// Copyright (C) 2024-2026 Whiterun LLC
//
// This software is licensed under the GNU Affero General Public License (AGPL), version 3.0 or later.
// A copy of the license can be found in the LICENSE file or at https://www.gnu.org/licenses/agpl-3.0.html

//! BLOB storage helpers for efficient database storage of hash types.
//!
//! Converts 32-byte hashes from TEXT (64-char hex) to BLOB (32 bytes) for ~50% storage savings.
//!
//! ## IMPORTANT: Byte Order (Endianness)
//!
//! Bitcoin hash types (Txid, BlockHash, TokenID, OutPointHash, PoolID) use **reversed byte display**.
//! When a hash is displayed as hex (e.g., in block explorers or APIs), it shows the bytes in
//! reverse order compared to how they're stored internally.
//!
//! This means:
//! - `hex.parse::<Txid>()` reverses the input bytes
//! - `Txid::to_hex()` reverses the output bytes
//! - `Txid::into_inner()` / `Txid::from_byte_array()` work with internal (non-reversed) bytes
//!
//! **NEVER use `hex::decode()` directly on user-provided hash hex strings!**
//! Instead, use `display_hex_to_blob::<TokenID>(hex)` or `hex.parse::<TokenID>()?.to_blob()`.
//!
//! **PubkeyHash is the exception** - it does NOT reverse bytes.

use anyhow::{Context, Result};
use std::str::FromStr;

use bitcoin_hashes::Hash;
use bitcoincash::{BlockHash, PubkeyHash, TokenID, Txid};
use riftenlabs_defi::chainutil::OutPointHash;

use crate::def::PoolID;

/// Trait for converting hash types to BLOB bytes for database storage.
pub trait ToBlob {
    fn to_blob(&self) -> Vec<u8>;
}

/// Trait for converting BLOB bytes back to hash types.
pub trait FromBlob: Sized {
    fn from_blob(bytes: &[u8]) -> Result<Self>;
}

// Implement ToBlob for 32-byte hash types
impl ToBlob for Txid {
    fn to_blob(&self) -> Vec<u8> {
        self.as_byte_array().to_vec()
    }
}

impl ToBlob for BlockHash {
    fn to_blob(&self) -> Vec<u8> {
        self.as_byte_array().to_vec()
    }
}

impl ToBlob for TokenID {
    fn to_blob(&self) -> Vec<u8> {
        self.as_byte_array().to_vec()
    }
}

impl ToBlob for OutPointHash {
    fn to_blob(&self) -> Vec<u8> {
        self.as_byte_array().to_vec()
    }
}

impl ToBlob for PoolID {
    fn to_blob(&self) -> Vec<u8> {
        self.as_byte_array().to_vec()
    }
}

// Implement ToBlob for 20-byte PubkeyHash
impl ToBlob for PubkeyHash {
    fn to_blob(&self) -> Vec<u8> {
        self.as_byte_array().to_vec()
    }
}

// Implement FromBlob for 32-byte hash types
impl FromBlob for Txid {
    fn from_blob(bytes: &[u8]) -> Result<Self> {
        let arr: [u8; 32] = bytes.try_into().context("Txid blob must be 32 bytes")?;
        Ok(Txid::from_byte_array(arr))
    }
}

impl FromBlob for BlockHash {
    fn from_blob(bytes: &[u8]) -> Result<Self> {
        let arr: [u8; 32] = bytes
            .try_into()
            .context("BlockHash blob must be 32 bytes")?;
        Ok(BlockHash::from_byte_array(arr))
    }
}

impl FromBlob for TokenID {
    fn from_blob(bytes: &[u8]) -> Result<Self> {
        let arr: [u8; 32] = bytes.try_into().context("TokenID blob must be 32 bytes")?;
        Ok(TokenID::from_byte_array(arr))
    }
}

impl FromBlob for OutPointHash {
    fn from_blob(bytes: &[u8]) -> Result<Self> {
        let arr: [u8; 32] = bytes
            .try_into()
            .context("OutPointHash blob must be 32 bytes")?;
        Ok(OutPointHash::from_byte_array(arr))
    }
}

impl FromBlob for PoolID {
    fn from_blob(bytes: &[u8]) -> Result<Self> {
        let arr: [u8; 32] = bytes.try_into().context("PoolID blob must be 32 bytes")?;
        Ok(PoolID::from_byte_array(arr))
    }
}

// Implement FromBlob for 20-byte PubkeyHash
impl FromBlob for PubkeyHash {
    fn from_blob(bytes: &[u8]) -> Result<Self> {
        let arr: [u8; 20] = bytes
            .try_into()
            .context("PubkeyHash blob must be 20 bytes")?;
        Ok(PubkeyHash::from_byte_array(arr))
    }
}

/// Convert a display-format hex string to blob bytes for database storage.
///
/// This correctly handles the byte reversal that Bitcoin hash types use.
/// Use this instead of `hex::decode()` for hash types!
///
/// # Example
/// ```ignore
/// // User provides token ID in display format (from API, block explorer, etc.)
/// let user_input = "abcd1234...";
/// let blob = display_hex_to_blob::<TokenID>(user_input)?;
/// // Now `blob` can be used in SQL queries against BLOB columns
/// ```
pub fn display_hex_to_blob<T>(hex: &str) -> Result<Vec<u8>>
where
    T: FromStr + ToBlob,
{
    let hash = T::from_str(hex).map_err(|_| anyhow::anyhow!("invalid hash hex"))?;
    Ok(hash.to_blob())
}

/// Convert blob bytes from database to display-format hex string.
///
/// This correctly handles the byte reversal that Bitcoin hash types use.
/// Use this instead of relying on SQL `hex()` function for hash types!
///
/// # Example
/// ```ignore
/// let blob: Vec<u8> = row.get(0)?;
/// let display_hex = blob_to_display_hex::<TokenID>(&blob)?;
/// // Now `display_hex` is in the format users expect
/// ```
pub fn blob_to_display_hex<T>(blob: &[u8]) -> Result<String>
where
    T: FromBlob + std::fmt::Display,
{
    let hash = T::from_blob(blob)?;
    Ok(hash.to_string())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_txid_roundtrip() {
        let hex = "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef";
        let txid = hex.parse::<Txid>().unwrap();
        let blob = txid.to_blob();
        assert_eq!(blob.len(), 32);
        let recovered = Txid::from_blob(&blob).unwrap();
        assert_eq!(txid, recovered);
        assert_eq!(recovered.to_string(), hex);
    }

    #[test]
    fn test_blockhash_roundtrip() {
        let hex = "fedcba9876543210fedcba9876543210fedcba9876543210fedcba9876543210";
        let hash = hex.parse::<BlockHash>().unwrap();
        let blob = hash.to_blob();
        assert_eq!(blob.len(), 32);
        let recovered = BlockHash::from_blob(&blob).unwrap();
        assert_eq!(hash, recovered);
    }

    #[test]
    fn test_token_id_roundtrip() {
        let hex = "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789";
        let token = hex.parse::<TokenID>().unwrap();
        let blob = token.to_blob();
        assert_eq!(blob.len(), 32);
        let recovered = TokenID::from_blob(&blob).unwrap();
        assert_eq!(token, recovered);
    }

    #[test]
    fn test_outpointhash_roundtrip() {
        let hex = "1111111111111111111111111111111111111111111111111111111111111111";
        let hash = hex.parse::<OutPointHash>().unwrap();
        let blob = hash.to_blob();
        assert_eq!(blob.len(), 32);
        let recovered = OutPointHash::from_blob(&blob).unwrap();
        assert_eq!(hash, recovered);
    }

    #[test]
    fn test_pubkeyhash_roundtrip() {
        let hex = "0123456789abcdef01230123456789abcdef0123";
        let pkh = hex.parse::<PubkeyHash>().unwrap();
        let blob = pkh.to_blob();
        assert_eq!(blob.len(), 20);
        let recovered = PubkeyHash::from_blob(&blob).unwrap();
        assert_eq!(pkh, recovered);
    }

    #[test]
    fn test_invalid_blob_size() {
        let short_blob = vec![0u8; 16];
        assert!(Txid::from_blob(&short_blob).is_err());
        assert!(BlockHash::from_blob(&short_blob).is_err());
        assert!(TokenID::from_blob(&short_blob).is_err());
        assert!(PubkeyHash::from_blob(&short_blob).is_err());
    }

    // ==================== ENDIANNESS TESTS ====================
    // These tests use asymmetric (non-palindromic) hex values to catch byte-order bugs.
    // The original tests used values like [0x11; 32] which are the same reversed.

    /// Proves that hex::decode() differs from from_hex().to_blob() for Bitcoin hash types.
    /// This is the core test that would have caught the LE/BE bug.
    #[test]
    fn test_hex_decode_differs_from_display_hex_to_blob() {
        // Asymmetric hex - NOT a palindrome, so reversal is detectable
        let display_hex = "0102030405060708091011121314151617181920212223242526272829303132";

        // WRONG: raw hex::decode (no byte reversal)
        let raw_bytes = hex::decode(display_hex).unwrap();

        // CORRECT: parse as TokenID then get blob (handles reversal)
        let token = display_hex.parse::<TokenID>().unwrap();
        let blob_bytes = token.to_blob();

        // These MUST be different because Bitcoin hashes reverse bytes for display
        assert_ne!(
            raw_bytes, blob_bytes,
            "hex::decode and to_blob MUST differ for Bitcoin hash types!"
        );

        // Verify the reversal: first byte of display becomes last byte of blob
        assert_eq!(raw_bytes[0], 0x01, "raw_bytes should start with 0x01");
        assert_eq!(
            blob_bytes[0], 0x32,
            "blob_bytes should start with 0x32 (reversed)"
        );
        assert_eq!(raw_bytes[31], 0x32, "raw_bytes should end with 0x32");
        assert_eq!(
            blob_bytes[31], 0x01,
            "blob_bytes should end with 0x01 (reversed)"
        );
    }

    /// Proves that SQL hex(blob) would produce wrong format compared to to_hex().
    #[test]
    fn test_sql_hex_vs_to_hex() {
        let display_hex = "0102030405060708091011121314151617181920212223242526272829303132";
        let token = display_hex.parse::<TokenID>().unwrap();
        let blob = token.to_blob();

        // Simulate what SQL hex() does: just uppercase hex of raw bytes (no reversal)
        let sql_hex_output = hex::encode(&blob).to_lowercase();

        // SQL hex() output is NOT what users expect
        assert_ne!(
            sql_hex_output, display_hex,
            "SQL hex() should NOT match display format"
        );

        // Correct way: parse blob back to TokenID and use to_hex()
        let recovered = TokenID::from_blob(&blob).unwrap();
        assert_eq!(
            recovered.to_string(),
            display_hex,
            "to_hex() should match original display format"
        );
    }

    /// Test the helper function display_hex_to_blob
    #[test]
    fn test_display_hex_to_blob_helper() {
        let display_hex = "0102030405060708091011121314151617181920212223242526272829303132";

        // Helper should produce same result as manual from_hex + to_blob
        let helper_result = display_hex_to_blob::<TokenID>(display_hex).unwrap();
        let manual_result = display_hex.parse::<TokenID>().unwrap().to_blob();

        assert_eq!(helper_result, manual_result);

        // And it should NOT equal raw hex::decode
        let raw_decode = hex::decode(display_hex).unwrap();
        assert_ne!(helper_result, raw_decode);
    }

    /// Test the helper function blob_to_display_hex
    #[test]
    fn test_blob_to_display_hex_helper() {
        let display_hex = "0102030405060708091011121314151617181920212223242526272829303132";
        let token = display_hex.parse::<TokenID>().unwrap();
        let blob = token.to_blob();

        // Helper should produce correct display format
        let helper_result = blob_to_display_hex::<TokenID>(&blob).unwrap();
        assert_eq!(helper_result, display_hex);

        // Raw hex::encode should NOT match
        let raw_encode = hex::encode(&blob);
        assert_ne!(raw_encode, display_hex);
    }

    /// Confirm PubkeyHash does NOT reverse bytes (it's the exception).
    #[test]
    fn test_pubkeyhash_does_not_reverse() {
        let hex_str = "0102030405060708091011121314151617181920";

        // For PubkeyHash, raw hex::decode SHOULD equal to_blob
        let raw_bytes = hex::decode(hex_str).unwrap();
        let pkh = hex_str.parse::<PubkeyHash>().unwrap();
        let blob_bytes = pkh.to_blob();

        assert_eq!(raw_bytes, blob_bytes, "PubkeyHash should NOT reverse bytes");
    }

    /// Test all Bitcoin hash types that DO reverse bytes.
    #[test]
    fn test_all_reversed_types() {
        let display_hex = "0102030405060708091011121314151617181920212223242526272829303132";
        let raw_bytes = hex::decode(display_hex).unwrap();

        // Txid reverses
        let txid_blob = display_hex.parse::<Txid>().unwrap().to_blob();
        assert_ne!(raw_bytes, txid_blob, "Txid should reverse");

        // BlockHash reverses
        let blockhash_blob = display_hex.parse::<BlockHash>().unwrap().to_blob();
        assert_ne!(raw_bytes, blockhash_blob, "BlockHash should reverse");

        // TokenID reverses
        let tokenid_blob = display_hex.parse::<TokenID>().unwrap().to_blob();
        assert_ne!(raw_bytes, tokenid_blob, "TokenID should reverse");

        // OutPointHash reverses
        let outpoint_blob = display_hex.parse::<OutPointHash>().unwrap().to_blob();
        assert_ne!(raw_bytes, outpoint_blob, "OutPointHash should reverse");

        // PoolID reverses
        let poolid_blob = display_hex.parse::<PoolID>().unwrap().to_blob();
        assert_ne!(raw_bytes, poolid_blob, "PoolID should reverse");
    }
}