use crate::{BlockHeaderData, BlockSourceError};
use crate::http::{BinaryResponse, JsonResponse};
use crate::utils::hex_to_uint256;

use bitcoin::blockdata::block::{Block, BlockHeader};
use bitcoin::consensus::encode;
use bitcoin::hash_types::{BlockHash, TxMerkleNode};
use bitcoin::hashes::hex::{ToHex, FromHex};

use serde::Deserialize;

use serde_json;

use std::convert::From;
use std::convert::TryFrom;
use std::convert::TryInto;

/// Conversion from `std::io::Error` into `BlockSourceError`.
impl From<std::io::Error> for BlockSourceError {
	fn from(e: std::io::Error) -> BlockSourceError {
		match e.kind() {
			std::io::ErrorKind::InvalidData => BlockSourceError::persistent(e),
			std::io::ErrorKind::InvalidInput => BlockSourceError::persistent(e),
			_ => BlockSourceError::transient(e),
		}
	}
}

/// Parses binary data as a block.
impl TryInto<Block> for BinaryResponse {
	type Error = std::io::Error;

	fn try_into(self) -> std::io::Result<Block> {
		match encode::deserialize(&self.0) {
			Err(_) => return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid block data")),
			Ok(block) => Ok(block),
		}
	}
}

/// Converts a JSON value into block header data. The JSON value may be an object representing a
/// block header or an array of such objects. In the latter case, the first object is converted.
impl TryInto<BlockHeaderData> for JsonResponse {
	type Error = std::io::Error;

	fn try_into(self) -> std::io::Result<BlockHeaderData> {
		let mut header = match self.0 {
			serde_json::Value::Array(mut array) if !array.is_empty() => array.drain(..).next().unwrap(),
			serde_json::Value::Object(_) => self.0,
			_ => return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "unexpected JSON type")),
		};

		if !header.is_object() {
			return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "expected JSON object"));
		}

		// Add an empty previousblockhash for the genesis block.
		if let None = header.get("previousblockhash") {
			let hash: BlockHash = Default::default();
			header.as_object_mut().unwrap().insert("previousblockhash".to_string(), serde_json::json!(hash.to_hex()));
		}

		match serde_json::from_value::<GetHeaderResponse>(header) {
			Err(_) => Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid header response")),
			Ok(response) => match response.try_into() {
				Err(_) => Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid header data")),
				Ok(header) => Ok(header),
			},
		}
	}
}

/// Response data from `getblockheader` RPC and `headers` REST requests.
#[derive(Deserialize)]
struct GetHeaderResponse {
	pub version: i32,
	pub merkleroot: String,
	pub time: u32,
	pub nonce: u32,
	pub bits: String,
	pub previousblockhash: String,

	pub chainwork: String,
	pub height: u32,
}

/// Converts from `GetHeaderResponse` to `BlockHeaderData`.
impl TryFrom<GetHeaderResponse> for BlockHeaderData {
	type Error = bitcoin::hashes::hex::Error;

	fn try_from(response: GetHeaderResponse) -> Result<Self, bitcoin::hashes::hex::Error> {
		Ok(BlockHeaderData {
			header: BlockHeader {
				version: response.version,
				prev_blockhash: BlockHash::from_hex(&response.previousblockhash)?,
				merkle_root: TxMerkleNode::from_hex(&response.merkleroot)?,
				time: response.time,
				bits: u32::from_be_bytes(<[u8; 4]>::from_hex(&response.bits)?),
				nonce: response.nonce,
			},
			chainwork: hex_to_uint256(&response.chainwork)?,
			height: response.height,
		})
	}
}


/// Converts a JSON value into a block. Assumes the block is hex-encoded in a JSON string.
impl TryInto<Block> for JsonResponse {
	type Error = std::io::Error;

	fn try_into(self) -> std::io::Result<Block> {
		match self.0.as_str() {
			None => Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "expected JSON string")),
			Some(hex_data) => match Vec::<u8>::from_hex(hex_data) {
				Err(_) => Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid hex data")),
				Ok(block_data) => match encode::deserialize(&block_data) {
					Err(_) => Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid block data")),
					Ok(block) => Ok(block),
				},
			},
		}
	}
}

/// Converts a JSON value into the best block hash and optional height.
impl TryInto<(BlockHash, Option<u32>)> for JsonResponse {
	type Error = std::io::Error;

	fn try_into(self) -> std::io::Result<(BlockHash, Option<u32>)> {
		if !self.0.is_object() {
			return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "expected JSON object"));
		}

		let hash = match &self.0["bestblockhash"] {
			serde_json::Value::String(hex_data) => match BlockHash::from_hex(&hex_data) {
				Err(_) => return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid hex data")),
				Ok(block_hash) => block_hash,
			},
			_ => return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "expected JSON string")),
		};

		let height = match &self.0["blocks"] {
			serde_json::Value::Null => None,
			serde_json::Value::Number(height) => match height.as_u64() {
				None => return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid height")),
				Some(height) => match height.try_into() {
					Err(_) => return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid height")),
					Ok(height) => Some(height),
				}
			},
			_ => return Err(std::io::Error::new(std::io::ErrorKind::InvalidData, "expected JSON number")),
		};

		Ok((hash, height))
	}
}

#[cfg(test)]
pub(crate) mod tests {
	use super::*;
	use bitcoin::blockdata::constants::genesis_block;
	use bitcoin::consensus::encode;
	use bitcoin::network::constants::Network;

	/// Converts from `BlockHeaderData` into a `GetHeaderResponse` JSON value.
	impl From<BlockHeaderData> for serde_json::Value {
		fn from(data: BlockHeaderData) -> Self {
			let BlockHeaderData { chainwork, height, header } = data;
			serde_json::json!({
				"chainwork": chainwork.to_string()["0x".len()..],
				"height": height,
				"version": header.version,
				"merkleroot": header.merkle_root.to_hex(),
				"time": header.time,
				"nonce": header.nonce,
				"bits": header.bits.to_hex(),
				"previousblockhash": header.prev_blockhash.to_hex(),
			})
		}
	}

	#[test]
	fn into_block_header_from_json_response_with_unexpected_type() {
		let response = JsonResponse(serde_json::json!(42));
		match TryInto::<BlockHeaderData>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "unexpected JSON type");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_header_from_json_response_with_unexpected_header_type() {
		let response = JsonResponse(serde_json::json!([42]));
		match TryInto::<BlockHeaderData>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "expected JSON object");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_header_from_json_response_with_invalid_header_response() {
		let block = genesis_block(Network::Bitcoin);
		let mut response = JsonResponse(BlockHeaderData {
			chainwork: block.header.work(),
			height: 0,
			header: block.header
		}.into());
		response.0["chainwork"].take();

		match TryInto::<BlockHeaderData>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "invalid header response");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_header_from_json_response_with_invalid_header_data() {
		let block = genesis_block(Network::Bitcoin);
		let mut response = JsonResponse(BlockHeaderData {
			chainwork: block.header.work(),
			height: 0,
			header: block.header
		}.into());
		response.0["chainwork"] = serde_json::json!("foobar");

		match TryInto::<BlockHeaderData>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "invalid header data");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_header_from_json_response_with_valid_header() {
		let block = genesis_block(Network::Bitcoin);
		let response = JsonResponse(BlockHeaderData {
			chainwork: block.header.work(),
			height: 0,
			header: block.header
		}.into());

		match TryInto::<BlockHeaderData>::try_into(response) {
			Err(e) => panic!("Unexpected error: {:?}", e),
			Ok(data) => {
				assert_eq!(data.chainwork, block.header.work());
				assert_eq!(data.height, 0);
				assert_eq!(data.header, block.header);
			},
		}
	}

	#[test]
	fn into_block_header_from_json_response_with_valid_header_array() {
		let genesis_block = genesis_block(Network::Bitcoin);
		let best_block_header = BlockHeader {
			prev_blockhash: genesis_block.block_hash(),
			..genesis_block.header
		};
		let chainwork = genesis_block.header.work() + best_block_header.work();
		let response = JsonResponse(serde_json::json!([
				serde_json::Value::from(BlockHeaderData {
					chainwork, height: 1, header: best_block_header,
				}),
				serde_json::Value::from(BlockHeaderData {
					chainwork: genesis_block.header.work(), height: 0, header: genesis_block.header,
				}),
		]));

		match TryInto::<BlockHeaderData>::try_into(response) {
			Err(e) => panic!("Unexpected error: {:?}", e),
			Ok(data) => {
				assert_eq!(data.chainwork, chainwork);
				assert_eq!(data.height, 1);
				assert_eq!(data.header, best_block_header);
			},
		}
	}

	#[test]
	fn into_block_header_from_json_response_without_previous_block_hash() {
		let block = genesis_block(Network::Bitcoin);
		let mut response = JsonResponse(BlockHeaderData {
			chainwork: block.header.work(),
			height: 0,
			header: block.header
		}.into());
		response.0.as_object_mut().unwrap().remove("previousblockhash");

		match TryInto::<BlockHeaderData>::try_into(response) {
			Err(e) => panic!("Unexpected error: {:?}", e),
			Ok(BlockHeaderData { chainwork: _, height: _, header }) => {
				assert_eq!(header, block.header);
			},
		}
	}

	#[test]
	fn into_block_from_invalid_binary_response() {
		let response = BinaryResponse(b"foo".to_vec());
		match TryInto::<Block>::try_into(response) {
			Err(_) => {},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_from_valid_binary_response() {
		let genesis_block = genesis_block(Network::Bitcoin);
		let response = BinaryResponse(encode::serialize(&genesis_block));
		match TryInto::<Block>::try_into(response) {
			Err(e) => panic!("Unexpected error: {:?}", e),
			Ok(block) => assert_eq!(block, genesis_block),
		}
	}

	#[test]
	fn into_block_from_json_response_with_unexpected_type() {
		let response = JsonResponse(serde_json::json!({ "result": "foo" }));
		match TryInto::<Block>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "expected JSON string");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_from_json_response_with_invalid_hex_data() {
		let response = JsonResponse(serde_json::json!("foobar"));
		match TryInto::<Block>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "invalid hex data");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_from_json_response_with_invalid_block_data() {
		let response = JsonResponse(serde_json::json!("abcd"));
		match TryInto::<Block>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "invalid block data");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_from_json_response_with_valid_block_data() {
		let genesis_block = genesis_block(Network::Bitcoin);
		let response = JsonResponse(serde_json::json!(encode::serialize_hex(&genesis_block)));
		match TryInto::<Block>::try_into(response) {
			Err(e) => panic!("Unexpected error: {:?}", e),
			Ok(block) => assert_eq!(block, genesis_block),
		}
	}

	#[test]
	fn into_block_hash_from_json_response_with_unexpected_type() {
		let response = JsonResponse(serde_json::json!("foo"));
		match TryInto::<(BlockHash, Option<u32>)>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "expected JSON object");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_hash_from_json_response_with_unexpected_bestblockhash_type() {
		let response = JsonResponse(serde_json::json!({ "bestblockhash": 42 }));
		match TryInto::<(BlockHash, Option<u32>)>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "expected JSON string");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_hash_from_json_response_with_invalid_hex_data() {
		let response = JsonResponse(serde_json::json!({ "bestblockhash": "foobar"} ));
		match TryInto::<(BlockHash, Option<u32>)>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "invalid hex data");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_hash_from_json_response_without_height() {
		let block = genesis_block(Network::Bitcoin);
		let response = JsonResponse(serde_json::json!({
			"bestblockhash": block.block_hash().to_hex(),
		}));
		match TryInto::<(BlockHash, Option<u32>)>::try_into(response) {
			Err(e) => panic!("Unexpected error: {:?}", e),
			Ok((hash, height)) => {
				assert_eq!(hash, block.block_hash());
				assert!(height.is_none());
			},
		}
	}

	#[test]
	fn into_block_hash_from_json_response_with_unexpected_blocks_type() {
		let block = genesis_block(Network::Bitcoin);
		let response = JsonResponse(serde_json::json!({
			"bestblockhash": block.block_hash().to_hex(),
			"blocks": "foo",
		}));
		match TryInto::<(BlockHash, Option<u32>)>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "expected JSON number");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_hash_from_json_response_with_invalid_height() {
		let block = genesis_block(Network::Bitcoin);
		let response = JsonResponse(serde_json::json!({
			"bestblockhash": block.block_hash().to_hex(),
			"blocks": std::u64::MAX,
		}));
		match TryInto::<(BlockHash, Option<u32>)>::try_into(response) {
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
				assert_eq!(e.get_ref().unwrap().to_string(), "invalid height");
			},
			Ok(_) => panic!("Expected error"),
		}
	}

	#[test]
	fn into_block_hash_from_json_response_with_height() {
		let block = genesis_block(Network::Bitcoin);
		let response = JsonResponse(serde_json::json!({
			"bestblockhash": block.block_hash().to_hex(),
			"blocks": 1,
		}));
		match TryInto::<(BlockHash, Option<u32>)>::try_into(response) {
			Err(e) => panic!("Unexpected error: {:?}", e),
			Ok((hash, height)) => {
				assert_eq!(hash, block.block_hash());
				assert_eq!(height.unwrap(), 1);
			},
		}
	}
}