// Copyright 2015-2017 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity.  If not, see <http://www.gnu.org/licenses/>.

extern crate ethereum_types;
extern crate tiny_keccak;

use std::io;
use tiny_keccak::Keccak;
pub use ethereum_types::H256;

/// Get the KECCAK (i.e. Keccak) hash of the empty bytes string.
pub const KECCAK_EMPTY: H256 = H256( [0xc5, 0xd2, 0x46, 0x01, 0x86, 0xf7, 0x23, 0x3c, 0x92, 0x7e, 0x7d, 0xb2, 0xdc, 0xc7, 0x03, 0xc0, 0xe5, 0x00, 0xb6, 0x53, 0xca, 0x82, 0x27, 0x3b, 0x7b, 0xfa, 0xd8, 0x04, 0x5d, 0x85, 0xa4, 0x70] );

/// The KECCAK of the RLP encoding of empty data.
pub const KECCAK_NULL_RLP: H256 = H256( [0x56, 0xe8, 0x1f, 0x17, 0x1b, 0xcc, 0x55, 0xa6, 0xff, 0x83, 0x45, 0xe6, 0x92, 0xc0, 0xf8, 0x6e, 0x5b, 0x48, 0xe0, 0x1b, 0x99, 0x6c, 0xad, 0xc0, 0x01, 0x62, 0x2f, 0xb5, 0xe3, 0x63, 0xb4, 0x21] );

/// The KECCAK of the RLP encoding of empty list.
pub const KECCAK_EMPTY_LIST_RLP: H256 = H256( [0x1d, 0xcc, 0x4d, 0xe8, 0xde, 0xc7, 0x5d, 0x7a, 0xab, 0x85, 0xb5, 0x67, 0xb6, 0xcc, 0xd4, 0x1a, 0xd3, 0x12, 0x45, 0x1b, 0x94, 0x8a, 0x74, 0x13, 0xf0, 0xa1, 0x42, 0xfd, 0x40, 0xd4, 0x93, 0x47] );

extern {
	/// Hashes input. Returns -1 if either out or input does not exist. Otherwise returns 0.
	pub fn keccak_256(out: *mut u8, outlen: usize, input: *const u8, inputlen: usize) -> i32;
	/// Hashes input. Returns -1 if either out or input does not exist. Otherwise returns 0.
	pub fn keccak_512(out: *mut u8, outlen: usize, input: *const u8, inputlen: usize) -> i32;
}

pub fn keccak<T: AsRef<[u8]>>(s: T) -> H256 {
	let mut result = [0u8; 32];
	write_keccak(s, &mut result);
	H256(result)
}

pub fn write_keccak<T: AsRef<[u8]>>(s: T, dest: &mut [u8]) {
	let input = s.as_ref();
	unsafe {
		// we can safely ignore keccak_256 output, cause we know that both input
		// and dest are properly allocated
		keccak_256(dest.as_mut_ptr(), dest.len(), input.as_ptr(), input.len());
	}
}

pub fn keccak_buffer(r: &mut io::BufRead) -> Result<H256, io::Error> {
	let mut output = [0u8; 32];
	let mut input = [0u8; 1024];
	let mut keccak = Keccak::new_keccak256();

	// read file
	loop {
		let some = r.read(&mut input)?;
		if some == 0 {
			break;
		}
		keccak.update(&input[0..some]);
	}

	keccak.finalize(&mut output);
	Ok(output.into())
}

#[cfg(test)]
mod tests {
	extern crate tempdir;

	use std::fs;
	use std::io::{Write, BufReader};
	use self::tempdir::TempDir;
	use super::{keccak, keccak_buffer, KECCAK_EMPTY};

	#[test]
	fn keccak_empty() {
		assert_eq!(keccak([0u8; 0]), KECCAK_EMPTY);
	}
	#[test]
	fn keccak_as() {
		assert_eq!(keccak([0x41u8; 32]), From::from("59cad5948673622c1d64e2322488bf01619f7ff45789741b15a9f782ce9290a8"));
	}

	#[test]
	fn should_keccak_a_file() {
		// given
		let tempdir = TempDir::new("keccak").unwrap();
		let mut path = tempdir.path().to_owned();
		path.push("should_keccak_a_file");
		// Prepare file
		{
			let mut file = fs::File::create(&path).unwrap();
			file.write_all(b"something").unwrap();
		}

		let mut file = BufReader::new(fs::File::open(&path).unwrap());
		// when
		let hash = keccak_buffer(&mut file).unwrap();

		// then
		assert_eq!(format!("{:x}", hash), "68371d7e884c168ae2022c82bd837d51837718a7f7dfb7aa3f753074a35e1d87");
	}
}