zakura-client-backend 0.1.0-rc2

use std::{
    collections::{BTreeMap, HashSet},
    convert::Infallible,
};

use assert_matches::assert_matches;

use sapling::zip32::ExtendedSpendingKey;
use transparent::{
    address::{Script, TransparentAddress},
    bundle::{Authorized, Bundle, OutPoint, TxIn, TxOut},
    keys::{NonHardenedChildIndex, TransparentKeyScope},
};
use zcash_keys::{
    address::Address,
    keys::{UnifiedAddressRequest, transparent::gap_limits::GapLimits},
};
use zcash_primitives::{
    block::BlockHash,
    transaction::{Transaction, TransactionData, TxVersion, fees::zip317},
};
use zcash_protocol::{
    consensus::{BlockHeight, BranchId, COINBASE_MATURITY_BLOCKS},
    local_consensus::LocalNetwork,
    value::Zatoshis,
};
use zip321::{Payment, TransactionRequest};

#[cfg(feature = "transparent-key-import")]
use {
    crate::{
        data_api::{
            AccountBirthday,
            chain::ChainState,
            wallet::{self, SpendingKeys},
        },
        wallet::TransparentAddressSource,
    },
    secp256k1::{Secp256k1, SecretKey},
    secrecy::Secret,
    std::collections::HashMap,
    zcash_protocol::consensus::{NetworkUpgrade, Parameters},
    zcash_script::{descriptor::sh, pattern::check_multisig, script},
};

use super::TestAccount;
use crate::{
    data_api::{
        Account as _, AccountBalance, Balance, CoinbaseFilter, InputSource as _, MaxSpendMode,
        TargetValue, WalletRead as _, WalletTest as _, WalletWrite,
        testing::{
            AddressType, DataStoreFactory, ShieldedPool, TestBuilder, TestCache, TestState,
            single_output_change_strategy,
        },
        wallet::{
            ConfirmationsPolicy, TargetHeight, decrypt_and_store_transaction,
            input_selection::{
                GreedyInputSelector, LockFilter, LockedInputPolicy, NoteSelection, SpendPolicy,
                TransparentSpendPolicy,
            },
        },
    },
    fees::{ChangeValue, StandardFeeRule, TransparentChangePolicy},
    wallet::{Exposure, OvkPolicy, WalletTransparentOutput},
};

pub use super::pool::locking::transparent_note_locking;

/// Checks whether the transparent balance of the given test `account` is as `expected`
/// considering the `confirmations_policy`.
fn check_balance<DSF>(
    st: &TestState<impl TestCache, <DSF as DataStoreFactory>::DataStore, LocalNetwork>,
    account: &TestAccount<<DSF as DataStoreFactory>::Account>,
    taddr: &TransparentAddress,
    confirmations_policy: ConfirmationsPolicy,
    expected: &Balance,
) where
    DSF: DataStoreFactory,
{
    // Check the wallet summary returns the expected transparent balance.
    let summary = st
        .wallet()
        .get_wallet_summary(confirmations_policy)
        .unwrap()
        .unwrap();
    let balance = summary.account_balances().get(&account.id()).unwrap();

    #[allow(deprecated)]
    let old_unshielded_value = balance.unshielded();
    assert_eq!(old_unshielded_value, expected.total());
    assert_eq!(balance.unshielded_regular_balance(), expected);
    assert_eq!(balance.unshielded_coinbase_balance(), &Balance::ZERO);
    assert_eq!(balance.unshielded_balance(), *expected);

    // Check the older APIs for consistency.
    let target_height = TargetHeight::from(st.wallet().chain_height().unwrap().unwrap() + 1);
    assert_eq!(
        st.wallet()
            .get_transparent_balances(account.id(), target_height, confirmations_policy)
            .unwrap()
            .get(taddr)
            .cloned()
            .map_or(Zatoshis::ZERO, |(_, b)| b.spendable_value()),
        expected.total(),
    );
    assert_eq!(
        st.wallet()
            .get_spendable_transparent_outputs(
                taddr,
                target_height,
                confirmations_policy,
                CoinbaseFilter::AllTransparentOutputs,
                LockFilter::Policy(&LockedInputPolicy::Exclude),
            )
            .unwrap()
            .into_iter()
            .map(|utxo| utxo.value())
            .sum::<Option<Zatoshis>>(),
        Some(expected.spendable_value()),
    );
}

pub fn put_received_transparent_utxo<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
    <<DSF as DataStoreFactory>::DataStore as WalletWrite>::UtxoRef: std::fmt::Debug + PartialEq,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let birthday = st.test_account().unwrap().birthday().height();
    let account_id = st.test_account().unwrap().id();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account_id, UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    let height_1 = birthday + 12345;
    st.wallet_mut().update_chain_tip(height_1).unwrap();

    let bal_absent = st
        .wallet()
        .get_transparent_balances(
            account_id,
            TargetHeight::from(height_1 + 1),
            ConfirmationsPolicy::MIN,
        )
        .unwrap();
    assert!(bal_absent.is_empty());

    // Create a fake transparent output.
    let value = Zatoshis::const_from_u64(100000);
    let outpoint = OutPoint::fake();
    let txout = TxOut::new(value, taddr.script().into());

    // Pretend the output's transaction was mined at `height_1`.
    let utxo = WalletTransparentOutput::from_parts(
        outpoint.clone(),
        txout.clone(),
        Some(height_1),
        Some(account_id),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    let res0 = st.wallet_mut().put_received_transparent_utxo(&utxo);
    assert_matches!(res0, Ok(_));

    let target_height = TargetHeight::from(height_1 + 1);
    // Confirm that we see the output unspent as of `height_1`.
    assert_matches!(
        st.wallet().get_spendable_transparent_outputs(
            taddr,
            target_height,
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        ).as_deref(),
        Ok([ret])
        if (ret.outpoint(), ret.txout(), ret.mined_height()) == (utxo.outpoint(), utxo.txout(), Some(height_1))
    );
    assert_matches!(
        st.wallet()
            .get_unspent_transparent_output(utxo.outpoint(), target_height),
        Ok(Some(ret))
        if (ret.outpoint(), ret.txout(), ret.mined_height()) == (utxo.outpoint(), utxo.txout(), Some(height_1))
    );

    // Change the mined height of the UTXO and upsert; we should get back
    // the same `UtxoId`.
    let height_2 = birthday + 34567;
    st.wallet_mut().update_chain_tip(height_2).unwrap();
    let utxo2 = WalletTransparentOutput::from_parts(
        outpoint,
        txout,
        Some(height_2),
        Some(account_id),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    let res1 = st.wallet_mut().put_received_transparent_utxo(&utxo2);
    assert_matches!(res1, Ok(id) if id == res0.unwrap());

    // Confirm that we no longer see any unspent outputs as of `height_1`.
    assert_matches!(
        st.wallet()
            .get_spendable_transparent_outputs(
                taddr,
                target_height,
                ConfirmationsPolicy::MIN,
                CoinbaseFilter::AllTransparentOutputs,
                LockFilter::Policy(&LockedInputPolicy::Exclude)
            )
            .as_deref(),
        Ok(&[])
    );

    // We can still look up the specific output, and it has the expected height.
    assert_matches!(
        st.wallet()
            .get_unspent_transparent_output(utxo2.outpoint(), target_height),
        Ok(Some(ret))
        if (ret.outpoint(), ret.txout(), ret.mined_height()) == (utxo2.outpoint(), utxo2.txout(), Some(height_2))
    );

    // If we include `height_2` then the output is returned.
    assert_matches!(
        st.wallet()
            .get_spendable_transparent_outputs(taddr, TargetHeight::from(height_2 + 1), ConfirmationsPolicy::MIN, CoinbaseFilter::AllTransparentOutputs, LockFilter::Policy(&LockedInputPolicy::Exclude))
            .as_deref(),
        Ok([ret]) if (ret.outpoint(), ret.txout(), ret.mined_height()) == (utxo.outpoint(), utxo.txout(), Some(height_2))
    );

    assert_matches!(
        st.wallet().get_transparent_balances(
            account_id,
            TargetHeight::from(height_2 + 1),
            ConfirmationsPolicy::MIN
        ),
        Ok(h) if h.get(taddr).map(|(_, b)| b.spendable_value()) == Some(value)
    );
}

pub fn transparent_balance_across_shielding<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    // Initialize the wallet with chain data that has no shielded notes for us.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // The wallet starts out with zero balance.
    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );

    // Create a fake transparent output.
    let value = Zatoshis::from_u64(100000).unwrap();
    let txout = TxOut::new(value, taddr.script().into());

    // Pretend the output was received in the chain tip.
    let height = st.wallet().chain_height().unwrap().unwrap();
    let utxo = WalletTransparentOutput::from_parts(
        OutPoint::fake(),
        txout,
        Some(height),
        Some(account.id()),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // The wallet should detect the balance as available
    let mut zero_or_one_conf_value = Balance::ZERO;

    // add the spendable value to the expected balance
    zero_or_one_conf_value.add_spendable_value(value).unwrap();

    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &zero_or_one_conf_value,
    );

    // Shield the output.
    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);
    let txid = st
        .shield_transparent_funds(
            &input_selector,
            &change_strategy,
            value,
            account.usk(),
            &[*taddr],
            account.id(),
            ConfirmationsPolicy::MIN,
        )
        .unwrap()[0];

    // The wallet should have zero transparent balance, because the shielding
    // transaction can be mined.
    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );

    // Mine the shielding transaction.
    let (mined_height, _) = st.generate_next_block_including(txid);
    st.scan_cached_blocks(mined_height, 1);

    // The wallet should still have zero transparent balance.
    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );

    // Unmine the shielding transaction via a reorg.
    st.wallet_mut()
        .truncate_to_height(mined_height - 1)
        .unwrap();
    assert_eq!(st.wallet().chain_height().unwrap(), Some(mined_height - 1));

    // The wallet should still have zero transparent balance.
    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );

    // Expire the shielding transaction.
    let expiry_height = st
        .wallet()
        .get_transaction(txid)
        .unwrap()
        .expect("Transaction exists in the wallet.")
        .expiry_height();
    st.wallet_mut().update_chain_tip(expiry_height).unwrap();

    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &zero_or_one_conf_value,
    );
}

/// Regression test for [PRO-291]: shielding a transparent balance composed of many P2PKH
/// UTXOs must not fail with `ChangeRequired` due to fee disagreement between the proposal
/// and builder layers.
///
/// At 150 P2PKH inputs the proposal-time fee computation (which uses
/// `STANDARD_P2PKH = 150` bytes per input) starts to diverge from the builder-time
/// fee computation (which historically used the actual serialized size, 149 bytes per
/// input) due to the `ceildiv(t_in_total_size, 150)` term in the ZIP 317 fee formula.
/// The discrepancy grows by one logical action (5000 zats) for every additional 150
/// inputs.
///
/// [PRO-291]: https://linear.app/zodl/issue/PRO-291
pub fn shielding_many_transparent_utxos<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    // Choose enough UTXOs to cross the first ceildiv(_, 150) boundary.
    const NUM_UTXOS: usize = 160;
    // Per-UTXO value comfortably above the marginal fee so none are treated as dust.
    const PER_UTXO: u64 = 100_000;

    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    // Initialize the wallet with chain data that has no shielded notes for us.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10_000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Add many distinct P2PKH UTXOs to the wallet, all at the same transparent address.
    let value = Zatoshis::const_from_u64(PER_UTXO);
    let txout = TxOut::new(value, taddr.script().into());
    let height = st.wallet().chain_height().unwrap().unwrap();
    for i in 0..NUM_UTXOS {
        let mut hash = [0u8; 32];
        hash[..4].copy_from_slice(&(i as u32).to_le_bytes());
        let outpoint = OutPoint::new(hash, 0);
        let utxo = WalletTransparentOutput::from_parts(
            outpoint,
            txout.clone(),
            Some(height),
            Some(account.id()),
            Some(TransparentKeyScope::EXTERNAL),
            None,
        )
        .unwrap();
        st.wallet_mut()
            .put_received_transparent_utxo(&utxo)
            .unwrap();
    }

    // Shield the transparent balance.
    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);
    let txids = st
        .shield_transparent_funds(
            &input_selector,
            &change_strategy,
            value,
            account.usk(),
            &[*taddr],
            account.id(),
            ConfirmationsPolicy::MIN,
        )
        .expect("shielding many P2PKH UTXOs should succeed");
    assert_eq!(txids.len(), 1);

    // After shielding, the transparent balance should be zero.
    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );
}

/// Verifies that `InputSource::get_spendable_transparent_outputs_for_addresses` returns the
/// spendable outputs for a *set* of addresses in a single call, equivalent to the union of
/// per-address queries, and honours subset and empty requests.
pub fn get_spendable_transparent_outputs_for_addresses<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();
    let birthday = st.test_account().unwrap().birthday().height();

    let height_1 = birthday + 12345;
    st.wallet_mut().update_chain_tip(height_1).unwrap();

    // Obtain three distinct transparent receivers for the account.
    let mut taddrs = Vec::new();
    while taddrs.len() < 3 {
        let (ua, _) = st
            .wallet_mut()
            .get_next_available_address(account_id, UnifiedAddressRequest::AllAvailableKeys)
            .unwrap()
            .expect("an address should be available within the gap limit");
        if let Some(taddr) = ua.transparent() {
            taddrs.push(*taddr);
        }
    }

    // Place one distinct UTXO at each address.
    let value = Zatoshis::const_from_u64(100_000);
    for (i, taddr) in taddrs.iter().enumerate() {
        let mut hash = [0u8; 32];
        hash[..4].copy_from_slice(&(i as u32).to_le_bytes());
        let utxo = WalletTransparentOutput::from_parts(
            OutPoint::new(hash, 0),
            TxOut::new(value, taddr.script().into()),
            Some(height_1),
            Some(account_id),
            Some(TransparentKeyScope::EXTERNAL),
            None,
        )
        .unwrap();
        st.wallet_mut()
            .put_received_transparent_utxo(&utxo)
            .unwrap();
    }

    let target_height = TargetHeight::from(height_1 + 1);
    let sorted = |mut v: Vec<TransparentAddress>| {
        v.sort();
        v
    };

    // The batched query over all three addresses returns one output per address.
    let all = st
        .wallet()
        .get_spendable_transparent_outputs_for_addresses(
            &taddrs,
            target_height,
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        )
        .unwrap();
    assert_eq!(all.len(), 3);
    assert_eq!(
        sorted(all.iter().map(|u| *u.recipient_address()).collect()),
        sorted(taddrs.clone()),
    );

    // It is equivalent to the union of per-address queries.
    let mut per_address = Vec::new();
    for taddr in &taddrs {
        per_address.extend(
            st.wallet()
                .get_spendable_transparent_outputs(
                    taddr,
                    target_height,
                    ConfirmationsPolicy::MIN,
                    CoinbaseFilter::AllTransparentOutputs,
                    LockFilter::Policy(&LockedInputPolicy::Exclude),
                )
                .unwrap(),
        );
    }
    assert_eq!(
        sorted(all.iter().map(|u| *u.recipient_address()).collect()),
        sorted(per_address.iter().map(|u| *u.recipient_address()).collect()),
    );

    // A subset request returns only the requested address's output.
    let subset = st
        .wallet()
        .get_spendable_transparent_outputs_for_addresses(
            &taddrs[..1],
            target_height,
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        )
        .unwrap();
    assert_eq!(subset.len(), 1);
    assert_eq!(subset[0].recipient_address(), &taddrs[0]);

    // An empty request returns no outputs.
    assert!(
        st.wallet()
            .get_spendable_transparent_outputs_for_addresses(
                &[],
                target_height,
                ConfirmationsPolicy::MIN,
                CoinbaseFilter::AllTransparentOutputs,
                LockFilter::Policy(&LockedInputPolicy::Exclude),
            )
            .unwrap()
            .is_empty()
    );
}

/// Verifies that a shielding proposal caps the number of transparent inputs in a single
/// transaction to the selector's configured fraction of block space, selecting the highest-value
/// UTXOs first and leaving the remainder unspent.
pub fn shielding_transparent_input_cap<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    // At 1% of block space the cap is (2_000_000 * 1 / 100) / 150 = 133 inputs.
    const BLOCK_SPACE_PERCENT: u32 = 1;
    const CAP: usize = 133;
    const NUM_UTXOS: usize = CAP + 7; // 140; the 7 smallest must be dropped.
    const BASE: u64 = 100_000;
    const STEP: u64 = 1_000;

    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    // Initialize the wallet with chain data that has no shielded notes for us.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10_000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Add `NUM_UTXOS` distinct-value P2PKH UTXOs at the same transparent address, so that
    // largest-first selection is unambiguous.
    let height = st.wallet().chain_height().unwrap().unwrap();
    for i in 0..NUM_UTXOS {
        let value = Zatoshis::const_from_u64(BASE + (i as u64) * STEP);
        let mut hash = [0u8; 32];
        hash[..4].copy_from_slice(&(i as u32).to_le_bytes());
        let utxo = WalletTransparentOutput::from_parts(
            OutPoint::new(hash, 0),
            TxOut::new(value, taddr.script().into()),
            Some(height),
            Some(account.id()),
            Some(TransparentKeyScope::EXTERNAL),
            None,
        )
        .unwrap();
        st.wallet_mut()
            .put_received_transparent_utxo(&utxo)
            .unwrap();
    }

    // Propose shielding with a 1%-of-block-space input cap.
    let input_selector =
        GreedyInputSelector::new().with_shielding_block_space_percent(BLOCK_SPACE_PERCENT);
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);
    let proposal = st
        .propose_shielding(
            &input_selector,
            &change_strategy,
            Zatoshis::const_from_u64(BASE),
            &[*taddr],
            account.id(),
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
        )
        .expect("shielding proposal should succeed");

    let inputs = proposal.steps().first().transparent_inputs();
    assert_eq!(
        inputs.len(),
        CAP,
        "the number of transparent inputs should be capped",
    );

    // The selected inputs must be the `CAP` highest-value UTXOs: the `NUM_UTXOS - CAP` smallest
    // are dropped, so the smallest selected value is `BASE + (NUM_UTXOS - CAP) * STEP`.
    let min_selected = inputs.iter().map(|u| u.value()).min().unwrap();
    assert_eq!(
        min_selected,
        Zatoshis::const_from_u64(BASE + ((NUM_UTXOS - CAP) as u64) * STEP),
        "the lowest-value UTXOs should be the ones left unspent",
    );
}

/// This test attempts to verify that transparent funds spendability is
/// accounted for properly given the different minimum confirmations values
/// that can be set when querying for balances.
pub fn transparent_balance_spendability<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    // Initialize the wallet with chain data that has no shielded notes for us.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // The wallet starts out with zero balance.
    check_balance::<DSF>(
        &st as &TestState<_, DSF::DataStore, _>,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );

    // Create a fake transparent output.
    let value = Zatoshis::from_u64(100000).unwrap();
    let txout = TxOut::new(value, taddr.script().into());

    // Pretend the output was received in the chain tip.
    let height = st.wallet().chain_height().unwrap().unwrap();
    let utxo = WalletTransparentOutput::from_parts(
        OutPoint::fake(),
        txout,
        Some(height),
        Some(account.id()),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // The wallet should detect the balance as available
    let mut zero_or_one_conf_value = Balance::ZERO;

    // add the spendable value to the expected balance
    zero_or_one_conf_value.add_spendable_value(value).unwrap();

    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::MIN,
        &zero_or_one_conf_value,
    );

    // now if we increase the number of confirmations our spendable balance should
    // be zero and the total balance equal to `value`
    let mut not_confirmed_yet_value = Balance::ZERO;

    not_confirmed_yet_value
        .add_pending_spendable_value(value)
        .unwrap();

    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::new_symmetrical_unchecked(2, false),
        &not_confirmed_yet_value,
    );

    // Add one extra block
    st.generate_empty_block();

    // Scan that block
    st.scan_cached_blocks(height, 1);

    // now we generate one more block and the balance should be the same as when the
    // check_balance function was called with zero or one confirmation.
    st.generate_empty_block();
    st.scan_cached_blocks(height + 1, 1);

    check_balance::<DSF>(
        &st,
        &account,
        taddr,
        ConfirmationsPolicy::new_symmetrical_unchecked(2, true),
        &zero_or_one_conf_value,
    );
}

/// Constructs a fake transparent-only coinbase transaction paying `value` to `taddr`.
///
/// The result is a structurally valid coinbase transaction (a single input spending the null
/// outpoint), which causes the receiving wallet to classify it as coinbase when it is stored
/// via [`decrypt_and_store_transaction`]. The `lock_time` parameter has no consensus meaning
/// here; distinct values may be used to give otherwise-identical coinbase transactions
/// distinct txids.
fn fake_transparent_coinbase_tx(
    lock_time: u32,
    value: Zatoshis,
    taddr: &TransparentAddress,
) -> Transaction {
    let coinbase_bundle = Bundle {
        vin: vec![TxIn::from_parts(
            OutPoint::NULL,
            Script::default(),
            u32::MAX,
        )],
        vout: vec![TxOut::new(value, taddr.script().into())],
        authorization: Authorized,
    };

    TransactionData::<zcash_primitives::transaction::Authorized>::from_parts(
        TxVersion::V5,
        BranchId::Nu5,
        lock_time,
        // Coinbase transactions do not expire.
        BlockHeight::from(0),
        // Coinbase transactions burn nothing.
        #[cfg(all(zcash_unstable = "nu7", feature = "zip-233"))]
        Zatoshis::ZERO,
        Some(coinbase_bundle),
        None,
        None,
        None,
    )
    .freeze()
    .unwrap()
}

/// Retrieves the [`AccountBalance`] for the given test account from the wallet summary.
fn get_account_balance<DSF>(
    st: &TestState<impl TestCache, <DSF as DataStoreFactory>::DataStore, LocalNetwork>,
    account: &TestAccount<<DSF as DataStoreFactory>::Account>,
    confirmations_policy: ConfirmationsPolicy,
) -> AccountBalance
where
    DSF: DataStoreFactory,
{
    let summary = st
        .wallet()
        .get_wallet_summary(confirmations_policy)
        .unwrap()
        .unwrap();
    *summary.account_balances().get(&account.id()).unwrap()
}

/// Verifies that transparent funds are reported in the correct `AccountBalance` bucket
/// (regular vs. coinbase), that immature coinbase value is reported as pending rather than
/// spendable, and that it becomes spendable upon reaching coinbase maturity.
pub fn transparent_coinbase_balance_split<DSF>(ds_factory: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(ds_factory)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    // Mine a coinbase output paying the wallet's transparent address at tx index 0.
    let coinbase_value = Zatoshis::const_from_u64(625_000_000);
    let coinbase_tx = fake_transparent_coinbase_tx(0, coinbase_value, taddr);
    let (h, _) = st.generate_next_block_from_tx(0, &coinbase_tx);
    st.scan_cached_blocks(h, 1);
    let params = *st.network();
    decrypt_and_store_transaction(&params, st.wallet_mut(), &coinbase_tx, Some(h)).unwrap();

    // Immature coinbase: the value is pending spendability in the coinbase bucket, not
    // spendable; the regular bucket is untouched.
    let balance = get_account_balance::<DSF>(&st, &account, ConfirmationsPolicy::MIN);
    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_regular_balance(), &Balance::ZERO);

    // The same holds when the confirmations policy itself is not yet satisfied (the coinbase
    // output has only one confirmation here), which exercises the pending-balance query.
    let balance = get_account_balance::<DSF>(
        &st,
        &account,
        ConfirmationsPolicy::new_symmetrical_unchecked(2, false),
    );
    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_regular_balance(), &Balance::ZERO);

    // Receive a regular (non-coinbase) UTXO. This output's transaction has no known tx_index,
    // so it must be classified as regular (non-coinbase) funds.
    let regular_value = Zatoshis::const_from_u64(100_000);
    let utxo = WalletTransparentOutput::from_parts(
        OutPoint::fake(),
        TxOut::new(regular_value, taddr.script().into()),
        Some(h),
        Some(account.id()),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // Mixed state: the regular value is spendable, the coinbase value remains pending, and the
    // combined accessors report the sums of the two buckets.
    let balance = get_account_balance::<DSF>(&st, &account, ConfirmationsPolicy::MIN);
    assert_eq!(
        balance.unshielded_regular_balance().spendable_value(),
        regular_value
    );
    assert_eq!(
        balance
            .unshielded_coinbase_balance()
            .value_pending_spendability(),
        coinbase_value
    );
    assert_eq!(
        balance.unshielded_balance(),
        (*balance.unshielded_regular_balance() + *balance.unshielded_coinbase_balance()).unwrap()
    );
    #[allow(deprecated)]
    let unshielded = balance.unshielded();
    assert_eq!(unshielded, (regular_value + coinbase_value).unwrap());
    assert_eq!(balance.total(), (regular_value + coinbase_value).unwrap());

    // Once the coinbase output reaches maturity, its value moves from pending to spendable.
    for _ in 0..COINBASE_MATURITY_BLOCKS {
        st.generate_empty_block();
    }
    st.scan_cached_blocks(h + 1, COINBASE_MATURITY_BLOCKS as usize);

    let balance = get_account_balance::<DSF>(&st, &account, ConfirmationsPolicy::MIN);
    assert_eq!(
        balance.unshielded_coinbase_balance().spendable_value(),
        coinbase_value
    );
    assert_eq!(
        balance
            .unshielded_coinbase_balance()
            .value_pending_spendability(),
        Zatoshis::ZERO
    );
    assert_eq!(
        balance.unshielded_regular_balance().spendable_value(),
        regular_value
    );
    assert_eq!(balance.total(), (regular_value + coinbase_value).unwrap());
}

/// Verifies that dust-valued (uneconomic) transparent outputs are reported in the
/// `uneconomic_value` field of the correct `AccountBalance` bucket (regular vs. coinbase).
pub fn transparent_coinbase_balance_dust<DSF>(ds_factory: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let dust_value = Zatoshis::const_from_u64(1000);
    assert!(dust_value <= zip317::MARGINAL_FEE);

    let mut st = TestBuilder::new()
        .with_data_store_factory(ds_factory)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    // Mine a dust coinbase output paying the wallet's transparent address at tx index 0.
    let coinbase_tx = fake_transparent_coinbase_tx(0, dust_value, taddr);
    let (h, _) = st.generate_next_block_from_tx(0, &coinbase_tx);
    st.scan_cached_blocks(h, 1);
    let params = *st.network();
    decrypt_and_store_transaction(&params, st.wallet_mut(), &coinbase_tx, Some(h)).unwrap();

    // Receive a dust regular (non-coinbase) UTXO.
    let utxo = WalletTransparentOutput::from_parts(
        OutPoint::fake(),
        TxOut::new(dust_value, taddr.script().into()),
        Some(h),
        Some(account.id()),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // Each dust output lands in the uneconomic value of its own bucket, and contributes to
    // neither spendable nor pending value.
    let balance = get_account_balance::<DSF>(&st, &account, ConfirmationsPolicy::MIN);
    assert_eq!(
        balance.unshielded_regular_balance().uneconomic_value(),
        dust_value
    );
    assert_eq!(
        balance.unshielded_coinbase_balance().uneconomic_value(),
        dust_value
    );
    assert_eq!(
        balance.uneconomic_value(),
        (dust_value + dust_value).unwrap()
    );
    assert_eq!(
        balance.unshielded_balance().spendable_value(),
        Zatoshis::ZERO
    );
    assert_eq!(
        balance.unshielded_balance().value_pending_spendability(),
        Zatoshis::ZERO
    );
    assert_eq!(balance.total(), Zatoshis::ZERO);

    // Dust classification takes precedence over coinbase maturity: after the coinbase output
    // matures, its value remains uneconomic rather than becoming spendable.
    for _ in 0..COINBASE_MATURITY_BLOCKS {
        st.generate_empty_block();
    }
    st.scan_cached_blocks(h + 1, COINBASE_MATURITY_BLOCKS as usize);

    let balance = get_account_balance::<DSF>(&st, &account, ConfirmationsPolicy::MIN);
    assert_eq!(
        balance.unshielded_coinbase_balance().uneconomic_value(),
        dust_value
    );
    assert_eq!(
        balance.unshielded_coinbase_balance().spendable_value(),
        Zatoshis::ZERO
    );
}

pub fn gap_limits<DSF>(ds_factory: DSF, cache: impl TestCache, gap_limits: GapLimits)
where
    DSF: DataStoreFactory,
    <DSF as DataStoreFactory>::AccountId: std::fmt::Debug,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(ds_factory)
        .with_block_cache(cache)
        .with_gap_limits(gap_limits)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let test_account = st.test_account().cloned().unwrap();
    let account_uuid = test_account.account().id();
    let ufvk = test_account.account().ufvk().unwrap().clone();

    let external_taddrs = st
        .wallet()
        .get_transparent_receivers(account_uuid, false, true)
        .unwrap();
    assert_eq!(
        u32::try_from(external_taddrs.len()).unwrap(),
        gap_limits.external()
    );
    let internal_taddrs = st
        .wallet()
        .get_transparent_receivers(account_uuid, true, false)
        .unwrap();
    assert_eq!(
        u32::try_from(internal_taddrs.len()).unwrap(),
        gap_limits.external() + gap_limits.internal()
    );
    let ephemeral_taddrs = st
        .wallet()
        .get_known_ephemeral_addresses(account_uuid, None)
        .unwrap();
    assert_eq!(
        u32::try_from(ephemeral_taddrs.len()).unwrap(),
        gap_limits.ephemeral()
    );

    // Add some funds to the wallet
    let (h0, _, _) = st.generate_next_block(
        &ufvk.sapling().unwrap(),
        AddressType::DefaultExternal,
        Zatoshis::const_from_u64(1000000),
    );
    st.scan_cached_blocks(h0, 1);

    // The previous operation was shielded-only, but unified address usage within the
    // valid transparent child index range still count towards the gap limit, so this
    // updates the gap limit by the index of the default Sapling receiver
    let external_taddrs = st
        .wallet()
        .get_transparent_receivers(account_uuid, false, true)
        .unwrap();
    assert_eq!(
        u32::try_from(external_taddrs.len()).unwrap(),
        gap_limits.external()
            + (u32::try_from(ufvk.sapling().unwrap().default_address().0).unwrap() + 1)
    );

    // Pick an address half way through the set of external taddrs
    let external_taddrs_sorted = external_taddrs
        .into_iter()
        .filter_map(|(addr, meta)| meta.address_index().map(|i| (i, addr)))
        .collect::<BTreeMap<_, _>>();
    let to = Address::from(
        *external_taddrs_sorted
            .get(&transparent::keys::NonHardenedChildIndex::from_index(4).unwrap())
            .expect("An address exists at index 4."),
    )
    .to_zcash_address(st.network());

    // Create a transaction & scan the block. Since the txid corresponds to one our wallet
    // generated, this should cause the gap limit to be bumped (generating addresses with index
    // 10..15)
    let txids = st
        .create_standard_transaction(&test_account, to, Zatoshis::const_from_u64(20000))
        .unwrap();
    let (h1, _) = st.generate_next_block_including(txids.head);

    // At this point, the transaction has been created, but since it has not been mined it does
    // not cause an update to the gap limit; we have to wait for the transaction to actually be
    // mined or we could bump the gap limit too soon and start generating addresses that will
    // never be inspected on wallet recovery.
    let external_taddrs = st
        .wallet()
        .get_transparent_receivers(account_uuid, false, true)
        .unwrap();
    assert_eq!(
        u32::try_from(external_taddrs.len()).unwrap(),
        gap_limits.external()
            + (u32::try_from(ufvk.sapling().unwrap().default_address().0).unwrap() + 1)
    );

    // Mine the block, then use `decrypt_and_store_transaction` to ensure that the wallet sees
    // the transaction as mined (since transparent handling doesn't get this from
    // `scan_cached_blocks`)
    st.scan_cached_blocks(h1, 1);
    let tx = st.wallet().get_transaction(txids.head).unwrap().unwrap();
    decrypt_and_store_transaction(&st.network().clone(), st.wallet_mut(), &tx, Some(h1)).unwrap();

    // Now that the transaction has been mined, the gap limit should have increased.
    let external_taddrs = st
        .wallet()
        .get_transparent_receivers(account_uuid, false, true)
        .unwrap();
    assert_eq!(
        u32::try_from(external_taddrs.len()).unwrap(),
        gap_limits.external() + 5
    );

    // The utxo query height should be equal to the minimum mined height among transactions
    // sent to any of the set of {addresses in the gap limit range | address prior to the gap}.
    let query_height = st.wallet().utxo_query_height(account_uuid).unwrap();
    assert_eq!(query_height, h0);
}

/// Builds a test 1-of-1 multisig redeem script from a single keypair.
#[cfg(feature = "transparent-key-import")]
fn build_test_redeem_script() -> (script::Redeem, secp256k1::SecretKey) {
    let secp = Secp256k1::new();
    let secret_key = SecretKey::from_slice(&[1u8; 32]).expect("valid secret key");
    let pubkey = secret_key.public_key(&secp);
    let redeem_script = script::Component(
        check_multisig(1, &[&pubkey.serialize()], false)
            .unwrap()
            .into_iter()
            .collect(),
    );
    (redeem_script, secret_key)
}

/// Tests that importing a standalone transparent public key succeeds.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_pubkey<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();

    let secp = Secp256k1::new();
    let secret_key = SecretKey::from_slice(&[1u8; 32]).expect("valid secret key");
    let pubkey = secret_key.public_key(&secp);
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_pubkey(account_id, pubkey),
        Ok(_)
    );
}

/// Tests that importing the same pubkey twice to the same account is idempotent.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_pubkey_idempotent<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();

    let secp = Secp256k1::new();
    let secret_key = SecretKey::from_slice(&[1u8; 32]).expect("valid secret key");
    let pubkey = secret_key.public_key(&secp);

    // First import
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_pubkey(account_id, pubkey),
        Ok(_)
    );

    // Snapshot state after first import
    let receivers_before = st
        .wallet()
        .get_transparent_receivers(account_id, false, true)
        .unwrap();

    // Second import to same account should also succeed (idempotent)
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_pubkey(account_id, pubkey),
        Ok(_)
    );

    // Verify wallet state is unchanged
    let receivers_after = st
        .wallet()
        .get_transparent_receivers(account_id, false, true)
        .unwrap();

    assert_eq!(receivers_before.len(), receivers_after.len());

    let taddr = TransparentAddress::from_pubkey(&pubkey);
    let metadata = receivers_after
        .get(&taddr)
        .expect("address should be present");
    assert!(matches!(
        metadata.source(),
        TransparentAddressSource::StandalonePubkey(_)
    ));
}

/// Tests that importing the same pubkey to a different account fails.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_pubkey_conflict<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account1_id = st.test_account().unwrap().id();

    let secp = Secp256k1::new();
    let secret_key = SecretKey::from_slice(&[1u8; 32]).expect("valid secret key");
    let pubkey = secret_key.public_key(&secp);

    // Import to first account
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_pubkey(account1_id, pubkey),
        Ok(_)
    );

    // Create a second account
    let birthday = AccountBirthday::from_parts(
        ChainState::empty(
            st.network()
                .activation_height(NetworkUpgrade::Sapling)
                .unwrap()
                - 1,
            BlockHash([0; 32]),
        ),
        None,
    );
    let seed2 = Secret::new(vec![42u8; 32]);
    let (account2_id, _) = st
        .wallet_mut()
        .create_account("account2", &seed2, &birthday, None)
        .unwrap();

    // Import same pubkey to second account should fail
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_pubkey(account2_id, pubkey),
        Err(_)
    );
}

/// Tests that a UTXO received at a standalone P2PKH address is reflected in the wallet balance.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_pubkey_balance<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
    <<DSF as DataStoreFactory>::DataStore as WalletWrite>::UtxoRef: std::fmt::Debug,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();
    let birthday = st.test_account().unwrap().birthday().height();

    let secp = Secp256k1::new();
    let secret_key = SecretKey::from_slice(&[1u8; 32]).expect("valid secret key");
    let pubkey = secret_key.public_key(&secp);

    // Import the public key.
    st.wallet_mut()
        .import_standalone_transparent_pubkey(account_id, pubkey)
        .unwrap();

    // Derive the P2PKH address.
    let taddr = TransparentAddress::from_pubkey(&pubkey);

    let height = birthday + 1000;
    st.wallet_mut().update_chain_tip(height).unwrap();

    // Create a fake UTXO at the P2PKH address.
    let value = Zatoshis::const_from_u64(50_000);
    let outpoint = OutPoint::fake();
    let txout = TxOut::new(value, taddr.script().into());
    let utxo = WalletTransparentOutput::from_parts(
        outpoint,
        txout,
        Some(height),
        Some(account_id),
        None,
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // Verify the balance is reflected via get_transparent_balances.
    let target_height = TargetHeight::from(height + 1);
    let balances = st
        .wallet()
        .get_transparent_balances(account_id, target_height, ConfirmationsPolicy::MIN)
        .unwrap();
    assert_eq!(
        balances.get(&taddr).map(|(_, b)| b.spendable_value()),
        Some(value),
    );

    // Verify the UTXO is returned by get_spendable_transparent_outputs.
    let utxos = st
        .wallet()
        .get_spendable_transparent_outputs(
            &taddr,
            target_height,
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        )
        .unwrap();
    assert_eq!(utxos.len(), 1);
    assert_eq!(utxos[0].value(), value);
}

/// Tests spending from a standalone P2PKH address by shielding its balance.
#[cfg(feature = "transparent-key-import")]
pub fn spend_from_standalone_pubkey<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let account_id = account.id();

    // Create a keypair and derive the P2PKH address.
    let secp = Secp256k1::new();
    let secret_key = SecretKey::from_slice(&[1u8; 32]).expect("valid secret key");
    let pubkey = secret_key.public_key(&secp);

    // Import the public key.
    st.wallet_mut()
        .import_standalone_transparent_pubkey(account_id, pubkey)
        .unwrap();

    // Derive the P2PKH address.
    let taddr = TransparentAddress::from_pubkey(&pubkey);

    // Initialize chain data with blocks (needed for shielding transaction creation).
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Create a fake UTXO at the P2PKH address.
    let value = Zatoshis::from_u64(100000).unwrap();
    let height = st.wallet().chain_height().unwrap().unwrap();
    let txout = TxOut::new(value, taddr.script().into());
    let utxo = WalletTransparentOutput::from_parts(
        OutPoint::fake(),
        txout,
        Some(height),
        Some(account_id),
        None,
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // Build SpendingKeys with the standalone key for the P2PKH address.
    let mut standalone_keys = HashMap::new();
    standalone_keys.insert(taddr, vec![secret_key]);
    let spending_keys = SpendingKeys::new(
        account.usk().clone(),
        #[cfg(feature = "transparent-key-import")]
        standalone_keys,
    );

    // Shield the P2PKH UTXO.
    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);

    let prover = ::zcash_proofs::prover::LocalTxProver::bundled();
    let network = *st.network();
    let txids = wallet::shield_transparent_funds(
        st.wallet_mut(),
        &network,
        &prover,
        &prover,
        &input_selector,
        &change_strategy,
        value,
        &spending_keys,
        &[taddr],
        account_id,
        ConfirmationsPolicy::MIN,
    )
    .unwrap();

    assert!(!txids.is_empty());

    // The wallet should have zero transparent balance after shielding.
    check_balance::<DSF>(
        &st,
        &account,
        &taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );

    // The shielded balance should now include the value minus the fee.
    let fee = st
        .get_tx_from_history(*txids.first())
        .unwrap()
        .unwrap()
        .fee_paid()
        .expect("fee should be known for wallet-created transactions");
    let summary = st
        .wallet()
        .get_wallet_summary(ConfirmationsPolicy::MIN)
        .unwrap()
        .unwrap();
    let account_balance = summary.account_balances().get(&account_id).unwrap();
    assert_eq!(
        account_balance
            .sapling_balance()
            .change_pending_confirmation(),
        (value - fee).unwrap(),
    );
}

/// Tests that importing a standalone P2SH address succeeds and the address appears
/// in `get_transparent_receivers` with the correct `TransparentAddressSource`.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_p2sh<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();
    let (redeem_script, _) = build_test_redeem_script();

    // Import should succeed
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_script(account_id, redeem_script.clone()),
        Ok(_)
    );

    // Verify the address appears in get_transparent_receivers
    let receivers = st
        .wallet()
        .get_transparent_receivers(account_id, false, true)
        .unwrap();

    // The P2SH address derived from the redeem script should be present
    let script_pubkey = sh(&redeem_script);
    let expected_addr =
        TransparentAddress::from_script_pubkey(&script_pubkey).expect("valid P2SH address");

    let metadata = receivers
        .get(&expected_addr)
        .expect("address should be present");
    assert!(matches!(
        metadata.source(),
        TransparentAddressSource::StandaloneScript(_)
    ));
}

/// Tests that importing the same P2SH address twice to the same account is idempotent.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_p2sh_idempotent<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();
    let (redeem_script, _) = build_test_redeem_script();

    // First import
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_script(account_id, redeem_script.clone()),
        Ok(_)
    );

    // Snapshot state after first import
    let receivers_before = st
        .wallet()
        .get_transparent_receivers(account_id, false, true)
        .unwrap();

    // Second import to same account should also succeed (idempotent)
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_script(account_id, redeem_script.clone()),
        Ok(_)
    );

    // Verify wallet state is unchanged
    let receivers_after = st
        .wallet()
        .get_transparent_receivers(account_id, false, true)
        .unwrap();

    assert_eq!(receivers_before.len(), receivers_after.len());

    let script_pubkey = sh(&redeem_script);
    let expected_addr =
        TransparentAddress::from_script_pubkey(&script_pubkey).expect("valid P2SH address");
    let metadata = receivers_after
        .get(&expected_addr)
        .expect("address should be present");
    assert!(matches!(
        metadata.source(),
        TransparentAddressSource::StandaloneScript(_)
    ));
}

/// Tests that importing the same P2SH address to a different account fails.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_p2sh_conflict<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account1_id = st.test_account().unwrap().id();
    let (redeem_script, _) = build_test_redeem_script();

    // Import to first account
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_script(account1_id, redeem_script.clone()),
        Ok(_)
    );

    // Create a second account
    let birthday = AccountBirthday::from_parts(
        ChainState::empty(
            st.network()
                .activation_height(NetworkUpgrade::Sapling)
                .unwrap()
                - 1,
            BlockHash([0; 32]),
        ),
        None,
    );
    let seed2 = Secret::new(vec![42u8; 32]);
    let (account2_id, _) = st
        .wallet_mut()
        .create_account("account2", &seed2, &birthday, None)
        .unwrap();

    // Import same redeem script to second account should fail
    assert_matches!(
        st.wallet_mut()
            .import_standalone_transparent_script(account2_id, redeem_script),
        Err(_)
    );
}

/// Tests that a UTXO received at a standalone P2SH address is reflected in the wallet balance.
#[cfg(feature = "transparent-key-import")]
pub fn import_standalone_transparent_p2sh_balance<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
    <<DSF as DataStoreFactory>::DataStore as WalletWrite>::UtxoRef: std::fmt::Debug,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();
    let birthday = st.test_account().unwrap().birthday().height();

    let (redeem_script, _) = build_test_redeem_script();

    // Import the P2SH address.
    st.wallet_mut()
        .import_standalone_transparent_script(account_id, redeem_script.clone())
        .unwrap();

    // Derive the expected transparent address from the redeem script.
    let script_pubkey = sh(&redeem_script);
    let taddr = TransparentAddress::from_script_pubkey(&script_pubkey).expect("valid P2SH address");

    let height = birthday + 1000;
    st.wallet_mut().update_chain_tip(height).unwrap();

    // Create a fake UTXO at the P2SH address.
    let value = Zatoshis::const_from_u64(50_000);
    let outpoint = OutPoint::fake();
    let txout = TxOut::new(value, taddr.script().into());
    let utxo = WalletTransparentOutput::from_parts(
        outpoint,
        txout,
        Some(height),
        Some(account_id),
        None,
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // Verify the balance is reflected via get_transparent_balances.
    let target_height = TargetHeight::from(height + 1);
    let balances = st
        .wallet()
        .get_transparent_balances(account_id, target_height, ConfirmationsPolicy::MIN)
        .unwrap();
    assert_eq!(
        balances.get(&taddr).map(|(_, b)| b.spendable_value()),
        Some(value),
    );

    // Verify the UTXO is returned by get_spendable_transparent_outputs.
    let utxos = st
        .wallet()
        .get_spendable_transparent_outputs(
            &taddr,
            target_height,
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        )
        .unwrap();
    assert_eq!(utxos.len(), 1);
    assert_eq!(utxos[0].value(), value);
}

/// Tests spending from a standalone P2SH (multisig) address by shielding its balance.
#[cfg(feature = "transparent-key-import")]
pub fn spend_from_standalone_p2sh<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let account_id = account.id();
    // Build the redeem script and get the signing key.
    let (redeem_script, secret_key) = build_test_redeem_script();

    // Import the P2SH address.
    st.wallet_mut()
        .import_standalone_transparent_script(account_id, redeem_script.clone())
        .unwrap();

    // Derive the P2SH address.
    let script_pubkey = sh(&redeem_script);
    let taddr = TransparentAddress::from_script_pubkey(&script_pubkey).expect("valid P2SH address");

    // Initialize chain data with blocks (needed for shielding transaction creation).
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Create a fake UTXO at the P2SH address.
    let value = Zatoshis::from_u64(100000).unwrap();
    let height = st.wallet().chain_height().unwrap().unwrap();
    let txout = TxOut::new(value, taddr.script().into());
    let utxo = WalletTransparentOutput::from_parts(
        OutPoint::fake(),
        txout,
        Some(height),
        Some(account_id),
        None,
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    // Build SpendingKeys with the standalone key for the P2SH address.
    let mut standalone_keys = HashMap::new();
    standalone_keys.insert(taddr, vec![secret_key]);
    let spending_keys = SpendingKeys::new(
        account.usk().clone(),
        #[cfg(feature = "transparent-key-import")]
        standalone_keys,
    );

    // Shield the P2SH UTXO.
    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);

    let prover = ::zcash_proofs::prover::LocalTxProver::bundled();
    let network = *st.network();
    let txids = wallet::shield_transparent_funds(
        st.wallet_mut(),
        &network,
        &prover,
        &prover,
        &input_selector,
        &change_strategy,
        value,
        &spending_keys,
        &[taddr],
        account_id,
        ConfirmationsPolicy::MIN,
    )
    .unwrap();

    assert!(!txids.is_empty());

    // The wallet should have zero transparent balance after shielding.
    check_balance::<DSF>(
        &st,
        &account,
        &taddr,
        ConfirmationsPolicy::MIN,
        &Balance::ZERO,
    );

    // The shielded balance should now include the value minus the fee.
    let fee = st
        .get_tx_from_history(*txids.first())
        .unwrap()
        .unwrap()
        .fee_paid()
        .expect("fee should be known for wallet-created transactions");
    let summary = st
        .wallet()
        .get_wallet_summary(ConfirmationsPolicy::MIN)
        .unwrap()
        .unwrap();
    let account_balance = summary.account_balances().get(&account_id).unwrap();
    assert_eq!(
        account_balance
            .sapling_balance()
            .change_pending_confirmation(),
        (value - fee).unwrap(),
    );
}

/// Tests [`WalletWrite::mark_transparent_addresses_exposed`] by observing the effect on the
/// address's exposure metadata via
/// [`WalletRead::get_transparent_address_metadata`](crate::data_api::WalletRead::get_transparent_address_metadata).
pub fn mark_transparent_addresses_exposed<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();
    let taddr = *st
        .wallet()
        .get_last_generated_address_matching(account_id, UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap()
        .transparent()
        .unwrap();

    let exposure_of = |st: &TestState<_, <DSF as DataStoreFactory>::DataStore, LocalNetwork>,
                       addr: &TransparentAddress|
     -> Exposure {
        st.wallet()
            .get_transparent_address_metadata(account_id, addr)
            .unwrap()
            .unwrap()
            .exposure()
    };

    // Calling with a very high height does not raise an already-recorded exposure,
    // and records the provided height if no prior exposure was tracked.
    let initial = exposure_of(&st, &taddr);
    let very_high = BlockHeight::from(u32::MAX);
    st.wallet_mut()
        .mark_transparent_addresses_exposed(&[(taddr, very_high)])
        .unwrap();
    match initial {
        Exposure::Exposed { at_height, .. } => assert_matches!(
            exposure_of(&st, &taddr),
            Exposure::Exposed { at_height: h, .. } if h == at_height
        ),
        Exposure::Unknown | Exposure::CannotKnow => assert_matches!(
            exposure_of(&st, &taddr),
            Exposure::Exposed { at_height: h, .. } if h == very_high
        ),
    }

    // Calling with a lower height lowers the recorded exposure.
    st.wallet_mut()
        .mark_transparent_addresses_exposed(&[(taddr, BlockHeight::from(0))])
        .unwrap();
    assert_matches!(
        exposure_of(&st, &taddr),
        Exposure::Exposed { at_height, .. } if at_height == BlockHeight::from(0)
    );

    // Calling with a higher height does not raise the recorded exposure.
    st.wallet_mut()
        .mark_transparent_addresses_exposed(&[(taddr, BlockHeight::from(100))])
        .unwrap();
    assert_matches!(
        exposure_of(&st, &taddr),
        Exposure::Exposed { at_height, .. } if at_height == BlockHeight::from(0)
    );

    // An address not tracked by the wallet must return an error.
    let unknown = TransparentAddress::PublicKeyHash([0u8; 20]);
    assert!(
        st.wallet_mut()
            .mark_transparent_addresses_exposed(&[(unknown, BlockHeight::from(1))])
            .is_err()
    );

    // An empty input is a no-op.
    st.wallet_mut()
        .mark_transparent_addresses_exposed(&[])
        .unwrap();
}

/// Tests that [`WalletWrite::mark_transparent_addresses_exposed`] correctly handles bulk
/// input: all addresses in a successful call must be marked, and an unrecognized address
/// must cause the entire call to be rolled back.
pub fn mark_transparent_addresses_exposed_bulk<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let gap_limits = GapLimits::new(5, 2, 2);
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_gap_limits(gap_limits)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account_id = st.test_account().unwrap().id();

    let mut receivers = st
        .wallet()
        .get_transparent_receivers(account_id, false, true)
        .unwrap()
        .into_iter()
        .filter_map(|(addr, meta)| {
            let exposure = meta.exposure();
            meta.address_index().map(|i| (i.index(), addr, exposure))
        })
        .collect::<Vec<_>>();
    receivers.sort_by_key(|(i, _, _)| *i);

    // Use known-unexposed receivers for the bulk-success test, so that the post-call
    // recorded height is exactly the one we pass in regardless of any default exposure
    // that address generation may set on other receivers.
    let unexposed = receivers
        .iter()
        .copied()
        .filter(|(_, _, exposure)| matches!(exposure, Exposure::Unknown))
        .collect::<Vec<_>>();
    assert!(
        unexposed.len() >= 2,
        "account should have at least 2 unexposed derived receivers"
    );

    // Mark two unexposed addresses at distinct heights in a single bulk call.
    let (_idx_a, addr_a, _) = unexposed[0];
    let (_idx_b, addr_b, _) = unexposed[1];
    let height_a = BlockHeight::from(10);
    let height_b = BlockHeight::from(20);
    st.wallet_mut()
        .mark_transparent_addresses_exposed(&[(addr_a, height_a), (addr_b, height_b)])
        .unwrap();

    let exposure_of = |st: &TestState<_, <DSF as DataStoreFactory>::DataStore, LocalNetwork>,
                       addr: &TransparentAddress|
     -> Exposure {
        st.wallet()
            .get_transparent_address_metadata(account_id, addr)
            .unwrap()
            .unwrap()
            .exposure()
    };
    assert_matches!(
        exposure_of(&st, &addr_a),
        Exposure::Exposed { at_height, .. } if at_height == height_a
    );
    assert_matches!(
        exposure_of(&st, &addr_b),
        Exposure::Exposed { at_height, .. } if at_height == height_b
    );

    // Now attempt a bulk call where the second entry is unrecognized. The whole call must
    // fail, and the first entry must not have been partially applied. Pick a third
    // receiver distinct from `addr_a`/`addr_b` — its prior exposure state is irrelevant
    // since the assertion is preservation, not a specific height.
    let (idx_c, addr_c, _) = *receivers
        .iter()
        .find(|(_, addr, _)| *addr != addr_a && *addr != addr_b)
        .expect("account should have a third derived receiver");
    let before = exposure_of(&st, &addr_c);
    let unknown = TransparentAddress::PublicKeyHash([0x7u8; 20]);
    assert!(
        st.wallet_mut()
            .mark_transparent_addresses_exposed(&[
                (addr_c, BlockHeight::from(5)),
                (unknown, BlockHeight::from(5)),
            ])
            .is_err()
    );
    assert_eq!(
        exposure_of(&st, &addr_c),
        before,
        "exposure at index {idx_c} must not change when bulk call fails atomically"
    );
}

/// Tests that [`WalletWrite::mark_transparent_addresses_exposed`] returns an error when
/// asked to mark an address that the wallet does not track.
pub fn mark_transparent_addresses_exposed_unknown_address<DSF>(dsf: DSF)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let unknown = TransparentAddress::PublicKeyHash([0u8; 20]);
    assert!(
        st.wallet_mut()
            .mark_transparent_addresses_exposed(&[(unknown, BlockHeight::from(1))])
            .is_err()
    );
}

/// Sets up a wallet whose account holds no shielded notes and a single spendable
/// transparent UTXO at its default external transparent receiver, returning the test
/// state, the account, the funding outpoint, and the UTXO value.
///
/// The chain is seeded with blocks containing notes that do *not* belong to the wallet,
/// so that target/anchor heights resolve while the account remains shielded-empty. This
/// isolates the transparent-UTXO selection path.
#[allow(clippy::type_complexity)]
fn setup_transparent_only_account<DSF>(
    dsf: DSF,
    cache: impl TestCache,
    utxo_value: Zatoshis,
) -> (
    TestState<impl TestCache, <DSF as DataStoreFactory>::DataStore, LocalNetwork>,
    TestAccount<<DSF as DataStoreFactory>::Account>,
    OutPoint,
)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = uaddr.transparent().unwrap();

    // Seed the chain with notes that do not belong to us so that heights resolve while
    // the account remains without any shielded notes.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Fund the account with a single transparent UTXO well above the marginal fee.
    let txout = TxOut::new(utxo_value, taddr.script().into());
    let height = st.wallet().chain_height().unwrap().unwrap();
    let outpoint = OutPoint::fake();
    let utxo = WalletTransparentOutput::from_parts(
        outpoint.clone(),
        txout,
        Some(height),
        Some(account.id()),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    (st, account, outpoint)
}

/// Builds a single-payment t->t [`TransactionRequest`] paying `amount` to a fixed
/// external transparent recipient.
fn t2t_request(network: &LocalNetwork, amount: Zatoshis) -> TransactionRequest {
    let recipient = TransparentAddress::PublicKeyHash([7u8; 20]);
    TransactionRequest::new(vec![Payment::without_memo(
        Address::Transparent(recipient).to_zcash_address(network),
        amount,
    )])
    .unwrap()
}

/// Regression test enforcing the privacy invariant: with the default
/// default spend policy (which permits no transparent spending), a transfer must NOT silently spend
/// the account's transparent UTXOs as a fallback. An account holding only transparent
/// funds must fail with [`InsufficientFunds`] rather than producing a t->t proposal.
///
/// [`InsufficientFunds`]: crate::data_api::error::Error::InsufficientFunds
pub fn propose_t2t_shielded_only_is_insufficient<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let utxo_value = Zatoshis::const_from_u64(100_000);
    let (mut st, account, _outpoint) = setup_transparent_only_account(dsf, cache, utxo_value);

    let network = *st.network();
    let request = t2t_request(&network, Zatoshis::const_from_u64(40_000));

    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);

    let result = st.propose_transfer_with_policy(
        account.id(),
        &input_selector,
        &change_strategy,
        request,
        ConfirmationsPolicy::MIN,
        &SpendPolicy::default(),
    );

    assert_matches!(
        result,
        Err(crate::data_api::error::Error::InsufficientFunds { .. }),
        "shielded-only policy must not spend transparent UTXOs as a fallback",
    );
}

/// With `TransparentSpendPolicy::any_account_addr` (the legacy `ANY_TADDR` behavior), a
/// transfer may spend the account's transparent UTXOs. Verifies that the funding UTXO is
/// selected as a transparent input and that the proposal balance is consistent.
pub fn propose_t2t_any_account_taddr<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let utxo_value = Zatoshis::const_from_u64(100_000);
    let transfer_amount = Zatoshis::const_from_u64(40_000);
    let (mut st, account, outpoint) = setup_transparent_only_account(dsf, cache, utxo_value);

    let network = *st.network();
    let request = t2t_request(&network, transfer_amount);

    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);

    let proposal = st
        .propose_transfer_with_policy(
            account.id(),
            &input_selector,
            &change_strategy,
            request,
            ConfirmationsPolicy::MIN,
            &SpendPolicy::default().with_transparent(TransparentSpendPolicy::any_account_addr()),
        )
        .expect("transparent spend must succeed under any-account-address transparent spending");

    // A pure t->t transfer is a single step (no ZIP-320 ephemeral roundtrip).
    assert_eq!(proposal.steps().len(), 1);
    let step = &proposal.steps().head;

    assert_eq!(
        step.transparent_inputs().len(),
        1,
        "expected exactly one transparent input selected from the account's UTXOs",
    );
    assert_eq!(step.transparent_inputs()[0].outpoint(), &outpoint);
    assert_eq!(step.transparent_inputs()[0].txout().value(), utxo_value);

    // `TransactionBalance::total()` is `change + fee`, which by the balance equation equals
    // input total minus the explicit payment.
    assert_eq!(
        step.balance().total(),
        (utxo_value - transfer_amount).unwrap(),
    );
    assert!(step.balance().fee_required() > Zatoshis::ZERO);
    assert!(!step.balance().proposed_change().is_empty());
}

/// Verifies that `GreedyInputSelector::propose_transaction` successfully re-gathers
/// transparent inputs when the initial fee-aware gather's estimate (which accounts only
/// for the transparent side of the transaction) turns out to be insufficient once the
/// real change strategy accounts for the additional shielded action required by a
/// shielded payment recipient.
///
/// This exercises the `ChangeError::InsufficientFunds` fallback path in
/// `GreedyInputSelector::propose_transaction`, which re-invokes
/// `InputSource::select_spendable_transparent_outputs` with a corrected `TargetValue`
/// when the first gather's reservation proves too small. Funding many small transparent
/// UTXOs forces the initial gather to stop with just enough inputs to cover the payment
/// under its own (transparent-only) fee estimate; the shielded payment output then pushes
/// the real required fee higher, so satisfying the request is only possible by gathering
/// additional inputs beyond that initial estimate.
pub fn propose_t2shielded_requires_transparent_regather<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = *uaddr.transparent().unwrap();

    // Seed the chain with notes that do not belong to us so that heights resolve.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10_000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Fund the account with many small transparent UTXOs, none of which alone are
    // remotely close to the payment amount, so that gathering enough of them to satisfy
    // the (larger, corrected) real requirement remains possible.
    let dust_value = Zatoshis::const_from_u64(10_000);
    let n_dust = 30;
    let height = st.wallet().chain_height().unwrap().unwrap();
    for i in 0..n_dust {
        let mut hash = [0u8; 32];
        hash[..4].copy_from_slice(&(i as u32).to_le_bytes());
        let utxo = WalletTransparentOutput::from_parts(
            OutPoint::new(hash, 0),
            TxOut::new(dust_value, taddr.script().into()),
            Some(height),
            Some(account.id()),
            Some(TransparentKeyScope::EXTERNAL),
            None,
        )
        .unwrap();
        st.wallet_mut()
            .put_received_transparent_utxo(&utxo)
            .unwrap();
    }

    // Pay a shielded recipient. The initial transparent gather's fee estimate accounts
    // only for the transparent inputs it selects; it does not (and cannot, since the
    // shielded payment output isn't known to `InputSource::select_spendable_transparent_outputs`)
    // account for the additional sapling action this payment requires, so the first pass
    // undershoots and a re-gather is required to actually satisfy the request.
    let network = *st.network();
    let recipient = ExtendedSpendingKey::master(&[1u8; 32])
        .to_diversifiable_full_viewing_key()
        .default_address()
        .1;
    let payment_amount = Zatoshis::const_from_u64(50_000);
    let request = TransactionRequest::new(vec![Payment::without_memo(
        Address::Sapling(recipient).to_zcash_address(&network),
        payment_amount,
    )])
    .unwrap();

    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);

    // Independently reproduce the initial gather that `GreedyInputSelector` will perform
    // (bounded only by the payment amount, since that's the only information available
    // before the shielded payment output's fee contribution is known). Comparing this to
    // the transparent inputs actually used by the successful proposal below demonstrates
    // that the proposal could only have succeeded via the re-gather fallback: the initial
    // gather's own reservation ignores the extra sapling action the payment requires, so
    // it cannot by itself have covered the real, higher requirement.
    let initial_gather = st
        .wallet()
        .select_spendable_transparent_outputs(
            account.id(),
            TargetHeight::from(height + 1),
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::NonCoinbaseOnly,
            None,
            TargetValue::AtLeast(payment_amount),
            usize::MAX,
            &StandardFeeRule::Zip317,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        )
        .expect("initial gather should succeed");
    let initial_gather_value: Zatoshis = initial_gather
        .iter()
        .map(|u| u.value())
        .fold(Zatoshis::ZERO, |acc, v| (acc + v).unwrap());

    let proposal = st
        .propose_transfer_with_policy(
            account.id(),
            &input_selector,
            &change_strategy,
            request,
            ConfirmationsPolicy::MIN,
            &SpendPolicy::default().with_transparent(TransparentSpendPolicy::any_account_addr()),
        )
        .expect(
            "transparent spend should succeed via the re-gather fallback despite the \
             initial gather's fee estimate being insufficient",
        );

    let step = &proposal.steps().head;
    let gathered_value: Zatoshis = step
        .transparent_inputs()
        .iter()
        .map(|i| i.txout().value())
        .fold(Zatoshis::ZERO, |acc, v| (acc + v).unwrap());
    assert!(
        gathered_value > initial_gather_value,
        "the successful proposal should have gathered more transparent value ({}) than \
         the insufficient initial gather ({})",
        u64::from(gathered_value),
        u64::from(initial_gather_value),
    );
    assert!(step.balance().fee_required() > Zatoshis::ZERO);
}

/// Consolidation subtracts already-selected transparent value from the shielded funding target.
pub fn prefer_consolidation_accounts_for_selected_transparent_value<DSF>(
    dsf: DSF,
    cache: impl TestCache,
) where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let ufvk = account.account().ufvk().unwrap();
    let sapling_fvk = ufvk.sapling().unwrap();
    let (start_height, _, _) = st.generate_next_block(
        &sapling_fvk,
        AddressType::DefaultExternal,
        Zatoshis::const_from_u64(600_000),
    );
    st.generate_next_block(
        &sapling_fvk,
        AddressType::DefaultExternal,
        Zatoshis::const_from_u64(500_000),
    );
    st.scan_cached_blocks(start_height, 2);

    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = *uaddr.transparent().unwrap();
    let utxo = WalletTransparentOutput::from_parts(
        OutPoint::fake(),
        TxOut::new(Zatoshis::const_from_u64(600_000), taddr.script().into()),
        st.wallet().chain_height().unwrap(),
        Some(account.id()),
        Some(TransparentKeyScope::EXTERNAL),
        None,
    )
    .unwrap();
    st.wallet_mut()
        .put_received_transparent_utxo(&utxo)
        .unwrap();

    let recipient = ExtendedSpendingKey::master(&[1u8; 32])
        .to_diversifiable_full_viewing_key()
        .default_address()
        .1;
    let request = TransactionRequest::new(vec![Payment::without_memo(
        Address::Sapling(recipient).to_zcash_address(st.network()),
        Zatoshis::const_from_u64(1_000_000),
    )])
    .unwrap();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);
    let spend_policy = SpendPolicy::default()
        .with_transparent(TransparentSpendPolicy::any_account_addr())
        .with_note_selection(NoteSelection::PreferConsolidation);

    let proposal = st
        .propose_transfer_with_policy(
            account.id(),
            &GreedyInputSelector::new(),
            &change_strategy,
            request,
            ConfirmationsPolicy::MIN,
            &spend_policy,
        )
        .expect("the mixed transparent and shielded inputs cover the payment and fee");
    let step = &proposal.steps().head;
    assert_eq!(step.transparent_inputs().len(), 1);
    assert_eq!(
        step.shielded_inputs()
            .expect("the proposal spends a shielded note")
            .notes()
            .len(),
        1,
    );
}

/// Verifies that `GreedyInputSelector::with_shielding_block_space_percent` also bounds the
/// transparent gather performed for general (non-shielding) transfers, not just shielding.
///
/// Funds more dust UTXOs than fit within a 1%-of-block-space cap, and requests a payment
/// whose post-fee cost can only be met by exceeding that cap. The gather must stop at the
/// cap rather than consuming every eligible UTXO, so the proposal fails with
/// [`InsufficientFunds`] instead of succeeding with an uncapped number of transparent inputs.
///
/// [`InsufficientFunds`]: crate::data_api::error::Error::InsufficientFunds
pub fn propose_transfer_transparent_input_cap<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    // At 1% of block space the cap is (2_000_000 * 1 / 100) / 150 = 133 inputs.
    const BLOCK_SPACE_PERCENT: u32 = 1;
    const CAP: usize = 133;
    const NUM_UTXOS: usize = CAP + 7; // 140; more than enough to exceed the cap.
    const DUST_VALUE: u64 = 10_000;

    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = *uaddr.transparent().unwrap();

    // Seed the chain with notes that do not belong to us so that heights resolve.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10_000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Fund the account with more dust UTXOs than fit within the cap.
    let height = st.wallet().chain_height().unwrap().unwrap();
    for i in 0..NUM_UTXOS {
        let mut hash = [0u8; 32];
        hash[..4].copy_from_slice(&(i as u32).to_le_bytes());
        let utxo = WalletTransparentOutput::from_parts(
            OutPoint::new(hash, 0),
            TxOut::new(Zatoshis::const_from_u64(DUST_VALUE), taddr.script().into()),
            Some(height),
            Some(account.id()),
            Some(TransparentKeyScope::EXTERNAL),
            None,
        )
        .unwrap();
        st.wallet_mut()
            .put_received_transparent_utxo(&utxo)
            .unwrap();
    }

    // Request a post-fee amount that is only reachable by gathering more than `CAP` inputs
    // (with the cap, `CAP` inputs net `DUST_VALUE * CAP - 5_000 * CAP = 5_000 * CAP`
    // post-fee; requesting exactly that much would succeed, so request more).
    let payment_amount = Zatoshis::const_from_u64(5_000 * (CAP as u64) + DUST_VALUE);

    let network = *st.network();
    let request = t2t_request(&network, payment_amount);

    let input_selector =
        GreedyInputSelector::new().with_shielding_block_space_percent(BLOCK_SPACE_PERCENT);
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);

    let result = st.propose_transfer_with_policy(
        account.id(),
        &input_selector,
        &change_strategy,
        request,
        ConfirmationsPolicy::MIN,
        &SpendPolicy::default().with_transparent(TransparentSpendPolicy::any_account_addr()),
    );

    assert_matches!(
        result,
        Err(crate::data_api::error::Error::InsufficientFunds { .. }),
        "the transparent gather should stop at the input cap rather than consuming every \
         eligible dust UTXO, so the request should fail rather than succeed with an \
         uncapped number of inputs",
    );
}

/// With a `TransparentSource::FromAddresses` transparent source, only the explicitly named transparent
/// addresses are eligible. Funds two of the account's external receivers but names only
/// one; the proposal must select solely from the named address.
pub fn propose_t2t_from_addresses<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();

    // Seed the chain with notes that do not belong to us so heights resolve.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Enumerate two distinct external transparent receivers belonging to the account.
    let external_taddrs = st
        .wallet()
        .get_transparent_receivers(account.id(), false, true)
        .unwrap();
    let mut taddrs_by_index = external_taddrs
        .into_iter()
        .filter_map(|(addr, meta)| meta.address_index().map(|i| (i, addr)))
        .collect::<BTreeMap<_, _>>()
        .into_values();
    let addr_named = taddrs_by_index.next().expect("at least one external taddr");
    let addr_other = taddrs_by_index
        .next()
        .expect("at least two external taddrs");

    // Fund both receivers with a spendable UTXO each. The unnamed address's UTXO is
    // inserted first AND holds strictly more value than the named address's, so that if
    // the address filter were not enforced, the value-descending gather would select the
    // unnamed address's UTXO (which alone covers the payment) and stop -- making this test
    // fail. The named UTXO must be selected by policy, not merely by gather order.
    let named_value = Zatoshis::const_from_u64(100_000);
    let other_value = Zatoshis::const_from_u64(150_000);
    let height = st.wallet().chain_height().unwrap().unwrap();
    let named_outpoint = OutPoint::new([1u8; 32], 0);
    let other_outpoint = OutPoint::new([2u8; 32], 0);
    for (addr, outpoint, value) in [
        (addr_other, other_outpoint.clone(), other_value),
        (addr_named, named_outpoint.clone(), named_value),
    ] {
        let utxo = WalletTransparentOutput::from_parts(
            outpoint,
            TxOut::new(value, addr.script().into()),
            Some(height),
            Some(account.id()),
            Some(TransparentKeyScope::EXTERNAL),
            None,
        )
        .unwrap();
        st.wallet_mut()
            .put_received_transparent_utxo(&utxo)
            .unwrap();
    }

    let network = *st.network();
    let request = t2t_request(&network, Zatoshis::const_from_u64(40_000));

    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling);

    let proposal = st
        .propose_transfer_with_policy(
            account.id(),
            &input_selector,
            &change_strategy,
            request,
            ConfirmationsPolicy::MIN,
            &SpendPolicy::default()
                .with_transparent(TransparentSpendPolicy::from_one_address(addr_named)),
        )
        .expect("transparent spend from named address must succeed");

    let step = &proposal.steps().head;
    let selected: Vec<&OutPoint> = step
        .transparent_inputs()
        .iter()
        .map(|i| i.outpoint())
        .collect();
    assert!(
        selected.contains(&&named_outpoint),
        "the named address's UTXO must be selected",
    );
    assert!(
        !selected.contains(&&other_outpoint),
        "an unnamed address's UTXO must not be selected",
    );
}

/// Verifies that the value-bounded `select_spendable_transparent_outputs` gather returns
/// only enough UTXOs to cover the requested `TargetValue`, rather than every spendable
/// output held by the account. This is the behavior that prevents wallets with large
/// numbers of small transparent UTXOs (e.g. recovered `zcashd` imports) from falling over
/// when a small transfer is requested.
pub fn value_bounded_transparent_gather<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();

    let account = st.test_account().cloned().unwrap();
    let uaddr = st
        .wallet()
        .get_last_generated_address_matching(account.id(), UnifiedAddressRequest::AllAvailableKeys)
        .unwrap()
        .unwrap();
    let taddr = *uaddr.transparent().unwrap();

    // Seed the chain with notes that do not belong to us so that heights resolve.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10_000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    for _ in 1..10 {
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    }
    st.scan_cached_blocks(start_height, 10);

    // Fund the account with many small dust UTXOs. Each is well above the marginal fee
    // (1_000 zats) so it's spendable, but tiny relative to the total. A naive "return
    // everything" gather would load all of these into memory; the value-bounded gather
    // should only return enough to cover the request.
    let dust_value = Zatoshis::const_from_u64(10_000);
    let n_dust = 50;
    let height = st.wallet().chain_height().unwrap().unwrap();
    for i in 0..n_dust {
        let mut hash = [0u8; 32];
        hash[..4].copy_from_slice(&(i as u32).to_le_bytes());
        let utxo = WalletTransparentOutput::from_parts(
            OutPoint::new(hash, 0),
            TxOut::new(dust_value, taddr.script().into()),
            Some(height),
            Some(account.id()),
            Some(TransparentKeyScope::EXTERNAL),
            None,
        )
        .unwrap();
        st.wallet_mut()
            .put_received_transparent_utxo(&utxo)
            .unwrap();
    }

    // Request 30_000 zats — 3x a single dust UTXO, but a small fraction of the total.
    let target = Zatoshis::const_from_u64(30_000);
    let target_height = TargetHeight::from(height + 1);

    let bound = st
        .wallet()
        .select_spendable_transparent_outputs(
            account.id(),
            target_height,
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
            None,
            TargetValue::AtLeast(target),
            usize::MAX,
            &StandardFeeRule::Zip317,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        )
        .expect("value-bounded gather should succeed");

    // The gather should return enough UTXOs to cover the target post-fee, not all 50.
    // Each UTXO is 10_000 zats. Under ZIP 317, `k` P2PKH inputs cost
    // `5_000 * max(2, k)` zats in marginal fee, so the post-fee value of the first `k`
    // gathered UTXOs is `10_000 * k - 5_000 * max(2, k)`. This first reaches the
    // 30_000-zat target at `k = 6` (60_000 - 30_000 = 30_000), one more than the 5
    // UTXOs (50_000 - 25_000 = 25_000) that would still fall short.
    assert!(
        !bound.is_empty(),
        "value-bounded gather should return at least one UTXO",
    );
    assert_eq!(
        bound.len(),
        6,
        "value-bounded gather should return exactly 6 UTXOs (10_000 zats each) to cover \
         30_000 zats net of the ZIP 317 marginal fee for 6 P2PKH inputs",
    );
    assert!(
        bound.len() < n_dust,
        "value-bounded gather should not return all {n_dust} UTXOs (returned {})",
        bound.len(),
    );
    // The summed value should meet the target.
    let total: Zatoshis = bound
        .iter()
        .map(|u| u.value())
        .fold(Zatoshis::ZERO, |acc, v| (acc + v).unwrap());
    assert!(
        total >= target,
        "value-bounded gather should cover the target (got {}, want >= {})",
        u64::from(total),
        u64::from(target),
    );

    // AllFunds should return all eligible UTXOs.
    let all = st
        .wallet()
        .select_spendable_transparent_outputs(
            account.id(),
            target_height,
            ConfirmationsPolicy::MIN,
            CoinbaseFilter::AllTransparentOutputs,
            None,
            TargetValue::AllFunds(MaxSpendMode::MaxSpendable),
            usize::MAX,
            &StandardFeeRule::Zip317,
            LockFilter::Policy(&LockedInputPolicy::Exclude),
        )
        .expect("AllFunds gather should succeed");
    assert_eq!(all.len(), n_dust);
}

/// Tests that [`WalletWrite::reserve_next_n_internal_addresses`] reserves sequential
/// internal-scope (change) addresses, that reservation observes the internal-scope gap
/// limit, and that internal-scope reservations are accounted independently of
/// ephemeral-scope reservations.
///
/// This test expects the data store to be configured with the default gap limits, under
/// which the internal-scope gap limit is 5.
///
/// The `is_reached_gap_limit` predicate must return `true` if and only if the provided
/// error is the backend's exact "reached gap limit" error variant, the scope reported by
/// that error is [`TransparentKeyScope::INTERNAL`], and the address index reported by that
/// error equals the provided expected index. It must not match any other error. (A
/// predicate is used because this test cannot name the backend's concrete error type
/// without inverting the crate dependency.)
pub fn reserve_next_n_internal_addresses_gap_limit<DSF>(
    dsf: DSF,
    cache: impl TestCache,
    is_reached_gap_limit: impl Fn(
        &<DSF::DataStore as crate::data_api::WalletRead>::Error,
        DSF::AccountId,
        u32,
    ) -> bool,
) where
    DSF: DataStoreFactory,
{
    let mut st = TestBuilder::new()
        .with_data_store_factory(dsf)
        .with_block_cache(cache)
        .with_account_from_sapling_activation(BlockHash([0; 32]))
        .build();
    let account_id = st.test_account().cloned().unwrap().id();

    // Seed the chain so that a chain height is known; address reservation records the
    // exposure height of each reserved address.
    let not_our_key = ExtendedSpendingKey::master(&[]).to_diversifiable_full_viewing_key();
    let not_our_value = Zatoshis::const_from_u64(10000);
    let (start_height, _, _) =
        st.generate_next_block(&not_our_key, AddressType::DefaultExternal, not_our_value);
    st.scan_cached_blocks(start_height, 1);

    // Reserving internal addresses yields distinct, sequentially-indexed addresses derived
    // under the internal (change) key scope.
    let reserved = st
        .wallet_mut()
        .reserve_next_n_internal_addresses(account_id, 3)
        .unwrap();
    assert_eq!(reserved.len(), 3);
    for (i, (_, meta)) in reserved.iter().enumerate() {
        assert_eq!(meta.scope(), Some(TransparentKeyScope::INTERNAL));
        assert_eq!(
            meta.address_index(),
            Some(NonHardenedChildIndex::const_from_index(
                u32::try_from(i).unwrap()
            )),
        );
    }
    // None of the reserved addresses have received funds, so the gap cannot advance: with
    // the default internal-scope gap limit of 5, only two more addresses may be reserved.
    // Reservation continues at the next sequential indices, so the returned addresses are
    // distinct from those of the first batch.
    let more = st
        .wallet_mut()
        .reserve_next_n_internal_addresses(account_id, 2)
        .unwrap();
    assert_eq!(more.len(), 2);
    for (i, (_, meta)) in more.iter().enumerate() {
        assert_eq!(meta.scope(), Some(TransparentKeyScope::INTERNAL));
        assert_eq!(
            meta.address_index(),
            Some(NonHardenedChildIndex::const_from_index(
                u32::try_from(reserved.len() + i).unwrap()
            )),
        );
    }
    let unique_addrs = reserved
        .iter()
        .chain(more.iter())
        .map(|(a, _)| *a)
        .collect::<HashSet<_>>();
    assert_eq!(unique_addrs.len(), reserved.len() + more.len());

    assert_matches!(
        st.wallet_mut().reserve_next_n_internal_addresses(account_id, 1),
        Err(e) if is_reached_gap_limit(&e, account_id, 5)
    );

    // Internal-scope reservations must not consume ephemeral-scope gap space.
    let ephemeral = st
        .wallet_mut()
        .reserve_next_n_ephemeral_addresses(account_id, 1)
        .unwrap();
    assert_eq!(ephemeral[0].1.scope(), Some(TransparentKeyScope::EPHEMERAL),);
    assert_eq!(
        ephemeral[0].1.address_index(),
        Some(NonHardenedChildIndex::const_from_index(0)),
    );
}

/// Tests the full lifecycle of a t->t transfer with transparent change: a change strategy
/// configured with [`TransparentChangePolicy::TransparentChangeAllowed`] must propose a
/// non-ephemeral transparent change output, and transaction creation must send that change
/// to a previously-unexposed internal-scope (change) transparent address of the spending
/// account, where it is recorded as received and becomes spendable once mined.
///
/// [`TransparentChangePolicy::TransparentChangeAllowed`]: crate::fees::TransparentChangePolicy::TransparentChangeAllowed
pub fn propose_t2t_with_transparent_change<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    let utxo_value = Zatoshis::const_from_u64(100_000);
    let transfer_amount = Zatoshis::const_from_u64(40_000);
    let (mut st, account, outpoint) = setup_transparent_only_account(dsf, cache, utxo_value);

    let network = *st.network();
    let request = t2t_request(&network, transfer_amount);

    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling)
            .with_transparent_change_policy(TransparentChangePolicy::TransparentChangeAllowed);

    let proposal = st
        .propose_transfer_with_policy(
            account.id(),
            &input_selector,
            &change_strategy,
            request,
            ConfirmationsPolicy::MIN,
            &SpendPolicy::default().with_transparent(TransparentSpendPolicy::any_account_addr()),
        )
        .expect("t->t proposal with transparent change must succeed");

    // A t->t transfer with non-ephemeral transparent change is a single step.
    assert_eq!(proposal.steps().len(), 1);
    let step = &proposal.steps().head;
    assert_eq!(step.transparent_inputs().len(), 1);
    assert_eq!(step.transparent_inputs()[0].outpoint(), &outpoint);
    assert!(step.shielded_inputs().is_none());

    // Under ZIP 317, one P2PKH input and two P2PKH outputs (the payment plus the change
    // output) require `5_000 * max(1, 2) = 10_000` zats in fees.
    let expected_fee = Zatoshis::const_from_u64(10_000);
    let expected_change = ((utxo_value - transfer_amount).unwrap() - expected_fee).unwrap();
    assert_eq!(step.balance().fee_required(), expected_fee);
    assert_eq!(
        step.balance().proposed_change(),
        [ChangeValue::transparent(expected_change)],
    );
    assert!(!step.balance().proposed_change()[0].is_ephemeral());

    // A proposal containing a transparent change output must survive a serialization
    // round trip.
    super::check_proposal_serialization_roundtrip(&network, st.wallet(), &proposal);

    // Creating the transaction should reserve an internal-scope address for the change.
    let txids = st
        .create_proposed_transactions::<Infallible, _, Infallible, _>(
            account.usk(),
            OvkPolicy::Sender,
            &proposal,
        )
        .expect("transaction creation must succeed");
    assert_eq!(txids.len(), 1);
    let txid = txids.head;

    // The transaction must be fully transparent, with exactly the payment and change outputs.
    let tx = st
        .wallet()
        .get_transaction(txid)
        .unwrap()
        .expect("the created transaction is retrievable");
    assert!(tx.sapling_bundle().is_none());
    #[cfg(feature = "orchard")]
    assert!(tx.orchard_bundle().is_none());
    let bundle = tx
        .transparent_bundle()
        .expect("the transaction has a transparent bundle");
    assert_eq!(bundle.vin.len(), 1);
    assert_eq!(bundle.vout.len(), 2);

    // Identify the change output as the output that does not pay the external recipient.
    let payment_recipient = TransparentAddress::PublicKeyHash([7u8; 20]);
    let change_outputs: Vec<_> = bundle
        .vout
        .iter()
        .filter(|out| out.recipient_address() != Some(payment_recipient))
        .collect();
    assert_eq!(change_outputs.len(), 1);
    let change_output = change_outputs[0];
    assert_eq!(change_output.value(), expected_change);
    let change_address = change_output
        .recipient_address()
        .expect("the change output pays a standard P2PKH address");

    // The change address must be an internal-scope (change) address of the spending account,
    // exposed at the current chain height by having been reserved for change.
    let receivers = st
        .wallet()
        .get_transparent_receivers(account.id(), true, false)
        .unwrap();
    let change_meta = receivers
        .get(&change_address)
        .expect("the change address belongs to the spending account");
    assert_eq!(change_meta.scope(), Some(TransparentKeyScope::INTERNAL));
    let cur_height = st.wallet().chain_height().unwrap().unwrap();
    assert_matches!(
        change_meta.exposure(),
        Exposure::Exposed { at_height, .. } if at_height == cur_height
    );

    // Mine the transaction; the change output should then be spendable at the change address.
    let (h, _) = st.generate_next_block_including(txid);
    st.scan_cached_blocks(h, 1);

    let mut expected_balance = Balance::ZERO;
    expected_balance
        .add_spendable_value(expected_change)
        .unwrap();
    check_balance::<DSF>(
        &st,
        &account,
        &change_address,
        ConfirmationsPolicy::MIN,
        &expected_balance,
    );
}

/// Tests that when a fully-transparent transaction balances exactly (input value equals
/// payments plus the minimum fee), no transparent change output is produced even when the
/// change strategy is configured with [`TransparentChangePolicy::TransparentChangeAllowed`].
///
/// [`TransparentChangePolicy::TransparentChangeAllowed`]: crate::fees::TransparentChangePolicy::TransparentChangeAllowed
pub fn propose_t2t_transparent_change_exact_match<DSF>(dsf: DSF, cache: impl TestCache)
where
    DSF: DataStoreFactory,
{
    // Under ZIP 317, one P2PKH input and one P2PKH output require the minimum fee of
    // 10_000 zats, so a 50_000-zat UTXO exactly covers a 40_000-zat payment.
    let utxo_value = Zatoshis::const_from_u64(50_000);
    let transfer_amount = Zatoshis::const_from_u64(40_000);
    let (mut st, account, _outpoint) = setup_transparent_only_account(dsf, cache, utxo_value);

    let network = *st.network();
    let request = t2t_request(&network, transfer_amount);

    let input_selector = GreedyInputSelector::new();
    let change_strategy =
        single_output_change_strategy(StandardFeeRule::Zip317, None, ShieldedPool::Sapling)
            .with_transparent_change_policy(TransparentChangePolicy::TransparentChangeAllowed);

    let proposal = st
        .propose_transfer_with_policy(
            account.id(),
            &input_selector,
            &change_strategy,
            request,
            ConfirmationsPolicy::MIN,
            &SpendPolicy::default().with_transparent(TransparentSpendPolicy::any_account_addr()),
        )
        .expect("exactly-balanced t->t proposal must succeed");

    assert_eq!(proposal.steps().len(), 1);
    let step = &proposal.steps().head;
    assert_eq!(
        step.balance().fee_required(),
        Zatoshis::const_from_u64(10_000),
    );
    assert_eq!(step.balance().proposed_change(), []);
}