use std::fmt::{Display, Formatter};
#[cfg(any(not(target_arch = "wasm32"), feature = "wasm-bindgen"))]
use std::time::Duration;

use celestia_proto::header::pb::ExtendedHeader as RawExtendedHeader;
use celestia_tendermint::block::header::Header;
use celestia_tendermint::block::{Commit, Height};
use celestia_tendermint::chain::id::Id;
use celestia_tendermint::{validator, Hash, Time};
use celestia_tendermint_proto::Protobuf;
use serde::{Deserialize, Serialize};

use crate::trust_level::DEFAULT_TRUST_LEVEL;
use crate::validator_set::ValidatorSetExt;
use crate::{
    bail_validation, bail_verification, DataAvailabilityHeader, Error, Result, ValidateBasic,
};

/// Information about a tendermint validator.
pub type Validator = validator::Info;
/// A collection of the tendermint validators.
pub type ValidatorSet = validator::Set;

#[cfg(any(not(target_arch = "wasm32"), feature = "wasm-bindgen"))]
const VERIFY_CLOCK_DRIFT: Duration = Duration::from_secs(10);

/// Block header together with the relevant Data Availability metadata.
///
/// [`ExtendedHeader`]s are used to announce and describe the blocks
/// in the Celestia network.
///
/// Before being used, each header should be validated and verified with a header you trust.
///
/// # Example
///
/// ```
/// # use celestia_types::ExtendedHeader;
/// # fn trusted_genesis_header() -> ExtendedHeader {
/// #     let s = include_str!("../test_data/chain1/extended_header_block_1.json");
/// #     serde_json::from_str(s).unwrap()
/// # }
/// # fn some_untrusted_header() -> ExtendedHeader {
/// #     let s = include_str!("../test_data/chain1/extended_header_block_27.json");
/// #     serde_json::from_str(s).unwrap()
/// # }
/// let genesis_header = trusted_genesis_header();
///
/// // fetch new header
/// let fetched_header = some_untrusted_header();
///
/// fetched_header.validate().expect("Invalid block header");
/// genesis_header.verify(&fetched_header).expect("Malicious header received");
/// ```
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(try_from = "RawExtendedHeader", into = "RawExtendedHeader")]
pub struct ExtendedHeader {
    /// Tendermint block header.
    pub header: Header,
    /// Commit metadata and signatures from validators committing the block.
    pub commit: Commit,
    /// Information about the set of validators commiting the block.
    pub validator_set: ValidatorSet,
    /// Header of the block data availability.
    pub dah: DataAvailabilityHeader,
}

impl Display for ExtendedHeader {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        write!(f, "hash: {}; height: {}", self.hash(), self.height())
    }
}

impl ExtendedHeader {
    /// Decode protobuf encoded header and then validate it.
    pub fn decode_and_validate(bytes: &[u8]) -> Result<Self> {
        let header = ExtendedHeader::decode(bytes)?;
        header.validate()?;
        Ok(header)
    }

    /// Get the block chain id.
    pub fn chain_id(&self) -> &Id {
        &self.header.chain_id
    }

    /// Get the block height.
    pub fn height(&self) -> Height {
        self.header.height
    }

    /// Get the block time.
    pub fn time(&self) -> Time {
        self.header.time
    }

    /// Get the block hash.
    pub fn hash(&self) -> Hash {
        self.commit.block_id.hash
    }

    /// Get the hash of the previous header.
    pub fn last_header_hash(&self) -> Hash {
        self.header
            .last_block_id
            .map(|block_id| block_id.hash)
            .unwrap_or_default()
    }

    /// Validate header.
    ///
    /// Performs a consistency check of the data included in the header.
    ///
    /// # Errors
    ///
    /// If validation fails, this function will return an error with a reason of failure.
    ///
    /// ```
    /// # use celestia_types::{ExtendedHeader, DataAvailabilityHeader};
    /// #
    /// # fn get_header(_: usize) -> ExtendedHeader {
    /// #     let s = include_str!("../test_data/chain1/extended_header_block_27.json");
    /// #     serde_json::from_str(s).unwrap()
    /// # }
    /// // fetch new header
    /// let mut fetched_header = get_header(15);
    ///
    /// assert!(fetched_header.validate().is_ok());
    ///
    /// fetched_header.dah = DataAvailabilityHeader::new_unchecked(vec![], vec![]);
    ///
    /// assert!(fetched_header.validate().is_err());
    /// ```
    pub fn validate(&self) -> Result<()> {
        self.header.validate_basic()?;
        self.commit.validate_basic()?;
        self.validator_set.validate_basic()?;

        // make sure the validator set is consistent with the header
        if self.validator_set.hash() != self.header.validators_hash {
            bail_validation!(
                "validator_set hash ({}) != header validators_hash ({})",
                self.validator_set.hash(),
                self.header.validators_hash,
            )
        }

        // ensure data root from raw header matches computed root
        if self.dah.hash() != self.header.data_hash {
            bail_validation!(
                "dah hash ({}) != header dah hash ({})",
                self.dah.hash(),
                self.header.data_hash,
            )
        }

        // Make sure the header is consistent with the commit.
        if self.commit.height != self.height() {
            bail_validation!(
                "commit height ({}) != header height ({})",
                self.commit.height,
                self.height(),
            )
        }

        if self.commit.block_id.hash != self.header.hash() {
            bail_validation!(
                "commit block_id hash ({}) != header hash ({})",
                self.commit.block_id.hash,
                self.header.hash(),
            )
        }

        self.validator_set.verify_commit_light(
            &self.header.chain_id,
            &self.height(),
            &self.commit,
        )?;

        self.dah.validate_basic()?;

        Ok(())
    }

    /// Verify an untrusted header.
    ///
    /// Ensures that the untrusted header can be trusted by verifying it against `self`.
    ///
    /// # Errors
    ///
    /// If validation fails, this function will return an error with a reason of failure.
    ///
    /// Please note that if verifying unadjacent headers, the verification will always
    /// fail if the validator set commiting those blocks was changed. If that is the case,
    /// consider verifying the untrusted header with a more recent or even previous header.
    pub fn verify(&self, untrusted: &ExtendedHeader) -> Result<()> {
        if untrusted.height() <= self.height() {
            bail_verification!(
                "untrusted header height({}) <= current trusted header({})",
                untrusted.height(),
                self.height()
            );
        }

        if untrusted.chain_id() != self.chain_id() {
            bail_verification!(
                "untrusted header has different chain {}, not {}",
                untrusted.chain_id(),
                self.chain_id()
            );
        }

        if !untrusted.time().after(self.time()) {
            bail_verification!(
                "untrusted header time ({}) must be after current trusted header ({})",
                untrusted.time(),
                self.time()
            );
        }

        #[cfg(any(not(target_arch = "wasm32"), feature = "wasm-bindgen"))]
        {
            let now = Time::now();
            let valid_until = now.checked_add(VERIFY_CLOCK_DRIFT).unwrap();

            if !untrusted.time().before(valid_until) {
                bail_verification!(
                    "new untrusted header has a time from the future {} (now: {}, clock_drift: {:?})",
                    untrusted.time(),
                    now,
                    VERIFY_CLOCK_DRIFT
                );
            }
        }

        // Optimization: If we are verifying an adjacent header we can avoid
        // `verify_commit_light_trusting` because we can just check the hash
        // of next validators and last header.
        if self.height().increment() == untrusted.height() {
            if untrusted.header.validators_hash != self.header.next_validators_hash {
                bail_verification!(
                    "expected old header next validators ({}) to match those from new header ({})",
                    self.header.next_validators_hash,
                    untrusted.header.validators_hash,
                );
            }

            if untrusted.last_header_hash() != self.hash() {
                bail_verification!(
                    "expected new header to point to last header hash ({}), but got {}",
                    self.hash(),
                    untrusted.last_header_hash()
                );
            }

            return Ok(());
        }

        self.validator_set.verify_commit_light_trusting(
            self.chain_id(),
            &untrusted.commit,
            DEFAULT_TRUST_LEVEL,
        )?;

        Ok(())
    }

    /// Verify a chain of adjacent untrusted headers.
    ///
    /// # Note
    ///
    /// This method does not do validation for optimization purposes.
    /// Validation should be done from before and ideally with
    /// [`ExtendedHeader::decode_and_validate`].
    ///
    /// # Errors
    ///
    /// If verification fails, this function will return an error with a reason of failure.
    /// This function will also return an error if untrusted headers are not adjacent
    /// to each other.
    ///
    /// # Example
    ///
    /// ```
    /// # use std::ops::Range;
    /// # use celestia_types::ExtendedHeader;
    /// # let s = include_str!("../test_data/chain3/extended_header_block_1_to_256.json");
    /// # let headers: Vec<ExtendedHeader> = serde_json::from_str(s).unwrap();
    /// # let trusted_genesis = || headers[0].clone();
    /// # // substract one as heights start from 1
    /// # let get_headers_range = |r: Range<usize>| (&headers[r.start - 1..r.end - 1]).to_vec();
    /// let genesis_header = trusted_genesis();
    /// let next_headers = get_headers_range(5..50);
    ///
    /// assert!(genesis_header.verify_range(&next_headers).is_ok());
    /// ```
    pub fn verify_range(&self, untrusted: &[ExtendedHeader]) -> Result<()> {
        let mut trusted = self;

        for (i, untrusted) in untrusted.iter().enumerate() {
            // All headers in `untrusted` must be adjacent to their previous
            // one. However we do not check if the first untrusted is adjacent
            // to `self`. This check is done in `verify_adjacent_range`.
            if i != 0 && trusted.height().increment() != untrusted.height() {
                bail_verification!(
                    "untrusted header height ({}) not adjacent to the current trusted ({})",
                    untrusted.height(),
                    trusted.height(),
                );
            }

            trusted.verify(untrusted)?;
            trusted = untrusted;
        }

        Ok(())
    }

    /// Verify a chain of adjacent untrusted headers and make sure
    /// they are adjacent to `self`.
    ///
    /// # Note
    ///
    /// This method does not do validation for optimization purposes.
    /// Validation should be done from before and ideally with
    /// [`ExtendedHeader::decode_and_validate`].
    ///
    /// # Errors
    ///
    /// If verification fails, this function will return an error with a reason of failure.
    /// This function will also return an error if untrusted headers and `self` don't form contiguous range
    ///
    /// # Example
    ///
    /// ```
    /// # use std::ops::Range;
    /// # use celestia_types::ExtendedHeader;
    /// # let s = include_str!("../test_data/chain3/extended_header_block_1_to_256.json");
    /// # let headers: Vec<ExtendedHeader> = serde_json::from_str(s).unwrap();
    /// # let trusted_genesis = || headers[0].clone();
    /// # // substract one as heights start from 1
    /// # let get_headers_range = |r: Range<usize>| (&headers[r.start - 1..r.end - 1]).to_vec();
    /// let genesis_header = trusted_genesis();
    /// let next_headers = get_headers_range(5..50);
    ///
    /// // fails, not adjacent to genesis
    /// assert!(genesis_header.verify_adjacent_range(&next_headers).is_err());
    ///
    /// let next_headers = get_headers_range(2..50);
    ///
    /// // succeeds
    /// genesis_header.verify_adjacent_range(&next_headers).unwrap();
    /// ```
    pub fn verify_adjacent_range(&self, untrusted: &[ExtendedHeader]) -> Result<()> {
        if untrusted.is_empty() {
            return Ok(());
        }

        // Check is first untrusted is adjacent to `self`.
        if self.height().increment() != untrusted[0].height() {
            bail_verification!(
                "untrusted header height ({}) not adjacent to the current trusted ({})",
                untrusted[0].height(),
                self.height(),
            );
        }

        self.verify_range(untrusted)
    }
}

impl Protobuf<RawExtendedHeader> for ExtendedHeader {}

impl TryFrom<RawExtendedHeader> for ExtendedHeader {
    type Error = Error;

    fn try_from(value: RawExtendedHeader) -> Result<Self, Self::Error> {
        let header = value.header.ok_or(Error::MissingHeader)?.try_into()?;
        let commit = value.commit.ok_or(Error::MissingCommit)?.try_into()?;
        let validator_set = value
            .validator_set
            .ok_or(Error::MissingValidatorSet)?
            .try_into()?;
        let dah = value
            .dah
            .ok_or(Error::MissingDataAvailabilityHeader)?
            .try_into()?;

        Ok(ExtendedHeader {
            header,
            commit,
            validator_set,
            dah,
        })
    }
}

impl From<ExtendedHeader> for RawExtendedHeader {
    fn from(value: ExtendedHeader) -> RawExtendedHeader {
        RawExtendedHeader {
            header: Some(value.header.into()),
            commit: Some(value.commit.into()),
            validator_set: Some(value.validator_set.into()),
            dah: Some(value.dah.into()),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::test_utils::{invalidate, unverify};

    #[cfg(target_arch = "wasm32")]
    use wasm_bindgen_test::wasm_bindgen_test as test;

    fn sample_eh_chain_1_block_1() -> ExtendedHeader {
        let s = include_str!("../test_data/chain1/extended_header_block_1.json");
        serde_json::from_str(s).unwrap()
    }

    fn sample_eh_chain_1_block_27() -> ExtendedHeader {
        let s = include_str!("../test_data/chain1/extended_header_block_27.json");
        serde_json::from_str(s).unwrap()
    }

    fn sample_eh_chain_2_block_1() -> ExtendedHeader {
        let s = include_str!("../test_data/chain2/extended_header_block_1.json");
        serde_json::from_str(s).unwrap()
    }

    fn sample_eh_chain_2_block_27() -> ExtendedHeader {
        let s = include_str!("../test_data/chain2/extended_header_block_27.json");
        serde_json::from_str(s).unwrap()
    }

    fn sample_eh_chain_2_block_28() -> ExtendedHeader {
        let s = include_str!("../test_data/chain2/extended_header_block_28.json");
        serde_json::from_str(s).unwrap()
    }

    fn sample_eh_chain_2_block_35() -> ExtendedHeader {
        let s = include_str!("../test_data/chain2/extended_header_block_35.json");
        serde_json::from_str(s).unwrap()
    }

    fn sample_eh_chain_3_block_1_to_256() -> Vec<ExtendedHeader> {
        let s = include_str!("../test_data/chain3/extended_header_block_1_to_256.json");
        serde_json::from_str(s).unwrap()
    }

    #[test]
    fn validate_correct() {
        sample_eh_chain_1_block_1().validate().unwrap();
        sample_eh_chain_1_block_27().validate().unwrap();

        sample_eh_chain_2_block_1().validate().unwrap();
        sample_eh_chain_2_block_27().validate().unwrap();
        sample_eh_chain_2_block_28().validate().unwrap();
        sample_eh_chain_2_block_35().validate().unwrap();
    }

    #[test]
    fn validate_validator_hash_mismatch() {
        let mut eh = sample_eh_chain_1_block_27();
        eh.header.validators_hash = Hash::None;

        eh.validate().unwrap_err();
    }

    #[test]
    fn validate_dah_hash_mismatch() {
        let mut eh = sample_eh_chain_1_block_27();
        eh.header.data_hash = Hash::Sha256([0; 32]);

        eh.validate().unwrap_err();
    }

    #[test]
    fn validate_commit_height_mismatch() {
        let mut eh = sample_eh_chain_1_block_27();
        eh.commit.height = 0xdeadbeefu32.into();

        eh.validate().unwrap_err();
    }

    #[test]
    fn validate_commit_block_hash_mismatch() {
        let mut eh = sample_eh_chain_1_block_27();
        eh.commit.block_id.hash = Hash::None;

        eh.validate().unwrap_err();
    }

    #[test]
    fn verify() {
        let eh_block_1 = sample_eh_chain_1_block_1();
        let eh_block_27 = sample_eh_chain_1_block_27();

        eh_block_1.verify(&eh_block_27).unwrap();

        let eh_block_1 = sample_eh_chain_2_block_1();
        let eh_block_27 = sample_eh_chain_2_block_27();

        eh_block_1.verify(&eh_block_27).unwrap();
    }

    #[test]
    fn verify_adjacent() {
        let eh_block_27 = sample_eh_chain_2_block_27();
        let eh_block_28 = sample_eh_chain_2_block_28();

        eh_block_27.verify(&eh_block_28).unwrap();
    }

    #[test]
    fn verify_invalid_validator() {
        let eh_block_27 = sample_eh_chain_2_block_27();
        let mut eh_block_28 = sample_eh_chain_2_block_28();

        eh_block_28.header.validators_hash = Hash::None;

        eh_block_27.verify(&eh_block_28).unwrap_err();
    }

    #[test]
    fn verify_invalid_last_block_hash() {
        let eh_block_27 = sample_eh_chain_2_block_27();
        let mut eh_block_28 = sample_eh_chain_2_block_28();

        eh_block_28.header.last_block_id.as_mut().unwrap().hash = Hash::None;

        eh_block_27.verify(&eh_block_28).unwrap_err();
    }

    #[test]
    fn verify_invalid_adjacent() {
        let eh_block_27 = sample_eh_chain_1_block_27();
        let eh_block_28 = sample_eh_chain_2_block_28();

        eh_block_27.verify(&eh_block_28).unwrap_err();
    }

    #[test]
    fn verify_same_chain_id_but_different_chain() {
        let eh_block_1 = sample_eh_chain_1_block_1();
        let eh_block_27 = sample_eh_chain_2_block_27();

        eh_block_1.verify(&eh_block_27).unwrap_err();
    }

    #[test]
    fn verify_invalid_height() {
        let eh_block_27 = sample_eh_chain_1_block_27();
        eh_block_27.verify(&eh_block_27).unwrap_err();
    }

    #[test]
    fn verify_invalid_chain_id() {
        let eh_block_1 = sample_eh_chain_1_block_1();
        let mut eh_block_27 = sample_eh_chain_1_block_27();

        eh_block_27.header.chain_id = "1112222".parse().unwrap();
        eh_block_1.verify(&eh_block_27).unwrap_err();
    }

    #[test]
    fn verify_invalid_time() {
        let eh_block_1 = sample_eh_chain_1_block_1();
        let mut eh_block_27 = sample_eh_chain_1_block_27();

        eh_block_27.header.time = eh_block_1.header.time;
        eh_block_1.verify(&eh_block_27).unwrap_err();
    }

    #[test]
    fn verify_time_from_the_future() {
        let eh_block_1 = sample_eh_chain_1_block_1();
        let mut eh_block_27 = sample_eh_chain_1_block_27();

        eh_block_27.header.time = Time::now().checked_add(Duration::from_secs(60)).unwrap();
        eh_block_1.verify(&eh_block_27).unwrap_err();
    }

    #[test]
    fn verify_range() {
        let eh_chain = sample_eh_chain_3_block_1_to_256();

        eh_chain[0].verify_range(&eh_chain[1..]).unwrap();
        eh_chain[0].verify_range(&eh_chain[..]).unwrap_err();
        eh_chain[0].verify_range(&eh_chain[10..]).unwrap();

        eh_chain[10].verify_range(&eh_chain[11..]).unwrap();
        eh_chain[10].verify_range(&eh_chain[100..]).unwrap();
        eh_chain[10].verify_range(&eh_chain[..9]).unwrap_err();
        eh_chain[10].verify_range(&eh_chain[10..]).unwrap_err();
    }

    #[test]
    fn verify_range_missing_height() {
        let eh_chain = sample_eh_chain_3_block_1_to_256();

        let mut headers = eh_chain[10..15].to_vec();
        headers.remove(2);
        eh_chain[0].verify_range(&headers).unwrap_err();
    }

    #[test]
    fn verify_range_duplicate_height() {
        let eh_chain = sample_eh_chain_3_block_1_to_256();

        let mut headers = eh_chain[10..15].to_vec();
        headers.insert(2, eh_chain[12].clone());
        eh_chain[0].verify_range(&headers).unwrap_err();
    }

    #[test]
    fn verify_range_bad_header_in_middle() {
        let eh_chain = sample_eh_chain_3_block_1_to_256();

        let mut headers = eh_chain[10..15].to_vec();

        unverify(&mut headers[2]);

        eh_chain[0].verify_range(&headers).unwrap_err();
    }

    #[test]
    fn verify_range_allow_invalid_header_in_middle() {
        let eh_chain = sample_eh_chain_3_block_1_to_256();

        let mut headers = eh_chain[10..15].to_vec();

        invalidate(&mut headers[2]);

        eh_chain[0].verify_range(&headers).unwrap();
    }

    #[test]
    fn verify_adjacent_range() {
        let eh_chain = sample_eh_chain_3_block_1_to_256();

        eh_chain[0].verify_adjacent_range(&eh_chain[1..]).unwrap();
        eh_chain[0]
            .verify_adjacent_range(&eh_chain[..])
            .unwrap_err();
        eh_chain[0]
            .verify_adjacent_range(&eh_chain[10..])
            .unwrap_err();

        eh_chain[10].verify_adjacent_range(&eh_chain[11..]).unwrap();
        eh_chain[10]
            .verify_adjacent_range(&eh_chain[100..])
            .unwrap_err();
        eh_chain[10]
            .verify_adjacent_range(&eh_chain[..9])
            .unwrap_err();
        eh_chain[10]
            .verify_adjacent_range(&eh_chain[10..])
            .unwrap_err();
    }
}