//! Block headers

use serde::{Deserialize, Serialize};
use tendermint_proto::v0_37::{
    types::{BlockId as RawBlockId, Header as RawHeader},
    version::Consensus as RawConsensusVersion,
};
use tendermint_proto::Protobuf;

use crate::{
    account, block, chain,
    crypto::Sha256,
    merkle::{self, MerkleHash},
    prelude::*,
    AppHash, Hash, Time,
};

/// Block `Header` values contain metadata about the block and about the
/// consensus, as well as commitments to the data in the current block, the
/// previous block, and the results returned by the application.
///
/// <https://github.com/tendermint/spec/blob/d46cd7f573a2c6a2399fcab2cde981330aa63f37/spec/core/data_structures.md#header>
#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[serde(try_from = "RawHeader", into = "RawHeader")]
pub struct Header {
    /// Header version
    pub version: Version,

    /// Chain ID
    pub chain_id: chain::Id,

    /// Current block height
    pub height: block::Height,

    /// Current timestamp
    pub time: Time,

    /// Previous block info
    pub last_block_id: Option<block::Id>,

    /// Commit from validators from the last block
    pub last_commit_hash: Option<Hash>,

    /// Merkle root of transaction hashes
    pub data_hash: Option<Hash>,

    /// Validators for the current block
    pub validators_hash: Hash,

    /// Validators for the next block
    pub next_validators_hash: Hash,

    /// Consensus params for the current block
    pub consensus_hash: Hash,

    /// State after txs from the previous block
    pub app_hash: AppHash,

    /// Root hash of all results from the txs from the previous block
    pub last_results_hash: Option<Hash>,

    /// Hash of evidence included in the block
    pub evidence_hash: Option<Hash>,

    /// Original proposer of the block
    pub proposer_address: account::Id,
}

impl Header {
    /// Computes the hash of this header.
    #[cfg(feature = "rust-crypto")]
    pub fn hash(&self) -> Hash {
        self.hash_with::<crate::crypto::default::Sha256>()
    }

    /// Hash this header with a Merkle hasher provided by a crypto provider.
    pub fn hash_with<H>(&self) -> Hash
    where
        H: MerkleHash + Sha256 + Default,
    {
        // Note that if there is an encoding problem this will
        // panic (as the golang code would):
        // https://github.com/tendermint/tendermint/blob/134fe2896275bb926b49743c1e25493f6b24cc31/types/block.go#L393
        // https://github.com/tendermint/tendermint/blob/134fe2896275bb926b49743c1e25493f6b24cc31/types/encoding_helper.go#L9:6

        let fields_bytes = vec![
            Protobuf::<RawConsensusVersion>::encode_vec(&self.version).unwrap(),
            self.chain_id.encode_vec().unwrap(),
            self.height.encode_vec().unwrap(),
            self.time.encode_vec().unwrap(),
            Protobuf::<RawBlockId>::encode_vec(&self.last_block_id.unwrap_or_default()).unwrap(),
            self.last_commit_hash
                .unwrap_or_default()
                .encode_vec()
                .unwrap(),
            self.data_hash.unwrap_or_default().encode_vec().unwrap(),
            self.validators_hash.encode_vec().unwrap(),
            self.next_validators_hash.encode_vec().unwrap(),
            self.consensus_hash.encode_vec().unwrap(),
            self.app_hash.encode_vec().unwrap(),
            self.last_results_hash
                .unwrap_or_default()
                .encode_vec()
                .unwrap(),
            self.evidence_hash.unwrap_or_default().encode_vec().unwrap(),
            self.proposer_address.encode_vec().unwrap(),
        ];

        Hash::Sha256(merkle::simple_hash_from_byte_vectors::<H>(&fields_bytes))
    }
}

/// `Version` contains the protocol version for the blockchain and the
/// application.
///
/// <https://github.com/tendermint/spec/blob/d46cd7f573a2c6a2399fcab2cde981330aa63f37/spec/core/data_structures.md#version>
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub struct Version {
    /// Block version
    pub block: u64,

    /// App version
    pub app: u64,
}

// =============================================================================
// Protobuf conversions
// =============================================================================

tendermint_pb_modules! {
    use super::{Header, Version};
    use crate::{block, Error};
    use pb::{
        types::Header as RawHeader,
        version::Consensus as RawConsensusVersion,
    };

    impl Protobuf<RawHeader> for Header {}

    impl TryFrom<RawHeader> for Header {
        type Error = Error;

        fn try_from(value: RawHeader) -> Result<Self, Self::Error> {
            // If last block id is unfilled, it is considered nil by Go.
            let last_block_id = value
                .last_block_id
                .map(TryInto::try_into)
                .transpose()?
                .filter(|l| l != &block::Id::default());
            let last_commit_hash = if value.last_commit_hash.is_empty() {
                None
            } else {
                Some(value.last_commit_hash.try_into()?)
            };
            let last_results_hash = if value.last_results_hash.is_empty() {
                None
            } else {
                Some(value.last_results_hash.try_into()?)
            };
            let height: block::Height = value.height.try_into()?;

            // Todo: fix domain logic
            // if last_block_id.is_none() && height.value() != 1 {
            //    return Err(Kind::InvalidHeader.context("last_block_id is null on non-first
            // height").into());
            //}
            if last_block_id.is_some() && height.value() == 1 {
                return Err(Error::invalid_first_header());
            }
            // if last_commit_hash.is_none() && height.value() != 1 {
            //    return Err(Kind::InvalidHeader.context("last_commit_hash is null on non-first
            // height").into());
            //}
            // if height.value() == 1 && last_commit_hash.is_some() &&
            // last_commit_hash.as_ref().unwrap() != simple_hash_from_byte_vectors(Vec::new()) {
            //    return Err(Kind::InvalidFirstHeader.context("last_commit_hash is not empty Merkle tree
            // on first height").into());
            //}
            // if last_results_hash.is_none() && height.value() != 1 {
            //    return Err(Kind::InvalidHeader.context("last_results_hash is null on non-first
            // height").into());
            //}
            // if last_results_hash.is_some() && height.value() == 1 {
            //    return Err(Kind::InvalidFirstHeader.context("last_results_hash is not ull on first
            // height").into());
            //}
            Ok(Header {
                version: value.version.ok_or_else(Error::missing_version)?.into(),
                chain_id: value.chain_id.try_into()?,
                height,
                time: value
                    .time
                    .ok_or_else(Error::missing_timestamp)?
                    .try_into()?,
                last_block_id,
                last_commit_hash,
                data_hash: if value.data_hash.is_empty() {
                    None
                } else {
                    Some(value.data_hash.try_into()?)
                },
                validators_hash: value.validators_hash.try_into()?,
                next_validators_hash: value.next_validators_hash.try_into()?,
                consensus_hash: value.consensus_hash.try_into()?,
                app_hash: value.app_hash.try_into()?,
                last_results_hash,
                evidence_hash: if value.evidence_hash.is_empty() {
                    None
                } else {
                    Some(value.evidence_hash.try_into()?)
                }, // Todo: Is it illegal to have evidence of wrongdoing in the first block?
                proposer_address: value.proposer_address.try_into()?,
            })
        }
    }

    impl From<Header> for RawHeader {
        fn from(value: Header) -> Self {
            RawHeader {
                version: Some(value.version.into()),
                chain_id: value.chain_id.into(),
                height: value.height.into(),
                time: Some(value.time.into()),
                last_block_id: value.last_block_id.map(Into::into),
                last_commit_hash: value.last_commit_hash.unwrap_or_default().into(),
                data_hash: value.data_hash.unwrap_or_default().into(),
                validators_hash: value.validators_hash.into(),
                next_validators_hash: value.next_validators_hash.into(),
                consensus_hash: value.consensus_hash.into(),
                app_hash: value.app_hash.into(),
                last_results_hash: value.last_results_hash.unwrap_or_default().into(),
                evidence_hash: value.evidence_hash.unwrap_or_default().into(),
                proposer_address: value.proposer_address.into(),
            }
        }
    }

    impl Protobuf<RawConsensusVersion> for Version {}

    impl From<RawConsensusVersion> for Version {
        fn from(value: RawConsensusVersion) -> Self {
            Version {
                block: value.block,
                app: value.app,
            }
        }
    }

    impl From<Version> for RawConsensusVersion {
        fn from(value: Version) -> Self {
            RawConsensusVersion {
                block: value.block,
                app: value.app,
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::Header;
    use crate::test::test_serialization_roundtrip;

    #[test]
    fn serialization_roundtrip() {
        let json_data = include_str!("../../tests/support/serialization/block/header.json");
        test_serialization_roundtrip::<Header>(json_data);
    }

    #[cfg(feature = "rust-crypto")]
    mod crypto {
        use super::*;
        use crate::{hash::Algorithm, Hash};

        #[test]
        fn header_hashing() {
            let expected_hash = Hash::from_hex_upper(
                Algorithm::Sha256,
                "F30A71F2409FB15AACAEDB6CC122DFA2525BEE9CAE521721B06BFDCA291B8D56",
            )
            .unwrap();
            let header: Header = serde_json::from_str(include_str!(
                "../../tests/support/serialization/block/header_with_known_hash.json"
            ))
            .unwrap();
            assert_eq!(expected_hash, header.hash());
        }
    }
}