//! # Crypto util functions

use crypto::digest::Digest;
use crypto::sha3::{Sha3, Sha3Mode};

/// Keccak-256 crypto hash length in bytes
pub const KECCAK256_BYTES: usize = 32;

/// Calculate Keccak-256 crypto hash
pub fn keccak256(data: &[u8]) -> [u8; KECCAK256_BYTES] {
    let mut sha3 = Sha3::new(Sha3Mode::Keccak256);
    sha3.input(data);

    let mut hash = [0u8; KECCAK256_BYTES];
    sha3.result(&mut hash);
    hash
}

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

    #[test]
    fn should_calculate_empty_keccak256() {
        assert_eq!(
            keccak256(b""),
            to_32bytes(
                "c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470",
            )
        );
    }

    #[test]
    fn should_calculate_small_keccak256() {
        assert_eq!(
            keccak256(b"emerald-rs"),
            to_32bytes(
                "f5ab12ff7b15bb4a5cd3d36a41bdbc8e54c180f7558cc4f8cd40acabda02dd84",
            )
        );
    }

    #[test]
    fn should_calculate_big_keccak256() {
        assert_eq!(
            keccak256(&[b'-'; 1024]),
            to_32bytes(
                "ea1da5135479c4eb22ed3743c379970895ed2d088fd5d79884b7493aaa49475b",
            )
        );
    }
}