pending_spendability
            + self.ironwood_balance.value_pending_spendability)
            .expect("Account balance cannot overflow MAX_MONEY")
    }

    /// Returns the value in the account of notes and transparent UTXOs that have value less than
    /// the marginal fee, and consequently cannot be spent except as a grace input.
    pub fn uneconomic_value(&self) -> Zatoshis {
        (self.sapling_balance.uneconomic_value
            + self.orchard_balance.uneconomic_value
            + self.ironwood_balance.uneconomic_value
            + self.unshielded_regular_balance.uneconomic_value
            + self.unshielded_coinbase_balance.uneconomic_value)
            .expect("Account balance cannot overflow MAX_MONEY")
    }
}

/// Source metadata for a ZIP 32-derived key.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct Zip32Derivation {
    seed_fingerprint: SeedFingerprint,
    account_index: zip32::AccountId,
    #[cfg(feature = "zcashd-compat")]
    legacy_address_index: Option<zcashd::LegacyAddressIndex>,
}

impl Zip32Derivation {
    /// Constructs new derivation metadata from its constituent parts.
    pub fn new(
        seed_fingerprint: SeedFingerprint,
        account_index: zip32::AccountId,
        #[cfg(feature = "zcashd-compat")] legacy_address_index: Option<zcashd::LegacyAddressIndex>,
    ) -> Self {
        Self {
            seed_fingerprint,
            account_index,
            #[cfg(feature = "zcashd-compat")]
            legacy_address_index,
        }
    }

    /// Returns the seed fingerprint.
    pub fn seed_fingerprint(&self) -> &SeedFingerprint {
        &self.seed_fingerprint
    }

    /// Returns the account-level index in the ZIP 32 derivation path.
    pub fn account_index(&self) -> zip32::AccountId {
        self.account_index
    }

    #[cfg(feature = "zcashd-compat")]
    pub fn legacy_address_index(&self) -> Option<zcashd::LegacyAddressIndex> {
        self.legacy_address_index
    }
}

/// An enumeration used to control what information is tracked by the wallet for
/// notes received by a given account.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub enum AccountPurpose {
    /// For spending accounts, the wallet will track information needed to spend
    /// received notes.
    Spending { derivation: Option<Zip32Derivation> },
    /// For view-only accounts, the wallet will not track spend information.
    ViewOnly,
}

/// The kinds of accounts supported by `zcash_client_backend`.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub enum AccountSource {
    /// An account derived from a known seed.
    Derived {
        derivation: Zip32Derivation,
        key_source: Option<String>,
    },

    /// An account imported from a viewing key.
    Imported {
        purpose: AccountPurpose,
        key_source: Option<String>,
    },
}

impl AccountSource {
    /// Returns the key derivation metadata for the account source, if any is available.
    pub fn key_derivation(&self) -> Option<&Zip32Derivation> {
        match self {
            AccountSource::Derived { derivation, .. } => Some(derivation),
            AccountSource::Imported {
                purpose: AccountPurpose::Spending { derivation },
                ..
            } => derivation.as_ref(),
            _ => None,
        }
    }

    /// Returns the application-level key source identifier.
    pub fn key_source(&self) -> Option<&str> {
        match self {
            AccountSource::Derived { key_source, .. } => key_source.as_ref().map(|s| s.as_str()),
            AccountSource::Imported { key_source, .. } => key_source.as_ref().map(|s| s.as_str()),
        }
    }
}

/// A set of capabilities that a client account must provide.
///
/// An account represents a distinct set of viewing keys within the wallet; the keys for an account
/// must not be shared with any other account in the wallet, and an application managing wallet
/// accounts must ensure that it either maintains spending keys that can be used for spending _all_
/// outputs detectable by the viewing keys of the account, or for none of them (i.e. the account is
/// view-only.)
///
/// Balance information is available for any full-viewing-key based account; for an
/// incoming-viewing-key only account balance cannot be determined because spends cannot be
/// detected, and so balance-related APIs and APIs that rely upon spentness checks MUST be
/// implemented to return errors if invoked for an IVK-only account.
///
/// For spending accounts in implementations that support the `transparent-key-import` feature,
/// care must be taken to ensure that spending keys corresponding to every imported transparent
/// address in an account are maintained by the application.
pub trait Account {
    type AccountId: Copy;

    /// Returns the unique identifier for the account.
    fn id(&self) -> Self::AccountId;

    /// Returns the human-readable name for the account, if any has been configured.
    fn name(&self) -> Option<&str>;

    /// Returns the birthday height for the account.
    fn birthday_height(&self) -> BlockHeight;

    /// Returns whether this account is derived or imported, and the derivation parameters
    /// if applicable.
    fn source(&self) -> &AccountSource;

    /// Returns whether the account is a spending account or a view-only account.
    fn purpose(&self) -> AccountPurpose {
        match self.source() {
            AccountSource::Derived { derivation, .. } => AccountPurpose::Spending {
                derivation: Some(derivation.clone()),
            },
            AccountSource::Imported { purpose, .. } => purpose.clone(),
        }
    }

    /// Returns the UFVK that the wallet backend has stored for the account, if any.
    ///
    /// Accounts for which this returns `None` cannot be used in wallet contexts, because
    /// they are unable to maintain an accurate balance.
    fn ufvk(&self) -> Option<&UnifiedFullViewingKey>;

    /// Returns the UIVK that the wallet backend has stored for the account.
    ///
    /// All accounts are required to have at least an incoming viewing key. This gives no
    /// indication about whether an account can be used in a wallet context; for that, use
    /// [`Account::ufvk`].
    fn uivk(&self) -> UnifiedIncomingViewingKey;
}

#[cfg(any(test, feature = "test-dependencies"))]
impl<A: Copy> Account for (A, UnifiedFullViewingKey, BlockHeight) {
    type AccountId = A;

    fn id(&self) -> A {
        self.0
    }

    fn name(&self) -> Option<&str> {
        None
    }

    fn birthday_height(&self) -> BlockHeight {
        self.2
    }

    fn source(&self) -> &AccountSource {
        &AccountSource::Imported {
            purpose: AccountPurpose::ViewOnly,
            key_source: None,
        }
    }

    fn ufvk(&self) -> Option<&UnifiedFullViewingKey> {
        Some(&self.1)
    }

    fn uivk(&self) -> UnifiedIncomingViewingKey {
        self.1.to_unified_incoming_viewing_key()
    }
}

#[cfg(any(test, feature = "test-dependencies"))]
impl<A: Copy> Account for (A, UnifiedIncomingViewingKey, BlockHeight) {
    type AccountId = A;

    fn id(&self) -> A {
        self.0
    }

    fn name(&self) -> Option<&str> {
        None
    }

    fn birthday_height(&self) -> BlockHeight {
        self.2
    }

    fn source(&self) -> &AccountSource {
        &AccountSource::Imported {
            purpose: AccountPurpose::ViewOnly,
            key_source: None,
        }
    }

    fn ufvk(&self) -> Option<&UnifiedFullViewingKey> {
        None
    }

    fn uivk(&self) -> UnifiedIncomingViewingKey {
        self.1.clone()
    }
}

/// Source metadata for an address in the wallet.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum AddressSource {
    /// The address was produced by HD derivation via a known path, with the given diversifier
    /// index.
    Derived {
        diversifier_index: DiversifierIndex,
        #[cfg(feature = "transparent-inputs")]
        transparent_key_scope: Option<TransparentKeyScope>,
    },
    /// No derivation information is available; this is common for imported addresses.
    #[cfg(feature = "transparent-key-import")]
    Standalone,
}

impl AddressSource {
    /// Returns the transparent key scope at which the address was derived, if this source metadata
    /// is for a transparent address derived from a UIVK in the wallet.
    #[cfg(feature = "transparent-inputs")]
    pub fn transparent_key_scope(&self) -> Option<&TransparentKeyScope> {
        match self {
            AddressSource::Derived {
                transparent_key_scope,
                ..
            } => transparent_key_scope.as_ref(),
            #[cfg(feature = "transparent-key-import")]
            AddressSource::Standalone => None,
        }
    }
}

/// Information about an address in the wallet.
#[derive(Clone)]
pub struct AddressInfo {
    address: Address,
    source: AddressSource,
}

impl AddressInfo {
    /// Constructs an `AddressInfo` from its constituent parts.
    pub fn from_parts(address: Address, source: AddressSource) -> Option<Self> {
        // Only allow `transparent_key_scope` to be set for transparent addresses.
        #[cfg(feature = "transparent-inputs")]
        let valid = source.transparent_key_scope().is_none()
            || matches!(address, Address::Transparent(_) | Address::Tex(_));
        #[cfg(not(feature = "transparent-inputs"))]
        let valid = true;

        valid.then_some(Self { address, source })
    }

    /// Returns the address itself.
    pub fn address(&self) -> &Address {
        &self.address
    }

    /// Returns the source metadata for the address.
    pub fn source(&self) -> AddressSource {
        self.source
    }

    /// Returns the key scope if this is a transparent address.
    #[cfg(feature = "transparent-inputs")]
    #[deprecated(
        since = "0.20.0",
        note = "use AddressSource::transparent_key_scope instead"
    )]
    pub fn transparent_key_scope(&self) -> Option<&TransparentKeyScope> {
        self.source.transparent_key_scope()
    }
}

/// A polymorphic ratio type, usually used for rational numbers.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Ratio<T> {
    numerator: T,
    denominator: T,
}

impl<T> Ratio<T> {
    /// Constructs a new Ratio from a numerator and a denominator.
    pub fn new(numerator: T, denominator: T) -> Self {
        Self {
            numerator,
            denominator,
        }
    }

    /// Returns the numerator of the ratio.
    pub fn numerator(&self) -> &T {
        &self.numerator
    }

    /// Returns the denominator of the ratio.
    pub fn denominator(&self) -> &T {
        &self.denominator
    }
}

/// A type representing the progress the wallet has made toward detecting all of the funds
/// belonging to the wallet.
///
/// The window over which progress is computed spans from the wallet's birthday to the current
/// chain tip. It is divided into two regions, the "Scan Window" which covers the region from the
/// wallet recovery height to the current chain tip, and the "Recovery Window" which covers the
/// range from the wallet birthday to the wallet recovery height. If no wallet recovery height is
/// available, the scan window will cover the entire range from the wallet birthday to the chain
/// tip.
///
/// Progress for both scanning and recovery is represented in terms of the ratio between notes
/// scanned and the total number of notes added to the chain in the relevant window. This ratio
/// should only be used to compute progress percentages for display, and the numerator and
/// denominator should not be treated as authoritative note counts. In the case that there are no
/// notes in a given block range, the denominator of these values will be zero, so callers should always
/// use checked division when converting the resulting values to percentages.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Progress {
    scan: Ratio<u64>,
    recovery: Option<Ratio<u64>>,
}

impl Progress {
    /// Constructs a new progress value from its constituent parts.
    pub fn new(scan: Ratio<u64>, recovery: Option<Ratio<u64>>) -> Self {
        Self { scan, recovery }
    }

    /// Returns the progress the wallet has made in scanning blocks for shielded notes belonging to
    /// the wallet between the wallet recovery height (or the wallet birthday if no recovery height
    /// is set) and the chain tip.
    pub fn scan(&self) -> Ratio<u64> {
        self.scan
    }

    /// Returns the progress the wallet has made in scanning blocks for shielded notes belonging to
    /// the wallet between the wallet birthday and the block height at which recovery from seed was
    /// initiated.
    ///
    /// Returns `None` if no recovery height is set for the wallet.
    pub fn recovery(&self) -> Option<Ratio<u64>> {
        self.recovery
    }
}

/// A type representing the potentially-spendable value of unspent outputs in the wallet.
///
/// The balances reported using this data structure may overestimate the total spendable value of
/// the wallet, in the case that the spend of a previously received shielded note has not yet been
/// detected by the process of scanning the chain. The balances reported using this data structure
/// can only be certain to be unspent in the case that [`Self::is_synced`] is true, and even in
/// this circumstance it is possible that a newly created transaction could conflict with a
/// not-yet-mined transaction in the mempool.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct WalletSummary<AccountId: Eq + Hash> {
    account_balances: HashMap<AccountId, AccountBalance>,
    chain_tip_height: BlockHeight,
    fully_scanned_height: BlockHeight,
    progress: Progress,
    next_sapling_subtree_index: u64,
    #[cfg(feature = "orchard")]
    next_orchard_subtree_index: u64,
    #[cfg(feature = "orchard")]
    next_ironwood_subtree_index: u64,
}

impl<AccountId: Eq + Hash> WalletSummary<AccountId> {
    /// Constructs a new [`WalletSummary`] from its constituent parts.
    pub fn new(
        account_balances: HashMap<AccountId, AccountBalance>,
        chain_tip_height: BlockHeight,
        fully_scanned_height: BlockHeight,
        progress: Progress,
        next_sapling_subtree_index: u64,
        #[cfg(feature = "orchard")] next_orchard_subtree_index: u64,
        #[cfg(feature = "orchard")] next_ironwood_subtree_index: u64,
    ) -> Self {
        Self {
            account_balances,
            chain_tip_height,
            fully_scanned_height,
            progress,
            next_sapling_subtree_index,
            #[cfg(feature = "orchard")]
            next_orchard_subtree_index,
            #[cfg(feature = "orchard")]
            next_ironwood_subtree_index,
        }
    }

    /// Returns the balances of accounts in the wallet, keyed by account ID.
    pub fn account_balances(&self) -> &HashMap<AccountId, AccountBalance> {
        &self.account_balances
    }

    /// Returns the height of the current chain tip.
    pub fn chain_tip_height(&self) -> BlockHeight {
        self.chain_tip_height
    }

    /// Returns the height below which all blocks have been scanned by the wallet, ignoring blocks
    /// below the wallet birthday.
    pub fn fully_scanned_height(&self) -> BlockHeight {
        self.fully_scanned_height
    }

    /// Returns the progress of scanning the chain to bring the wallet up to date.
    ///
    /// This progress metric is intended as an indicator of how close the wallet is to
    /// general usability, including the ability to spend existing funds that were
    /// previously spendable.
    ///
    /// The window over which progress is computed spans from the wallet's birthday to the current
    /// chain tip. It is divided into two segments: a "recovery" segment, between the wallet
    /// birthday and the recovery height (currently the height at which recovery from seed was
    /// initiated, but how this boundary is computed may change in the future), and a "scan"
    /// segment, between the recovery height and the current chain tip.
    ///
    /// When converting the ratios returned here to percentages, checked division must be used in
    /// order to avoid divide-by-zero errors. A zero denominator in a returned ratio indicates that
    /// there are no shielded notes to be scanned in the associated block range.
    pub fn progress(&self) -> Progress {
        self.progress
    }

    /// Returns the Sapling subtree index that should start the next range of subtree
    /// roots passed to [`WalletCommitmentTrees::put_sapling_subtree_roots`].
    pub fn next_sapling_subtree_index(&self) -> u64 {
        self.next_sapling_subtree_index
    }

    /// Returns the Orchard subtree index that should start the next range of subtree
    /// roots passed to [`WalletCommitmentTrees::put_orchard_subtree_roots`].
    #[cfg(feature = "orchard")]
    pub fn next_orchard_subtree_index(&self) -> u64 {
        self.next_orchard_subtree_index
    }

    /// Returns the Ironwood subtree index that should start the next range of subtree
    /// roots passed to [`WalletCommitmentTrees::put_ironwood_subtree_roots`].
    #[cfg(feature = "orchard")]
    pub fn next_ironwood_subtree_index(&self) -> u64 {
        self.next_ironwood_subtree_index
    }

    /// Returns whether or not wallet scanning is complete.
    pub fn is_synced(&self) -> bool {
        self.chain_tip_height == self.fully_scanned_height
    }
}

/// A predicate that can be used to choose whether or not a particular note is retained in note
/// selection.
pub trait NoteRetention<NoteRef> {
    /// Returns whether the specified Sapling note should be retained.
    fn should_retain_sapling(&self, note: &ReceivedNote<NoteRef, sapling::Note>) -> bool;
    /// Returns whether the specified Orchard note should be retained.
    #[cfg(feature = "orchard")]
    fn should_retain_orchard(&self, note: &ReceivedNote<NoteRef, orchard::note::Note>) -> bool;
    /// Returns whether the specified Ironwood note should be retained. Ironwood notes are
    /// Orchard-shaped, so this uses the same note type as Orchard.
    #[cfg(feature = "orchard")]
    fn should_retain_ironwood(&self, note: &ReceivedNote<NoteRef, orchard::note::Note>) -> bool;
}

pub(crate) struct SimpleNoteRetention {
    pub(crate) sapling: bool,
    #[cfg(feature = "orchard")]
    pub(crate) orchard: bool,
    #[cfg(feature = "orchard")]
    pub(crate) ironwood: bool,
}

impl<NoteRef> NoteRetention<NoteRef> for SimpleNoteRetention {
    fn should_retain_sapling(&self, _: &ReceivedNote<NoteRef, sapling::Note>) -> bool {
        self.sapling
    }

    #[cfg(feature = "orchard")]
    fn should_retain_orchard(&self, _: &ReceivedNote<NoteRef, orchard::note::Note>) -> bool {
        self.orchard
    }

    #[cfg(feature = "orchard")]
    fn should_retain_ironwood(&self, _: &ReceivedNote<NoteRef, orchard::note::Note>) -> bool {
        self.ironwood
    }
}

/// Shielded outputs that were received by the wallet.
#[derive(Debug)]
pub struct ReceivedNotes<NoteRef> {
    sapling: Vec<ReceivedNote<NoteRef, sapling::Note>>,
    #[cfg(feature = "orchard")]
    orchard: Vec<ReceivedNote<NoteRef, orchard::note::Note>>,
    // Ironwood notes are Orchard-shaped `orchard::note::Note` values (note plaintext version 3),
    // but are tracked as a distinct pool so that Orchard and Ironwood value and bundle action
    // counts are accounted for separately.
    #[cfg(feature = "orchard")]
    ironwood: Vec<ReceivedNote<NoteRef, orchard::note::Note>>,
}

/// The necessary and optional notes returned for consolidation-aware input selection.
///
/// `funding` contains the notes selected to fund the requested value. `additional` contains
/// disjoint, ordinarily spendable notes that the input selector may add when doing so does not
/// change the transaction's fee or observable shape.
#[derive(Debug)]
pub struct ConsolidationNotes<NoteRef> {
    funding: ReceivedNotes<NoteRef>,
    additional: ReceivedNotes<NoteRef>,
}

impl<NoteRef> ConsolidationNotes<NoteRef> {
    /// Constructs a consolidation selection from its necessary and optional notes.
    ///
    /// `funding` and `additional` must be disjoint and contain notes only from the requested
    /// source pool. `additional` must also obey the caller's candidate limit and use the same
    /// preferred lock tier as `funding`.
    pub fn from_parts(funding: ReceivedNotes<NoteRef>, additional: ReceivedNotes<NoteRef>) -> Self {
        Self {
            funding,
            additional,
        }
    }

    /// Consumes this selection and returns its necessary and optional notes.
    pub fn into_parts(self) -> (ReceivedNotes<NoteRef>, ReceivedNotes<NoteRef>) {
        (self.funding, self.additional)
    }
}

impl<NoteRef> ReceivedNotes<NoteRef> {
    /// Construct a new empty [`ReceivedNotes`].
    pub fn empty() -> Self {
        Self::new(
            vec![],
            #[cfg(feature = "orchard")]
            vec![],
            #[cfg(feature = "orchard")]
            vec![],
        )
    }

    /// Construct a new [`ReceivedNotes`] from its constituent parts.
    pub fn new(
        sapling: Vec<ReceivedNote<NoteRef, sapling::Note>>,
        #[cfg(feature = "orchard")] orchard: Vec<ReceivedNote<NoteRef, orchard::note::Note>>,
        #[cfg(feature = "orchard")] ironwood: Vec<ReceivedNote<NoteRef, orchard::note::Note>>,
    ) -> Self {
        Self {
            sapling,
            #[cfg(feature = "orchard")]
            orchard,
            #[cfg(feature = "orchard")]
            ironwood,
        }
    }

    /// Returns the set of spendable Sapling notes.
    pub fn sapling(&self) -> &[ReceivedNote<NoteRef, sapling::Note>] {
        self.sapling.as_ref()
    }

    /// Consumes this value and returns the Sapling notes contained within it.
    pub fn take_sapling(self) -> Vec<ReceivedNote<NoteRef, sapling::Note>> {
        self.sapling
    }

    /// Returns the set of spendable Orchard notes.
    #[cfg(feature = "orchard")]
    pub fn orchard(&self) -> &[ReceivedNote<NoteRef, orchard::note::Note>] {
        self.orchard.as_ref()
    }

    /// Consumes this value and returns the Orchard notes contained within it.
    #[cfg(feature = "orchard")]
    pub fn take_orchard(self) -> Vec<ReceivedNote<NoteRef, orchard::note::Note>> {
        self.orchard
    }

    /// Returns the set of spendable Ironwood notes.
    #[cfg(feature = "orchard")]
    pub fn ironwood(&self) -> &[ReceivedNote<NoteRef, orchard::note::Note>] {
        self.ironwood.as_ref()
    }

    /// Consumes this value and returns the Ironwood notes contained within it.
    #[cfg(feature = "orchard")]
    pub fn take_ironwood(self) -> Vec<ReceivedNote<NoteRef, orchard::note::Note>> {
        self.ironwood
    }

    /// Computes the total value of Sapling notes.
    pub fn sapling_value(&self) -> Result<Zatoshis, BalanceError> {
        self.sapling.iter().try_fold(Zatoshis::ZERO, |acc, n| {
            (acc + n.note_value()?).ok_or(BalanceError::Overflow)
        })
    }

    /// Computes the total value of Orchard notes.
    #[cfg(feature = "orchard")]
    pub fn orchard_value(&self) -> Result<Zatoshis, BalanceError> {
        self.orchard.iter().try_fold(Zatoshis::ZERO, |acc, n| {
            (acc + n.note_value()?).ok_or(BalanceError::Overflow)
        })
    }

    /// Computes the total value of Ironwood notes.
    #[cfg(feature = "orchard")]
    pub fn ironwood_value(&self) -> Result<Zatoshis, BalanceError> {
        self.ironwood.iter().try_fold(Zatoshis::ZERO, |acc, n| {
            (acc + n.note_value()?).ok_or(BalanceError::Overflow)
        })
    }

    /// Computes the total value of spendable inputs
    pub fn total_value(&self) -> Result<Zatoshis, BalanceError> {
        #[cfg(not(feature = "orchard"))]
        return self.sapling_value();

        #[cfg(feature = "orchard")]
        return (self.sapling_value()? + self.orchard_value()? + self.ironwood_value()?)
            .ok_or(BalanceError::Overflow);
    }

    /// Returns whether the collection contains no notes in any pool.
    pub fn is_empty(&self) -> bool {
        #[cfg(not(feature = "orchard"))]
        return self.sapling.is_empty();

        #[cfg(feature = "orchard")]
        return self.sapling.is_empty() && self.orchard.is_empty() && self.ironwood.is_empty();
    }

    /// Appends each pool's notes from `other` to this collection.
    pub(crate) fn append(&mut self, mut other: Self) {
        self.sapling.append(&mut other.sapling);
        #[cfg(feature = "orchard")]
        {
            self.orchard.append(&mut other.orchard);
            self.ironwood.append(&mut other.ironwood);
        }
    }

    /// Consumes this collection, returning one holding only the OLDEST single note whose value
    /// alone is at least `value`, drawn from the first pool in `sources` that holds one; the
    /// result is empty when no single note qualifies. Age is the note's commitment tree
    /// position, which is assigned in strict chain order.
    ///
    /// This is the best-effort reduction behind the default implementation of
    /// [`InputSource::select_single_spendable_note`]: it can only choose among the notes it
    /// holds, so a covering note the producing selection did not surface cannot be found here.
    pub fn into_single_covering(mut self, value: Zatoshis, sources: &[ShieldedPool]) -> Self {
        fn take_oldest_covering<NoteRef, N>(
            notes: &mut Vec<ReceivedNote<NoteRef, N>>,
            covers: impl Fn(&ReceivedNote<NoteRef, N>) -> bool,
        ) -> Option<ReceivedNote<NoteRef, N>> {
            let idx = notes
                .iter()
                .enumerate()
                .filter(|(_, n)| covers(n))
                .min_by_key(|(_, n)| n.note_commitment_tree_position())
                .map(|(idx, _)| idx)?;
            Some(notes.swap_remove(idx))
        }

        for pool in sources {
            match pool {
                ShieldedPool::Sapling => {
                    if let Some(note) = take_oldest_covering(&mut self.sapling, |n| {
                        n.note_value().is_ok_and(|v| v >= value)
                    }) {
                        return Self::new(
                            vec![note],
                            #[cfg(feature = "orchard")]
                            vec![],
                            #[cfg(feature = "orchard")]
                            vec![],
                        );
                    }
                }
                #[cfg(feature = "orchard")]
                ShieldedPool::Orchard => {
                    if let Some(note) = take_oldest_covering(&mut self.orchard, |n| {
                        n.note_value().is_ok_and(|v| v >= value)
                    }) {
                        return Self::new(vec![], vec![note], vec![]);
                    }
                }
                #[cfg(feature = "orchard")]
                ShieldedPool::Ironwood => {
                    if let Some(note) = take_oldest_covering(&mut self.ironwood, |n| {
                        n.note_value().is_ok_and(|v| v >= value)
                    }) {
                        return Self::new(vec![], vec![], vec![note]);
                    }
                }
                #[cfg(not(feature = "orchard"))]
                ShieldedPool::Orchard | ShieldedPool::Ironwood => {}
            }
        }
        Self::empty()
    }

    /// Consumes this [`ReceivedNotes`] value and produces a vector of
    /// [`ReceivedNote<NoteRef, Note>`] values.
    pub fn into_vec(
        self,
        retention: &impl NoteRetention<NoteRef>,
    ) -> Vec<ReceivedNote<NoteRef, Note>> {
        let iter = self.sapling.into_iter().filter_map(|n| {
            retention
                .should_retain_sapling(&n)
                .then(|| n.map_note(Note::Sapling))
        });

        #[cfg(feature = "orchard")]
        let iter = iter.chain(self.orchard.into_iter().filter_map(|n| {
            retention.should_retain_orchard(&n).then(|| {
                n.map_note(|note| Note::Orchard {
                    note,
                    pool: orchard::ValuePool::Orchard,
                })
            })
        }));

        // Ironwood notes are `orchard::note::Note` values, so they are emitted as `Note::Orchard`;
        // the transaction builder routes them to the Ironwood bundle by their version 3 plaintext.
        #[cfg(feature = "orchard")]
        let iter = iter.chain(self.ironwood.into_iter().filter_map(|n| {
            retention.should_retain_ironwood(&n).then(|| {
                n.map_note(|note| Note::Orchard {
                    note,
                    pool: orchard::ValuePool::Ironwood,
                })
            })
        }));

        iter.collect()
    }
}

/// A type describing the mined-ness of transactions that should be returned in response to a
/// [`TransactionDataRequest`].
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[cfg(feature = "transparent-inputs")]
pub enum TransactionStatusFilter {
    /// Only mined transactions should be returned.
    Mined,
    /// Only mempool transactions should be returned.
    Mempool,
    /// Both mined transactions and transactions in the mempool should be returned.
    All,
}

/// A type used to filter transactions to be returned in response to a [`TransactionDataRequest`],
/// in terms of the spentness of the transaction's transparent outputs.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[cfg(feature = "transparent-inputs")]
pub enum OutputStatusFilter {
    /// Only transactions that have currently-unspent transparent outputs should be returned.
    Unspent,
    /// All transactions corresponding to the data request should be returned, irrespective of
    /// whether or not those transactions produce transparent outputs that are currently unspent.
    All,
}

/// Payload data for [`TransactionDataRequest::TransactionsInvolvingAddress`].
///
/// Values of this type are not constructed directly, but are instead constructed using
/// [`TransactionDataRequest::transactions_involving_address`].
#[cfg(feature = "transparent-inputs")]
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Getters, CopyGetters)]
pub struct TransactionsInvolvingAddress {
    /// The address to request transactions and/or UTXOs for.
    #[getset(get_copy = "pub")]
    address: TransparentAddress,
    /// Only transactions mined at heights greater than or equal to this height should be
    /// returned.
    #[getset(get_copy = "pub")]
    block_range_start: BlockHeight,
    /// If set, only transactions mined at heights less than this height should be returned.
    #[getset(get_copy = "pub")]
    block_range_end: Option<BlockHeight>,
    /// If a `request_at` time is set, the caller evaluating this request should attempt to
    /// retrieve transaction data related to the specified address at a time that is as close
    /// as practical to the specified instant, and in a fashion that decorrelates this request
    /// to a light wallet server from other requests made by the same caller.
    ///
    /// This may be ignored by callers that are able to satisfy the request without exposing
    /// correlations between addresses to untrusted parties; for example, a wallet application
    /// that uses a private, trusted-for-privacy supplier of chain data can safely ignore this
    /// field.
    #[getset(get_copy = "pub")]
    request_at: Option<SystemTime>,
    /// The caller should respond to this request only with transactions that conform to the
    /// specified transaction status filter.
    #[getset(get = "pub")]
    tx_status_filter: TransactionStatusFilter,
    /// The caller should respond to this request only with transactions containing outputs
    /// that conform to the specified output status filter.
    #[getset(get = "pub")]
    output_status_filter: OutputStatusFilter,
}

/// A request for transaction data enhancement, spentness check, or discovery
/// of spends from a given transparent address within a specific block range.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum TransactionDataRequest {
    /// Information about the chain's view of a transaction is requested.
    ///
    /// The caller evaluating this request on behalf of the wallet backend should respond to this
    /// request by determining the status of the specified transaction with respect to the main
    /// chain; if using `lightwalletd` for access to chain data, this may be obtained by
    /// interpreting the results of the `GetTransaction` RPC method. It should then call
    /// [`WalletWrite::set_transaction_status`] to provide the resulting transaction status
    /// information to the wallet backend.
    GetStatus(TxId),
    /// Transaction enhancement (download of complete raw transaction data) is requested.
    ///
    /// The caller evaluating this request on behalf of the wallet backend should respond to this
    /// request by providing complete data for the specified transaction to
    /// [`wallet::decrypt_and_store_transaction`]; if using `lightwalletd` for access to chain
    /// state, this may be obtained via the `GetTransaction` RPC method. If no data is available
    /// for the specified transaction, this should be reported to the backend using
    /// [`WalletWrite::set_transaction_status`]. A [`TransactionDataRequest::Enhancement`] request
    /// subsumes any previously existing [`TransactionDataRequest::GetStatus`] request.
    Enhancement(TxId),
    /// Information about transactions that receive or spend funds belonging to the specified
    /// transparent address is requested.
    ///
    /// Fully transparent transactions, and transactions that do not contain either shielded inputs
    /// or shielded outputs belonging to the wallet, may not be discovered by the process of
    /// out-of-order chain scanning due to race conditions related to advancing the transparent
    /// address gap limit; as a consequence, the wallet must actively query to find transactions
    /// that spend such funds. Ideally we'd be able to query by [`OutPoint`] but this is not
    /// currently functionality that is supported by the light wallet server; for full-node wallets
    /// or other arrangements that allow privacy-preserving retrieval of individually identifying
    /// information such as backends that support private information retrieval (PIR) consider
    /// enabling the `spend-index` feature.
    ///
    /// The caller evaluating this request on behalf of the wallet backend should respond to this
    /// request by detecting transactions involving the specified address within the provided block
    /// range; if using `lightwalletd` for access to chain data, this may be performed using the
    /// `GetTaddressTxids` RPC method. It should then call [`wallet::decrypt_and_store_transaction`]
    /// for each transaction so detected. If no transactions are detected within the given range,
    /// the caller should instead invoke [`WalletWrite::notify_address_checked`] with
    /// `block_end_height - 1` as the `as_of_height` argument.
    #[cfg(feature = "transparent-inputs")]
    TransactionsInvolvingAddress(TransactionsInvolvingAddress),
    /// The main-chain transaction that spends of a specific transparent output, or confirmation
    /// that the output remains unspent, is requested.
    ///
    /// When the `spend-index` feature is enabled, `GetSpendingTx` requests will be emitted by the
    /// backend instead of [`TransactionDataRequest::TransactionsInvolvingAddress`], in
    /// circumstances when spentness determination is needed. This feature should only be enabled
    /// for wallets whose chain-data source can resolve the spend of an individual outpoint
    /// directly — for example a full node that maintains a spent-outpoint index. It avoids needing
    /// to retrieve potentially large amounts of transaction history (in the cas of a
    /// heavily-reused address) just to discover whether one output was spent.
    ///
    /// The caller evaluating this request on behalf of the wallet backend should determine whether
    /// `outpoint` has been spent on the main chain. Spentness should be taken from an
    /// authoritative source (e.g. the node's UTXO set); the spend index is used only to identify
    /// the spending transaction. If the output is spent, the caller should provide the spending
    /// transaction to [`wallet::decrypt_and_store_transaction`]. If the output is confirmed
    /// unspent as of some height, the caller should invoke
    /// [`WalletWrite::notify_output_verified_unspent`] with that height. If the output is known to
    /// be spent but the spending transaction cannot yet be resolved (e.g. an index is still being
    /// built — see ZcashFoundation/zebra#10806), the caller should do nothing, so that the request
    /// is re-issued and retried later.
    #[cfg(feature = "spend-index")]
    GetSpendingTx(OutPoint),
}

impl TransactionDataRequest {
    /// Constructs a request for Information about transactions that receive or spend funds
    /// belonging to the specified transparent address.
    ///
    /// # Parameters:
    /// - `address`: The address to request transactions and/or UTXOs for.
    /// - `block_range_start`: Only transactions mined at heights greater than or equal to this
    ///   height should be returned.
    /// - `block_range_end`: Only transactions mined at heights less than this height should be
    ///   returned.
    /// - `request_at`: If a `request_at` time is set, the caller evaluating this request should attempt to
    ///   retrieve transaction data related to the specified address at a time that is as close
    ///   as practical to the specified instant, and in a fashion that decorrelates this request
    ///   to a light wallet server from other requests made by the same caller. This may be ignored
    ///   by callers that are able to satisfy the request without exposing correlations between
    ///   addresses to untrusted parties; for example, a wallet application that uses a private,
    ///   trusted-for-privacy supplier of chain data can safely ignore this field.
    /// - `tx_status_filter`: The caller should respond to this request only with transactions that
    ///   conform to the specified transaction status filter.
    /// - `output_status_filter: The caller should respond to this request only with transactions
    ///   containing outputs that conform to the specified output status filter.
    ///
    /// See [`TransactionDataRequest::TransactionsInvolvingAddress`] for more information.
    #[cfg(feature = "transparent-inputs")]
    pub fn transactions_involving_address(
        address: TransparentAddress,
        block_range_start: BlockHeight,
        block_range_end: Option<BlockHeight>,
        request_at: Option<SystemTime>,
        tx_status_filter: TransactionStatusFilter,
        output_status_filter: OutputStatusFilter,
    ) -> Self {
        TransactionDataRequest::TransactionsInvolvingAddress(TransactionsInvolvingAddress {
            address,
            block_range_start,
            block_range_end,
            request_at,
            tx_status_filter,
            output_status_filter,
        })
    }
}

/// Metadata about the status of a transaction obtained by inspecting the chain state.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum TransactionStatus {
    /// The requested transaction ID was not recognized by the node.
    TxidNotRecognized,
    /// The requested transaction ID corresponds to a transaction that is recognized by the node,
    /// but is in the mempool or is otherwise not mined in the main chain (but may have been mined
    /// on a fork that was reorged away).
    NotInMainChain,
    /// The requested transaction ID corresponds to a transaction that has been included in the
    /// block at the provided height.
    Mined(BlockHeight),
}

/// Metadata about the structure of unspent outputs in a single pool within a wallet account.
///
/// This type is often used to represent a filtered view of outputs in the account that were
/// selected according to the conditions imposed by a [`NoteFilter`].
#[derive(Debug, Clone)]
pub struct PoolMeta {
    note_count: usize,
    value: Zatoshis,
}

impl PoolMeta {
    /// Constructs a new [`PoolMeta`] value from its constituent parts.
    pub fn new(note_count: usize, value: Zatoshis) -> Self {
        Self { note_count, value }
    }

    /// Returns the number of unspent outputs in the account, potentially selected in accordance
    /// with some [`NoteFilter`].
    pub fn note_count(&self) -> usize {
        self.note_count
    }

    /// Returns the total value of unspent outputs in the account that are accounted for in
    /// [`Self::note_count`].
    pub fn value(&self) -> Zatoshis {
        self.value
    }
}

/// Metadata about the structure of the wallet for a particular account.
///
/// At present this just contains counts of unspent outputs in each pool, but it may be extended in
/// the future to contain note values or other more detailed information about wallet structure.
///
/// Values of this type are intended to be used in selection of change output values. A value of
/// this type may represent filtered data, and may therefore not count all of the unspent notes in
/// the wallet.
///
/// A [`AccountMeta`] value is normally produced by querying the wallet database via passing a
/// [`NoteFilter`] to [`InputSource::get_account_metadata`].
#[derive(Debug, Clone)]
pub struct AccountMeta {
    sapling: Option<PoolMeta>,
    orchard: Option<PoolMeta>,
    ironwood: Option<PoolMeta>,
}

impl AccountMeta {
    /// Constructs a new [`AccountMeta`] value from its constituent parts.
    ///
    /// Ironwood metadata is tracked separately from Orchard, as Ironwood is a distinct pool.
    pub fn new(
        sapling: Option<PoolMeta>,
        orchard: Option<PoolMeta>,
        ironwood: Option<PoolMeta>,
    ) -> Self {
        Self {
            sapling,
            orchard,
            ironwood,
        }
    }

    /// Returns metadata about Sapling notes belonging to the account for which this was generated.
    ///
    /// Returns [`None`] if no metadata is available or it was not possible to evaluate the query
    /// described by a [`NoteFilter`] given the available wallet data.
    pub fn sapling(&self) -> Option<&PoolMeta> {
        self.sapling.as_ref()
    }

    /// Returns metadata about Orchard notes belonging to the account for which this was generated.
    ///
    /// Returns [`None`] if no metadata is available or it was not possible to evaluate the query
    /// described by a [`NoteFilter`] given the available wallet data.
    pub fn orchard(&self) -> Option<&PoolMeta> {
        self.orchard.as_ref()
    }

    /// Returns metadata about Ironwood notes belonging to the account for which this was generated.
    ///
    /// Ironwood notes are Orchard-shaped but belong to a pool distinct from Orchard. Returns
    /// [`None`] if no metadata is available or it was not possible to evaluate the query described
    /// by a [`NoteFilter`] given the available wallet data.
    pub fn ironwood(&self) -> Option<&PoolMeta> {
        self.ironwood.as_ref()
    }

    fn sapling_note_count(&self) -> Option<usize> {
        self.sapling.as_ref().map(|m| m.note_count)
    }

    fn orchard_note_count(&self) -> Option<usize> {
        self.orchard.as_ref().map(|m| m.note_count)
    }

    fn ironwood_note_count(&self) -> Option<usize> {
        self.ironwood.as_ref().map(|m| m.note_count)
    }

    /// Returns the number of unspent notes in the wallet for the given shielded pool.
    pub fn note_count(&self, protocol: ShieldedPool) -> Option<usize> {
        match protocol {
            ShieldedPool::Sapling => self.sapling_note_count(),
            ShieldedPool::Orchard => self.orchard_note_count(),
            ShieldedPool::Ironwood => self.ironwood_note_count(),
        }
    }

    /// Returns the total number of unspent shielded notes belonging to the account for which this
    /// was generated.
    ///
    /// Returns [`None`] if no metadata is available or it was not possible to evaluate the query
    /// described by a [`NoteFilter`] given the available wallet data. If metadata is available
    /// only for a single pool, the metadata for that pool will be returned.
    pub fn total_note_count(&self) -> Option<usize> {
        [
            self.sapling_note_count(),
            self.orchard_note_count(),
            self.ironwood_note_count(),
        ]
        .into_iter()
        .flatten()
        .reduce(|a, b| a + b)
    }

    fn sapling_value(&self) -> Option<Zatoshis> {
        self.sapling.as_ref().map(|m| m.value)
    }

    fn orchard_value(&self) -> Option<Zatoshis> {
        self.orchard.as_ref().map(|m| m.value)
    }

    fn ironwood_value(&self) -> Option<Zatoshis> {
        self.ironwood.as_ref().map(|m| m.value)
    }

    /// Returns the total value of shielded notes represented by [`Self::total_note_count`]
    ///
    /// Returns [`None`] if no metadata is available or it was not possible to evaluate the query
    /// described by a [`NoteFilter`] given the available wallet data. If metadata is available
    /// only for a single pool, the metadata for that pool will be returned.
    pub fn total_value(&self) -> Option<Zatoshis> {
        [
            self.sapling_value(),
            self.orchard_value(),
            self.ironwood_value(),
        ]
        .into_iter()
        .flatten()
        .reduce(|a, b| (a + b).expect("Does not overflow Zcash maximum value."))
    }
}

/// A `u8` value in the range 0..=MAX
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct BoundedU8<const MAX: u8>(u8);

impl<const MAX: u8> BoundedU8<MAX> {
    /// Creates a constant `BoundedU8` from a [`u8`] value.
    ///
    /// Panics: if the value is outside the range `0..=MAX`.
    pub const fn new_const(value: u8) -> Self {
        assert!(value <= MAX);
        Self(value)
    }

    /// Creates a `BoundedU8` from a [`u8`] value.
    ///
    /// Returns `None` if the provided value is outside the range `0..=MAX`.
    pub fn new(value: u8) -> Option<Self> {
        if value <= MAX {
            Some(Self(value))
        } else {
            None
        }
    }

    /// Returns the wrapped [`u8`] value.
    pub fn value(&self) -> u8 {
        self.0
    }
}

impl<const MAX: u8> From<BoundedU8<MAX>> for u8 {
    fn from(value: BoundedU8<MAX>) -> Self {
        value.0
    }
}

impl<const MAX: u8> From<BoundedU8<MAX>> for usize {
    fn from(value: BoundedU8<MAX>) -> Self {
        usize::from(value.0)
    }
}

/// A small query language for filtering notes belonging to an account.
///
/// A filter described using this language is applied to notes individually. It is primarily
/// intended for retrieval of account metadata in service of making determinations for how to
/// allocate change notes, and is not currently intended for use in broader note selection
/// contexts.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum NoteFilter {
    /// Selects notes having value strictly greater than the provided value.
    ExceedsMinValue(Zatoshis),
    /// Selects notes having value greater than or equal to approximately the n'th percentile of
    /// previously sent notes in the account, irrespective of pool. The wrapped value must be in
    /// the range `1..=99`. The value `n` is respected in a best-effort fashion; results are likely
    /// to be inaccurate if the account has not yet completed scanning or if insufficient send data
    /// is available to establish a distribution.
    // TODO: it might be worthwhile to add an optional parameter here that can be used to ignore
    // low-valued (test/memo-only) sends when constructing the distribution to be drawn from.
    ExceedsPriorSendPercentile(BoundedU8<99>),
    /// Selects notes having value greater than or equal to the specified percentage of the account
    /// balance across all shielded pools. The wrapped value must be in the range `1..=99`
    ExceedsBalancePercentage(BoundedU8<99>),
    /// A note will be selected if it satisfies both of the specified conditions.
    ///
    /// If it is not possible to evaluate one of the conditions (for example,
    /// [`NoteFilter::ExceedsPriorSendPercentile`] cannot be evaluated if no sends have been
    /// performed) then that condition will be ignored. If neither condition can be evaluated,
    /// then the entire condition cannot be evaluated.
    Combine(Box<NoteFilter>, Box<NoteFilter>),
    /// A note will be selected if it satisfies the first condition; if it is not possible to
    /// evaluate that condition (for example, [`NoteFilter::ExceedsPriorSendPercentile`] cannot
    /// be evaluated if no sends have been performed) then the second condition will be used for
    /// evaluation.
    Attempt {
        condition: Box<NoteFilter>,
        fallback: Box<NoteFilter>,
    },
}

impl NoteFilter {
    /// Constructs a [`NoteFilter::Combine`] query node.
    pub fn combine(l: NoteFilter, r: NoteFilter) -> Self {
        Self::Combine(Box::new(l), Box::new(r))
    }

    /// Constructs a [`NoteFilter::Attempt`] query node.
    pub fn attempt(condition: NoteFilter, fallback: NoteFilter) -> Self {
        Self::Attempt {
            condition: Box::new(condition),
            fallback: Box::new(fallback),
        }
    }
}

/// Controls which transparent outputs are eligible for selection. This is an
/// input-selection control only; it does not encode any consensus rule.
#[cfg(feature = "transparent-inputs")]
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum CoinbaseFilter {
    /// Select all spendable transparent outputs.
    #[default]
    AllTransparentOutputs,
    /// Select only coinbase transparent outputs.
    ///
    /// Coinbase transactions are identified by having `tx_index == 0` within
    /// their containing block. Outputs for which the transaction index is
    /// unknown are conservatively treated as non-coinbase and will be excluded
    /// when this filter is active.
    CoinbaseOnly,
    /// Select only non-coinbase transparent outputs.
    ///
    /// Used for general (non-shielding) transfers, which may produce transparent
    /// change; coinbase funds must instead be shielded via
    /// [`propose_shielding_coinbase`](crate::data_api::wallet::propose_shielding_coinbase).
    /// Outputs whose transaction index is unknown are treated as non-coinbase
    /// and are included.
    NonCoinbaseOnly,
}

/// A trait representing the capability to query a data store for unspent transaction outputs
/// belonging to a account.
#[cfg_attr(feature = "test-dependencies", delegatable_trait)]
pub trait InputSource {
    /// The type of errors produced by a wallet backend.
    type Error: Debug;

    /// Backend-specific account identifier.
    ///
    /// An account identifier corresponds to at most a single unified spending key's worth of spend
    /// authority, such that both received notes and change spendable by that spending authority
    /// will be interpreted as belonging to that account. This might be a database identifier type
    /// or a UUID.
    type AccountId: Copy + Debug + Eq + Hash;

    /// Backend-specific note identifier.
    ///
    /// For example, this might be a database identifier type or a UUID.
    type NoteRef: Copy + Debug + Eq + Ord;

    /// Fetches a spendable note by indexing into a transaction's shielded outputs for the
    /// specified shielded protocol.
    ///
    /// Returns `Ok(None)` if the note is not known to belong to the wallet or if the note
    /// is not spendable as of the given height. Locked outputs are selected according to
    /// `lock_filter` (see [`LockFilter`]; a [`LockFilter::Policy`] carrying the default
    /// [`LockedInputPolicy::Exclude`] selects none).
    ///
    /// [`LockedInputPolicy::Exclude`]: crate::data_api::wallet::input_selection::LockedInputPolicy::Exclude
    fn get_spendable_note(
        &self,
        txid: &TxId,
        protocol: ShieldedPool,
        index: u32,
        target_height: TargetHeight,
        lock_filter: LockFilter<'_>,
    ) -> Result<Option<ReceivedNote<Self::NoteRef, Note>>, Self::Error>;

    /// Returns whether an anchor is COMPUTABLE at `height` for spends from the given pool: whether
    /// this data source can produce the note commitment tree root, and witnesses to it, as of the
    /// end of that block.
    ///
    /// A height inside the wallet's scanned range need not qualify: tree states are only
    /// materialized at the heights the wallet chose to retain, and a wallet that scanned past
    /// NU6.3 activation before boundary checkpointing was repaired is permanently missing the
    /// anchor-retention boundaries whose blocks carried no shielded outputs. Such a hole cannot be
    /// backfilled from local state, so a caller deciding whether to anchor at a retained boundary
    /// should consult this before committing to it, and fall back rather than propose a
    /// transaction that cannot be built.
    fn anchor_computable(
        &self,
        protocol: ShieldedPool,
        height: BlockHeight,
    ) -> Result<bool, Self::Error>;

    /// Returns a list of spendable notes sufficient to cover the specified target value, if
    /// possible. Only spendable notes corresponding to the specified shielded protocol will
    /// be included. Locked outputs are selected according to `lock_filter` (see [`LockFilter`];
    /// a [`LockFilter::Policy`] carrying the default `Exclude` selects none).
    #[allow(clippy::too_many_arguments)]
    fn select_spendable_notes(
        &self,
        account: Self::AccountId,
        target_value: TargetValue,
        sources: &[ShieldedPool],
        target_height: TargetHeight,
        confirmations_policy: ConfirmationsPolicy,
        exclude: &[Self::NoteRef],
        lock_filter: LockFilter<'_>,
    ) -> Result<ReceivedNotes<Self::NoteRef>, Self::Error>;

    /// Returns notes for consolidation-aware selection from `source`.
    ///
    /// The `funding` part of the result contains notes selected toward `value`. The `additional`
    /// part contains at most `max_additional_notes` disjoint notes that may be added
    /// opportunistically. The input selector validates that the funding covers the target and
    /// that adding any optional notes stays within its bounded consolidation envelope while
    /// preserving the transaction's fee and observable shape.
    ///
    /// Implementations backed by a queryable store should minimize the funding-note count within
    /// lock-tier preference, and return the smallest eligible notes from the funding tier as
    /// additional candidates. The default implementation preserves the data source's ordinary
    /// funding behavior and returns no additional candidates.
    #[allow(clippy::too_many_arguments)]
    fn select_spendable_notes_for_consolidation(
        &self,
        account: Self::AccountId,
        value: Zatoshis,
        source: ShieldedPool,
        target_height: TargetHeight,
        confirmations_policy: ConfirmationsPolicy,
        exclude: &[Self::NoteRef],
        lock_filter: LockFilter<'_>,
        _max_additional_notes: usize,
    ) -> Result<ConsolidationNotes<Self::NoteRef>, Self::Error> {
        self.select_spendable_notes(
            account,
            TargetValue::AtLeast(value),
            &[source],
            target_height,
            confirmations_policy,
            exclude,
            lock_filter,
        )
        .map(|funding| ConsolidationNotes::from_parts(funding, ReceivedNotes::empty()))
    }

    /// Returns the OLDEST single spendable note whose value alone is at least `value`, drawn
    /// from the first pool in `sources` (in the given preference order) that holds one. The
    /// returned collection contains at most one note; it is empty when no single eligible note
    /// covers the value.
    ///
    /// This is the selection primitive behind
    /// [`NoteSelection::PreferSingle`](crate::data_api::wallet::input_selection::NoteSelection):
    /// a ZIP 318 migration transfer spends exactly one note, so a canonical pool crossing must
    /// be funded from one.
    ///
    /// The default implementation is BEST-EFFORT: it reports a note only when
    /// [`Self::select_spendable_notes`] happens to surface one that covers the value on its
    /// own. An implementation backed by a queryable store should override it with a direct
    /// query, so that a covering note is found whenever one exists.
    #[allow(clippy::too_many_arguments)]
    fn select_single_spendable_note(
        &self,
        account: Self::AccountId,
        value: Zatoshis,
        sources: &[ShieldedPool],
        target_height: TargetHeight,
        confirmations_policy: ConfirmationsPolicy,
        exclude: &[Self::NoteRef],
        lock_filter: LockFilter<'_>,
    ) -> Result<ReceivedNotes<Self::NoteRef>, Self::Error> {
        self.select_spendable_notes(
            account,
            TargetValue::AtLeast(value),
            sources,
            target_height,
            confirmations_policy,
            exclude,
            lock_filter,
        )
        .map(|notes| notes.into_single_covering(value, sources))
    }

    /// Returns the list of notes belonging to the wallet that are unspent as of the specified
    /// target height. Locked outputs are selected according to `lock_filter` (see [`LockFilter`];
    /// a [`LockFilter::Policy`] carrying the default `Exclude` selects none).
    fn select_unspent_notes(
        &self,
        account: Self::AccountId,
        sources: &[ShieldedPool],
        target_height: TargetHeight,
        exclude: &[Self::NoteRef],
        lock_filter: LockFilter<'_>,
    ) -> Result<ReceivedNotes<Self::NoteRef>, Self::Error>;

    /// Returns metadata describing the structure of the wallet for the specified account.
    ///
    /// The returned metadata value must exclude:
    /// - notes that are not considered spendable as of the given `target_height`
    /// - unspent notes excluded by the provided selector;
    /// - unspent notes identified in the given `exclude` list.
    /// - locked notes not admitted by `lock_filter` (see [`LockFilter`]; a [`LockFilter::Policy`]
    ///   carrying the default `Exclude` admits none).
    ///
    /// Implementations of this method may limit the complexity of supported queries. Such
    /// limitations should be clearly documented for the implementing type.
    fn get_account_metadata(
        &self,
        account: Self::AccountId,
        selector: &NoteFilter,
        target_height: TargetHeight,
        exclude: &[Self::NoteRef],
        lock_filter: LockFilter<'_>,
    ) -> Result<AccountMeta, Self::Error>;

    /// Fetches the transparent output corresponding to the provided `outpoint` if it is considered
    /// spendable as of the provided `target_height`.
    ///
    /// Returns `Ok(None)` if the UTXO is not known to belong to the wallet or would not be
    /// spendable in a transaction mined in the block at the target height.
    #[cfg(feature = "transparent-inputs")]
    fn get_unspent_transparent_output(
        &self,
        _outpoint: &OutPoint,
        _target_height: TargetHeight,
    ) -> Result<Option<WalletTransparentOutput<Self::AccountId>>, Self::Error> {
        unimplemented!(
            "InputSource::get_spendable_transparent_output must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns the list of unspent transparent outputs received by this wallet at `address`
    /// such that, at height `target_height`:
    /// * the transaction that produced the output had or will have at least the required number of
    ///   confirmations according to the provided [`ConfirmationsPolicy`]; and
    /// * the output can potentially be spent in a transaction mined in a block at the given
    ///   `target_height` (also taking into consideration the coinbase maturity rule).
    ///
    /// The `output_filter` parameter controls which transparent outputs are eligible. When set
    /// to [`CoinbaseFilter::CoinbaseOnly`], only outputs from coinbase transactions
    /// should be returned.
    ///
    /// Any output that is potentially spent by an unmined transaction in the mempool should be
    /// excluded unless the spending transaction will be expired at `target_height`.
    /// Locked outputs are selected according to `lock_filter` (see [`LockFilter`]; a
    /// [`LockFilter::Policy`] carrying the default `Exclude` selects none).
    #[cfg(feature = "transparent-inputs")]
    fn get_spendable_transparent_outputs(
        &self,
        _address: &TransparentAddress,
        _target_height: TargetHeight,
        _confirmations_policy: ConfirmationsPolicy,
        _output_filter: CoinbaseFilter,
        _lock_filter: LockFilter<'_>,
    ) -> Result<Vec<WalletTransparentOutput<Self::AccountId>>, Self::Error> {
        unimplemented!(
            "InputSource::get_spendable_transparent_outputs must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns the list of spendable transparent outputs received by this wallet at any of the
    /// given `addresses`, subject to the same spendability conditions as
    /// [`InputSource::get_spendable_transparent_outputs`].
    ///
    /// This is the batched equivalent of calling
    /// [`InputSource::get_spendable_transparent_outputs`] once per address. It exists so that data
    /// stores can satisfy a multi-address request with a single query rather than one query per
    /// address, which is prohibitively expensive for wallets that hold large numbers of transparent
    /// addresses (as occurs when shielding). The default implementation simply iterates over
    /// `addresses`; data stores should override it with a batched query where possible.
    ///
    /// Each returned output identifies its receiving address via
    /// [`WalletTransparentOutput::recipient_address`].
    #[cfg(feature = "transparent-inputs")]
    fn get_spendable_transparent_outputs_for_addresses(
        &self,
        addresses: &[TransparentAddress],
        target_height: TargetHeight,
        confirmations_policy: ConfirmationsPolicy,
        output_filter: CoinbaseFilter,
        lock_filter: LockFilter<'_>,
    ) -> Result<Vec<WalletTransparentOutput<Self::AccountId>>, Self::Error> {
        let mut outputs = Vec::new();
        for address in addresses {
            outputs.extend(self.get_spendable_transparent_outputs(
                address,
                target_height,
                confirmations_policy,
                output_filter,
                lock_filter,
            )?);
        }
        Ok(outputs)
    }

    /// Returns the spendable transparent outputs received by `account` whose total post-fee
    /// value (sum of values minus the cumulative marginal fee cost of the gathered inputs
    /// themselves, per `fee_rule`) is at least `target_value`, or `max_inputs` outputs
    /// (whichever is reached first).
    ///
    /// The gather is intended to scale to wallets with large numbers of transparent addresses and
    /// UTXOs: it returns a value-bounded subset rather than every spendable output, so the
    /// selector does not need to materialize the wallet's full UTXO set. Data stores should
    /// implement this with a single query that orders eligible UTXOs by descending value and
    /// accumulates them, recomputing the cumulative fee via `fee_rule` at each step, stopping
    /// once the post-fee cumulative value meets the bound. This produces a tighter result than a
    /// static value bound, without requiring a separate round trip to correct an under-estimated
    /// headroom.
    ///
    /// `max_inputs` bounds the number of transparent inputs a single transaction may consume,
    /// independent of `target_value`: even a small requested value could otherwise require an
    /// unbounded number of inputs for a wallet holding a very large number of small (e.g. dust)
    /// UTXOs. When the cap is reached before the value target, the returned set's post-fee value
    /// may be less than `target_value`; the caller's input-selection loop is expected to surface
    /// this as an `InsufficientFunds` error, the same as for any other value shortfall.
    ///
    /// `fee_rule` is fixed to [`StandardFeeRule`] (rather than being generic over the caller's
    /// actual [`ChangeStrategy`]) so that implementations of this method do not need to be
    /// generic over an arbitrary fee rule type. This is a heuristic bound only: the transaction's
    /// real fee is still computed by the caller's actual change strategy, and if this gather's
    /// estimate turns out to be insufficient, the caller's input-selection loop will surface an
    /// `InsufficientFunds` error and can re-invoke this method with a corrected `target_value`.
    ///
    /// For `TargetValue::AllFunds`, no value bound is applied and the gather returns every
    /// eligible output up to `max_inputs`.
    ///
    /// When `address_allow_list` is `Some`, only outputs received at one of the listed
    /// transparent addresses are eligible; when `None`, outputs received at any of the
    /// account's transparent addresses are eligible. The restriction must be applied
    /// *within* the gather (not to its results), so that outputs excluded by the allow list
    /// do not consume the value bound.
    ///
    /// This is the value-bounded counterpart to [`InputSource::get_spendable_transparent_outputs`]
    /// and [`InputSource::get_spendable_transparent_outputs_for_addresses`], intended for use by
    /// general (non-shielding) input selection in `propose_transaction`.
    ///
    /// [`ChangeStrategy`]: crate::fees::ChangeStrategy
    #[cfg(feature = "transparent-inputs")]
    #[allow(clippy::too_many_arguments)]
    fn select_spendable_transparent_outputs(
        &self,
        account: Self::AccountId,
        target_height: TargetHeight,
        confirmations_policy: ConfirmationsPolicy,
        output_filter: CoinbaseFilter,
        address_allow_list: Option<&[TransparentAddress]>,
        target_value: TargetValue,
        max_inputs: usize,
        fee_rule: &StandardFeeRule,
        lock_filter: LockFilter<'_>,
    ) -> Result<Vec<WalletTransparentOutput<Self::AccountId>>, Self::Error> {
        let _ = (
            account,
            target_height,
            confirmations_policy,
            output_filter,
            address_allow_list,
            target_value,
            max_inputs,
            fee_rule,
            lock_filter,
        );
        unimplemented!(
            "InputSource::select_spendable_transparent_outputs must be overridden for \
             wallets to use the value-bounded transparent input gather in propose_transaction"
        )
    }
}

/// Read-only operations required for light wallet functions.
///
/// This trait defines the read-only portion of the storage interface atop which
/// higher-level wallet operations are implemented. It serves to allow wallet functions to
/// be abstracted away from any particular data storage substrate.
#[cfg_attr(feature = "test-dependencies", delegatable_trait)]
pub trait WalletRead {
    /// The type of errors that may be generated when querying a wallet data store.
    type Error: Debug;

    /// The type of the account identifier.
    ///
    /// An account identifier corresponds to at most a single unified spending key's worth of spend
    /// authority, such that both received notes and change spendable by that spending authority
    /// will be interpreted as belonging to that account.
    type AccountId: Copy + Debug + Eq + Hash;

    /// The concrete account type used by this wallet backend.
    type Account: Account<AccountId = Self::AccountId>;

    /// Returns a vector with the IDs of all accounts known to this wallet.
    fn get_account_ids(&self) -> Result<Vec<Self::AccountId>, Self::Error>;

    /// Returns the account corresponding to the given ID, if any.
    fn get_account(
        &self,
        account_id: Self::AccountId,
    ) -> Result<Option<Self::Account>, Self::Error>;

    /// Returns the account corresponding to a given [`SeedFingerprint`] and
    /// [`zip32::AccountId`], if any.
    fn get_derived_account(
        &self,
        derivation: &Zip32Derivation,
    ) -> Result<Option<Self::Account>, Self::Error>;

    /// Verifies that the given seed corresponds to the viewing key for the specified account.
    ///
    /// Returns:
    /// - `Ok(true)` if the viewing key for the specified account can be derived from the
    ///   provided seed.
    /// - `Ok(false)` if the derived viewing key does not match, or the specified account is not
    ///   present in the database.
    /// - `Err(_)` if a Unified Spending Key cannot be derived from the seed for the
    ///   specified account or the account has no known ZIP-32 derivation.
    fn validate_seed(
        &self,
        account_id: Self::AccountId,
        seed: &SecretVec<u8>,
    ) -> Result<bool, Self::Error>;

    /// Checks whether the given seed is relevant to any of the derived accounts (where
    /// [`Account::source`] is [`AccountSource::Derived`]) in the wallet.
    ///
    /// This API does not check whether the seed is relevant to any imported account,
    /// because that would require brute-forcing the ZIP 32 account index space.
    fn seed_relevance_to_derived_accounts(
        &self,
        seed: &SecretVec<u8>,
    ) -> Result<SeedRelevance<Self::AccountId>, Self::Error>;

    /// Returns the account corresponding to a given [`UnifiedFullViewingKey`], if any.
    fn get_account_for_ufvk(
        &self,
        ufvk: &UnifiedFullViewingKey,
    ) -> Result<Option<Self::Account>, Self::Error>;

    /// Returns information about every address tracked for this account.
    fn list_addresses(&self, account: Self::AccountId) -> Result<Vec<AddressInfo>, Self::Error>;

    /// Returns the wallet account that controls the given address, if any.
    ///
    /// Backends that can answer this query from an indexed lookup should implement it
    /// directly. Backends without such an index can delegate to
    /// [`defaults::find_account_for_address`], which implements the semantics described below
    /// using [`UnifiedIncomingViewingKey::decrypt_diversifiers`] and a linear scan over
    /// [`Self::get_account_ids`] / [`Self::list_addresses`].
    ///
    /// # Unified Addresses
    ///
    /// For a Unified Address each account's [`UnifiedIncomingViewingKey`] is asked, via
    /// [`UnifiedIncomingViewingKey::decrypt_diversifiers`], whether it could have derived any
    /// shielded receiver of the UA. An account matches if at least one shielded receiver is
    /// attributable to it — including receivers that have never been previously exposed by
    /// the wallet. If the shielded receivers of the UA are attributable to more than one
    /// account, this is treated as an inconsistent ("frankenstein") address and
    /// [`FindAccountForAddressError::UnifiedAddressConflict`] is returned rather than
    /// arbitrarily selecting one account.
    ///
    /// Backends are permitted to additionally resolve UAs by exact match against their
    /// tracked-address index before (or instead of) running the UIVK-algebra step, provided
    /// the exact-match result is consistent with at least one account identified by the
    /// algebraic step.
    ///
    /// # Non-Unified Addresses
    ///
    /// Backends should resolve bare shielded addresses (Sapling) via the same UIVK-algebraic
    /// path where feasible, so that an address derivable from an account's UIVK is resolved
    /// whether or not it has been previously exposed. Backends that do not can treat a bare
    /// shielded address as an exact-match lookup over their tracked-address index.
    ///
    /// Transparent and TEX addresses are resolved by exact match against tracked addresses
    /// only, since a diversifier index cannot be recovered from a transparent receiver alone.
    ///
    /// # Returns
    ///
    /// - `Ok(Some(account_id))` if the address is controlled by a single account known to
    ///   this wallet.
    /// - `Ok(None)` if no receiver of the address is recognized as belonging to any account.
    /// - `Err(FindAccountForAddressError::Backend(_))` if the lookup fails due to a
    ///   backend error.
    /// - `Err(FindAccountForAddressError::UnifiedAddressConflict)` if the provided address
    ///   is a Unified Address whose receiver components map to different accounts.
    ///
    /// [`UnifiedIncomingViewingKey`]: zcash_keys::keys::UnifiedIncomingViewingKey
    /// [`UnifiedIncomingViewingKey::decrypt_diversifiers`]: zcash_keys::keys::UnifiedIncomingViewingKey::decrypt_diversifiers
    /// [`FindAccountForAddressError::UnifiedAddressConflict`]: error::FindAccountForAddressError::UnifiedAddressConflict
    fn find_account_for_address<P: consensus::Parameters>(
        &self,
        params: &P,
        address: &zcash_keys::address::Address,
    ) -> Result<Option<Self::AccountId>, error::FindAccountForAddressError<Self::Error>>;

    /// Returns the most recently generated unified address for the specified account that conforms
    /// to the specified address filter, if the account identifier specified refers to a valid
    /// account for this wallet.
    ///
    /// This will return `Ok(None)` if no previously generated address conforms to the specified
    /// request.
    fn get_last_generated_address_matching(
        &self,
        account: Self::AccountId,
        address_filter: UnifiedAddressRequest,
    ) -> Result<Option<UnifiedAddress>, Self::Error>;

    /// Returns the birthday height for the given account, or an error if the account is not known
    /// to the wallet.
    fn get_account_birthday(&self, account: Self::AccountId) -> Result<BlockHeight, Self::Error>;

    /// Returns the birthday height for the wallet.
    ///
    /// This returns the earliest birthday height among accounts maintained by this wallet,
    /// or `Ok(None)` if the wallet has no initialized accounts.
    fn get_wallet_birthday(&self) -> Result<Option<BlockHeight>, Self::Error>;

    /// Returns the height at which the wallet as a whole will have exited recovery mode.
    ///
    /// This returns the latest `recover_until` height among accounts maintained by this
    /// wallet (see [`AccountBirthday::recover_until`]), or `Ok(None)` if no account has a
    /// recovery horizon set (for example, in a wallet whose accounts were all created at
    /// the chain tip rather than restored from backup). Heights below the returned value,
    /// exclusive, are in scope for wallet recovery for at least one account.
    fn get_wallet_recover_until(&self) -> Result<Option<BlockHeight>, Self::Error>;

    /// Returns a [`WalletSummary`] that represents the sync status and the wallet balances as of
    /// the chain tip given the specified confirmation policy for all accounts known to the wallet,
    /// or `Ok(None)` if the wallet has no summary data available.
    fn get_wallet_summary(
        &self,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Result<Option<WalletSummary<Self::AccountId>>, Self::Error>;

    /// Returns the height of the chain as known to the wallet as of the most recent call to
    /// [`WalletWrite::update_chain_tip`].
    ///
    /// This will return `Ok(None)` if the height of the current consensus chain tip is unknown.
    fn chain_height(&self) -> Result<Option<BlockHeight>, Self::Error>;

    /// Returns the interval on which this wallet retains note commitment tree checkpoints as
    /// durable anchors.
    ///
    /// A ZIP 318 pool migration anchors each of its pool-crossing transfers to a boundary of this
    /// interval, and proves the transfer long after that boundary has passed; the proof can only be
    /// constructed if the wallet kept the boundary's checkpoint. Reading the grid back off the
    /// wallet that maintains it — rather than configuring the migration separately — is what
    /// guarantees the two agree.
    ///
    /// The default implementation returns [`AnchorRetentionInterval::ZIP_318`], which matches the
    /// retention a backend performs if it does not configure the interval. A backend that DOES make
    /// retention configurable must override this to report the interval it actually retains, or
    /// migrations over it will draw anchors it has pruned.
    ///
    /// [`AnchorRetentionInterval::ZIP_318`]: anchor_retention::AnchorRetentionInterval::ZIP_318
    fn anchor_retention_interval(&self) -> anchor_retention::AnchorRetentionInterval {
        anchor_retention::AnchorRetentionInterval::ZIP_318
    }

    /// Returns the ZIP 318 pool-migration parameters in force for this wallet: the specified
    /// values, with the anchor bucket grid taken from [`Self::anchor_retention_interval`].
    ///
    /// Every decision that depends on the grid must consult this rather than the network defaults,
    /// so that a wallet retaining a non-standard interval is treated consistently: bucketing an
    /// anchor and judging the resulting transaction a canonical crossing are the same question
    /// asked twice, and they must be asked of the same grid. Overriding
    /// [`Self::anchor_retention_interval`] is sufficient; this composes it.
    fn pool_migration_params(&self) -> anchor_retention::PoolMigrationParams {
        anchor_retention::PoolMigrationParams::new(self.anchor_retention_interval())
    }

    /// Returns the block hash for the block at the given height, if the
    /// associated block data is available. Returns `Ok(None)` if the hash
    /// is not found in the database.
    fn get_block_hash(&self, block_height: BlockHeight) -> Result<Option<BlockHash>, Self::Error>;

    /// Returns the available block metadata for the block at the specified height, if any.
    fn block_metadata(&self, height: BlockHeight) -> Result<Option<BlockMetadata>, Self::Error>;

    /// Returns the metadata for the block at the height to which the wallet has been fully
    /// scanned.
    ///
    /// This is the height for which the wallet has fully trial-decrypted this and all preceding
    /// blocks above the wallet's birthday height. Along with this height, this method returns
    /// metadata describing the state of the wallet's note commitment trees as of the end of that
    /// block.
    fn block_fully_scanned(&self) -> Result<Option<BlockMetadata>, Self::Error>;

    /// Returns the block height and hash for the block at the maximum scanned block height.
    ///
    /// This will return `Ok(None)` if no blocks have been scanned.
    fn get_max_height_hash(&self) -> Result<Option<(BlockHeight, BlockHash)>, Self::Error>;

    /// Returns block metadata for the maximum height that the wallet has scanned.
    ///
    /// If the wallet is fully synced, this will be equivalent to `block_fully_scanned`;
    /// otherwise the maximal scanned height is likely to be greater than the fully scanned height
    /// due to the fact that out-of-order scanning can leave gaps.
    fn block_max_scanned(&self) -> Result<Option<BlockMetadata>, Self::Error>;

    /// Returns a vector of suggested scan ranges based upon the current wallet state.
    ///
    /// This method should only be used in cases where the [`CompactBlock`] data that will be made
    /// available to `scan_cached_blocks` for the requested block ranges includes note commitment
    /// tree size information for each block; or else the scan is likely to fail if notes belonging
    /// to the wallet are detected.
    ///
    /// The returned range(s) may include block heights beyond the current chain tip. Ranges are
    /// returned in order of descending priority, and higher-priority ranges should always be
    /// scanned before lower-priority ranges; in particular, ranges with [`ScanPriority::Verify`]
    /// priority must always be scanned first in order to avoid blockchain continuity errors in the
    /// case of a reorg.
    ///
    /// [`CompactBlock`]: crate::proto::compact_formats::CompactBlock
    /// [`ScanPriority::Verify`]: crate::data_api::scanning::ScanPriority
    fn suggest_scan_ranges(&self) -> Result<Vec<ScanRange>, Self::Error>;

    /// Returns the default target height (for the block in which a new
    /// transaction would be mined) and anchor height (to use for a new
    /// transaction), given the range of block heights that the backend
    /// knows about.
    ///
    /// This will return `Ok(None)` if no block data is present in the database.
    fn get_target_and_anchor_heights(
        &self,
        min_confirmations: NonZeroU32,
    ) -> Result<Option<(TargetHeight, BlockHeight)>, Self::Error>;

    /// Returns the block height in which the specified transaction was mined, or `Ok(None)` if the
    /// transaction is not known to the wallet or not in the main chain.
    fn get_tx_height(&self, txid: TxId) -> Result<Option<BlockHeight>, Self::Error>;

    /// Returns all unified full viewing keys known to this wallet.
    fn get_unified_full_viewing_keys(
        &self,
    ) -> Result<HashMap<Self::AccountId, UnifiedFullViewingKey>, Self::Error>;

    /// Returns the memo for a note.
    ///
    /// Returns `Ok(None)` if the note is known to the wallet but memo data has not yet been
    /// populated for that note, or if the note identifier does not correspond to a note
    /// that is known to the wallet.
    fn get_memo(&self, note_id: NoteId) -> Result<Option<Memo>, Self::Error>;

    /// Returns the transaction with the given txid, if known to the wallet.
    ///
    /// Returns `None` if the txid is not known to the wallet or if the raw transaction data is not
    /// available.
    fn get_transaction(&self, txid: TxId) -> Result<Option<Transaction>, Self::Error>;

    /// Returns the nullifiers for Sapling notes that the wallet is tracking, along with their
    /// associated account IDs, that are either unspent or have not yet been confirmed as spent (in
    /// that a spending transaction known to the wallet has not yet been included in a block).
    fn get_sapling_nullifiers(
        &self,
        query: NullifierQuery,
    ) -> Result<Vec<(Self::AccountId, sapling::Nullifier)>, Self::Error>;

    /// Returns the nullifiers for Orchard notes that the wallet is tracking, along with their
    /// associated account IDs, that are either unspent or have not yet been confirmed as spent (in
    /// that a spending transaction known to the wallet has not yet been included in a block).
    #[cfg(feature = "orchard")]
    fn get_orchard_nullifiers(
        &self,
        _query: NullifierQuery,
    ) -> Result<Vec<(Self::AccountId, orchard::note::Nullifier)>, Self::Error> {
        unimplemented!(
            "WalletRead::get_orchard_nullifiers must be overridden for wallets to use the `orchard` feature"
        )
    }

    /// Returns the nullifiers for Ironwood notes that the wallet is tracking, along with their
    /// associated account IDs, that are either unspent or have not yet been confirmed as spent.
    /// Ironwood nullifiers are Orchard-shaped but are tracked as a separate pool.
    ///
    /// This is a required method (like [`WalletRead::get_sapling_nullifiers`]) rather than
    /// defaulting to a panic: it is called on the scan path, so a backend that does not override it
    /// would abort the process on the first scan. Requiring it surfaces the omission at compile
    /// time instead.
    #[cfg(feature = "orchard")]
    fn get_ironwood_nullifiers(
        &self,
        query: NullifierQuery,
    ) -> Result<Vec<(Self::AccountId, orchard::note::Nullifier)>, Self::Error>;

    /// Returns the set of non-ephemeral transparent receivers associated with the given
    /// account controlled by this wallet.
    ///
    /// The set contains all non-ephemeral transparent receivers that are known to have
    /// been derived under this account. Wallets should scan the chain for UTXOs sent to
    /// these receivers.
    ///
    /// # Parameters
    /// - `account`: The identifier for the account from which transparent receivers should be
    ///   returned.
    /// - `include_change`: A flag indicating whether transparent change addresses should be
    ///   returned.
    /// - `include_standalone`: A flag indicating whether imported standalone addresses associated
    ///   with the account should be returned. The value of this flag is ignored unless the
    ///   `transparent-key-import` feature is enabled.
    ///
    /// Use [`Self::get_ephemeral_transparent_receivers`] to obtain the ephemeral transparent
    /// receivers.
    #[cfg(feature = "transparent-inputs")]
    fn get_transparent_receivers(
        &self,
        _account: Self::AccountId,
        _include_change: bool,
        _include_standalone: bool,
    ) -> Result<HashMap<TransparentAddress, TransparentAddressMetadata>, Self::Error> {
        unimplemented!(
            "WalletRead::get_transparent_receivers must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns the set of previously-exposed ephemeral transparent receivers generated by the given
    /// account controlled by this wallet.
    ///
    /// The set contains all ephemeral transparent receivers that are known to have been derived
    /// under this account within `exposure_depth` blocks of the chain tip. Wallets may scan the
    /// chain for UTXOs sent to these receivers, but should do so in a fashion that does not reveal
    /// that they are controlled by the same wallet. If the [`next_check_time`] field is set for a
    /// returned [`TransparentAddressMetadata`], the wallet application should defer any query to
    /// any public light wallet server for this address until [`next_check_time`] has passed; when
    /// using a light wallet server that is trusted for privacy, this delay may be omitted.
    ///
    /// # Parameters
    /// - `account`: The identifier for the account from which transparent receivers should be
    ///   returned.
    /// - `exposure_depth`: Implementations of this method should return only addresses exposed at
    ///   heights greater than `chain_tip_height - exposure_depth`.
    /// - `exclude_used`: When set to `true`, do not return addresses that are known to have
    ///   already received funds in a transaction.
    ///
    /// [`next_check_time`]: TransparentAddressMetadata::next_check_time
    #[cfg(feature = "transparent-inputs")]
    fn get_ephemeral_transparent_receivers(
        &self,
        _account: Self::AccountId,
        _exposure_depth: u32,
        _exclude_used: bool,
    ) -> Result<HashMap<TransparentAddress, TransparentAddressMetadata>, Self::Error> {
        unimplemented!(
            "WalletRead::get_ephemeral_transparent_receivers must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns a mapping from each transparent receiver associated with the specified account
    /// to the key scope for that address and the balance of funds given the specified target
    /// height and confirmations policy.
    #[cfg(feature = "transparent-inputs")]
    fn get_transparent_balances(
        &self,
        _account: Self::AccountId,
        _target_height: TargetHeight,
        _confirmations_policy: ConfirmationsPolicy,
    ) -> Result<TransparentBalances, Self::Error> {
        unimplemented!(
            "WalletRead::get_transparent_balances must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns the metadata associated with a given transparent receiver in an account
    /// controlled by this wallet, if available.
    ///
    /// This is equivalent to (but may be implemented more efficiently than):
    /// ```compile_fail
    /// Ok(
    ///     if let Some(result) = self.get_transparent_receivers(account, true)?.get(address) {
    ///         Some(result.clone())
    ///     } else {
    ///         self.get_ephemeral_transparent_receivers(account, u32::MAX, false)?
    ///             .get(address)
    ///             .cloned()
    ///     },
    /// )
    /// ```
    ///
    /// Returns `Ok(None)` if the address is not recognized, or we do not have metadata for it.
    /// Returns `Ok(Some(metadata))` if we have the metadata.
    #[cfg(feature = "transparent-inputs")]
    fn get_transparent_address_metadata(
        &self,
        _account: Self::AccountId,
        _address: &TransparentAddress,
    ) -> Result<Option<TransparentAddressMetadata>, Self::Error> {
        unimplemented!(
            "WalletRead::get_transparent_address_metadata must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns the maximum block height at which a transparent output belonging to the wallet has
    /// been observed.
    ///
    /// We must start looking for UTXOs for addresses within the current gap limit as of the block
    /// height at which they might have first been revealed. This would have occurred when the gap
    /// advanced as a consequence of a transaction being mined. The address at the start of the current
    /// gap was potentially first revealed after the address at index `gap_start - (gap_limit + 1)`
    /// received an output in a mined transaction; therefore, we take that height to be where we
    /// should start searching for UTXOs.
    #[cfg(feature = "transparent-inputs")]
    fn utxo_query_height(&self, _account: Self::AccountId) -> Result<BlockHeight, Self::Error> {
        unimplemented!(
            "WalletRead::utxo_query_height must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns a vector of [`TransactionDataRequest`] values that describe information needed by
    /// the wallet to complete its view of transaction history.
    ///
    /// Requests for the same transaction data may be returned repeatedly by successive data
    /// requests. The caller of this method should consider the latest set of requests returned
    /// by this method to be authoritative and to subsume that returned by previous calls.
    ///
    /// Callers should poll this method on a regular interval, not as part of ordinary chain
    /// scanning, which already produces requests for transaction data enhancement. Note that
    /// responding to a set of transaction data requests may result in the creation of new
    /// transaction data requests, such as when it is necessary to fill in purely-transparent
    /// transaction history by walking the chain backwards via transparent inputs.
    fn transaction_data_requests(&self) -> Result<Vec<TransactionDataRequest>, Self::Error>;

    /// Returns a vector of [`ReceivedTransactionOutput`] values describing the outputs of the
    /// specified transaction that were received by the wallet. The number of confirmations until
    /// each received output will be considered spendable is determined based upon the specified
    /// target height and confirmations policy.
    fn get_received_outputs(
        &self,
        txid: TxId,
        target_height: TargetHeight,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Result<Vec<ReceivedTransactionOutput>, Self::Error>;
}

/// Read-only operations required for testing light wallet functions.
///
/// These methods expose internal details or unstable interfaces, primarily to enable use
/// of the [`testing`] framework. They should not be used in production software.
#[cfg(any(test, feature = "test-dependencies"))]
#[cfg_attr(feature = "test-dependencies", delegatable_trait)]
pub trait WalletTest: InputSource + WalletRead {
    /// Returns a vector of transaction summaries.
    ///
    /// Currently test-only, as production use could return a very large number of results; either
    /// pagination or a streaming design will be necessary to stabilize this feature for production
    /// use.
    fn get_tx_history(
        &self,
    ) -> Result<
        Vec<testing::TransactionSummary<<Self as WalletRead>::AccountId>>,
        <Self as WalletRead>::Error,
    >;

    /// Returns the note IDs for shielded notes sent by the wallet in a particular
    /// transaction.
    fn get_sent_note_ids(
        &self,
        _txid: &TxId,
        _protocol: ShieldedPool,
    ) -> Result<Vec<NoteId>, <Self as WalletRead>::Error>;

    /// Returns the outputs for a transaction sent by the wallet.
    #[allow(clippy::type_complexity)]
    fn get_sent_outputs(
        &self,
        txid: &TxId,
    ) -> Result<Vec<OutputOfSentTx>, <Self as WalletRead>::Error>;

    #[allow(clippy::type_complexity)]
    fn get_checkpoint_history(
        &self,
        protocol: &ShieldedPool,
    ) -> Result<
        Vec<(BlockHeight, Option<incrementalmerkletree::Position>)>,
        <Self as WalletRead>::Error,
    >;

    /// Fetches the transparent output corresponding to the provided `outpoint`.
    /// Allows selecting unspendable outputs for testing purposes.
    ///
    /// # Parameters
    /// - `outpoint`: The identifier for the output to be retrieved.
    /// - `spendable_as_of`: The target height of a transaction under construction that will spend the
    ///   returned output. If this is `None`, no spendability checks are performed.
    ///
    /// Returns `Ok(None)` if the UTXO is not known to belong to the wallet or if `spendable_as_of`
    /// is set and the output is available to be spent by the wallet in a transaction that is
    /// intended to be mined at the target height.
    #[cfg(feature = "transparent-inputs")]
    fn get_transparent_output(
        &self,
        _outpoint: &OutPoint,
        _spendable_as_of: Option<TargetHeight>,
    ) -> Result<
        Option<WalletTransparentOutput<<Self as WalletRead>::AccountId>>,
        <Self as InputSource>::Error,
    > {
        unimplemented!(
            "WalletTest::get_transparent_output must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Returns all the notes that have been received by the wallet.
    fn get_notes(
        &self,
        protocol: ShieldedPool,
    ) -> Result<Vec<ReceivedNote<Self::NoteRef, Note>>, <Self as InputSource>::Error>;

    /// Returns a vector of ephemeral transparent addresses associated with the given
    /// account controlled by this wallet, along with their metadata. The result includes
    /// reserved addresses, and addresses for the backend's configured gap limit worth
    /// of additional indices (capped to the maximum index).
    ///
    /// If `index_range` is some `Range`, it limits the result to addresses with indices
    /// in that range. An `index_range` of `None` is defined to be equivalent to
    /// `0..(1u32 << 31)`.
    ///
    /// Wallets should scan the chain for UTXOs sent to these ephemeral transparent
    /// receivers, but do not need to do so regularly. Under expected usage, outputs
    /// would only be detected with these receivers in the following situations:
    ///
    /// - This wallet created a payment to a ZIP 320 (TEX) address, but the second
    ///   transaction (that spent the output sent to the ephemeral address) did not get
    ///   mined before it expired.
    ///   - In this case the output will already be known to the wallet (because it
    ///     stores the transactions that it creates).
    ///
    /// - Another wallet app using the same seed phrase created a payment to a ZIP 320
    ///   address, and this wallet queried for the ephemeral UTXOs after the first
    ///   transaction was mined but before the second transaction was mined.
    ///   - In this case, the output should not be considered unspent until the expiry
    ///     height of the transaction it was received in has passed. Wallets creating
    ///     payments to TEX addresses generally set the same expiry height for the first
    ///     and second transactions, meaning that this wallet does not need to observe
    ///     the second transaction to determine when it would have expired.
    ///
    /// - A TEX address recipient decided to return funds that the wallet had sent to
    ///   them.
    ///
    /// In all cases, the wallet should re-shield the unspent outputs, in a separate
    /// transaction per ephemeral address, before re-spending the funds.
    #[cfg(feature = "transparent-inputs")]
    fn get_known_ephemeral_addresses(
        &self,
        _account: <Self as WalletRead>::AccountId,
        _index_range: Option<Range<NonHardenedChildIndex>>,
    ) -> Result<Vec<(TransparentAddress, TransparentAddressMetadata)>, <Self as WalletRead>::Error>
    {
        unimplemented!(
            "WalletRead::get_known_ephemeral_addresses must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// If a given ephemeral address might have been reserved, i.e. would be included in
    /// the result of `get_known_ephemeral_addresses(account_id, None)` for any of the
    /// wallet's accounts, then return `Ok(Some(account_id))`. Otherwise return `Ok(None)`.
    ///
    /// This is equivalent to (but may be implemented more efficiently than):
    /// ```compile_fail
    /// for account_id in self.get_account_ids()? {
    ///     if self
    ///         .get_known_ephemeral_addresses(account_id, None)?
    ///         .into_iter()
    ///         .any(|(known_addr, _)| &known_addr == address)
    ///     {
    ///         return Ok(Some(account_id));
    ///     }
    /// }
    /// Ok(None)
    /// ```
    #[cfg(feature = "transparent-inputs")]
    fn find_account_for_ephemeral_address(
        &self,
        address: &TransparentAddress,
    ) -> Result<Option<<Self as WalletRead>::AccountId>, <Self as WalletRead>::Error> {
        for account_id in self.get_account_ids()? {
            if self
                .get_known_ephemeral_addresses(account_id, None)?
                .into_iter()
                .any(|(known_addr, _)| &known_addr == address)
            {
                return Ok(Some(account_id));
            }
        }
        Ok(None)
    }

    /// Performs final checks at the conclusion of each test.
    ///
    /// This method allows wallet backend developers to perform any necessary consistency
    /// checks or cleanup. By default it does nothing.
    fn finally(&self) {}
}

/// The output of a transaction sent by the wallet.
///
/// This type is opaque, and exists for use by tests defined in this crate.
#[cfg(any(test, feature = "test-dependencies"))]
#[allow(dead_code)]
#[derive(Clone, Debug)]
pub struct OutputOfSentTx {
    value: Zatoshis,
    external_recipient: Option<Address>,
    #[cfg(feature = "transparent-inputs")]
    ephemeral_address: Option<(Address, NonHardenedChildIndex)>,
}

#[cfg(any(test, feature = "test-dependencies"))]
impl OutputOfSentTx {
    /// Constructs an output from its test-relevant parts.
    ///
    /// If the output is to an ephemeral address, `ephemeral_address` should contain the
    /// address along with the `address_index` it was derived from under the BIP 32 path
    /// `m/44'/<coin_type>'/<account>'/2/<address_index>`.
    pub fn from_parts(
        value: Zatoshis,
        external_recipient: Option<Address>,
        #[cfg(feature = "transparent-inputs")] ephemeral_address: Option<(
            Address,
            NonHardenedChildIndex,
        )>,
    ) -> Self {
        Self {
            value,
            external_recipient,
            #[cfg(feature = "transparent-inputs")]
            ephemeral_address,
        }
    }

    /// Returns the value of the output.
    pub fn value(&self) -> Zatoshis {
        self.value
    }

    /// Returns the recipient of the sent output.
    pub fn external_recipient(&self) -> Option<&Address> {
        self.external_recipient.as_ref()
    }

    /// Returns the ephemeral address to which the output was sent, along with the non-hardened
    /// transparent child index at which that address was derived.
    #[cfg(feature = "transparent-inputs")]
    pub fn ephemeral_address(&self) -> Option<&(Address, NonHardenedChildIndex)> {
        self.ephemeral_address.as_ref()
    }
}

/// The relevance of a seed to a given wallet.
///
/// This is the return type for [`WalletRead::seed_relevance_to_derived_accounts`].
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum SeedRelevance<A: Copy> {
    /// The seed is relevant to at least one derived account within the wallet.
    Relevant { account_ids: NonEmpty<A> },
    /// The seed is not relevant to any of the derived accounts within the wallet.
    NotRelevant,
    /// The wallet contains no derived accounts.
    NoDerivedAccounts,
    /// The wallet contains no accounts.
    NoAccounts,
}

/// Metadata describing the sizes of the zcash note commitment trees as of a particular block.
#[derive(Debug, Clone, Copy)]
pub struct BlockMetadata {
    block_height: BlockHeight,
    block_hash: BlockHash,
    sapling_tree_size: Option<u32>,
    #[cfg(feature = "orchard")]
    orchard_tree_size: Option<u32>,
    #[cfg(feature = "orchard")]
    ironwood_tree_size: Option<u32>,
}

impl BlockMetadata {
    /// Constructs a new [`BlockMetadata`] value from its constituent parts.
    pub fn from_parts(
        block_height: BlockHeight,
        block_hash: BlockHash,
        sapling_tree_size: Option<u32>,
        #[cfg(feature = "orchard")] orchard_tree_size: Option<u32>,
        #[cfg(feature = "orchard")] ironwood_tree_size: Option<u32>,
    ) -> Self {
        Self {
            block_height,
            block_hash,
            sapling_tree_size,
            #[cfg(feature = "orchard")]
            orchard_tree_size,
            #[cfg(feature = "orchard")]
            ironwood_tree_size,
        }
    }

    /// Returns the block height.
    pub fn block_height(&self) -> BlockHeight {
        self.block_height
    }

    /// Returns the hash of the block
    pub fn block_hash(&self) -> BlockHash {
        self.block_hash
    }

    /// Returns the size of the Sapling note commitment tree for the final treestate of the block
    /// that this [`BlockMetadata`] describes, if available.
    pub fn sapling_tree_size(&self) -> Option<u32> {
        self.sapling_tree_size
    }

    /// Returns the size of the Orchard note commitment tree for the final treestate of the block
    /// that this [`BlockMetadata`] describes, if available.
    #[cfg(feature = "orchard")]
    pub fn orchard_tree_size(&self) -> Option<u32> {
        self.orchard_tree_size
    }

    /// Returns the size of the Ironwood note commitment tree for the final treestate of the block
    /// that this [`BlockMetadata`] describes, if available.
    #[cfg(feature = "orchard")]
    pub fn ironwood_tree_size(&self) -> Option<u32> {
        self.ironwood_tree_size
    }
}

/// The protocol-specific note commitment and nullifier data extracted from the per-transaction
/// shielded bundles in [`CompactBlock`], used by the wallet for note commitment tree maintenance
/// and spend detection.
///
/// [`CompactBlock`]: crate::proto::compact_formats::CompactBlock
pub struct ScannedBundles<NoteCommitment, NF> {
    final_tree_size: u32,
    commitments: Vec<(NoteCommitment, Retention<BlockHeight>)>,
    nullifier_map: Vec<(TxIndex, TxId, Vec<NF>)>,
}

impl<NoteCommitment, NF> ScannedBundles<NoteCommitment, NF> {
    pub(crate) fn new(
        final_tree_size: u32,
        commitments: Vec<(NoteCommitment, Retention<BlockHeight>)>,
        nullifier_map: Vec<(TxIndex, TxId, Vec<NF>)>,
    ) -> Self {
        Self {
            final_tree_size,
            nullifier_map,
            commitments,
        }
    }

    /// Returns the size of the note commitment tree as of the end of the scanned block.
    pub fn final_tree_size(&self) -> u32 {
        self.final_tree_size
    }

    /// Returns the vector of nullifiers for each transaction in the block.
    ///
    /// The returned tuple is keyed by both transaction ID and the index of the transaction within
    /// the block, so that either the txid or the combination of the block hash available from
    /// [`ScannedBlock::block_hash`] and returned transaction index may be used to uniquely
    /// identify the transaction, depending upon the needs of the caller.
    pub fn nullifier_map(&self) -> &[(TxIndex, TxId, Vec<NF>)] {
        &self.nullifier_map
    }

    /// Returns the ordered list of note commitments to be added to the note commitment
    /// tree.
    pub fn commitments(&self) -> &[(NoteCommitment, Retention<BlockHeight>)] {
        &self.commitments
    }
}

/// A struct used to return the vectors of note commitments for a [`ScannedBlock`]
/// as owned values.
pub struct ScannedBlockCommitments {
    /// The ordered vector of note commitments for Sapling outputs of the block.
    pub sapling: Vec<(sapling::Node, Retention<BlockHeight>)>,
    /// The ordered vector of note commitments for Orchard outputs of the block.
    /// Present only when the `orchard` feature is enabled.
    #[cfg(feature = "orchard")]
    pub orchard: Vec<(orchard::tree::MerkleHashOrchard, Retention<BlockHeight>)>,
    /// The ordered vector of note commitments for Ironwood outputs of the block.
    /// Present only when the `orchard` feature is enabled.
    #[cfg(feature = "orchard")]
    pub ironwood: Vec<(orchard::tree::MerkleHashOrchard, Retention<BlockHeight>)>,
}

/// The subset of information that is relevant to this wallet that has been
/// decrypted and extracted from a [`CompactBlock`].
///
/// [`CompactBlock`]: crate::proto::compact_formats::CompactBlock
pub struct ScannedBlock<AccountId> {
    block_height: BlockHeight,
    block_hash: BlockHash,
    block_time: u32,
    transactions: Vec<WalletTx<AccountId>>,
    sapling: ScannedBundles<sapling::Node, sapling::Nullifier>,
    #[cfg(feature = "orchard")]
    orchard: ScannedBundles<orchard::tree::MerkleHashOrchard, orchard::note::Nullifier>,
    #[cfg(feature = "orchard")]
    ironwood: ScannedBundles<orchard::tree::MerkleHashOrchard, orchard::note::Nullifier>,
}

impl<AccountId> ScannedBlock<AccountId> {
    /// Constructs a new `ScannedBlock`
    pub(crate) fn from_parts(
        block_height: BlockHeight,
        block_hash: BlockHash,
        block_time: u32,
        transactions: Vec<WalletTx<AccountId>>,
        sapling: ScannedBundles<sapling::Node, sapling::Nullifier>,
        #[cfg(feature = "orchard")] orchard: ScannedBundles<
            orchard::tree::MerkleHashOrchard,
            orchard::note::Nullifier,
        >,
        #[cfg(feature = "orchard")] ironwood: ScannedBundles<
            orchard::tree::MerkleHashOrchard,
            orchard::note::Nullifier,
        >,
    ) -> Self {
        Self {
            block_height,
            block_hash,
            block_time,
            transactions,
            sapling,
            #[cfg(feature = "orchard")]
            orchard,
            #[cfg(feature = "orchard")]
            ironwood,
        }
    }

    /// Returns the height of the block that was scanned.
    pub fn height(&self) -> BlockHeight {
        self.block_height
    }

    /// Returns the block hash of the block that was scanned.
    pub fn block_hash(&self) -> BlockHash {
        self.block_hash
    }

    /// Returns the block time of the block that was scanned, as a Unix timestamp in seconds.
    pub fn block_time(&self) -> u32 {
        self.block_time
    }

    /// Returns the list of transactions from this block that are relevant to the wallet.
    pub fn transactions(&self) -> &[WalletTx<AccountId>] {
        &self.transactions
    }

    /// Returns the Sapling note commitment tree and nullifier data for the block.
    pub fn sapling(&self) -> &ScannedBundles<sapling::Node, sapling::Nullifier> {
        &self.sapling
    }

    /// Returns the Orchard note commitment tree and nullifier data for the block.
    #[cfg(feature = "orchard")]
    pub fn orchard(
        &self,
    ) -> &ScannedBundles<orchard::tree::MerkleHashOrchard, orchard::note::Nullifier> {
        &self.orchard
    }

    /// Returns the Ironwood note commitment tree and nullifier data for the block.
    #[cfg(feature = "orchard")]
    pub fn ironwood(
        &self,
    ) -> &ScannedBundles<orchard::tree::MerkleHashOrchard, orchard::note::Nullifier> {
        &self.ironwood
    }

    /// Consumes `self` and returns the lists of Sapling, Orchard, and Ironwood note commitments
    /// associated with the scanned block as an owned value.
    pub fn into_commitments(self) -> ScannedBlockCommitments {
        ScannedBlockCommitments {
            sapling: self.sapling.commitments,
            #[cfg(feature = "orchard")]
            orchard: self.orchard.commitments,
            #[cfg(feature = "orchard")]
            ironwood: self.ironwood.commitments,
        }
    }

    /// Returns the [`BlockMetadata`] corresponding to the scanned block.
    pub fn to_block_metadata(&self) -> BlockMetadata {
        BlockMetadata {
            block_height: self.block_height,
            block_hash: self.block_hash,
            sapling_tree_size: Some(self.sapling.final_tree_size),
            #[cfg(feature = "orchard")]
            orchard_tree_size: Some(self.orchard.final_tree_size),
            #[cfg(feature = "orchard")]
            ironwood_tree_size: Some(self.ironwood.final_tree_size),
        }
    }
}

/// A trait representing a decryptable transaction.
pub trait DecryptableTransaction<AccountId> {
    type DecryptedSaplingOutput;
    #[cfg(feature = "orchard")]
    type DecryptedOrchardOutput;
}

impl<AccountId> DecryptableTransaction<AccountId> for Transaction {
    type DecryptedSaplingOutput = DecryptedOutput<sapling::Note, AccountId>;
    #[cfg(feature = "orchard")]
    type DecryptedOrchardOutput = DecryptedOutput<(orchard::Note, orchard::ValuePool), AccountId>;
}

/// A transaction that was detected during scanning of the blockchain,
/// including its decrypted Sapling and/or Orchard outputs.
///
/// The purpose of this struct is to permit atomic updates of the
/// wallet database when transactions are successfully decrypted.
pub struct DecryptedTransaction<'a, Tx: DecryptableTransaction<AccountId>, AccountId> {
    mined_height: Option<BlockHeight>,
    tx: &'a Tx,
    sapling_outputs: Vec<Tx::DecryptedSaplingOutput>,
    #[cfg(feature = "orchard")]
    orchard_outputs: Vec<Tx::DecryptedOrchardOutput>,
    #[cfg(feature = "orchard")]
    ironwood_outputs: Vec<Tx::DecryptedOrchardOutput>,
}

impl<'a, Tx: DecryptableTransaction<AccountId>, AccountId> DecryptedTransaction<'a, Tx, AccountId> {
    /// Constructs a new [`DecryptedTransaction`] from its constituent parts.
    ///
    /// Ironwood outputs are Orchard-shaped but belong to a distinct pool, and are passed and
    /// tracked separately from Orchard outputs.
    pub fn new(
        mined_height: Option<BlockHeight>,
        tx: &'a Tx,
        sapling_outputs: Vec<Tx::DecryptedSaplingOutput>,
        #[cfg(feature = "orchard")] orchard_outputs: Vec<Tx::DecryptedOrchardOutput>,
        #[cfg(feature = "orchard")] ironwood_outputs: Vec<Tx::DecryptedOrchardOutput>,
    ) -> Self {
        Self {
            mined_height,
            tx,
            sapling_outputs,
            #[cfg(feature = "orchard")]
            orchard_outputs,
            #[cfg(feature = "orchard")]
            ironwood_outputs,
        }
    }

    /// Returns the height at which the transaction was mined, if known.
    pub fn mined_height(&self) -> Option<BlockHeight> {
        self.mined_height
    }
    /// Returns the raw transaction data.
    pub fn tx(&self) -> &Tx {
        self.tx
    }
    /// Returns the Sapling outputs that were decrypted from the transaction.
    pub fn sapling_outputs(&self) -> &[Tx::DecryptedSaplingOutput] {
        &self.sapling_outputs
    }
    /// Returns the Orchard outputs that were decrypted from the transaction.
    #[cfg(feature = "orchard")]
    pub fn orchard_outputs(&self) -> &[Tx::DecryptedOrchardOutput] {
        &self.orchard_outputs
    }

    /// Returns the Ironwood outputs that were decrypted from the transaction.
    ///
    /// Ironwood outputs are Orchard-shaped but belong to a pool distinct from Orchard.
    #[cfg(feature = "orchard")]
    pub fn ironwood_outputs(&self) -> &[Tx::DecryptedOrchardOutput] {
        &self.ironwood_outputs
    }

    /// Returns whether the transaction has decrypted outputs
    pub fn has_decrypted_outputs(&self) -> bool {
        let has_sapling = !self.sapling_outputs.is_empty();
        #[cfg(feature = "orchard")]
        let has_orchard = !self.orchard_outputs.is_empty() || !self.ironwood_outputs.is_empty();
        #[cfg(not(feature = "orchard"))]
        let has_orchard = false;

        has_sapling || has_orchard
    }
}

/// A transaction that was constructed and sent by the wallet.
///
/// The purpose of this struct is to permit atomic updates of the
/// wallet database when transactions are created and submitted
/// to the network.
pub struct SentTransaction<'a, AccountId> {
    tx: &'a Transaction,
    created: time::OffsetDateTime,
    target_height: TargetHeight,
    funding_account: AccountId,
    outputs: &'a [SentTransactionOutput<AccountId>],
    fee_amount: Zatoshis,
    #[cfg(feature = "transparent-inputs")]
    utxos_spent: &'a [OutPoint],
}

impl<'a, AccountId> SentTransaction<'a, AccountId> {
    /// Constructs a new [`SentTransaction`] from its constituent parts.
    ///
    /// ### Parameters
    /// - `tx`: the raw transaction data
    /// - `created`: the system time at which the transaction was created
    /// - `target_height`: the target height that was used in the construction of the transaction
    /// - `funding_account`: the account that spent funds in creation of the transaction
    /// - `outputs`: the outputs created by the transaction, including those sent to external
    ///   recipients which may not otherwise be recoverable
    /// - `fee_amount`: the fee value paid by the transaction
    /// - `utxos_spent`: the UTXOs controlled by the wallet that were spent in this transaction
    pub fn new(
        tx: &'a Transaction,
        created: time::OffsetDateTime,
        target_height: TargetHeight,
        funding_account: AccountId,
        outputs: &'a [SentTransactionOutput<AccountId>],
        fee_amount: Zatoshis,
        #[cfg(feature = "transparent-inputs")] utxos_spent: &'a [OutPoint],
    ) -> Self {
        Self {
            tx,
            created,
            target_height,
            funding_account,
            outputs,
            fee_amount,
            #[cfg(feature = "transparent-inputs")]
            utxos_spent,
        }
    }

    /// Returns the transaction that was sent.
    pub fn tx(&self) -> &Transaction {
        self.tx
    }
    /// Returns the timestamp of the transaction's creation.
    pub fn created(&self) -> time::OffsetDateTime {
        self.created
    }
    /// Returns the id for the account that created the outputs.
    pub fn funding_account(&self) -> &AccountId {
        &self.funding_account
    }
    /// Returns the outputs of the transaction.
    pub fn outputs(&self) -> &[SentTransactionOutput<AccountId>] {
        self.outputs
    }
    /// Returns the fee paid by the transaction.
    pub fn fee_amount(&self) -> Zatoshis {
        self.fee_amount
    }
    /// Returns the list of UTXOs spent in the created transaction.
    #[cfg(feature = "transparent-inputs")]
    pub fn utxos_spent(&self) -> &[OutPoint] {
        self.utxos_spent
    }

    /// Returns the block height that this transaction was created to target.
    pub fn target_height(&self) -> TargetHeight {
        self.target_height
    }
}

/// High-level information about the output of a transaction received by the wallet.
///
/// This type is capable of representing both shielded and transparent outputs. It does not
/// internally store the transaction ID, so it must be interpreted in the context of a caller
/// having requested output information for a specific transaction.
pub struct ReceivedTransactionOutput {
    pool_type: PoolType,
    output_index: usize,
    value: Zatoshis,
    confirmations_until_spendable: u32,
}

impl ReceivedTransactionOutput {
    /// Constructs a [`ReceivedTransactionOutput`] from its constituent parts.
    pub fn from_parts(
        pool_type: PoolType,
        output_index: usize,
        value: Zatoshis,
        confirmations_until_spendable: u32,
    ) -> Self {
        Self {
            pool_type,
            output_index,
            value,
            confirmations_until_spendable,
        }
    }

    /// Returns the pool in which the output value was received.
    pub fn pool_type(&self) -> PoolType {
        self.pool_type
    }

    /// Returns the index of the output among the transaction's outputs to the associated pool.
    pub fn output_index(&self) -> usize {
        self.output_index
    }

    /// Returns the value of the output.
    pub fn value(&self) -> Zatoshis {
        self.value
    }

    /// Returns the number of confirmations required for the output to be treated as spendable,
    /// given a [`ConfirmationsPolicy`] that was specified at the time of the request for this
    /// data.
    pub fn confirmations_until_spendable(&self) -> u32 {
        self.confirmations_until_spendable
    }
}

/// Identifies one of the wallet-maintained note commitment trees.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum NoteCommitmentTree {
    /// The Sapling note commitment tree.
    Sapling,
    /// The Orchard note commitment tree.
    #[cfg(feature = "orchard")]
    Orchard,
    /// The Ironwood note commitment tree.
    #[cfg(feature = "orchard")]
    Ironwood,
}

/// An output of a transaction generated by the wallet.
///
/// This type is capable of representing both shielded and transparent outputs.
pub struct SentTransactionOutput<AccountId> {
    output_index: usize,
    note_commitment_tree: Option<NoteCommitmentTree>,
    recipient: Recipient<AccountId>,
    value: Zatoshis,
    memo: Option<MemoBytes>,
}

impl<AccountId> SentTransactionOutput<AccountId> {
    /// Constructs a new [`SentTransactionOutput`] from its constituent parts.
    ///
    /// ### Fields:
    /// * `output_index` - the index of the output or action in the sent transaction
    /// * `recipient` - the recipient of the output, either a Zcash address or a
    ///   wallet-internal account and the note belonging to the wallet created by
    ///   the output
    /// * `value` - the value of the output, in zatoshis
    /// * `memo` - the memo that was sent with this output
    pub fn from_parts(
        output_index: usize,
        recipient: Recipient<AccountId>,
        value: Zatoshis,
        memo: Option<MemoBytes>,
    ) -> Self {
        Self {
            output_index,
            note_commitment_tree: None,
            recipient,
            value,
            memo,
        }
    }

    /// Constructs a new [`SentTransactionOutput`] with explicit note commitment tree metadata.
    pub(crate) fn from_parts_in_tree(
        note_commitment_tree: Option<NoteCommitmentTree>,
        output_index: usize,
        recipient: Recipient<AccountId>,
        value: Zatoshis,
        memo: Option<MemoBytes>,
    ) -> Self {
        Self {
            output_index,
            note_commitment_tree,
            recipient,
            value,
            memo,
        }
    }

    /// Returns the index within the transaction that contains the recipient output.
    ///
    /// - If `recipient_address` is a Sapling address, this is an index into the Sapling
    ///   outputs of the transaction.
    /// - If `recipient_address` is a transparent address, this is an index into the
    ///   transparent outputs of the transaction.
    pub fn output_index(&self) -> usize {
        self.output_index
    }
    /// Returns the note commitment tree for this output, if known.
    pub fn note_commitment_tree(&self) -> Option<NoteCommitmentTree> {
        self.note_commitment_tree
    }
    /// Returns the recipient address of the transaction, or the account id and
    /// resulting note/outpoint for wallet-internal outputs.
    pub fn recipient(&self) -> &Recipient<AccountId> {
        &self.recipient
    }
    /// Returns the value of the newly created output.
    pub fn value(&self) -> Zatoshis {
        self.value
    }
    /// Returns the memo that was attached to the output, if any. This will only be `None`
    /// for transparent outputs.
    pub fn memo(&self) -> Option<&MemoBytes> {
        self.memo.as_ref()
    }
}

/// A data structure used to set the birthday height for an account, and ensure that the initial
/// note commitment tree state is recorded at that height.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct AccountBirthday {
    prior_chain_state: ChainState,
    recover_until: Option<BlockHeight>,
}

/// Errors that can occur in the construction of an [`AccountBirthday`] from a [`TreeState`].
#[derive(Debug)]
#[non_exhaustive]
pub enum BirthdayError {
    /// The block height of the [`TreeState`] was out of range for a [`BlockHeight`].
    HeightInvalid(TryFromIntError),
    /// The note commitment tree frontiers of the [`TreeState`] could not be decoded.
    Decode(io::Error),
}

impl fmt::Display for BirthdayError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            BirthdayError::HeightInvalid(e) => {
                write!(f, "Invalid block height for account birthday: {e}")
            }
            BirthdayError::Decode(e) => write!(
                f,
                "Failed to decode the note commitment tree state for the account birthday: {e}"
            ),
        }
    }
}

impl std::error::Error for BirthdayError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            BirthdayError::HeightInvalid(e) => Some(e),
            BirthdayError::Decode(e) => Some(e),
        }
    }
}

impl From<TryFromIntError> for BirthdayError {
    fn from(value: TryFromIntError) -> Self {
        Self::HeightInvalid(value)
    }
}

impl From<io::Error> for BirthdayError {
    fn from(value: io::Error) -> Self {
        Self::Decode(value)
    }
}

impl AccountBirthday {
    /// Constructs a new [`AccountBirthday`] from its constituent parts.
    ///
    /// * `prior_chain_state`: The chain state prior to the birthday height of the account. The
    ///   birthday height is defined as the height of the first block to be scanned in wallet
    ///   recovery.
    /// * `recover_until`: An optional height at which the wallet should exit "recovery mode". In
    ///   order to avoid confusing shifts in wallet balance and spendability that may temporarily be
    ///   visible to a user during the process of recovering from seed, wallets may optionally set a
    ///   "recover until" height. The wallet is considered to be in "recovery mode" until there
    ///   exist no unscanned ranges between the wallet's birthday height and the provided
    ///   `recover_until` height, exclusive.
    pub fn from_parts(prior_chain_state: ChainState, recover_until: Option<BlockHeight>) -> Self {
        Self {
            prior_chain_state,
            recover_until,
        }
    }

    /// Constructs a new [`AccountBirthday`] from a [`TreeState`] returned from `lightwalletd`.
    ///
    /// * `treestate`: The tree state corresponding to the last block prior to the wallet's
    ///   birthday height.
    /// * `recover_until`: An optional height at which the wallet should exit "recovery mode". In
    ///   order to avoid confusing shifts in wallet balance and spendability that may temporarily be
    ///   visible to a user during the process of recovering from seed, wallets may optionally set a
    ///   "recover until" height. The wallet is considered to be in "recovery mode" until there
    ///   exist no unscanned ranges between the wallet's birthday height and the provided
    ///   `recover_until` height, exclusive.
    pub fn from_treestate(
        treestate: TreeState,
        recover_until: Option<BlockHeight>,
    ) -> Result<Self, BirthdayError> {
        Ok(Self {
            prior_chain_state: treestate.to_chain_state()?,
            recover_until,
        })
    }

    /// Returns the Sapling note commitment tree frontier as of the end of the block at
    /// [`Self::height`].
    pub fn sapling_frontier(
        &self,
    ) -> &Frontier<sapling::Node, { sapling::NOTE_COMMITMENT_TREE_DEPTH }> {
        self.prior_chain_state.final_sapling_tree()
    }

    /// Returns the Orchard note commitment tree frontier as of the end of the block at
    /// [`Self::height`].
    #[cfg(feature = "orchard")]
    pub fn orchard_frontier(
        &self,
    ) -> &Frontier<orchard::tree::MerkleHashOrchard, { orchard::NOTE_COMMITMENT_TREE_DEPTH as u8 }>
    {
        self.prior_chain_state.final_orchard_tree()
    }

    /// Returns the birthday height of the account.
    pub fn height(&self) -> BlockHeight {
        self.prior_chain_state.block_height() + 1
    }

    /// Returns the height at which the wallet should exit "recovery mode".
    pub fn recover_until(&self) -> Option<BlockHeight> {
        self.recover_until
    }

    /// Returns the [`ChainState`] corresponding to the last block prior to the wallet's birthday
    pub fn prior_chain_state(&self) -> &ChainState {
        &self.prior_chain_state
    }

    #[cfg(any(test, feature = "test-dependencies"))]
    /// Constructs a new [`AccountBirthday`] at the given network upgrade's activation,
    /// with no "recover until" height.
    ///
    /// # Panics
    ///
    /// Panics if the activation height for the given network upgrade is not set.
    pub fn from_activation<P: zcash_protocol::consensus::Parameters>(
        params: &P,
        network_upgrade: NetworkUpgrade,
        prior_block_hash: BlockHash,
    ) -> AccountBirthday {
        AccountBirthday::from_parts(
            ChainState::empty(
                params.activation_height(network_upgrade).unwrap() - 1,
                prior_block_hash,
            ),
            None,
        )
    }

    #[cfg(any(test, feature = "test-dependencies"))]
    /// Constructs a new [`AccountBirthday`] at Sapling activation, with no
    /// "recover until" height.
    ///
    /// # Panics
    ///
    /// Panics if the Sapling activation height is not set.
    pub fn from_sapling_activation<P: zcash_protocol::consensus::Parameters>(
        params: &P,
        prior_block_hash: BlockHash,
    ) -> AccountBirthday {
        Self::from_activation(params, NetworkUpgrade::Sapling, prior_block_hash)
    }
}

/// This trait encapsulates the write capabilities required to update stored wallet data.
///
/// # Adding accounts
///
/// This trait provides several methods for adding accounts to the wallet data:
/// - [`WalletWrite::create_account`]
/// - [`WalletWrite::import_account_hd`]
/// - [`WalletWrite::import_account_ufvk`]
///
/// All of these methods take an [`AccountBirthday`]. The birthday height is defined as
/// the minimum block height that will be scanned for funds belonging to the wallet. If
/// `birthday.height()` is below the current chain tip, the account addition operation
/// will trigger a re-scan of the blocks at and above the provided height.
///
/// The order in which you call these methods will affect the resulting wallet structure:
/// - If only [`WalletWrite::create_account`] is used, the resulting accounts will have
///   sequential [ZIP 32] account indices within each given seed.
/// - If [`WalletWrite::import_account_hd`] is used to import accounts with non-sequential
///   ZIP 32 account indices from the same seed, a call to [`WalletWrite::create_account`]
///   will use the ZIP 32 account index just after the highest-numbered existing account.
/// - If an account is added to the wallet, and then a later call to one of the methods
///   would produce a UFVK that collides with that account on any FVK component (i.e.
///   Sapling, Orchard, or transparent), an error will be returned. This can occur in the
///   following cases:
///   - An account is created via [`WalletWrite::create_account`] with an auto-selected
///     ZIP 32 account index, and that index is later imported explicitly via either
///     [`WalletWrite::import_account_ufvk`] or [`WalletWrite::import_account_hd`].
///   - An account is imported via [`WalletWrite::import_account_ufvk`] or
///     [`WalletWrite::import_account_hd`], and then the ZIP 32 account index
///     corresponding to that account's UFVK is later imported either implicitly
///     via [`WalletWrite::create_account`], or explicitly via a call to
///     [`WalletWrite::import_account_ufvk`] or [`WalletWrite::import_account_hd`].
///
/// Note that an error will be returned on an FVK collision even if the UFVKs do not
/// match exactly, e.g. if they have different subsets of components.
///
/// An account is treated as having a single root of spending authority that spans the shielded and
/// transparent rules for the purpose of balance, transaction listing, and so forth. However,
/// transparent keys imported via `WalletWrite::import_standalone_transparent_pubkey` or
/// `WalletWrite::import_standalone_transparent_script` (available with the
/// `transparent-key-import` feature) break this abstraction slightly, so wallets using this API
/// need to be cautious to enforce the invariant that the wallet either maintains access to the
/// keys required to spend **ALL** outputs received by the account, or that it **DOES NOT** offer
/// any spending capability for the account, i.e. the account is treated as view-only for all
/// user-facing operations.
///
/// A future change to this trait might introduce a method to "upgrade" an imported
/// account with derivation information. See [zcash/librustzcash#1284] for details.
///
/// Users of the `WalletWrite` trait should generally distinguish in their APIs and wallet UIs
/// between creating a new account, and importing an account that previously existed. By
/// convention, wallets should only allow a new account to be generated for a seed after confirmed
/// funds have been received by the newest existing account for that seed; this allows automated
/// account recovery to discover and recover all funds within a particular seed.
///
/// # Creating a new wallet
///
/// To create a new wallet:
/// - Generate a new [BIP 39] mnemonic phrase, using a crate like [`bip0039`].
/// - Derive the corresponding seed from the mnemonic phrase.
/// - Use [`WalletWrite::create_account`] with the resulting seed.
///
/// Callers should construct the [`AccountBirthday`] using [`AccountBirthday::from_treestate`] for
/// the block at height `chain_tip_height - 100`. Setting the birthday height to a tree state below
/// the pruning depth ensures that reorgs cannot cause funds intended for the wallet to be missed;
/// otherwise, if the chain tip height were used for the wallet birthday, a transaction targeted at
/// a height greater than the chain tip could be mined at a height below that tip as part of a
/// reorg.
///
/// # Restoring a wallet from backup
///
/// To restore a backed-up wallet:
/// - Derive the seed from its BIP 39 mnemonic phrase.
/// - Use [`WalletWrite::import_account_hd`] once for each ZIP 32 account index that the
///   user wants to restore.
/// - If the highest previously-used ZIP 32 account index was _not_ restored by the user,
///   remember this index separately as `index_max`. The first time the user wants to
///   generate a new account, use [`WalletWrite::import_account_hd`] to create the account
///   `index_max + 1`.
/// - [`WalletWrite::create_account`] can be used to generate subsequent new accounts in
///   the restored wallet.
///
/// Automated account recovery has not yet been implemented by this crate. A wallet app
/// that supports multiple accounts can implement it manually by tracking account balances
/// relative to [`WalletSummary::fully_scanned_height`], and creating new accounts as
/// funds appear in existing accounts.
///
/// If the number of accounts is known in advance, the wallet should create all accounts before
/// scanning the chain so that the scan can be done in a single pass for all accounts.
///
/// [ZIP 32]: https://zips.z.cash/zip-0032
/// [zcash/librustzcash#1284]: https://github.com/zcash/librustzcash/issues/1284
/// [BIP 39]: https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki
/// [`bip0039`]: https://crates.io/crates/bip0039
#[cfg_attr(feature = "test-dependencies", delegatable_trait)]
pub trait WalletWrite:
    WalletRead
    + OutputLockStore<
        AccountId = <Self as WalletRead>::AccountId,
        Error = <Self as WalletRead>::Error,
    >
{
    /// The type of identifiers used to look up transparent UTXOs.
    type UtxoRef;

    /// Tells the wallet to track the next available account-level spend authority for the provided
    /// seed value, given the current set of [ZIP 316] account identifiers known to the wallet database.
    ///
    /// The "next available account" is defined as the ZIP-32 account index immediately following
    /// the highest existing account index among all accounts in the wallet that share the given
    /// seed. Users of the [`WalletWrite`] trait that only call this method are guaranteed to have
    /// accounts with sequential indices.
    ///
    /// Returns the account identifier for the newly-created wallet database entry, along with the
    /// associated [`UnifiedSpendingKey`]. Note that the unique account identifier should *not* be
    /// assumed equivalent to the ZIP 32 account index. It is an opaque identifier for a pool of
    /// funds or set of outputs controlled by a single spending authority.
    ///
    /// The ZIP-32 account index may be obtained by calling [`WalletRead::get_account`]
    /// with the returned account identifier.
    ///
    /// The [`WalletWrite`] trait documentation has more details about account creation and import.
    ///
    /// # Arguments
    /// - `account_name`: A human-readable name for the account.
    /// - `seed`: The 256-byte (at least) HD seed from which to derive the account UFVK.
    /// - `birthday`: Metadata about where to start scanning blocks to find transactions intended
    ///   for the account.
    /// - `key_source`: A string identifier or other metadata describing the source of the seed.
    ///   This is treated as opaque metadata by the wallet backend; it is provided for use by
    ///   applications which need to track additional identifying information for an account.
    ///
    /// # Implementation notes
    ///
    /// Implementations of this method **MUST NOT** "fill in gaps" by selecting an account index
    /// that is lower than any existing account index among all accounts in the wallet that share
    /// the given seed.
    ///
    /// # Panics
    ///
    /// Panics if the length of the seed is not between 32 and 252 bytes inclusive.
    ///
    /// [ZIP 316]: https://zips.z.cash/zip-0316
    fn create_account(
        &mut self,
        account_name: &str,
        seed: &SecretVec<u8>,
        birthday: &AccountBirthday,
        key_source: Option<&str>,
    ) -> Result<(<Self as WalletRead>::AccountId, UnifiedSpendingKey), <Self as WalletRead>::Error>;

    /// Tells the wallet to track a specific account index for a given seed.
    ///
    /// Returns details about the imported account, including the unique account identifier for
    /// the newly-created wallet database entry, along with the associated [`UnifiedSpendingKey`].
    /// Note that the unique account identifier should *not* be assumed equivalent to the ZIP 32
    /// account index. It is an opaque identifier for a pool of funds or set of outputs controlled
    /// by a single spending authority.
    ///
    /// Import accounts with indices that are exactly one greater than the highest existing account
    /// index to ensure account indices are contiguous, thereby facilitating automated account
    /// recovery.
    ///
    /// The [`WalletWrite`] trait documentation has more details about account creation and import.
    ///
    /// # Arguments
    /// - `account_name`: A human-readable name for the account.
    /// - `seed`: The 256-byte (at least) HD seed from which to derive the account UFVK.
    /// - `account_index`: The ZIP 32 account-level component of the HD derivation path at
    ///   which to derive the account's UFVK.
    /// - `birthday`: Metadata about where to start scanning blocks to find transactions intended
    ///   for the account.
    /// - `key_source`: A string identifier or other metadata describing the source of the seed.
    ///   This is treated as opaque metadata by the wallet backend; it is provided for use by
    ///   applications which need to track additional identifying information for an account.
    ///
    /// # Panics
    ///
    /// Panics if the length of the seed is not between 32 and 252 bytes inclusive.
    ///
    /// [ZIP 316]: https://zips.z.cash/zip-0316
    fn import_account_hd(
        &mut self,
        account_name: &str,
        seed: &SecretVec<u8>,
        account_index: zip32::AccountId,
        birthday: &AccountBirthday,
        key_source: Option<&str>,
    ) -> Result<(Self::Account, UnifiedSpendingKey), <Self as WalletRead>::Error>;

    /// Tells the wallet to track an account using a unified full viewing key.
    ///
    /// Returns details about the imported account, including the unique account identifier for
    /// the newly-created wallet database entry. Unlike the other account creation APIs
    /// ([`Self::create_account`] and [`Self::import_account_hd`]), no spending key is returned
    /// because the wallet has no information about how the UFVK was derived.
    ///
    /// Certain optimizations are possible for accounts which will never be used to spend funds. If
    /// `spending_key_available` is `false`, the wallet may choose to optimize for this case, in
    /// which case any attempt to spend funds from the account will result in an error.
    ///
    /// The [`WalletWrite`] trait documentation has more details about account creation and import.
    ///
    /// # Arguments
    /// - `account_name`: A human-readable name for the account.
    /// - `unified_key`: The UFVK used to detect transactions involving the account.
    /// - `birthday`: Metadata about where to start scanning blocks to find transactions intended
    ///   for the account.
    /// - `purpose`: Metadata describing whether or not data required for spending should be
    ///   tracked by the wallet.
    /// - `key_source`: A string identifier or other metadata describing the source of the seed.
    ///   This is treated as opaque metadata by the wallet backend; it is provided for use by
    ///   applications which need to track additional identifying information for an account.
    fn import_account_ufvk(
        &mut self,
        account_name: &str,
        unified_key: &UnifiedFullViewingKey,
        birthday: &AccountBirthday,
        purpose: AccountPurpose,
        key_source: Option<&str>,
    ) -> Result<Self::Account, <Self as WalletRead>::Error>;

    /// Deletes the specified account, and all transactions that exclusively involve it, from the
    /// wallet database.
    ///
    /// WARNING: This is a destructive operation and may result in the permanent loss of
    /// potentially important information that is not recoverable from chain data, including:
    /// * Data about transactions sent by the account for which [`OvkPolicy::Discard`] (or
    ///   [`OvkPolicy::Custom`] with random OVKs) was used;
    /// * Data related to transactions that the account attempted to send that expired or were
    ///   otherwise invalidated without having been mined in the main chain;
    /// * Data related to transactions that were observed in the mempool as having inputs or
    ///   outputs that involved the account, but that were never mined in the main chain;
    /// * Data related to transactions that were received by the wallet in a mined block, where
    ///   that block was later un-mined in a chain reorg and the transaction was either invalidated
    ///   or was never re-mined.
    ///
    /// [`OvkPolicy::Discard`]: crate::wallet::OvkPolicy::Discard
    /// [`OvkPolicy::Custom`]: crate::wallet::OvkPolicy::Custom
    fn delete_account(
        &mut self,
        account: <Self as WalletRead>::AccountId,
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Imports the given pubkey into the account without key derivation information, and adds the
    /// associated transparent p2pkh address.
    ///
    /// The imported address will contribute to the balance of the account (for UFVK-based
    /// accounts), but spending funds held by this address requires the associated spending keys to
    /// be provided explicitly when calling [`create_proposed_transactions`]. By extension, calls
    /// to [`propose_shielding`] must only include addresses for which the spending application
    /// holds or can obtain the spending keys.
    ///
    /// [`create_proposed_transactions`]: crate::data_api::wallet::create_proposed_transactions
    /// [`propose_shielding`]: crate::data_api::wallet::propose_shielding
    #[cfg(feature = "transparent-key-import")]
    fn import_standalone_transparent_pubkey(
        &mut self,
        _account: <Self as WalletRead>::AccountId,
        _pubkey: secp256k1::PublicKey,
    ) -> Result<(), <Self as WalletRead>::Error> {
        unimplemented!(
            "WalletWrite::import_standalone_transparent_pubkey must be overridden for wallets to use the `transparent-key-import` feature"
        )
    }

    /// Imports a batch of standalone transparent pubkeys into the account, adding the associated
    /// transparent p2pkh addresses. See [`import_standalone_transparent_pubkey`] for the semantics
    /// and spending limitations that apply to each imported pubkey.
    ///
    /// This is equivalent to calling [`import_standalone_transparent_pubkey`] once per pubkey, but
    /// implementations may validate the target account a single time for the whole batch. The
    /// default implementation calls [`import_standalone_transparent_pubkey`] for each pubkey; a
    /// pubkey whose receiver address is already known to the wallet is skipped.
    ///
    /// [`import_standalone_transparent_pubkey`]: Self::import_standalone_transparent_pubkey
    #[cfg(feature = "transparent-key-import")]
    fn import_standalone_transparent_pubkeys(
        &mut self,
        account: <Self as WalletRead>::AccountId,
        pubkeys: &[secp256k1::PublicKey],
    ) -> Result<(), <Self as WalletRead>::Error> {
        for pubkey in pubkeys {
            self.import_standalone_transparent_pubkey(account, *pubkey)?;
        }
        Ok(())
    }

    /// Imports the given redeem script into the account without key derivation information, and
    /// adds the associated transparent p2sh address.
    ///
    /// The imported address will contribute to the balance of the account (for UFVK-based
    /// accounts), but spending funds held by this address requires the associated spending keys to
    /// be provided explicitly when calling [`create_proposed_transactions`]. By extension, calls
    /// to [`propose_shielding`] must only include addresses for which the spending application
    /// holds or can obtain the spending keys.
    ///
    /// [`create_proposed_transactions`]: crate::data_api::wallet::create_proposed_transactions
    /// [`propose_shielding`]: crate::data_api::wallet::propose_shielding
    ///
    /// # Spending limitations
    ///
    /// P2PKH-in-P2SH scripts are unsupported by PCZT at this time, so the only way to spend
    /// from such an address is to use the [`create_proposed_transactions`] signing path.
    #[cfg(feature = "transparent-key-import")]
    fn import_standalone_transparent_script(
        &mut self,
        _account: <Self as WalletRead>::AccountId,
        _script: zcash_script::script::Redeem,
    ) -> Result<(), <Self as WalletRead>::Error> {
        unimplemented!(
            "WalletWrite::import_standalone_transparent_script must be overridden for wallets to use the `transparent-key-import` feature"
        )
    }

    /// Generates, persists, and marks as exposed the next available diversified address for the
    /// specified account, given the current addresses known to the wallet.
    ///
    /// Returns `Ok(None)` if the account identifier does not correspond to a known
    /// account.
    fn get_next_available_address(
        &mut self,
        account: <Self as WalletRead>::AccountId,
        request: UnifiedAddressRequest,
    ) -> Result<Option<(UnifiedAddress, DiversifierIndex)>, <Self as WalletRead>::Error>;

    /// Generates, persists, and marks as exposed a diversified address for the specified account
    /// at the provided diversifier index.
    ///
    /// Returns `Ok(None)` in the case that it is not possible to generate an address conforming
    /// to the provided request at the specified diversifier index. Such a result might arise from
    /// the diversifier index not being valid for a [`ReceiverRequirement::Require`]'ed receiver.
    /// Some implementations of this trait may return `Err(_)` in some cases to expose more
    /// information, which is only accessible in a backend-specific context.
    ///
    /// Address generation should fail if an address has already been exposed for the given
    /// diversifier index and the given request produced an address having different receivers than
    /// what was originally exposed.
    ///
    /// # WARNINGS
    /// If an address generated using this method has a transparent receiver and the
    /// chosen diversifier index would be outside the wallet's internally-configured gap limit,
    /// funds sent to these address are **likely to not be discovered on recovery from seed**. It
    /// up to the caller of this method to either ensure that they only request transparent
    /// receivers with indices within the range of a reasonable gap limit, or that they ensure that
    /// their wallet provides backup facilities that can be used to ensure that funds sent to such
    /// addresses are recoverable after a loss of wallet data.
    ///
    /// [`ReceiverRequirement::Require`]: zcash_keys::keys::ReceiverRequirement::Require
    fn get_address_for_index(
        &mut self,
        account: <Self as WalletRead>::AccountId,
        diversifier_index: DiversifierIndex,
        request: UnifiedAddressRequest,
    ) -> Result<Option<UnifiedAddress>, <Self as WalletRead>::Error>;

    /// Updates the wallet's view of the blockchain.
    ///
    /// This method is used to provide the wallet with information about the state of the
    /// blockchain, and detect any previously scanned data that needs to be re-validated
    /// before proceeding with scanning. It should be called at wallet startup prior to calling
    /// [`WalletRead::suggest_scan_ranges`] in order to provide the wallet with the information it
    /// needs to correctly prioritize scanning operations.
    fn update_chain_tip(
        &mut self,
        tip_height: BlockHeight,
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Drops the scan work queued below `height`, except where retained by
    /// `retain_with_priority`. Returns the number of queue entries removed or altered.
    ///
    /// If `retain_with_priority` is `None`, no entries below `height` are retained,
    /// irrespective of their priority. If it is `Some(priority)`, entries with that
    /// priority and greater are retained (left untouched, even where they straddle
    /// `height`), as are entries with the bookkeeping priorities
    /// [`ScanPriority::Scanned`] and [`ScanPriority::Ignored`] — those record which
    /// regions of the chain the backend has already covered or deliberately skips, and
    /// removing them would cause the backend to forget coverage state it maintains
    /// itself (use the `None` form when that full reset is the intent). Entries with
    /// priorities between the bookkeeping ones and the retained threshold are pruned.
    ///
    /// Pruning must not leave a gap in the queue's coverage: implementations are required
    /// to preserve contiguity across whatever remains below `height`, which in general
    /// means demoting pruned ranges to [`ScanPriority::Ignored`] rather than deleting them
    /// outright. Only coverage below the lowest retained entry may be deleted, since that
    /// merely raises the floor of the queue. A caller may therefore observe that the total
    /// span of the queue is unchanged and that the pruned region is now `Ignored`.
    ///
    /// This is a queue-hygiene operation. The primary use case is discarding historic scan
    /// ranges that no remaining account justifies: [`WalletWrite::delete_account`] does not
    /// modify the scan queue, so the deep ranges queued for a since-deleted account's
    /// birthday would otherwise still be scanned even though no remaining account can have
    /// notes below its own birthday. In that case, pass the wallet birthday
    /// ([`WalletRead::get_wallet_birthday`]) as `height` and retain
    /// [`ScanPriority::OpenAdjacent`] and greater — the priorities that may legitimately
    /// reach below the wallet birthday in service of note witnesses.
    fn prune_scan_queue_below(
        &mut self,
        height: BlockHeight,
        retain_with_priority: Option<ScanPriority>,
    ) -> Result<u64, <Self as WalletRead>::Error>;

    /// Updates the state of the wallet database by persisting the provided block information,
    /// along with the note commitments that were detected when scanning the block for transactions
    /// pertaining to this wallet.
    ///
    /// ### Arguments
    /// - `from_state` must be the chain state for the block height prior to the first
    ///   block in `blocks`.
    /// - `blocks` must be sequential, in order of increasing block height.
    fn put_blocks(
        &mut self,
        from_state: &ChainState,
        blocks: Vec<ScannedBlock<<Self as WalletRead>::AccountId>>,
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Adds a transparent UTXO received by the wallet to the data store.
    fn put_received_transparent_utxo(
        &mut self,
        output: &WalletTransparentOutput<<Self as WalletRead>::AccountId>,
    ) -> Result<Self::UtxoRef, <Self as WalletRead>::Error>;

    /// Caches a decrypted transaction in the persistent wallet store.
    fn store_decrypted_tx(
        &mut self,
        received_tx: DecryptedTransaction<Transaction, <Self as WalletRead>::AccountId>,
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Sets the trust status of the given transaction to either trusted or untrusted.
    ///
    /// The outputs of a trusted transaction will be available for spending with
    /// [`ConfirmationsPolicy::trusted`] confirmations even if the output is not wallet-internal.
    fn set_tx_trust(
        &mut self,
        txid: TxId,
        trusted: bool,
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Saves information about transactions constructed by the wallet to the persistent
    /// wallet store.
    ///
    /// This must be called before the transactions are sent to the network.
    ///
    /// Transactions that have been stored by this method should be retransmitted while it
    /// is still possible that they could be mined.
    ///
    /// Implementations must unlock any locked outputs that are recorded as spent by the
    /// stored transactions. Once spend records exist, the outputs are protected from
    /// double-selection by the spend tracking mechanism, so the explicit locks are no
    /// longer needed.
    fn store_transactions_to_be_sent(
        &mut self,
        transactions: &[SentTransaction<<Self as WalletRead>::AccountId>],
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Truncates the wallet database to at most the specified height.
    ///
    /// Implementations of this method may choose a lower block height to which the data store will
    /// be truncated if it is not possible to truncate exactly to the specified height. Upon
    /// successful truncation, this method returns the height to which the data store was actually
    /// truncated.
    ///
    /// This method assumes that the state of the underlying data store is consistent up to a
    /// particular block height. Since it is possible that a chain reorg might invalidate some
    /// stored state, this method must be implemented in order to allow users of this API to
    /// "reset" the data store to correctly represent chainstate as of at most the requested block
    /// height.
    ///
    /// After calling this method, the block at the returned height will be the most recent block
    /// and all other operations will treat this block as the chain tip for balance determination
    /// purposes.
    ///
    /// There may be restrictions on heights to which it is possible to truncate. Specifically, it
    /// will only be possible to truncate to heights at which is is possible to create a witness
    /// given the current state of the wallet's note commitment tree.
    fn truncate_to_height(
        &mut self,
        max_height: BlockHeight,
    ) -> Result<BlockHeight, <Self as WalletRead>::Error>;

    /// Truncates the wallet database to the specified chain state.
    ///
    /// In contrast to [`truncate_to_height`], this method allows the caller to truncate the wallet
    /// database to a precise height by providing additional chain state information needed for
    /// note commitment tree maintenance after the truncation.
    ///
    /// [`truncate_to_height`]: WalletWrite::truncate_to_height
    fn truncate_to_chain_state(
        &mut self,
        chain_state: ChainState,
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Rewinds the wallet to the specified chain state, preserving wallet data which has been
    /// confirmed beyond the pruning depth, and lowering the birthday height of selected accounts
    /// to the block following the chain state.
    ///
    /// In contrast to [`truncate_to_chain_state`], which unconditionally removes wallet state
    /// above `chain_state.block_height()`, this rewinds the scan queue to the target height but
    /// only rewinds blocks, note commitment trees, transactions, transparent UTXO observations,
    /// and nullifier-map entries as far back as the implementation's pruning floor; data at or
    /// below that floor is preserved.
    ///
    /// `reset_account_birthdays` selects which accounts (if any) may have their birthday
    /// metadata lowered as a result of this rewind. The semantics are:
    ///
    /// - Every account in `reset_account_birthdays` has its birthday metadata updated to
    ///   `chain_state.block_height() + 1` (with corresponding tree sizes taken from
    ///   `chain_state`) if and only if the new birthday is less than the account's existing
    ///   birthday. Existing birthdays are never raised by this method.
    /// - Accounts that are *not* in `reset_account_birthdays` are never modified, regardless of
    ///   the rewind target. Note that this only governs per-account birthday metadata:
    ///   rescanning of blocks that re-enter the scan queue applies to *all* accounts in the
    ///   wallet, since scanning is performed against all viewing keys.
    /// - If `reset_account_birthdays` is empty and *every* account in the wallet has a birthday
    ///   greater than `chain_state.block_height() + 1` (the value to which a reset birthday
    ///   would be lowered), this method returns [`RewindError::RewindBeyondBirthdays`] and no
    ///   other state is modified. So long as at least one account in the wallet already has a
    ///   birthday at or below `chain_state.block_height() + 1`, this error is not returned —
    ///   such an account already provides the wallet with an anchor at or below the new
    ///   birthday floor, so no reset is required. The reported map contains every account in
    ///   the wallet along with its existing birthday height; the caller may re-invoke the
    ///   method with any subset of those accounts included in `reset_account_birthdays`.
    ///
    /// Implementations may also return an [`Err`] (typically via [`RewindError::DataSource`])
    /// if `reset_account_birthdays` contains identifiers that do not correspond to accounts in
    /// the wallet.
    ///
    /// [`truncate_to_chain_state`]: WalletWrite::truncate_to_chain_state
    fn rewind_to_chain_state(
        &mut self,
        chain_state: ChainState,
        reset_account_birthdays: HashSet<<Self as WalletRead>::AccountId>,
    ) -> Result<(), RewindError<<Self as WalletRead>::AccountId, <Self as WalletRead>::Error>>;

    /// Reserves the next `n` available ephemeral addresses for the given account.
    /// This cannot be undone, so as far as possible, errors associated with transaction
    /// construction should have been reported before calling this method.
    ///
    /// To ensure that sufficient information is stored on-chain to allow recovering
    /// funds sent back to any of the used addresses, a "gap limit" of 20 addresses
    /// should be observed as described in [BIP 44].
    ///
    /// Returns an error if there is insufficient space within the gap limit to allocate
    /// the given number of addresses, or if the account identifier does not correspond
    /// to a known account.
    ///
    /// [BIP 44]: https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki#user-content-Address_gap_limit
    #[cfg(feature = "transparent-inputs")]
    fn reserve_next_n_ephemeral_addresses(
        &mut self,
        _account_id: <Self as WalletRead>::AccountId,
        _n: usize,
    ) -> Result<Vec<(TransparentAddress, TransparentAddressMetadata)>, <Self as WalletRead>::Error>
    {
        unimplemented!(
            "WalletWrite::reserve_next_n_ephemeral_addresses must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Reserves the next `n` available internal-scope (change) transparent addresses for
    /// the given account, as described in [BIP 44] under the `change` path level. This
    /// cannot be undone, so as far as possible, errors associated with transaction
    /// construction should have been reported before calling this method.
    ///
    /// Internal-scope transparent addresses are used to receive change for transactions
    /// having fully-transparent value flows, when the change strategy in use is configured
    /// with [`TransparentChangePolicy::TransparentChangeAllowed`].
    ///
    /// To ensure that funds sent to internal-scope addresses are recoverable, implementations
    /// of this method should observe a gap limit as described in [BIP 44]; change addresses
    /// receive funds immediately upon reservation, so a smaller gap limit than the one used
    /// for external addresses may be observed.
    ///
    /// Returns an error if there is insufficient space within the gap limit to allocate
    /// the given number of addresses, or if the account identifier does not correspond
    /// to a known account.
    ///
    /// [BIP 44]: https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki
    /// [`TransparentChangePolicy::TransparentChangeAllowed`]: crate::fees::TransparentChangePolicy::TransparentChangeAllowed
    #[cfg(feature = "transparent-inputs")]
    fn reserve_next_n_internal_addresses(
        &mut self,
        _account_id: <Self as WalletRead>::AccountId,
        _n: usize,
    ) -> Result<Vec<(TransparentAddress, TransparentAddressMetadata)>, <Self as WalletRead>::Error>
    {
        unimplemented!(
            "WalletWrite::reserve_next_n_internal_addresses must be overridden for wallets to \
             create transactions that produce transparent change"
        )
    }

    /// Updates the wallet backend with respect to the status of a specific transaction, from the
    /// perspective of the main chain.
    ///
    /// Fully transparent transactions, and transactions that do not contain either shielded inputs
    /// or shielded outputs belonging to the wallet, may not be discovered by the process of chain
    /// scanning; as a consequence, the wallet must actively query to determine whether such
    /// transactions have been mined.
    fn set_transaction_status(
        &mut self,
        _txid: TxId,
        _status: TransactionStatus,
    ) -> Result<(), <Self as WalletRead>::Error>;

    /// Schedules a UTXO check for the given address at a random time that has an expected value of
    /// `offset_seconds` from the current system time.
    ///
    /// Returns the time at which the check has been scheduled, or `None` if the address is not
    /// being tracked by the wallet.
    #[cfg(feature = "transparent-inputs")]
    fn schedule_next_check(
        &mut self,
        _address: &TransparentAddress,
        _offset_seconds: u32,
    ) -> Result<Option<SystemTime>, <Self as WalletRead>::Error> {
        unimplemented!(
            "WalletWrite::schedule_next_check must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Informs the wallet backend that the given transparent addresses are known to have been
    /// exposed externally at or before the block height paired with each address.
    ///
    /// This method is intended for use when a wallet has learned, through means outside the
    /// observation of the chain by this backend, that addresses under the wallet's control have
    /// been disclosed to an external party. Calling this method ensures that the wallet's exposure
    /// metadata accounts for the earlier disclosures.
    ///
    /// If the wallet already tracks an earlier exposure for an address, the earlier height is
    /// retained.
    ///
    /// The operation is atomic: if any address in `exposures` is not known to the wallet,
    /// implementations must roll back all updates performed during the call and return an
    /// implementation-defined error identifying the first unrecognized address.
    /// Passing an empty slice is a no-op.
    #[cfg(feature = "transparent-inputs")]
    fn mark_transparent_addresses_exposed(
        &mut self,
        _exposures: &[(TransparentAddress, BlockHeight)],
    ) -> Result<(), <Self as WalletRead>::Error> {
        unimplemented!(
            "WalletWrite::mark_transparent_addresses_exposed must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Notifies the wallet backend that the given query for transactions involving a particular
    /// address has completed evaluation.
    ///
    /// # Arguments
    /// - `request`: the [`TransactionsInvolvingAddress`] request that was executed.
    /// - `as_of_height`: The maximum height among blocks that were inspected in the process of
    ///   performing the requested check.
    #[cfg(feature = "transparent-inputs")]
    fn notify_address_checked(
        &mut self,
        _request: TransactionsInvolvingAddress,
        _as_of_height: BlockHeight,
    ) -> Result<(), <Self as WalletRead>::Error> {
        unimplemented!(
            "WalletWrite::notify_address_checked must be overridden for wallets to use the `transparent-inputs` feature"
        )
    }

    /// Notifies the wallet backend that a specific transparent output was confirmed unspent as of
    /// the given height, in response to a [`TransactionDataRequest::GetSpendingTx`]
    /// request.
    ///
    /// # Arguments
    /// - `outpoint`: the transparent outpoint whose spend status was checked.
    /// - `as_of_height`: the maximum height among blocks that were inspected, and through which
    ///   the outpoint is confirmed to remain unspent.
    #[cfg(feature = "spend-index")]
    fn notify_output_verified_unspent(
        &mut self,
        _outpoint: OutPoint,
        _as_of_height: BlockHeight,
    ) -> Result<(), <Self as WalletRead>::Error> {
        unimplemented!(
            "WalletWrite::notify_output_verified_unspent must be overridden for wallets to use the `spend-index` feature"
        )
    }
}

/// Applies a batch of note commitment tree changes — shards, an optional replacement tree
/// cap, and a checkpoint delta — directly to the given tree's backing [`ShardStore`].
///
/// `shards` must be in ascending shard-index order; stores may reject sequences that would
/// leave gaps in the tree. Checkpoint removals are applied before additions, so that a
/// checkpoint whose data has changed may appear in both lists.
///
/// This is the shared implementation of the [`WalletCommitmentTrees`] `put_*_shards`
/// provided methods.
///
/// NOTE: This procedure must be called only within a the context of a transaction, such as
/// in the scope of a `with_*_tree_mut` call; otherwise, failure of an intermediate step could
/// lead to data corruption.
fn apply_tree_changes<H, S, const DEPTH: u8, const SHARD_HEIGHT: u8>(
    tree: &mut ShardTree<S, DEPTH, SHARD_HEIGHT>,
    shards: &[shardtree::LocatedPrunableTree<H>],
    cap: Option<&shardtree::PrunableTree<H>>,
    checkpoints_remove: &[BlockHeight],
    checkpoints_add: &[(BlockHeight, shardtree::store::Checkpoint)],
) -> Result<(), ShardTreeError<S::Error>>
where
    H: incrementalmerkletree::Hashable + Clone + PartialEq,
    S: ShardStore<H = H, CheckpointId = BlockHeight>,
{
    for shard in shards {
        tree.store_mut()
            .put_shard(shard.clone())
            .map_err(ShardTreeError::Storage)?;
    }
    if let Some(cap) = cap {
        tree.store_mut()
            .put_cap(cap.clone())
            .map_err(ShardTreeError::Storage)?;
    }
    for height in checkpoints_remove {
        tree.store_mut()
            .remove_checkpoint(height)
            .map_err(ShardTreeError::Storage)?;
    }
    for (height, checkpoint) in checkpoints_add {
        tree.store_mut()
            .add_checkpoint(*height, checkpoint.clone())
            .map_err(ShardTreeError::Storage)?;
    }
    Ok(())
}

/// This trait describes a capability for manipulating wallet note commitment trees.
#[cfg_attr(feature = "test-dependencies", delegatable_trait)]
pub trait WalletCommitmentTrees {
    type Error: Debug;

    /// The type of the backing [`ShardStore`] for the Sapling note commitment tree.
    type SaplingShardStore<'a>: ShardStore<H = sapling::Node, CheckpointId = BlockHeight, Error = Self::Error>;

    /// Evaluates the given callback function with a reference to the Sapling
    /// note commitment tree maintained by the wallet.
    fn with_sapling_tree_mut<F, A, E>(&mut self, callback: F) -> Result<A, E>
    where
        for<'a> F: FnMut(
            &'a mut ShardTree<
                Self::SaplingShardStore<'a>,
                { sapling::NOTE_COMMITMENT_TREE_DEPTH },
                SAPLING_SHARD_HEIGHT,
            >,
        ) -> Result<A, E>,
        E: From<ShardTreeError<Self::Error>>;

    /// Adds a sequence of Sapling note commitment tree subtree roots to the data store.
    ///
    /// Each such value should be the Merkle root of a subtree of the Sapling note commitment tree
    /// containing 2^[`SAPLING_SHARD_HEIGHT`] note commitments.
    fn put_sapling_subtree_roots(
        &mut self,
        start_index: u64,
        roots: &[CommitmentTreeRoot<sapling::Node>],
    ) -> Result<(), ShardTreeError<Self::Error>>;

    /// Returns the stored root hash of the completed Sapling subtree with the given index,
    /// or `Ok(None)` if no root is recorded for that subtree.
    ///
    /// This is the store's record of the subtree root as most recently provided via
    /// [`WalletCommitmentTrees::put_sapling_subtree_roots`] (i.e. the chain-authoritative
    /// root obtained from a chain data provider), or as recorded when a locally-completed
    /// subtree was persisted.
    fn get_sapling_subtree_root(
        &mut self,
        index: u64,
    ) -> Result<Option<sapling::Node>, ShardTreeError<Self::Error>>;

    /// The type of the backing [`ShardStore`] for the Orchard note commitment tree.
    #[cfg(feature = "orchard")]
    type OrchardShardStore<'a>: ShardStore<
            H = orchard::tree::MerkleHashOrchard,
            CheckpointId = BlockHeight,
            Error = Self::Error,
        >;

    /// Evaluates the given callback function with a reference to the Orchard
    /// note commitment tree maintained by the wallet.
    #[cfg(feature = "orchard")]
    fn with_orchard_tree_mut<F, A, E>(&mut self, callback: F) -> Result<A, E>
    where
        for<'a> F: FnMut(
            &'a mut ShardTree<
                Self::OrchardShardStore<'a>,
                { ORCHARD_SHARD_HEIGHT * 2 },
                ORCHARD_SHARD_HEIGHT,
            >,
        ) -> Result<A, E>,
        E: From<ShardTreeError<Self::Error>>;

    /// Adds a sequence of Orchard note commitment tree subtree roots to the data store.
    ///
    /// Each such value should be the Merkle root of a subtree of the Orchard note commitment tree
    /// containing 2^[`ORCHARD_SHARD_HEIGHT`] note commitments.
    #[cfg(feature = "orchard")]
    fn put_orchard_subtree_roots(
        &mut self,
        start_index: u64,
        roots: &[CommitmentTreeRoot<orchard::tree::MerkleHashOrchard>],
    ) -> Result<(), ShardTreeError<Self::Error>>;

    /// Returns the stored root hash of the completed Orchard subtree with the given index,
    /// or `Ok(None)` if no root is recorded for that subtree.
    ///
    /// This is the store's record of the subtree root as most recently provided via
    /// [`WalletCommitmentTrees::put_orchard_subtree_roots`] (i.e. the chain-authoritative
    /// root obtained from a chain data provider), or as recorded when a locally-completed
    /// subtree was persisted.
    #[cfg(feature = "orchard")]
    fn get_orchard_subtree_root(
        &mut self,
        index: u64,
    ) -> Result<Option<orchard::tree::MerkleHashOrchard>, ShardTreeError<Self::Error>>;

    /// Evaluates the given callback with the Ironwood note commitment tree
    /// maintained by the wallet, if this backend has one.
    ///
    /// The default implementation reports that no Ironwood tree is available.
    /// Backends that track Ironwood note commitments should override this and
    /// provide their separate Ironwood tree.
    #[cfg(feature = "orchard")]
    fn with_ironwood_tree_mut<F, A, E>(&mut self, _callback: F) -> Result<Option<A>, E>
    where
        for<'a> F: FnMut(
            &'a mut ShardTree<
                Self::OrchardShardStore<'a>,
                { ORCHARD_SHARD_HEIGHT * 2 },
                ORCHARD_SHARD_HEIGHT,
            >,
        ) -> Result<A, E>,
        E: From<ShardTreeError<Self::Error>>,
    {
        Ok(None)
    }

    /// Adds a sequence of Ironwood note commitment tree subtree roots to the data store, if this
    /// backend tracks an Ironwood tree.
    ///
    /// Each such value should be the Merkle root of a subtree of the Ironwood note commitment tree
    /// containing 2^[`ORCHARD_SHARD_HEIGHT`] note commitments; Ironwood shares the Orchard note
    /// commitment tree's shape, so the same shard height applies.
    ///
    /// The default implementation is a no-op, for backends that do not track an Ironwood tree
    /// (mirroring [`WalletCommitmentTrees::with_ironwood_tree_mut`]). Backends that track Ironwood
    /// note commitments should override this.
    #[cfg(feature = "orchard")]
    fn put_ironwood_subtree_roots(
        &mut self,
        _start_index: u64,
        _roots: &[CommitmentTreeRoot<orchard::tree::MerkleHashOrchard>],
    ) -> Result<(), ShardTreeError<Self::Error>> {
        Ok(())
    }

    /// Returns the stored root hash of the completed Ironwood subtree with the given
    /// index, or `Ok(None)` if no root is recorded for that subtree (in particular, if
    /// this backend does not track an Ironwood tree — the default implementation).
    #[cfg(feature = "orchard")]
    fn get_ironwood_subtree_root(
        &mut self,
        _index: u64,
    ) -> Result<Option<orchard::tree::MerkleHashOrchard>, ShardTreeError<Self::Error>> {
        Ok(None)
    }

    /// Applies a batch of changes — shards, an optional replacement tree cap, and a
    /// checkpoint delta — to the wallet's Sapling note commitment tree.
    ///
    /// `shards` must be in ascending shard-index order; stores may reject sequences that
    /// would leave gaps in the tree. Checkpoint removals are applied before additions, so
    /// that a checkpoint whose data has changed may appear in both lists.
    ///
    /// This is intended for wallet stores that accumulate note commitment tree updates
    /// outside the backing store (for example, in an in-memory tree) and flush them in
    /// batches. The default implementation applies the changes through
    /// [`WalletCommitmentTrees::with_sapling_tree_mut`].
    fn put_sapling_shards(
        &mut self,
        shards: &[shardtree::LocatedPrunableTree<sapling::Node>],
        cap: Option<&shardtree::PrunableTree<sapling::Node>>,
        checkpoints_remove: &[BlockHeight],
        checkpoints_add: &[(BlockHeight, shardtree::store::Checkpoint)],
    ) -> Result<(), ShardTreeError<Self::Error>> {
        self.with_sapling_tree_mut(|tree| {
            apply_tree_changes(tree, shards, cap, checkpoints_remove, checkpoints_add)
        })
    }

    /// Applies a batch of changes — shards, an optional replacement tree cap, and a
    /// checkpoint delta — to the wallet's Orchard note commitment tree.
    ///
    /// `shards` must be in ascending shard-index order; stores may reject sequences that
    /// would leave gaps in the tree. Checkpoint removals are applied before additions, so
    /// that a checkpoint whose data has changed may appear in both lists.
    ///
    /// This is intended for wallet stores that accumulate note commitment tree updates
    /// outside the backing store (for example, in an in-memory tree) and flush them in
    /// batches. The default implementation applies the changes through
    /// [`WalletCommitmentTrees::with_orchard_tree_mut`].
    #[cfg(feature = "orchard")]
    fn put_orchard_shards(
        &mut self,
        shards: &[shardtree::LocatedPrunableTree<orchard::tree::MerkleHashOrchard>],
        cap: Option<&shardtree::PrunableTree<orchard::tree::MerkleHashOrchard>>,
        checkpoints_remove: &[BlockHeight],
        checkpoints_add: &[(BlockHeight, shardtree::store::Checkpoint)],
    ) -> Result<(), ShardTreeError<Self::Error>> {
        self.with_orchard_tree_mut(|tree| {
            apply_tree_changes(tree, shards, cap, checkpoints_remove, checkpoints_add)
        })
    }

    /// Applies a batch of changes — shards, an optional replacement tree cap, and a
    /// checkpoint delta — to the wallet's Ironwood note commitment tree, if this backend
    /// tracks one.
    ///
    /// `shards` must be in ascending shard-index order; stores may reject sequences that
    /// would leave gaps in the tree. Checkpoint removals are applied before additions, so
    /// that a checkpoint whose data has changed may appear in both lists.
    ///
    /// The default implementation applies the changes through
    /// [`WalletCommitmentTrees::with_ironwood_tree_mut`]; for backends that do not track an
    /// Ironwood tree (see that method's documentation), the changes are ignored.
    #[cfg(feature = "orchard")]
    fn put_ironwood_shards(
        &mut self,
        shards: &[shardtree::LocatedPrunableTree<orchard::tree::MerkleHashOrchard>],
        cap: Option<&shardtree::PrunableTree<orchard::tree::MerkleHashOrchard>>,
        checkpoints_remove: &[BlockHeight],
        checkpoints_add: &[(BlockHeight, shardtree::store::Checkpoint)],
    ) -> Result<(), ShardTreeError<Self::Error>> {
        self.with_ironwood_tree_mut(|tree| {
            apply_tree_changes(tree, shards, cap, checkpoints_remove, checkpoints_add)
        })?;
        Ok(())
    }

    /// Releases all retained ("anchor") checkpoints with height strictly less than `max_height`
    /// from the wallet's note commitment trees, allowing them to be pruned normally.
    ///
    /// Anchor checkpoints are established during scanning (and may be created directly via
    /// [`ShardTree::ensure_retained`]); they are otherwise exempt from automatic pruning of excess
    /// checkpoints. This releases the retention of those that have aged below `max_height` in the
    /// Sapling and (when the `orchard` feature is enabled) the Orchard and Ironwood trees.
    fn remove_retained_checkpoints_below(
        &mut self,
        max_height: BlockHeight,
    ) -> Result<(), ShardTreeError<Self::Error>> {
        self.with_sapling_tree_mut(|tree| {
            for height in tree
                .store()
                .retained_checkpoints()
                .map_err(ShardTreeError::Storage)?
            {
                if height < max_height {
                    tree.remove_retained_checkpoint(&height)?;
                }
            }
            Ok::<_, ShardTreeError<Self::Error>>(())
        })?;

        #[cfg(feature = "orchard")]
        self.with_orchard_tree_mut(|tree| {
            for height in tree
                .store()
                .retained_checkpoints()
                .map_err(ShardTreeError::Storage)?
            {
                if height < max_height {
                    tree.remove_retained_checkpoint(&height)?;
                }
            }
            Ok::<_, ShardTreeError<Self::Error>>(())
        })?;

        // A backend that does not track an Ironwood tree returns `None` here and is left unchanged.
        #[cfg(feature = "orchard")]
        self.with_ironwood_tree_mut(|tree| {
            for height in tree
                .store()
                .retained_checkpoints()
                .map_err(ShardTreeError::Storage)?
            {
                if height < max_height {
                    tree.remove_retained_checkpoint(&height)?;
                }
            }
            Ok::<_, ShardTreeError<Self::Error>>(())
        })?;

        Ok(())
    }
}

/// Property tests for the [`Balance`] bucket arithmetic.
///
/// These pin the accounting semantics the locked-value bucket joined: every bucket except
/// `uneconomic_value` participates in [`Balance::total`] and in the shared overflow guard,
/// while `uneconomic_value` is guarded only against its own overflow and never contributes
/// to the total.
#[cfg(test)]
mod balance_tests {
    use proptest::prelude::*;
    use zcash_protocol::value::{BalanceError, MAX_MONEY, Zatoshis};

    use super::Balance;

    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
    enum Bucket {
        Spendable = 0,
        Locked = 1,
        PendingChange = 2,
        PendingSpendable = 3,
        Uneconomic = 4,
    }
    use Bucket::*;

    const ALL_BUCKETS: [Bucket; 5] = [
        Spendable,
        Locked,
        PendingChange,
        PendingSpendable,
        Uneconomic,
    ];
    /// The buckets that participate in `Balance::total` and its overflow guard.
    const TOTAL_BUCKETS: [Bucket; 4] = [Spendable, Locked, PendingChange, PendingSpendable];

    fn apply(balance: &mut Balance, bucket: Bucket, value: Zatoshis) -> Result<(), BalanceError> {
        match bucket {
            Spendable => balance.add_spendable_value(value),
            Locked => balance.add_locked_value(value),
            PendingChange => balance.add_pending_change_value(value),
            PendingSpendable => balance.add_pending_spendable_value(value),
            Uneconomic => balance.add_uneconomic_value(value),
        }
    }

    fn get(balance: &Balance, bucket: Bucket) -> Zatoshis {
        match bucket {
            Spendable => balance.spendable_value(),
            Locked => balance.locked_value(),
            PendingChange => balance.change_pending_confirmation(),
            PendingSpendable => balance.value_pending_spendability(),
            Uneconomic => balance.uneconomic_value(),
        }
    }

    fn arb_bucket() -> impl Strategy<Value = Bucket> {
        prop_oneof![
            Just(Spendable),
            Just(Locked),
            Just(PendingChange),
            Just(PendingSpendable),
            Just(Uneconomic),
        ]
    }

    /// A bucket and a value to add to it. Values are mostly small (so most sequences stay
    /// within `MAX_MONEY`) with occasional near-cap draws to exercise the overflow guards.
    fn arb_add() -> impl Strategy<Value = (Bucket, u64)> {
        (
            arb_bucket(),
            prop_oneof![
                3 => 0u64..=1_000_000,
                1 => 0u64..=MAX_MONEY,
            ],
        )
    }

    proptest! {
        /// Bucket adds succeed exactly while their overflow guard permits, mutate only the
        /// requested bucket, and leave the balance untouched on failure. `total()` is always
        /// the sum of the four participating buckets. (In particular this establishes that
        /// the `unwrap` inside each guarded add is unreachable.)
        #[test]
        fn add_total_consistency(adds in proptest::collection::vec(arb_add(), 0..12)) {
            let mut balance = Balance::ZERO;
            // The model: per-bucket totals, indexed by bucket discriminant.
            let mut model = [0u64; 5];

            for (bucket, v) in adds {
                let value = Zatoshis::from_u64(v).unwrap();
                let before = balance;
                let result = apply(&mut balance, bucket, value);

                let total: u64 = TOTAL_BUCKETS.iter().map(|b| model[*b as usize]).sum();
                let expect_ok = match bucket {
                    Uneconomic => model[Uneconomic as usize] + v <= MAX_MONEY,
                    _ => total + v <= MAX_MONEY,
                };
                if expect_ok {
                    prop_assert!(result.is_ok());
                    model[bucket as usize] += v;
                } else {
                    prop_assert!(result.is_err());
                    prop_assert_eq!(
                        balance, before,
                        "a failed add must leave the balance unchanged"
                    );
                }

                let total: u64 = TOTAL_BUCKETS.iter().map(|b| model[*b as usize]).sum();
                prop_assert_eq!(balance.total(), Zatoshis::from_u64(total).unwrap());
                for b in ALL_BUCKETS {
                    prop_assert_eq!(
                        get(&balance, b),
                        Zatoshis::from_u64(model[b as usize]).unwrap()
                    );
                }
            }
        }

        /// `Balance + Balance` is componentwise addition: it succeeds exactly when the
        /// combined total and the combined uneconomic value each remain within `MAX_MONEY`,
        /// and on success every bucket of the sum is the sum of the corresponding buckets.
        #[test]
        fn balance_addition_is_componentwise(
            a in proptest::collection::vec(arb_add(), 0..6),
            b in proptest::collection::vec(arb_add(), 0..6),
        ) {
            let build = |adds: &[(Bucket, u64)]| {
                let mut balance = Balance::ZERO;
                for (bucket, v) in adds {
                    let _ = apply(&mut balance, *bucket, Zatoshis::from_u64(*v).unwrap());
                }
                balance
            };
            let ba = build(&a);
            let bb = build(&b);

            let combined_total = u64::from(ba.total()) + u64::from(bb.total());
            let combined_uneconomic =
                u64::from(ba.uneconomic_value()) + u64::from(bb.uneconomic_value());
            match ba + bb {
                Ok(sum) => {
                    prop_assert!(combined_total <= MAX_MONEY);
                    prop_assert!(combined_uneconomic <= MAX_MONEY);
                    for bucket in ALL_BUCKETS {
                        prop_assert_eq!(
                            u64::from(get(&sum, bucket)),
                            u64::from(get(&ba, bucket)) + u64::from(get(&bb, bucket))
                        );
                    }
                    prop_assert_eq!(u64::from(sum.total()), combined_total);
                }
                Err(_) => {
                    prop_assert!(
                        combined_total > MAX_MONEY || combined_uneconomic > MAX_MONEY,
                        "balance addition failed although no component overflows"
                    );
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use incrementalmerkletree::{
        Address as TreeAddress, Hashable, Level, Marking, Position, Retention,
    };
    use shardtree::store::{Checkpoint, memory::MemoryShardStore};
    use zcash_keys::{
        address::{Address, UnifiedAddress},
        keys::UnifiedAddressRequest,
    };

    use super::*;

    #[cfg(feature = "orchard")]
    use crate::data_api::error::FindAccountForAddressError;
    use crate::data_api::testing::{
        MockWalletDb, pool::ShieldedPoolTester, sapling::SaplingPoolTester,
    };

    use transparent::address::TransparentAddress;
    use zip32::DiversifierIndex;

    #[test]
    fn put_sapling_shards_flushes_through_the_interface() {
        let mut db = MockWalletDb::new(zcash_protocol::consensus::Network::TestNetwork);

        // Build a shard-rooted subtree the same way `put_blocks` does, with a checkpoint on
        // the final leaf.
        let leaf = <sapling::Node as Hashable>::empty_leaf();
        let checkpoint_height = BlockHeight::from(3);
        let commitments = (0u64..4).map(|i| {
            (
                leaf,
                if i == 3 {
                    Retention::Checkpoint {
                        id: checkpoint_height,
                        marking: Marking::None,
                    }
                } else {
                    Retention::Ephemeral
                },
            )
        });
        let built = shardtree::LocatedTree::from_iter(
            Position::from(0)..Position::from(4),
            Level::from(SAPLING_SHARD_HEIGHT),
            commitments,
        )
        .expect("commitments produce a subtree");
        let checkpoints_add = built
            .checkpoints
            .iter()
            .map(|(height, position)| (*height, Checkpoint::at_position(*position)))
            .collect::<Vec<_>>();

        db.put_sapling_shards(&[built.subtree], None, &[], &checkpoints_add)
            .expect("bulk flush succeeds");

        // The shard and checkpoint are visible through the standard tree access path.
        db.with_sapling_tree_mut(|tree| {
            assert!(
                tree.store()
                    .get_shard(TreeAddress::from_parts(
                        Level::from(SAPLING_SHARD_HEIGHT),
                        0
                    ))
                    .map_err(ShardTreeError::Storage)?
                    .is_some()
            );
            assert_eq!(
                tree.store()
                    .max_checkpoint_id()
                    .map_err(ShardTreeError::Storage)?,
                Some(checkpoint_height)
            );
            Ok::<_, ShardTreeError<_>>(())
        })
        .expect("tree reads succeed");

        // Removals are applied before additions, so a checkpoint set can be replaced in a
        // single call.
        let new_height = BlockHeight::from(7);
        db.put_sapling_shards(
            &[],
            None,
            &[checkpoint_height],
            &[(new_height, Checkpoint::tree_empty())],
        )
        .expect("checkpoint replacement succeeds");

        db.with_sapling_tree_mut(|tree| {
            assert_eq!(
                tree.store()
                    .max_checkpoint_id()
                    .map_err(ShardTreeError::Storage)?,
                Some(new_height)
            );
            assert_eq!(
                tree.store()
                    .checkpoint_count()
                    .map_err(ShardTreeError::Storage)?,
                1
            );
            Ok::<_, ShardTreeError<_>>(())
        })
        .expect("tree reads succeed");
    }

    /// Exercises [`apply_tree_changes`] — the shared implementation of the `put_*_shards`
    /// provided methods — directly over a [`MemoryShardStore`] of the given node type.
    ///
    /// [`MemoryShardStore`]: shardtree::store::memory::MemoryShardStore
    fn check_apply_tree_changes<H>()
    where
        H: incrementalmerkletree::Hashable + Clone + PartialEq + core::fmt::Debug,
    {
        let mut tree: ShardTree<
            MemoryShardStore<H, BlockHeight>,
            { SAPLING_SHARD_HEIGHT * 2 },
            SAPLING_SHARD_HEIGHT,
        > = ShardTree::new(MemoryShardStore::empty(), 100);

        // Build a shard-rooted subtree the same way `put_blocks` does, with a checkpoint on
        // the final leaf.
        let leaf = H::empty_leaf();
        let checkpoint_height = BlockHeight::from(3);
        let commitments = (0u64..4).map(|i| {
            (
                leaf.clone(),
                if i == 3 {
                    Retention::Checkpoint {
                        id: checkpoint_height,
                        marking: Marking::None,
                    }
                } else {
                    Retention::Ephemeral
                },
            )
        });
        let built = shardtree::LocatedTree::from_iter(
            Position::from(0)..Position::from(4),
            Level::from(SAPLING_SHARD_HEIGHT),
            commitments,
        )
        .expect("commitments produce a subtree");
        let checkpoints_add = built
            .checkpoints
            .iter()
            .map(|(height, position)| (*height, Checkpoint::at_position(*position)))
            .collect::<Vec<_>>();

        apply_tree_changes(&mut tree, &[built.subtree], None, &[], &checkpoints_add)
            .expect("bulk flush succeeds");

        assert!(
            tree.store()
                .get_shard(TreeAddress::from_parts(
                    Level::from(SAPLING_SHARD_HEIGHT),
                    0
                ))
                .expect("shard read succeeds")
                .is_some()
        );
        assert_eq!(
            tree.store()
                .max_checkpoint_id()
                .expect("checkpoint read succeeds"),
            Some(checkpoint_height)
        );

        // Removals are applied before additions, so a checkpoint set can be replaced in a
        // single call.
        let new_height = BlockHeight::from(7);
        apply_tree_changes(
            &mut tree,
            &[],
            None,
            &[checkpoint_height],
            &[(new_height, Checkpoint::tree_empty())],
        )
        .expect("checkpoint replacement succeeds");

        assert_eq!(
            tree.store()
                .max_checkpoint_id()
                .expect("checkpoint read succeeds"),
            Some(new_height)
        );
        assert_eq!(
            tree.store()
                .checkpoint_count()
                .expect("checkpoint read succeeds"),
            1
        );
    }

    #[test]
    fn apply_tree_changes_supports_every_pool_node_type() {
        check_apply_tree_changes::<sapling::Node>();
        // Orchard and Ironwood both use `MerkleHashOrchard` trees of the same shape.
        #[cfg(feature = "orchard")]
        check_apply_tree_changes::<orchard::tree::MerkleHashOrchard>();
    }

    #[cfg(feature = "orchard")]
    #[test]
    fn put_ironwood_shards_is_ignored_without_an_ironwood_tree() {
        // `MockWalletDb` does not track an Ironwood tree, so the default
        // `with_ironwood_tree_mut` reports no tree and the changes are ignored rather than
        // returning an error.
        let mut db = MockWalletDb::new(zcash_protocol::consensus::Network::TestNetwork);
        db.put_ironwood_shards(
            &[],
            None,
            &[],
            &[(BlockHeight::from(1), Checkpoint::tree_empty())],
        )
        .expect("ignored on backends without an Ironwood tree");
    }

    #[test]
    fn account_meta_totals_include_ironwood() {
        let meta = AccountMeta::new(
            Some(PoolMeta::new(2, Zatoshis::const_from_u64(200))),
            Some(PoolMeta::new(3, Zatoshis::const_from_u64(300))),
            Some(PoolMeta::new(5, Zatoshis::const_from_u64(500))),
        );
        assert_eq!(meta.note_count(ShieldedPool::Ironwood), Some(5));
        assert_eq!(meta.total_note_count(), Some(10));
        assert_eq!(meta.total_value(), Some(Zatoshis::const_from_u64(1000)));

        // With metadata for only the Ironwood pool, the totals reflect that pool alone.
        let ironwood_only = AccountMeta::new(
            None,
            None,
            Some(PoolMeta::new(4, Zatoshis::const_from_u64(400))),
        );
        assert_eq!(ironwood_only.note_count(ShieldedPool::Ironwood), Some(4));
        assert_eq!(ironwood_only.total_note_count(), Some(4));
        assert_eq!(
            ironwood_only.total_value(),
            Some(Zatoshis::const_from_u64(400))
        );
    }

    fn derived_source() -> AddressSource {
        AddressSource::Derived {
            diversifier_index: DiversifierIndex::default(),
            #[cfg(feature = "transparent-inputs")]
            transparent_key_scope: None,
        }
    }

    fn address_info_of(address: Address) -> AddressInfo {
        AddressInfo::from_parts(address, derived_source())
            .expect("test address metadata must be valid")
    }

    fn transparent_address_for_tag(tag: u8) -> TransparentAddress {
        TransparentAddress::PublicKeyHash([tag; 20])
    }

    fn sapling_address_for_tag(tag: u8) -> sapling::PaymentAddress {
        match SaplingPoolTester::sk_default_address(&SaplingPoolTester::sk(&[tag; 32])) {
            Address::Sapling(pa) => pa,
            other => panic!("expected Sapling address, got {other:?}"),
        }
    }

    fn unified_account_with(
        transparent: Option<TransparentAddress>,
        sapling: Option<sapling::PaymentAddress>,
        #[cfg(feature = "orchard")] orchard: Option<orchard::Address>,
    ) -> Address {
        UnifiedAddress::from_receivers(
            #[cfg(feature = "orchard")]
            Some(orchard).flatten(),
            Some(sapling).flatten(),
            transparent,
        )
        .expect("test UA must be valid")
        .into()
    }

    #[test]
    fn find_account_for_transparent_address_returns_matching_account() {
        let wallet = MockWalletDb::from_account_addresses(
            zcash_protocol::consensus::Network::MainNetwork,
            [
                (
                    1,
                    vec![address_info_of(Address::Transparent(
                        transparent_address_for_tag(1),
                    ))],
                ),
                (
                    2,
                    vec![address_info_of(Address::Transparent(
                        transparent_address_for_tag(2),
                    ))],
                ),
            ],
        );
        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &Address::Transparent(transparent_address_for_tag(1)),
        );
        assert_eq!(result.unwrap(), Some(1));
    }

    #[test]
    fn find_account_for_transparent_receiver_in_unified_address_returns_matching_account() {
        let transparent = transparent_address_for_tag(1);
        let sapling_address = sapling_address_for_tag(11);

        #[cfg(feature = "orchard")]
        {
            let wallet = MockWalletDb::from_account_addresses(
                zcash_protocol::consensus::Network::MainNetwork,
                [(
                    1,
                    vec![address_info_of(unified_account_with(
                        Some(transparent),
                        Some(sapling_address),
                        None,
                    ))],
                )],
            );
            let result = wallet.find_account_for_address(
                &zcash_protocol::consensus::Network::MainNetwork,
                &Address::Transparent(transparent),
            );
            assert_eq!(result.unwrap(), Some(1));
        }
        #[cfg(not(feature = "orchard"))]
        {
            let wallet = MockWalletDb::from_account_addresses(
                zcash_protocol::consensus::Network::MainNetwork,
                [(
                    1,
                    vec![address_info_of(unified_account_with(
                        Some(transparent),
                        Some(sapling_address),
                    ))],
                )],
            );
            let result = wallet.find_account_for_address(
                &zcash_protocol::consensus::Network::MainNetwork,
                &Address::Transparent(transparent),
            );
            assert_eq!(result.unwrap(), Some(1));
        }
    }

    #[test]
    fn find_account_for_address_returns_none_when_simple_address_is_unknown() {
        let address = Address::Transparent(transparent_address_for_tag(1));
        let wallet = MockWalletDb::from_account_addresses(
            zcash_protocol::consensus::Network::MainNetwork,
            [(1, vec![address_info_of(address)])],
        );

        let other_address = Address::Transparent(transparent_address_for_tag(9));
        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &other_address,
        );

        assert_eq!(result.unwrap(), None);
    }

    fn test_ufvk(seed_tag: u8) -> zcash_keys::keys::UnifiedFullViewingKey {
        zcash_keys::keys::UnifiedSpendingKey::from_seed(
            &zcash_protocol::consensus::Network::MainNetwork,
            &[seed_tag; 32],
            zip32::AccountId::ZERO,
        )
        .expect("valid seed")
        .to_unified_full_viewing_key()
    }

    #[test]
    fn find_account_for_unified_address_returns_account_when_receivers_map_to_same_account() {
        let ufvk = test_ufvk(1);
        let wallet = MockWalletDb::from_account_ufvks(
            zcash_protocol::consensus::Network::MainNetwork,
            [(1, ufvk.clone())],
        );

        let (ua, _) = ufvk
            .default_address(UnifiedAddressRequest::AllAvailableKeys)
            .expect("default address must be derivable");

        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &Address::Unified(ua),
        );

        assert_eq!(result.unwrap(), Some(1));
    }

    #[test]
    fn find_account_for_unified_address_returns_none_when_no_receiver_matches() {
        let wallet = MockWalletDb::from_account_ufvks(
            zcash_protocol::consensus::Network::MainNetwork,
            [(1, test_ufvk(1))],
        );

        // A UA derived from a different seed — no account in the wallet owns any of its
        // shielded receivers.
        let (ua_from_other_seed, _) = test_ufvk(99)
            .default_address(UnifiedAddressRequest::AllAvailableKeys)
            .expect("default address must be derivable");

        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &Address::Unified(ua_from_other_seed),
        );

        assert_eq!(result.unwrap(), None);
    }

    #[test]
    fn find_account_for_sapling_address_resolves_via_uivk_algebra_when_not_previously_exposed() {
        // A bare Sapling address derivable from an account's UIVK must resolve even when the
        // wallet has never stored (and therefore never "exposed") that address.
        let ufvk = test_ufvk(1);
        let wallet = MockWalletDb::from_account_ufvks(
            zcash_protocol::consensus::Network::MainNetwork,
            [(1, ufvk.clone())],
        );

        let (ua, _) = ufvk
            .default_address(UnifiedAddressRequest::AllAvailableKeys)
            .expect("default address must be derivable");
        let sapling_pa = *ua.sapling().expect("sapling receiver");

        // `wallet` has no stored addresses: only the account's UFVK. The list_addresses scan
        // would therefore miss this address; only the synthesized-UA algebraic path can
        // resolve it.
        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &Address::Sapling(sapling_pa),
        );

        assert_eq!(result.unwrap(), Some(1));
    }

    #[test]
    fn find_account_for_address_returns_none_for_empty_wallet() {
        let wallet = MockWalletDb::from_account_addresses(
            zcash_protocol::consensus::Network::MainNetwork,
            std::iter::empty(),
        );

        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &Address::Transparent(transparent_address_for_tag(1)),
        );
        assert_eq!(result.unwrap(), None);

        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &Address::Sapling(sapling_address_for_tag(1)),
        );
        assert_eq!(result.unwrap(), None);
    }

    #[cfg(feature = "orchard")]
    #[test]
    fn find_account_for_unified_address_errors_when_receivers_map_to_different_accounts() {
        let ufvk1 = test_ufvk(1);
        let ufvk2 = test_ufvk(2);
        let wallet = MockWalletDb::from_account_ufvks(
            zcash_protocol::consensus::Network::MainNetwork,
            [(1, ufvk1.clone()), (2, ufvk2.clone())],
        );

        let (ua1, _) = ufvk1
            .default_address(UnifiedAddressRequest::AllAvailableKeys)
            .expect("default address must be derivable");
        let (ua2, _) = ufvk2
            .default_address(UnifiedAddressRequest::AllAvailableKeys)
            .expect("default address must be derivable");

        // A frankenstein UA whose Sapling receiver is from account 1 and whose Orchard
        // receiver is from account 2.
        let frankenstein = UnifiedAddress::from_receivers(
            Some(ua2.orchard().copied().expect("orchard receiver")),
            Some(ua1.sapling().copied().expect("sapling receiver")),
            None,
        )
        .expect("sapling+orchard UA must be valid");

        let result = wallet.find_account_for_address(
            &zcash_protocol::consensus::Network::MainNetwork,
            &Address::Unified(frankenstein),
        );

        assert!(matches!(
            result,
            Err(FindAccountForAddressError::UnifiedAddressConflict)
        ));
    }

    /// Each unshielded mutator updates only its own bucket, and transparent mutations leave the
    /// shielded aggregates untouched.
    #[test]
    fn account_balance_unshielded_split_mutators() {
        let mut balance = AccountBalance::ZERO;

        let regular_value = Zatoshis::const_from_u64(100_000);
        let coinbase_value = Zatoshis::const_from_u64(50_000);

        balance
            .with_unshielded_regular_balance_mut(|bal| bal.add_spendable_value(regular_value))
            .unwrap();
        balance
            .with_unshielded_coinbase_balance_mut(|bal| {
                bal.add_pending_spendable_value(coinbase_value)
            })
            .unwrap();

        // The regular bucket contains only the regular value.
        assert_eq!(
            balance.unshielded_regular_balance().spendable_value(),
            regular_value
        );
        assert_eq!(balance.unshielded_regular_balance().total(), regular_value);
        assert_eq!(
            balance
                .unshielded_regular_balance()
                .value_pending_spendability(),
            Zatoshis::ZERO
        );

        // The coinbase bucket contains only the coinbase value, as pending.
        assert_eq!(
            balance.unshielded_coinbase_balance().spendable_value(),
            Zatoshis::ZERO
        );
        assert_eq!(
            balance
                .unshielded_coinbase_balance()
                .value_pending_spendability(),
            coinbase_value
        );
        assert_eq!(
            balance.unshielded_coinbase_balance().total(),
            coinbase_value
        );

        // The shielded-only aggregates are unaffected by transparent mutations.
        assert_eq!(balance.spendable_value(), Zatoshis::ZERO);
        assert_eq!(balance.change_pending_confirmation(), Zatoshis::ZERO);
        assert_eq!(balance.value_pending_spendability(), Zatoshis::ZERO);
        assert_eq!(balance.sapling_balance(), &Balance::ZERO);
        assert_eq!(balance.orchard_balance(), &Balance::ZERO);
        assert_eq!(balance.ironwood_balance(), &Balance::ZERO);
    }

    /// `unshielded_balance` returns the sum of the regular and coinbase buckets, and the
    /// account-level aggregates include both buckets.
    #[test]
    fn account_balance_unshielded_balance_is_sum() {
        let mut balance = AccountBalance::ZERO;

        let regular_spendable = Zatoshis::const_from_u64(100_000);
        let regular_dust = Zatoshis::const_from_u64(100);
        let coinbase_pending = Zatoshis::const_from_u64(625_000_000);
        let coinbase_dust = Zatoshis::const_from_u64(42);

        balance
            .with_unshielded_regular_balance_mut(|bal| {
                bal.add_spendable_value(regular_spendable)?;
                bal.add_uneconomic_value(regular_dust)
            })
            .unwrap();
        balance
            .with_unshielded_coinbase_balance_mut(|bal| {
                bal.add_pending_spendable_value(coinbase_pending)?;
                bal.add_uneconomic_value(coinbase_dust)
            })
            .unwrap();

        // The by-value combined balance is the field-wise sum of both buckets.
        let combined = balance.unshielded_balance();
        assert_eq!(
            combined,
            (*balance.unshielded_regular_balance() + *balance.unshielded_coinbase_balance())
                .unwrap()
        );
        assert_eq!(combined.spendable_value(), regular_spendable);
        assert_eq!(combined.value_pending_spendability(), coinbase_pending);
        assert_eq!(
            combined.uneconomic_value(),
            (regular_dust + coinbase_dust).unwrap()
        );

        // The deprecated accessor reports the sum of both buckets' totals.
        #[allow(deprecated)]
        let unshielded = balance.unshielded();
        assert_eq!(
            unshielded,
            (balance.unshielded_regular_balance().total()
                + balance.unshielded_coinbase_balance().total())
            .unwrap()
        );

        // The account total and uneconomic value include both buckets. (`Balance::total`
        // excludes uneconomic value, so the dust does not appear in the account total.)
        assert_eq!(
            balance.total(),
            (regular_spendable + coinbase_pending).unwrap()
        );
        assert_eq!(
            balance.uneconomic_value(),
            (regular_dust + coinbase_dust).unwrap()
        );
    }

    /// The `check_total` invariant rejects mutations that would cause the sum of the regular and
    /// coinbase transparent buckets to exceed `MAX_MONEY`.
    #[test]
    fn account_balance_unshielded_overflow_rejected() {
        let max_money = Zatoshis::const_from_u64(zcash_protocol::value::MAX_MONEY);
        let mut balance = AccountBalance::ZERO;

        // Fill the regular bucket up to MAX_MONEY; this is fine on its own.
        balance
            .with_unshielded_regular_balance_mut(|bal| bal.add_spendable_value(max_money))
            .unwrap();
        assert_eq!(balance.total(), max_money);

        // Any further value in the coinbase bucket must be rejected by the account-level
        // invariant check, even though the coinbase bucket does not overflow on its own.
        let result: Result<(), BalanceError> =
            balance.with_unshielded_coinbase_balance_mut(|bal| {
                bal.add_pending_spendable_value(Zatoshis::const_from_u64(1))
            });
        assert!(matches!(result, Err(BalanceError::Overflow)));
    }
}