pczt/

lib.rs

//! The Partially Created Zcash Transaction (PCZT) format.
//!
//! This format enables splitting up the logical steps of creating a Zcash transaction
//! across distinct entities. The entity roles roughly match those specified in
//! [BIP 174: Partially Signed Bitcoin Transaction Format] and [BIP 370: PSBT Version 2],
//! with additional Zcash-specific roles.
//!
//! [BIP 174: Partially Signed Bitcoin Transaction Format]: https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki
//! [BIP 370: PSBT Version 2]: https://github.com/bitcoin/bips/blob/master/bip-0370.mediawiki
//!
#![cfg_attr(feature = "std", doc = "## Feature flags")]
#![cfg_attr(feature = "std", doc = document_features::document_features!())]
//!

#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![cfg_attr(docsrs, doc(auto_cfg))]
// Catch documentation errors caused by code changes.
#![deny(rustdoc::broken_intra_doc_links)]

#[macro_use]
extern crate alloc;
// The crate itself needs only `alloc`; the unit tests lean on `proptest`, which is a `std` crate.
#[cfg(test)]
extern crate std;

use alloc::vec::Vec;

use getset::Getters;

use zcash_protocol::PoolType;
#[cfg(any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"))]
use zcash_protocol::constants::{V6_TX_VERSION, V6_VERSION_GROUP_ID};
#[cfg(all(
    any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"),
    zcash_unstable = "nu7",
    feature = "zip-233",
))]
use zcash_protocol::value::Zatoshis;
#[cfg(any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"))]
use {
    common::{Global, determine_lock_time},
    zcash_primitives::transaction::{Authorization, TransactionData, TxVersion},
    zcash_protocol::{
        consensus::{BranchId, OrchardProtocolRevision},
        constants::{V5_TX_VERSION, V5_VERSION_GROUP_ID},
    },
};

#[cfg(any(feature = "io-finalizer", feature = "signer"))]
use zcash_primitives::transaction::sighash_v6::v6_signature_hash;
#[cfg(any(feature = "io-finalizer", feature = "signer"))]
use {
    blake2b_simd::Hash as Blake2bHash,
    zcash_primitives::transaction::{
        TxDigests, sighash::SignableInput, sighash_v5::v5_signature_hash,
    },
};

pub mod roles;

pub mod common;
pub mod orchard;
pub mod sapling;
pub mod transparent;

pub(crate) const MAGIC_BYTES: &[u8; 4] = b"PCZT";
pub(crate) const PCZT_VERSION_1: u32 = 1;
pub(crate) const PCZT_VERSION_2: u32 = 2;

const VERSIONED_HEADER_LEN: usize = 8;

pub(crate) enum HeaderParseError {
    InvalidMagic,
    TooShort,
}

pub(crate) fn parse_header<'a>(
    bytes: &'a [u8],
    magic: &[u8; 4],
) -> Result<(u32, &'a [u8]), HeaderParseError> {
    if bytes.len() < VERSIONED_HEADER_LEN {
        return Err(HeaderParseError::TooShort);
    }
    if &bytes[..4] != magic {
        return Err(HeaderParseError::InvalidMagic);
    }

    let version = u32::from_le_bytes(bytes[4..8].try_into().unwrap());
    Ok((version, &bytes[VERSIONED_HEADER_LEN..]))
}

pub(crate) fn serialize_header(magic: &[u8; 4], version: u32) -> Vec<u8> {
    let mut bytes = Vec::with_capacity(VERSIONED_HEADER_LEN);
    bytes.extend_from_slice(magic);
    bytes.extend_from_slice(&version.to_le_bytes());
    bytes
}

/// Parses a PCZT from its encoding.
pub fn parse(bytes: &[u8]) -> Result<Pczt, ParseError> {
    Pczt::parse(bytes)
}

/// A partially-created Zcash transaction.
#[derive(Clone, Debug, Getters)]
pub struct Pczt {
    /// Global fields that are relevant to the transaction as a whole.
    #[getset(get = "pub")]
    pub(crate) global: common::Global,

    //
    // Protocol-specific fields.
    //
    // Unlike the `TransactionData` type in `zcash_primitives`, these are not optional.
    // This is because a PCZT does not always contain a semantically-valid transaction,
    // and there may be phases where we need to store protocol-specific metadata before
    // it has been determined whether there are protocol-specific inputs or outputs.
    //
    #[getset(get = "pub")]
    pub(crate) transparent: transparent::Bundle,
    #[getset(get = "pub")]
    pub(crate) sapling: sapling::Bundle,
    #[getset(get = "pub")]
    pub(crate) orchard: orchard::Bundle,
    #[getset(get = "pub")]
    pub(crate) ironwood: orchard::Bundle,
}

/// Types and operations for the v1 Pczt encoding.
pub mod v1 {
    use alloc::vec::Vec;
    use serde::{Deserialize, Serialize};

    use crate::{common, orchard, sapling, transparent};

    /// The in-memory type used for derived serialization of the v1 Pczt encoding.
    #[derive(Clone, Debug, Serialize, Deserialize)]
    pub struct Pczt {
        global: common::Global,
        transparent: transparent::Bundle,
        sapling: sapling::v1::Bundle,
        orchard: orchard::v1::Bundle,
    }

    impl Pczt {
        pub fn serialize(&self) -> Vec<u8> {
            let bytes = crate::serialize_header(crate::MAGIC_BYTES, crate::PCZT_VERSION_1);
            postcard::to_extend(&self, bytes).expect("can serialize into memory")
        }
    }

    /// Encodes the in-memory [`super::Pczt`] into the v1 serialization type [`Pczt`].
    impl TryFrom<super::Pczt> for Pczt {
        type Error = super::EncodingError;

        fn try_from(pczt: super::Pczt) -> Result<Self, Self::Error> {
            // The v1 format predates the v6 transaction format; a parser of the v1
            // encoding could parse a v6 PCZT but never extract a transaction from it.
            if pczt.global.tx_version == zcash_protocol::constants::V6_TX_VERSION {
                return Err(super::EncodingError::UnsupportedTxVersion);
            }

            // The v1 format cannot represent an Ironwood bundle in any state other
            // than the canonical empty one; a parser of the v1 encoding will
            // reconstruct exactly that value.
            if pczt.ironwood != orchard::EMPTY_IRONWOOD {
                return Err(super::EncodingError::UnsupportedTxVersion);
            }

            Ok(Self {
                global: pczt.global,
                transparent: pczt.transparent,
                sapling: sapling::v1::Bundle::try_from(pczt.sapling)?,
                orchard: orchard::v1::Bundle::try_from(pczt.orchard)?,
            })
        }
    }

    impl From<Pczt> for super::Pczt {
        fn from(pczt: Pczt) -> Self {
            Self {
                global: pczt.global,
                transparent: pczt.transparent,
                sapling: pczt.sapling.into(),
                orchard: pczt.orchard.into(),
                ironwood: orchard::EMPTY_IRONWOOD,
            }
        }
    }

    #[cfg(test)]
    mod tests {
        use zcash_protocol::consensus::BranchId;

        use crate::roles::creator::Creator;

        #[test]
        fn v1_refuses_v6_pczts_and_non_canonical_ironwood_bundles() {
            // A v6 tx cannot be encoded as a v1 PCZT, even when its Ironwood bundle is
            // canonically empty.
            let pczt = Creator::new(
                BranchId::Nu6_3.into(),
                10_000_000,
                133,
                Some([0; 32]),
                Some([0; 32]),
            )
            .unwrap()
            .build()
            .unwrap();
            assert!(matches!(
                super::Pczt::try_from(pczt),
                Err(crate::EncodingError::UnsupportedTxVersion)
            ));

            // A v5 tx carrying non-canonical Ironwood bundle data cannot be encoded
            // as a v1 PCZT, because the data would be dropped.
            let mut pczt = Creator::new(
                BranchId::Nu6.into(),
                10_000_000,
                133,
                Some([0; 32]),
                Some([0; 32]),
            )
            .unwrap()
            .build()
            .unwrap();
            pczt.ironwood.bsk = Some([1; 32]);
            assert!(matches!(
                super::Pczt::try_from(pczt),
                Err(crate::EncodingError::UnsupportedTxVersion)
            ));
        }
    }
}

/// Types and operations for the v2 Pczt encoding.
pub mod v2 {
    use alloc::vec::Vec;
    use serde::{Deserialize, Serialize};

    use crate::{common, orchard, sapling, transparent};

    /// The in-memory type used for derived serialization of the v2 Pczt encoding.
    #[derive(Clone, Debug, Serialize, Deserialize)]
    pub struct Pczt {
        global: common::Global,
        // This value is set to `None` if the transparent bundle is empty,
        // meaning inputs and outputs are empty.
        transparent: Option<transparent::Bundle>,
        // This value is set to `None` if the Sapling bundle is empty,
        // meaning every field has its empty/default value.
        sapling: Option<sapling::Bundle>,
        // This value is set to `None` if the Orchard bundle is empty,
        // meaning actions, value sum, anchor, zkproof, and bsk are all
        // empty. Flags and note version are not checked, as values can be
        // defaulted there.
        orchard: Option<orchard::v2::Bundle>,
        ironwood: Option<orchard::v2::Bundle>,
    }

    impl Pczt {
        pub fn serialize(&self) -> Vec<u8> {
            let bytes = crate::serialize_header(crate::MAGIC_BYTES, crate::PCZT_VERSION_2);
            postcard::to_extend(&self, bytes).expect("can serialize into memory")
        }
    }

    /// Encodes the in-memory [`super::Pczt`] into the v2 serialization type [`Pczt`],
    /// omitting empty Transparent, Sapling, and Orchard bundles.
    impl TryFrom<super::Pczt> for Pczt {
        type Error = super::EncodingError;

        fn try_from(pczt: super::Pczt) -> Result<Self, Self::Error> {
            Ok(Self {
                global: pczt.global,
                transparent: (pczt.transparent != transparent::EMPTY_BUNDLE)
                    .then_some(pczt.transparent),
                sapling: sapling::v2::encode(pczt.sapling),
                orchard: orchard::v2::encode(pczt.orchard, &orchard::EMPTY_ORCHARD)?,
                ironwood: orchard::v2::encode(pczt.ironwood, &orchard::EMPTY_IRONWOOD)?,
            })
        }
    }

    impl Pczt {
        pub(super) fn into_logical(self) -> Result<super::Pczt, super::ParseError> {
            Ok(super::Pczt {
                global: self.global,
                transparent: self.transparent.unwrap_or(transparent::EMPTY_BUNDLE),
                sapling: self.sapling.unwrap_or(sapling::EMPTY_BUNDLE),
                orchard: self
                    .orchard
                    .map(orchard::v2::Bundle::into_logical)
                    .transpose()?
                    .unwrap_or(orchard::EMPTY_ORCHARD),
                ironwood: self
                    .ironwood
                    .map(orchard::v2::Bundle::into_logical)
                    .transpose()?
                    .unwrap_or(orchard::EMPTY_IRONWOOD),
            })
        }
    }

    #[cfg(test)]
    mod tests {
        use zcash_protocol::consensus::BranchId;

        use super::Pczt;
        use crate::{orchard::NoteVersion, roles::creator::Creator};

        #[test]
        fn empty_bundles_encode_as_none_and_decode_as_empty() {
            // Absent anchors: the shielded bundles carry no anchor and no
            // spends/actions, so they are fully empty and omitted.
            let pczt = Creator::new(BranchId::Nu6_3.into(), 10_000_000, 133, None, None)
                .unwrap()
                .build()
                .unwrap();

            let encoded = Pczt::try_from(pczt).unwrap();

            assert!(encoded.transparent.is_none());
            assert!(encoded.sapling.is_none());
            assert!(encoded.orchard.is_none());
            assert!(encoded.ironwood.is_none());

            let decoded = crate::parse(&encoded.serialize()).unwrap();

            assert!(decoded.transparent.inputs.is_empty());
            assert!(decoded.transparent.outputs.is_empty());
            assert!(decoded.sapling.spends.is_empty());
            assert!(decoded.sapling.outputs.is_empty());
            assert!(decoded.sapling.anchor.is_none());
            assert!(decoded.orchard.actions.is_empty());
            assert_eq!(decoded.orchard.note_version, NoteVersion::V2);
            {
                assert!(decoded.ironwood.actions.is_empty());
                assert_eq!(decoded.ironwood.note_version, NoteVersion::V3);
            }
        }

        #[test]
        fn anchored_bundles_are_preserved() {
            // A Sapling/Orchard bundle with a non-empty anchor differs from its
            // empty form, so it must not be omitted even with no spends/actions,
            // and the anchor must survive the v2 round-trip.
            let pczt = Creator::new(
                BranchId::Nu6.into(),
                10_000_000,
                133,
                Some([1; 32]),
                Some([2; 32]),
            )
            .unwrap()
            .build()
            .unwrap();

            let encoded = Pczt::try_from(pczt).unwrap();

            assert!(encoded.transparent.is_none());
            assert!(encoded.sapling.is_some());
            assert!(encoded.orchard.is_some());

            let decoded = crate::parse(&encoded.serialize()).unwrap();

            assert_eq!(decoded.sapling.anchor, Some([1; 32]));
            assert_eq!(decoded.orchard.anchor, Some([2; 32]));
        }

        #[test]
        fn non_canonical_orchard_flags_and_note_version_prevent_omission() {
            let mut pczt = Creator::new(
                BranchId::Nu6.into(),
                10_000_000,
                133,
                Some([0; 32]),
                Some([0; 32]),
            )
            .unwrap()
            .build()
            .unwrap();
            pczt.orchard.flags = 0;
            pczt.orchard.note_version = NoteVersion::V3;

            // A bundle whose flags or note version differ from the canonical empty
            // bundle is not omitted, so that those fields round-trip losslessly.
            let encoded = Pczt::try_from(pczt.clone()).unwrap();
            assert!(encoded.orchard.is_some());

            let decoded = encoded.into_logical().unwrap();
            assert_eq!(decoded.orchard, pczt.orchard);
            assert_eq!(decoded.orchard.flags, 0);
            assert_eq!(decoded.orchard.note_version, NoteVersion::V3);
        }
    }
}

/// Errors that can occur while serializing a PCZT.
#[derive(Debug)]
#[non_exhaustive]
pub enum EncodingError {
    /// The requested transaction version cannot be represented in this PCZT
    /// encoding.
    UnsupportedTxVersion,
    /// The v1 PCZT encoding does not support this Orchard note plaintext version.
    UnsupportedOrchardNoteVersion,
    /// The PCZT contains data that can only be represented in v2.
    RequiresV2,
}

impl Pczt {
    /// Whether this PCZT carries any inputs or outputs in the given pool.
    ///
    /// Every bundle is always present as a value, so its existence says nothing; this asks whether
    /// it holds anything.
    pub fn has_data_in_pool(&self, pool: PoolType) -> bool {
        match pool {
            PoolType::TRANSPARENT => {
                !self.transparent.inputs().is_empty() || !self.transparent.outputs().is_empty()
            }
            PoolType::SAPLING => {
                !self.sapling.spends().is_empty() || !self.sapling.outputs().is_empty()
            }
            PoolType::ORCHARD => !self.orchard.actions().is_empty(),
            PoolType::IRONWOOD => !self.ironwood.actions().is_empty(),
        }
    }

    /// Parses a PCZT from its encoding.
    pub fn parse(bytes: &[u8]) -> Result<Self, ParseError> {
        let (version, body) = parse_header(bytes, MAGIC_BYTES).map_err(|e| match e {
            HeaderParseError::InvalidMagic => ParseError::NotPczt,
            HeaderParseError::TooShort => ParseError::TooShort,
        })?;
        match version {
            PCZT_VERSION_1 => postcard::from_bytes::<v1::Pczt>(body)
                .map(Pczt::from)
                .map_err(ParseError::Invalid),
            PCZT_VERSION_2 => postcard::from_bytes::<v2::Pczt>(body)
                .map_err(ParseError::Invalid)
                .and_then(v2::Pczt::into_logical),
            _ => Err(ParseError::UnknownVersion(version)),
        }
    }

    /// Serializes this PCZT in the minimal encoding version capable of
    /// representing its content: the v1 encoding whenever the PCZT is
    /// representable in it (maximizing compatibility with receivers that
    /// predate the v2 encoding), and the v2 encoding otherwise.
    ///
    /// To force a specific PCZT version, use [`v1::Pczt`] or [`v2::Pczt`]
    /// directly.
    pub fn serialize(self) -> Result<Vec<u8>, EncodingError> {
        // Fast pre-checks for the conditions that most commonly rule out the
        // v1 encoding, avoiding the speculative clone below.
        if self.global.tx_version != zcash_protocol::constants::V6_TX_VERSION
            && self.ironwood == orchard::EMPTY_IRONWOOD
        {
            // The full v1-representability conditions live in the bundle
            // conversions; attempting the conversion is the single source of
            // truth for them.
            if let Ok(v1) = v1::Pczt::try_from(self.clone()) {
                return Ok(v1.serialize());
            }
        }
        Ok(v2::Pczt::try_from(self)?.serialize())
    }

    /// Resolves derived or compact field representations carried by this PCZT.
    ///
    /// For improved efficiency, callers that will pass the same PCZT through
    /// multiple roles should call this once up front. Parsing also resolves fields
    /// defensively.
    #[cfg(feature = "orchard")]
    pub fn resolve_fields(&mut self) -> Result<(), ::orchard::pczt::ParseError> {
        self.orchard.resolve_fields()?;
        self.ironwood.resolve_fields()
    }

    /// Parses this PCZT's bundles and constructs a `TransactionData` using caller-provided
    /// bundle extraction closures.
    ///
    /// This handles bundle parsing, version validation, consensus branch ID parsing,
    /// lock time computation, and final assembly, delegating bundle extraction to the
    /// caller via closures that receive references to the parsed bundles.
    #[cfg(any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"))]
    pub(crate) fn extract_tx_data<A, E>(
        self,
        anchor_requirement: common::AnchorRequirement,
        extract_transparent: impl FnOnce(
            &::transparent::pczt::Bundle,
        ) -> Result<
            Option<::transparent::bundle::Bundle<A::TransparentAuth>>,
            E,
        >,
        extract_sapling: impl FnOnce(
            &::sapling::pczt::Bundle,
        ) -> Result<
            Option<::sapling::Bundle<A::SaplingAuth, zcash_protocol::value::ZatBalance>>,
            E,
        >,
        extract_orchard: impl FnOnce(
            &::orchard::pczt::Bundle,
        ) -> Result<
            Option<::orchard::Bundle<A::OrchardAuth, zcash_protocol::value::ZatBalance>>,
            E,
        >,
        extract_ironwood: impl FnOnce(
            &::orchard::pczt::Bundle,
        ) -> Result<
            Option<::orchard::Bundle<A::OrchardAuth, zcash_protocol::value::ZatBalance>>,
            E,
        >,
    ) -> Result<ParsedPczt<A>, E>
    where
        A: Authorization,
        E: From<ExtractError>,
    {
        let Pczt {
            global,
            transparent,
            sapling,
            orchard,
            ironwood,
        } = self;

        let consensus_branch_id = BranchId::try_from(global.consensus_branch_id)
            .map_err(|_| ExtractError::UnknownConsensusBranchId)?;
        let orchard_protocol_revision = consensus_branch_id
            .orchard_protocol_revision()
            // The v5 and v6 transaction formats do not exist prior to NU5, so no
            // transaction could be extracted under such a branch in any case.
            .ok_or(ExtractError::UnsupportedConsensusBranchId)?;

        let version = match (global.tx_version, global.version_group_id) {
            (V5_TX_VERSION, V5_VERSION_GROUP_ID) => Ok(TxVersion::V5),
            (V6_TX_VERSION, V6_VERSION_GROUP_ID) => Ok(TxVersion::V6),
            (version, version_group_id) => Err(ExtractError::UnsupportedTxVersion {
                version,
                version_group_id,
            }),
        }?;

        match version {
            // Only the v6 transaction format carries an Ironwood bundle.
            TxVersion::Sprout(_) | TxVersion::V3 | TxVersion::V4 | TxVersion::V5 => {
                if ironwood != crate::orchard::EMPTY_IRONWOOD {
                    return Err(ExtractError::IronwoodNotSupported.into());
                }
            }
            // The v6 transaction format does not exist prior to NU6.3 (the first
            // upgrade under which the Orchard protocol is at revision V3).
            TxVersion::V6 => {
                if orchard_protocol_revision < OrchardProtocolRevision::V3 {
                    return Err(ExtractError::UnsupportedConsensusBranchId.into());
                }
            }
        }

        let transparent = transparent
            .into_parsed()
            .map_err(ExtractError::TransparentParse)?;
        let sapling = sapling
            .into_parsed(anchor_requirement)
            .map_err(ExtractError::SaplingParse)?;
        let orchard_bundle_version = crate::orchard::bundle_version_for_revision(
            orchard_protocol_revision,
            ::orchard::ValuePool::Orchard,
        )
        .expect("the Orchard pool is supported under every protocol revision");
        let orchard = orchard
            .into_parsed_with_version(orchard_bundle_version, anchor_requirement)
            .map_err(ExtractError::OrchardParse)?;
        let ironwood = ironwood
            .into_ironwood_parsed(anchor_requirement)
            .map_err(ExtractError::IronwoodParse)?;

        let lock_time = determine_lock_time(&global, transparent.inputs())
            .ok_or(ExtractError::IncompatibleLockTimes)?;

        let transparent_bundle = extract_transparent(&transparent)?;
        let sapling_bundle = extract_sapling(&sapling.bundle)?;
        let orchard_bundle = extract_orchard(&orchard.bundle)?;
        let ironwood_bundle = extract_ironwood(&ironwood.bundle)?;

        let tx_data = match version {
            TxVersion::V6 => TransactionData::from_parts_v6(
                consensus_branch_id,
                lock_time,
                global.expiry_height.into(),
                #[cfg(all(zcash_unstable = "nu7", feature = "zip-233"))]
                Zatoshis::ZERO,
                transparent_bundle,
                sapling_bundle,
                orchard_bundle,
                ironwood_bundle,
            ),
            _ => TransactionData::from_parts(
                version,
                consensus_branch_id,
                lock_time,
                global.expiry_height.into(),
                #[cfg(all(zcash_unstable = "nu7", feature = "zip-233"))]
                Zatoshis::ZERO,
                transparent_bundle,
                None,
                sapling_bundle,
                orchard_bundle,
            ),
        };

        Ok(ParsedPczt {
            global,
            transparent,
            sapling,
            orchard,
            ironwood,
            tx_data,
        })
    }

    /// Gets the effects of this transaction.
    #[cfg(any(feature = "io-finalizer", feature = "signer"))]
    pub fn into_effects(self) -> Result<TransactionData<EffectsOnly>, ExtractError> {
        let anchor_requirement =
            common::AnchorRequirement::for_pre_authorization(self.global.tx_version);

        self.extract_tx_data(
            anchor_requirement,
            |t| {
                t.extract_effects()
                    .map_err(ExtractError::TransparentExtract)
            },
            |s| s.extract_effects().map_err(ExtractError::SaplingExtract),
            |o| o.extract_effects().map_err(ExtractError::OrchardExtract),
            |i| i.extract_effects().map_err(ExtractError::IronwoodExtract),
        )
        .map(|parsed| parsed.tx_data)
    }
}

/// The result of parsing a PCZT and constructing its `TransactionData`.
#[cfg(any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"))]
#[cfg_attr(
    not(any(feature = "io-finalizer", feature = "signer")),
    allow(dead_code)
)]
pub(crate) struct ParsedPczt<A: Authorization> {
    pub(crate) global: Global,
    pub(crate) transparent: ::transparent::pczt::Bundle,
    pub(crate) sapling: crate::sapling::Parsed,
    pub(crate) orchard: crate::orchard::Parsed,
    pub(crate) ironwood: crate::orchard::Parsed,
    pub(crate) tx_data: TransactionData<A>,
}

#[cfg(any(feature = "io-finalizer", feature = "signer"))]
pub struct EffectsOnly;

#[cfg(any(feature = "io-finalizer", feature = "signer"))]
impl Authorization for EffectsOnly {
    type TransparentAuth = ::transparent::bundle::EffectsOnly;
    type SaplingAuth = ::sapling::bundle::EffectsOnly;
    type OrchardAuth = ::orchard::bundle::EffectsOnly;
}

/// Helper to produce the correct sighash for a PCZT.
#[cfg(any(feature = "io-finalizer", feature = "signer"))]
pub(crate) fn sighash(
    tx_data: &TransactionData<EffectsOnly>,
    signable_input: &SignableInput,
    txid_parts: &TxDigests<Blake2bHash>,
) -> [u8; 32] {
    match tx_data.version() {
        TxVersion::V5 => v5_signature_hash(tx_data, signable_input, txid_parts),
        TxVersion::V6 => v6_signature_hash(tx_data, signable_input, txid_parts),
        _ => unreachable!("PCZT only supports v5 and v6 transaction data"),
    }
    .as_ref()
    .try_into()
    .expect("correct length")
}

/// Errors that can occur while parsing PCZT bundles and extracting transaction data.
#[cfg(any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"))]
#[derive(Debug)]
#[non_exhaustive]
pub enum ExtractError {
    /// The PCZT's transparent inputs have incompatible lock time requirements.
    IncompatibleLockTimes,
    /// An error occurred extracting the Ironwood protocol bundle from the Ironwood PCZT bundle.
    IronwoodExtract(::orchard::pczt::TxExtractorError),
    /// The PCZT carries Ironwood bundle data, but its transaction version does not
    /// support an Ironwood bundle.
    IronwoodNotSupported,
    /// An error occurred parsing the Ironwood PCZT bundle from the PCZT data.
    IronwoodParse(crate::orchard::ParseError),
    /// An error occurred extracting the Orchard protocol bundle from the Orchard PCZT bundle.
    OrchardExtract(::orchard::pczt::TxExtractorError),
    /// An error occurred parsing the Orchard PCZT bundle from the PCZT data.
    OrchardParse(crate::orchard::ParseError),
    /// An error occurred extracting the Sapling protocol bundle from the Sapling PCZT bundle.
    SaplingExtract(::sapling::pczt::TxExtractorError),
    /// An error occurred parsing the Sapling PCZT bundle from the PCZT data.
    SaplingParse(crate::sapling::ParseError),
    /// An error occurred extracting the transparent protocol bundle from the
    /// transparent PCZT bundle.
    TransparentExtract(::transparent::pczt::TxExtractorError),
    /// An error occurred parsing the transparent PCZT bundle from the PCZT data.
    TransparentParse(::transparent::pczt::ParseError),
    /// The consensus branch ID requested by the PCZT does not correspond to a
    /// known network upgrade.
    UnknownConsensusBranchId,
    /// The network upgrade for the PCZT's consensus branch ID predates the v5
    /// transaction format, so no transaction can be extracted from it.
    UnsupportedConsensusBranchId,
    /// The PCZT specifies an unsupported transaction version.
    UnsupportedTxVersion { version: u32, version_group_id: u32 },
}

#[cfg(any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"))]
impl core::fmt::Display for ExtractError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            ExtractError::IncompatibleLockTimes => {
                write!(f, "the transparent inputs have incompatible lock times")
            }
            ExtractError::IronwoodExtract(e) => {
                write!(f, "could not extract the Ironwood bundle: {e}")
            }
            ExtractError::IronwoodNotSupported => write!(
                f,
                "the PCZT carries Ironwood bundle data, but its transaction version has no \
                 Ironwood bundle"
            ),
            ExtractError::IronwoodParse(e) => {
                write!(f, "could not parse the Ironwood bundle: {e:?}")
            }
            ExtractError::OrchardExtract(e) => {
                write!(f, "could not extract the Orchard bundle: {e}")
            }
            ExtractError::OrchardParse(e) => write!(f, "could not parse the Orchard bundle: {e:?}"),
            ExtractError::SaplingExtract(e) => {
                write!(f, "could not extract the Sapling bundle: {e}")
            }
            ExtractError::SaplingParse(e) => write!(f, "could not parse the Sapling bundle: {e:?}"),
            ExtractError::TransparentExtract(e) => {
                write!(f, "could not extract the transparent bundle: {e:?}")
            }
            ExtractError::TransparentParse(e) => {
                write!(f, "could not parse the transparent bundle: {e:?}")
            }
            ExtractError::UnknownConsensusBranchId => write!(f, "unknown consensus branch ID"),
            ExtractError::UnsupportedConsensusBranchId => write!(
                f,
                "the consensus branch ID predates the v5 transaction format"
            ),
            ExtractError::UnsupportedTxVersion {
                version,
                version_group_id,
            } => write!(
                f,
                "unsupported transaction version {version} (version group ID {version_group_id})"
            ),
        }
    }
}

#[cfg(any(feature = "io-finalizer", feature = "signer", feature = "tx-extractor"))]
impl core::error::Error for ExtractError {}

/// Errors that can occur while parsing a PCZT.
#[derive(Debug)]
pub enum ParseError {
    /// The bytes do not contain a PCZT.
    NotPczt,
    /// The PCZT encoding was invalid.
    Invalid(postcard::Error),
    /// The PCZT encoding omitted a field that is required by the logical PCZT
    /// type.
    MissingRequiredField(&'static str),
    /// The bytes are too short to contain a PCZT.
    TooShort,
    /// The PCZT has an unknown version.
    UnknownVersion(u32),
}

impl core::fmt::Display for ParseError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            ParseError::NotPczt => write!(f, "the bytes do not contain a PCZT"),
            ParseError::Invalid(e) => write!(f, "invalid PCZT encoding: {e}"),
            ParseError::MissingRequiredField(field) => {
                write!(f, "the PCZT encoding omitted the required field {field}")
            }
            ParseError::TooShort => write!(f, "the bytes are too short to contain a PCZT"),
            ParseError::UnknownVersion(v) => write!(f, "unknown PCZT version {v}"),
        }
    }
}

impl core::error::Error for ParseError {}

#[cfg(all(test, any(feature = "io-finalizer", feature = "signer")))]
mod extraction_tests {
    use zcash_protocol::consensus::BranchId;

    use crate::{ExtractError, roles::creator::Creator};

    #[test]
    fn v5_pczt_with_ironwood_data_does_not_extract() {
        let mut pczt = Creator::new(
            BranchId::Nu6.into(),
            10_000_000,
            133,
            Some([0; 32]),
            Some([0; 32]),
        )
        .unwrap()
        .build()
        .unwrap();
        pczt.ironwood.bsk = Some([1; 32]);
        assert!(matches!(
            pczt.into_effects(),
            Err(ExtractError::IronwoodNotSupported)
        ));
    }

    #[test]
    fn v6_pczt_with_pre_nu6_3_branch_does_not_extract() {
        let mut pczt = Creator::new(
            BranchId::Nu6_3.into(),
            10_000_000,
            133,
            Some([0; 32]),
            Some([0; 32]),
        )
        .unwrap()
        .build()
        .unwrap();
        pczt.global.consensus_branch_id = BranchId::Nu6_2.into();
        assert!(matches!(
            pczt.into_effects(),
            Err(ExtractError::UnsupportedConsensusBranchId)
        ));
    }
}

#[cfg(test)]
mod serialize_tests {
    use zcash_protocol::consensus::BranchId;

    use crate::roles::creator::Creator;

    fn encoding_version(bytes: &[u8]) -> u32 {
        assert_eq!(&bytes[..4], crate::MAGIC_BYTES);
        u32::from_le_bytes(bytes[4..8].try_into().unwrap())
    }

    #[test]
    fn serialize_emits_minimal_encoding() {
        // A v1-representable (v5, canonical-empty Ironwood) PCZT serializes as v1.
        let pczt = Creator::new(
            BranchId::Nu6.into(),
            10_000_000,
            133,
            Some([0; 32]),
            Some([0; 32]),
        )
        .unwrap()
        .build()
        .unwrap();
        let bytes = pczt.clone().serialize().unwrap();
        assert_eq!(encoding_version(&bytes), crate::PCZT_VERSION_1);
        // The minimal encoding still round-trips through the ordinary parser.
        assert!(crate::Pczt::parse(&bytes).is_ok());

        // Non-canonical Ironwood data forces the v2 encoding.
        let mut with_ironwood = pczt.clone();
        with_ironwood.ironwood.bsk = Some([1; 32]);
        assert_eq!(
            encoding_version(&with_ironwood.serialize().unwrap()),
            crate::PCZT_VERSION_2,
        );

        // An Orchard note-plaintext version the v1 encoding cannot carry
        // forces the v2 encoding.
        let mut with_note_v3 = pczt;
        with_note_v3.orchard.note_version = crate::orchard::NoteVersion::V3;
        assert_eq!(
            encoding_version(&with_note_v3.serialize().unwrap()),
            crate::PCZT_VERSION_2,
        );

        // A v6 transaction forces the v2 encoding.
        let v6 = Creator::new(
            BranchId::Nu6_3.into(),
            10_000_000,
            133,
            Some([0; 32]),
            Some([0; 32]),
        )
        .unwrap()
        .build()
        .unwrap();
        assert_eq!(
            encoding_version(&v6.serialize().unwrap()),
            crate::PCZT_VERSION_2,
        );
    }
}