use hash::*;
use secp256k1::Secp256k1;
use secp256k1::key;
use rand::os::OsRng;

pub type Secret=H256;
pub type Public=H512;

pub use ::sha3::Hashable;

#[derive(Debug)]
pub enum CryptoError {
	InvalidSecret,
	InvalidPublic,
	InvalidSignature,
	InvalidMessage,
	Io(::std::io::Error),
}

impl From<::secp256k1::Error> for CryptoError {
	fn from(e: ::secp256k1::Error) -> CryptoError {
		match e {
			::secp256k1::Error::InvalidMessage => CryptoError::InvalidMessage,
			::secp256k1::Error::InvalidPublicKey => CryptoError::InvalidPublic,
			::secp256k1::Error::InvalidSignature => CryptoError::InvalidSignature,
			::secp256k1::Error::InvalidSecretKey => CryptoError::InvalidSecret,
			_ => panic!("Crypto error: {:?}", e),
		}
	}
}

impl From<::std::io::Error> for CryptoError {
	fn from(err: ::std::io::Error) -> CryptoError {
		CryptoError::Io(err)
	}
}

#[derive(Debug, PartialEq, Eq)]
/// secp256k1 Key pair
///
/// Use `create()` to create a new random key pair. 
/// 
/// # Example
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::crypto::*;
/// use ethcore_util::hash::*;
/// fn main() {
///   let pair = KeyPair::create().unwrap();
///   let message = H256::random();
///   let signature = ec::sign(pair.secret(), &message).unwrap();
///
///   assert!(ec::verify(pair.public(), &signature, &message).unwrap());
///   assert_eq!(ec::recover(&signature, &message).unwrap(), *pair.public());
/// }
/// ```
pub struct KeyPair {
	secret: Secret,
	public: Public,
}

impl KeyPair {
	/// Create a pair from secret key
	pub fn from_secret(secret: Secret) -> Result<KeyPair, CryptoError> {
		let context = Secp256k1::new();
		let s: key::SecretKey = try!(key::SecretKey::from_slice(&context, &secret));
		let pub_key = try!(key::PublicKey::from_secret_key(&context, &s));
		let serialized = pub_key.serialize_vec(&context, false);
		let p: Public = Public::from_slice(&serialized[1..65]);
		Ok(KeyPair {
			secret: secret,
			public: p,
		})
	}
	/// Create a new random key pair
	pub fn create() -> Result<KeyPair, CryptoError> {
		let context = Secp256k1::new();
		let mut rng = try!(OsRng::new());
		let (sec, publ) = try!(context.generate_keypair(&mut rng));
		let serialized = publ.serialize_vec(&context, false);
		let p: Public = Public::from_slice(&serialized[1..65]);
		let s: Secret = unsafe { ::std::mem::transmute(sec) };
		Ok(KeyPair {
			secret: s,
			public: p,
		})
	}
	/// Returns public key
	pub fn public(&self) -> &Public {
		&self.public
	}
	/// Returns private key
	pub fn secret(&self) -> &Secret {
		&self.secret
	}
}

pub mod ec {
	use hash::*;
	use crypto::*;

	pub type Signature = H520;
	/// Recovers Public key from signed message hash.
	pub fn recover(signature: &Signature, message: &H256) -> Result<Public, CryptoError> {
		use secp256k1::*;
		let context = Secp256k1::new();
		let rsig = try!(RecoverableSignature::from_compact(&context, &signature[0..64], try!(RecoveryId::from_i32(signature[64] as i32))));
		let publ = try!(context.recover(&try!(Message::from_slice(&message)), &rsig));
		let serialized = publ.serialize_vec(&context, false);
		let p: Public = Public::from_slice(&serialized[1..65]);
		Ok(p)
	}
	/// Returns siganture of message hash.
	pub fn sign(secret: &Secret, message: &H256) -> Result<Signature, CryptoError> {
		use secp256k1::*;
		let context = Secp256k1::new();
		let sec: &key::SecretKey = unsafe { ::std::mem::transmute(secret) };
		let s = try!(context.sign_recoverable(&try!(Message::from_slice(&message)), sec));
		let (rec_id, data) = s.serialize_compact(&context);
		let mut signature: ec::Signature = unsafe { ::std::mem::uninitialized() };
		signature.clone_from_slice(&data);
		signature[64] = rec_id.to_i32() as u8;
		Ok(signature)
	}
	/// Verify signature.
	pub fn verify(public: &Public, signature: &Signature, message: &H256) -> Result<bool, CryptoError> {
		use secp256k1::*;
		let context = Secp256k1::new();
		let rsig = try!(RecoverableSignature::from_compact(&context, &signature[0..64], try!(RecoveryId::from_i32(signature[64] as i32))));
		let sig = rsig.to_standard(&context);

		let mut pdata: [u8; 65] = [4u8; 65];
		let ptr = pdata[1..].as_mut_ptr();
		let src = public.as_ptr();
		unsafe { ::std::ptr::copy_nonoverlapping(src, ptr, 64) };
		let publ = try!(key::PublicKey::from_slice(&context, &pdata));
		match context.verify(&try!(Message::from_slice(&message)), &sig, &publ) {
			Ok(_) => Ok(true),
			Err(Error::IncorrectSignature) => Ok(false),
			Err(x) => Err(<CryptoError as From<Error>>::from(x))
		}
	}
}

pub mod ecdh {
	use crypto::*;

	pub fn agree(secret: &Secret, public: &Public, ) -> Result<Secret, CryptoError> {
		use secp256k1::*;
		let context = Secp256k1::new();
		let mut pdata: [u8; 65] = [4u8; 65];
		let ptr = pdata[1..].as_mut_ptr();
		let src = public.as_ptr();
		unsafe { ::std::ptr::copy_nonoverlapping(src, ptr, 64) };
		let publ = try!(key::PublicKey::from_slice(&context, &pdata));
		let sec: &key::SecretKey = unsafe { ::std::mem::transmute(secret) };
		let shared = ecdh::SharedSecret::new_raw(&context, &publ, &sec);
		let s: Secret = unsafe { ::std::mem::transmute(shared) };
		Ok(s)
	}
}

pub mod ecies {
	use hash::*;
	use bytes::*;
	use crypto::*;

	pub fn encrypt(public: &Public, plain: &[u8]) -> Result<Bytes, CryptoError> {
		use ::rcrypto::digest::Digest;
		use ::rcrypto::sha2::Sha256;
		use ::rcrypto::hmac::Hmac;
		use ::rcrypto::mac::Mac;
		let r = try!(KeyPair::create());
		let z = try!(ecdh::agree(r.secret(), public));
		let mut key = [0u8; 32];
		let mut mkey = [0u8; 32];
		kdf(&z, &[0u8; 0], &mut key);
		let mut hasher = Sha256::new();
		let mkey_material = &key[16..32];
		hasher.input(mkey_material);
		hasher.result(&mut mkey);
		let ekey = &key[0..16];

		let mut msg = vec![0u8; (1 + 64 + 16 + plain.len() + 32)];
		msg[0] = 0x04u8;
		{
			let msgd = &mut msg[1..];
			r.public().copy_to(&mut msgd[0..64]);
			{
				let cipher = &mut msgd[(64 + 16)..(64 + 16 + plain.len())];
				aes::encrypt(ekey, &H128::new(), plain, cipher);
			}
			let mut hmac = Hmac::new(Sha256::new(), &mkey);
			{
				let cipher_iv = &msgd[64..(64 + 16 + plain.len())];
				hmac.input(cipher_iv);
			}
			hmac.raw_result(&mut msgd[(64 + 16 + plain.len())..]);
		}
		Ok(msg)
	}

	pub fn decrypt(secret: &Secret, encrypted: &[u8]) -> Result<Bytes, CryptoError> {
		use ::rcrypto::digest::Digest;
		use ::rcrypto::sha2::Sha256;
		use ::rcrypto::hmac::Hmac;
		use ::rcrypto::mac::Mac;

		let meta_len = encrypted.len() - (1 + 64 + 16 + 32);
		if encrypted.len() < meta_len  || encrypted[0] < 2 || encrypted[0] > 4 {
			return Err(CryptoError::InvalidMessage); //invalid message: publickey
		}
		
		let e = &encrypted[1..];
		let p = Public::from_slice(&e[0..64]);
		let z = try!(ecdh::agree(secret, &p));
		let mut key = [0u8; 32];
		kdf(&z, &[0u8; 0], &mut key);
		let ekey = &key[0..16];
		let mkey_material = &key[16..32];
		let mut hasher = Sha256::new();
		let mut mkey = [0u8; 32];
		hasher.input(mkey_material);
		hasher.result(&mut mkey);

		let clen = encrypted.len() - meta_len;
		let cypher_with_iv = &e[64..(64+16+clen)];
		let cypher_iv = &cypher_with_iv[0..16];
		let cypher_no_iv = &cypher_with_iv[16..];
		let msg_mac = &e[(64+16+clen)..];

		// Verify tag
		let mut hmac = Hmac::new(Sha256::new(), &mkey);
		hmac.input(cypher_iv);
		let mut mac = H256::new();
		hmac.raw_result(&mut mac);
		if &mac[..] != msg_mac {
			return Err(CryptoError::InvalidMessage);
		}

		let mut msg = vec![0u8; clen];
		aes::decrypt(ekey, &H128::new(), cypher_no_iv, &mut msg[..]);
		Ok(msg)
	}

	fn kdf(secret: &Secret, s1: &[u8], dest: &mut [u8]) {
		use ::rcrypto::digest::Digest;
		use ::rcrypto::sha2::Sha256;
		let mut hasher = Sha256::new();
		// SEC/ISO/Shoup specify counter size SHOULD be equivalent
		// to size of hash output, however, it also notes that
		// the 4 bytes is okay. NIST specifies 4 bytes.
		let mut ctr = 1u32;
		let mut written = 0usize;
		while written < dest.len() {
			let ctrs = [(ctr >> 24) as u8, (ctr >> 16) as u8, (ctr >> 8) as u8, ctr as u8];
			hasher.input(&ctrs);
			hasher.input(secret);
			hasher.input(s1);
			hasher.result(&mut dest[written..(written + 32)]);
			hasher.reset();
			written += 32;
			ctr += 1;
		}
	}
}

pub mod aes {
	use hash::*;
	use ::rcrypto::blockmodes::*;
	use ::rcrypto::aessafe::*;
	use ::rcrypto::symmetriccipher::*;
	use ::rcrypto::buffer::*;

	pub fn encrypt(k: &[u8], iv: &H128, plain: &[u8], dest: &mut [u8]) {
		let mut encryptor = CtrMode::new(AesSafe128Encryptor::new(k), iv[..].to_vec());
		encryptor.encrypt(&mut RefReadBuffer::new(plain), &mut RefWriteBuffer::new(dest), true).expect("Invalid length or padding");
	}

	pub fn decrypt(k: &[u8], iv: &H128, encrypted: &[u8], dest: &mut [u8]) {
		let mut encryptor = CtrMode::new(AesSafe128Encryptor::new(k), iv[..].to_vec());
		encryptor.decrypt(&mut RefReadBuffer::new(encrypted), &mut RefWriteBuffer::new(dest), true).expect("Invalid length or padding");
	}
}


#[cfg(test)]
mod tests {

	use std::str::FromStr;
	use hash::*;
	use crypto::*;

	#[test]
	fn test_signature() {
		let pair = KeyPair::create().unwrap();
		let message = H256::random();
		let signature = ec::sign(pair.secret(), &message).unwrap();

		assert!(ec::verify(pair.public(), &signature, &message).unwrap());
		assert_eq!(ec::recover(&signature, &message).unwrap(), *pair.public());
	}

	#[test]
	fn test_invalid_key() {
		assert!(KeyPair::from_secret(Secret::from_str("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff").unwrap()).is_err());
		assert!(KeyPair::from_secret(Secret::from_str("0000000000000000000000000000000000000000000000000000000000000000").unwrap()).is_err());
		assert!(KeyPair::from_secret(Secret::from_str("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141").unwrap()).is_err());
	}

	#[test]
	fn test_key() {
		let pair = KeyPair::from_secret(Secret::from_str("6f7b0d801bc7b5ce7bbd930b84fd0369b3eb25d09be58d64ba811091046f3aa2").unwrap()).unwrap();
		assert_eq!(pair.public().hex(), "101b3ef5a4ea7a1c7928e24c4c75fd053c235d7b80c22ae5c03d145d0ac7396e2a4ffff9adee3133a7b05044a5cee08115fd65145e5165d646bde371010d803c");
	}
}