//! Errors that can occur when checking consensus rules.
//!
//! Each error variant corresponds to a consensus rule, so enumerating
//! all possible verification failures enumerates the consensus rules we
//! implement, and ensures that we don't reject blocks or transactions
//! for a non-enumerated reason.

use thiserror::Error;

use zebra_chain::{orchard, sapling, sprout, transparent};

use crate::BoxError;

#[cfg(any(test, feature = "proptest-impl"))]
use proptest_derive::Arbitrary;

#[derive(Error, Copy, Clone, Debug, PartialEq, Eq)]
pub enum SubsidyError {
    #[error("no coinbase transaction in block")]
    NoCoinbase,

    #[error("founders reward output not found")]
    FoundersRewardNotFound,
}

#[derive(Error, Clone, Debug, PartialEq, Eq)]
#[cfg_attr(any(test, feature = "proptest-impl"), derive(Arbitrary))]
pub enum TransactionError {
    #[error("first transaction must be coinbase")]
    CoinbasePosition,

    #[error("coinbase input found in non-coinbase transaction")]
    CoinbaseAfterFirst,

    #[error("coinbase transaction MUST NOT have any transparent (PrevOut) inputs")]
    CoinbaseHasPrevOutInput,

    #[error("coinbase transaction MUST NOT have any JoinSplit descriptions")]
    CoinbaseHasJoinSplit,

    #[error("coinbase transaction MUST NOT have any Spend descriptions")]
    CoinbaseHasSpend,

    #[error("coinbase transaction MUST NOT have any Output descriptions pre-Heartwood")]
    CoinbaseHasOutputPreHeartwood,

    #[error("coinbase transaction MUST NOT have the EnableSpendsOrchard flag set")]
    CoinbaseHasEnableSpendsOrchard,

    #[error("coinbase inputs MUST NOT exist in mempool")]
    CoinbaseInMempool,

    #[error("coinbase transaction failed subsidy validation")]
    #[cfg_attr(any(test, feature = "proptest-impl"), proptest(skip))]
    Subsidy(#[from] SubsidyError),

    #[error("transaction version number MUST be >= 4")]
    WrongVersion,

    #[error("transaction version {0} not supported by the network upgrade {1:?}")]
    UnsupportedByNetworkUpgrade(u32, zebra_chain::parameters::NetworkUpgrade),

    #[error("must have at least one input: transparent, shielded spend, or joinsplit")]
    NoInputs,

    #[error("must have at least one output: transparent, shielded output, or joinsplit")]
    NoOutputs,

    #[error("if there are no Spends or Outputs, the value balance MUST be 0.")]
    BadBalance,

    #[error("could not verify a transparent script")]
    #[cfg_attr(any(test, feature = "proptest-impl"), proptest(skip))]
    Script(#[from] zebra_script::Error),

    #[error("spend description cv and rk MUST NOT be of small order")]
    SmallOrder,

    // XXX change this when we align groth16 verifier errors with bellman
    // and add a from annotation when the error type is more precise
    #[error("spend proof MUST be valid given a primary input formed from the other fields except spendAuthSig")]
    Groth16,

    #[error(
        "Sprout joinSplitSig MUST represent a valid signature under joinSplitPubKey of dataToBeSigned"
    )]
    #[cfg_attr(any(test, feature = "proptest-impl"), proptest(skip))]
    Ed25519(#[from] zebra_chain::primitives::ed25519::Error),

    #[error("Sapling bindingSig MUST represent a valid signature under the transaction binding validating key bvk of SigHash")]
    #[cfg_attr(any(test, feature = "proptest-impl"), proptest(skip))]
    RedJubjub(zebra_chain::primitives::redjubjub::Error),

    #[error("Orchard bindingSig MUST represent a valid signature under the transaction binding validating key bvk of SigHash")]
    #[cfg_attr(any(test, feature = "proptest-impl"), proptest(skip))]
    RedPallas(zebra_chain::primitives::redpallas::Error),

    // temporary error type until #1186 is fixed
    #[error("Downcast from BoxError to redjubjub::Error failed")]
    InternalDowncastError(String),

    #[error("adding to the sprout pool is disabled after Canopy")]
    DisabledAddToSproutPool,

    #[error("could not calculate the transaction fee")]
    IncorrectFee,

    #[error("transparent double-spend: {_0:?} is spent twice")]
    DuplicateTransparentSpend(transparent::OutPoint),

    #[error("sprout double-spend: duplicate nullifier: {_0:?}")]
    DuplicateSproutNullifier(sprout::Nullifier),

    #[error("sapling double-spend: duplicate nullifier: {_0:?}")]
    DuplicateSaplingNullifier(sapling::Nullifier),

    #[error("orchard double-spend: duplicate nullifier: {_0:?}")]
    DuplicateOrchardNullifier(orchard::Nullifier),

    #[error("must have at least one active orchard flag")]
    NotEnoughFlags,
}

impl From<BoxError> for TransactionError {
    fn from(mut err: BoxError) -> Self {
        // TODO: handle redpallas::Error, ScriptInvalid, InvalidSignature
        match err.downcast::<zebra_chain::primitives::redjubjub::Error>() {
            Ok(e) => return TransactionError::RedJubjub(*e),
            Err(e) => err = e,
        }

        // buffered transaction verifier service error
        match err.downcast::<TransactionError>() {
            Ok(e) => return *e,
            Err(e) => err = e,
        }

        TransactionError::InternalDowncastError(format!(
            "downcast to known transaction error type failed, original error: {:?}",
            err,
        ))
    }
}

impl From<SubsidyError> for BlockError {
    fn from(err: SubsidyError) -> BlockError {
        BlockError::Transaction(TransactionError::Subsidy(err))
    }
}

#[derive(Error, Clone, Debug, PartialEq, Eq)]
pub enum BlockError {
    #[error("block contains invalid transactions")]
    Transaction(#[from] TransactionError),

    #[error("block has no transactions")]
    NoTransactions,

    #[error("block has mismatched merkle root")]
    BadMerkleRoot {
        actual: zebra_chain::block::merkle::Root,
        expected: zebra_chain::block::merkle::Root,
    },

    #[error("block contains duplicate transactions")]
    DuplicateTransaction,

    #[error("block {0:?} is already in the chain at depth {1:?}")]
    AlreadyInChain(zebra_chain::block::Hash, u32),

    #[error("invalid block {0:?}: missing block height")]
    MissingHeight(zebra_chain::block::Hash),

    #[error("invalid block height {0:?} in {1:?}: greater than the maximum height {2:?}")]
    MaxHeight(
        zebra_chain::block::Height,
        zebra_chain::block::Hash,
        zebra_chain::block::Height,
    ),

    #[error("invalid difficulty threshold in block header {0:?} {1:?}")]
    InvalidDifficulty(zebra_chain::block::Height, zebra_chain::block::Hash),

    #[error("block {0:?} has a difficulty threshold {2:?} that is easier than the {3:?} difficulty limit {4:?}, hash: {1:?}")]
    TargetDifficultyLimit(
        zebra_chain::block::Height,
        zebra_chain::block::Hash,
        zebra_chain::work::difficulty::ExpandedDifficulty,
        zebra_chain::parameters::Network,
        zebra_chain::work::difficulty::ExpandedDifficulty,
    ),

    #[error(
        "block {0:?} on {3:?} has a hash {1:?} that is easier than its difficulty threshold {2:?}"
    )]
    DifficultyFilter(
        zebra_chain::block::Height,
        zebra_chain::block::Hash,
        zebra_chain::work::difficulty::ExpandedDifficulty,
        zebra_chain::parameters::Network,
    ),

    #[error("transaction has wrong consensus branch id for block network upgrade")]
    WrongTransactionConsensusBranchId,
}