// Copyright 2017-2019 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate 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.

// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.

// tag::description[]
//! Simple ECDSA API.
// end::description[]

#[cfg(feature = "full_crypto")]
use rstd::vec::Vec;

use rstd::cmp::Ordering;
use codec::{Encode, Decode};

#[cfg(feature = "full_crypto")]
use core::convert::{TryFrom, TryInto};
#[cfg(feature = "std")]
use substrate_bip39::seed_from_entropy;
#[cfg(feature = "std")]
use bip39::{Mnemonic, Language, MnemonicType};
#[cfg(feature = "full_crypto")]
use crate::{hashing::blake2_256, crypto::{Pair as TraitPair, DeriveJunction, SecretStringError}};
#[cfg(feature = "std")]
use crate::crypto::Ss58Codec;
#[cfg(feature = "std")]
use serde::{de, Serializer, Serialize, Deserializer, Deserialize};
use crate::crypto::{Public as TraitPublic, UncheckedFrom, CryptoType, Derive};
#[cfg(feature = "full_crypto")]
use secp256k1::{PublicKey, SecretKey};

/// A secret seed (which is bytewise essentially equivalent to a SecretKey).
///
/// We need it as a different type because `Seed` is expected to be AsRef<[u8]>.
#[cfg(feature = "full_crypto")]
type Seed = [u8; 32];

/// The ECDSA 33-byte compressed public key.
#[derive(Clone, Encode, Decode)]
pub struct Public(pub [u8; 33]);

impl PartialOrd for Public {
	fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
		Some(self.cmp(other))
	}
}

impl Ord for Public {
	fn cmp(&self, other: &Self) -> Ordering {
		self.0[..].cmp(&other.0[..])
	}
}

impl PartialEq for Public {
	fn eq(&self, other: &Self) -> bool {
		&self.0[..] == &other.0[..]
	}
}

impl Eq for Public {}

impl Default for Public {
	fn default() -> Self {
		Public([0u8; 33])
	}
}

/// A key pair.
#[cfg(feature = "full_crypto")]
#[derive(Clone)]
pub struct Pair {
	public: PublicKey,
	secret: SecretKey,
}

impl AsRef<[u8; 33]> for Public {
	fn as_ref(&self) -> &[u8; 33] {
		&self.0
	}
}

impl AsRef<[u8]> for Public {
	fn as_ref(&self) -> &[u8] {
		&self.0[..]
	}
}

impl AsMut<[u8]> for Public {
	fn as_mut(&mut self) -> &mut [u8] {
		&mut self.0[..]
	}
}

impl rstd::convert::TryFrom<&[u8]> for Public {
	type Error = ();

	fn try_from(data: &[u8]) -> Result<Self, Self::Error> {
		if data.len() == 33 {
			let mut inner = [0u8; 33];
			inner.copy_from_slice(data);
			Ok(Public(inner))
		} else {
			Err(())
		}
	}
}

impl From<Public> for [u8; 33] {
	fn from(x: Public) -> Self {
		x.0
	}
}

#[cfg(feature = "full_crypto")]
impl From<Pair> for Public {
	fn from(x: Pair) -> Self {
		x.public()
	}
}

impl UncheckedFrom<[u8; 33]> for Public {
	fn unchecked_from(x: [u8; 33]) -> Self {
		Public(x)
	}
}

#[cfg(feature = "std")]
impl std::fmt::Display for Public {
	fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
		write!(f, "{}", self.to_ss58check())
	}
}

#[cfg(feature = "std")]
impl std::fmt::Debug for Public {
	fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
		let s = self.to_ss58check();
		write!(f, "{} ({}...)", crate::hexdisplay::HexDisplay::from(&&self.0[..]), &s[0..8])
	}
}

#[cfg(feature = "std")]
impl Serialize for Public {
	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: Serializer {
		serializer.serialize_str(&self.to_ss58check())
	}
}

#[cfg(feature = "std")]
impl<'de> Deserialize<'de> for Public {
	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where D: Deserializer<'de> {
		Public::from_ss58check(&String::deserialize(deserializer)?)
			.map_err(|e| de::Error::custom(format!("{:?}", e)))
	}
}

#[cfg(feature = "full_crypto")]
impl rstd::hash::Hash for Public {
	fn hash<H: rstd::hash::Hasher>(&self, state: &mut H) {
		self.0.hash(state);
	}
}

/// A signature (a 512-bit value).
#[derive(Encode, Decode)]
pub struct Signature([u8; 65]);

impl rstd::convert::TryFrom<&[u8]> for Signature {
	type Error = ();

	fn try_from(data: &[u8]) -> Result<Self, Self::Error> {
		if data.len() == 65 {
			let mut inner = [0u8; 65];
			inner.copy_from_slice(data);
			Ok(Signature(inner))
		} else {
			Err(())
		}
	}
}

impl Clone for Signature {
	fn clone(&self) -> Self {
		let mut r = [0u8; 65];
		r.copy_from_slice(&self.0[..]);
		Signature(r)
	}
}

impl Default for Signature {
	fn default() -> Self {
		Signature([0u8; 65])
	}
}

impl PartialEq for Signature {
	fn eq(&self, b: &Self) -> bool {
		self.0[..] == b.0[..]
	}
}

impl Eq for Signature {}

impl From<Signature> for [u8; 65] {
	fn from(v: Signature) -> [u8; 65] {
		v.0
	}
}

impl AsRef<[u8; 65]> for Signature {
	fn as_ref(&self) -> &[u8; 65] {
		&self.0
	}
}

impl AsRef<[u8]> for Signature {
	fn as_ref(&self) -> &[u8] {
		&self.0[..]
	}
}

impl AsMut<[u8]> for Signature {
	fn as_mut(&mut self) -> &mut [u8] {
		&mut self.0[..]
	}
}

#[cfg(feature = "std")]
impl std::fmt::Debug for Signature {
	fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
		write!(f, "{}", crate::hexdisplay::HexDisplay::from(&self.0))
	}
}

#[cfg(feature = "full_crypto")]
impl rstd::hash::Hash for Signature {
	fn hash<H: rstd::hash::Hasher>(&self, state: &mut H) {
		rstd::hash::Hash::hash(&self.0[..], state);
	}
}

impl Signature {
	/// A new instance from the given 65-byte `data`.
	///
	/// NOTE: No checking goes on to ensure this is a real signature. Only use it if
	/// you are certain that the array actually is a signature. GIGO!
	pub fn from_raw(data: [u8; 65]) -> Signature {
		Signature(data)
	}

	/// Recover the public key from this signature and a message.
	#[cfg(feature = "full_crypto")]
	pub fn recover<M: AsRef<[u8]>>(&self, message: M) -> Option<Public> {
		let message = secp256k1::Message::parse(&blake2_256(message.as_ref()));
		let sig: (_, _) = self.try_into().ok()?;
		secp256k1::recover(&message, &sig.0, &sig.1).ok()
			.map(|recovered| Public(recovered.serialize_compressed()))
	}
}

#[cfg(feature = "full_crypto")]
impl From<(secp256k1::Signature, secp256k1::RecoveryId)> for Signature {
	fn from(x: (secp256k1::Signature, secp256k1::RecoveryId)) -> Signature {
		let mut r = Self::default();
		r.0[0..64].copy_from_slice(&x.0.serialize()[..]);
		r.0[64] = x.1.serialize();
		r
	}
}

#[cfg(feature = "full_crypto")]
impl<'a> TryFrom<&'a Signature> for (secp256k1::Signature, secp256k1::RecoveryId) {
	type Error = ();
	fn try_from(x: &'a Signature) -> Result<(secp256k1::Signature, secp256k1::RecoveryId), Self::Error> {
		Ok((
			secp256k1::Signature::parse_slice(&x.0[0..64]).expect("hardcoded to 64 bytes; qed"),
			secp256k1::RecoveryId::parse(x.0[64]).map_err(|_| ())?,
		))
	}
}

/// An error type for SS58 decoding.
#[cfg(feature = "std")]
#[derive(Clone, Copy, Eq, PartialEq, Debug)]
pub enum PublicError {
	/// Bad alphabet.
	BadBase58,
	/// Bad length.
	BadLength,
	/// Unknown version.
	UnknownVersion,
	/// Invalid checksum.
	InvalidChecksum,
}

impl Public {
	/// A new instance from the given 33-byte `data`.
	///
	/// NOTE: No checking goes on to ensure this is a real public key. Only use it if
	/// you are certain that the array actually is a pubkey. GIGO!
	pub fn from_raw(data: [u8; 33]) -> Self {
		Public(data)
	}

	/// Return a slice filled with raw data.
	pub fn as_array_ref(&self) -> &[u8; 33] {
		self.as_ref()
	}
}

impl TraitPublic for Public {
	/// A new instance from the given slice that should be 33 bytes long.
	///
	/// NOTE: No checking goes on to ensure this is a real public key. Only use it if
	/// you are certain that the array actually is a pubkey. GIGO!
	fn from_slice(data: &[u8]) -> Self {
		let mut r = [0u8; 33];
		r.copy_from_slice(data);
		Public(r)
	}
}

impl Derive for Public {}

/// Derive a single hard junction.
#[cfg(feature = "full_crypto")]
fn derive_hard_junction(secret_seed: &Seed, cc: &[u8; 32]) -> Seed {
	("Secp256k1HDKD", secret_seed, cc).using_encoded(|data| {
		let mut res = [0u8; 32];
		res.copy_from_slice(blake2_rfc::blake2b::blake2b(32, &[], data).as_bytes());
		res
	})
}

/// An error when deriving a key.
#[cfg(feature = "full_crypto")]
pub enum DeriveError {
	/// A soft key was found in the path (and is unsupported).
	SoftKeyInPath,
}

#[cfg(feature = "full_crypto")]
impl TraitPair for Pair {
	type Public = Public;
	type Seed = Seed;
	type Signature = Signature;
	type DeriveError = DeriveError;

	/// Generate new secure (random) key pair and provide the recovery phrase.
	///
	/// You can recover the same key later with `from_phrase`.
	#[cfg(feature = "std")]
	fn generate_with_phrase(password: Option<&str>) -> (Pair, String, Seed) {
		let mnemonic = Mnemonic::new(MnemonicType::Words12, Language::English);
		let phrase = mnemonic.phrase();
		let (pair, seed) = Self::from_phrase(phrase, password)
			.expect("All phrases generated by Mnemonic are valid; qed");
		(
			pair,
			phrase.to_owned(),
			seed,
		)
	}

	/// Generate key pair from given recovery phrase and password.
	#[cfg(feature = "std")]
	fn from_phrase(phrase: &str, password: Option<&str>) -> Result<(Pair, Seed), SecretStringError> {
		let big_seed = seed_from_entropy(
			Mnemonic::from_phrase(phrase, Language::English)
				.map_err(|_| SecretStringError::InvalidPhrase)?.entropy(),
			password.unwrap_or(""),
		).map_err(|_| SecretStringError::InvalidSeed)?;
		let mut seed = Seed::default();
		seed.copy_from_slice(&big_seed[0..32]);
		Self::from_seed_slice(&big_seed[0..32]).map(|x| (x, seed))
	}

	/// Make a new key pair from secret seed material.
	///
	/// You should never need to use this; generate(), generate_with_phrase
	fn from_seed(seed: &Seed) -> Pair {
		Self::from_seed_slice(&seed[..]).expect("seed has valid length; qed")
	}

	/// Make a new key pair from secret seed material. The slice must be 32 bytes long or it
	/// will return `None`.
	///
	/// You should never need to use this; generate(), generate_with_phrase
	fn from_seed_slice(seed_slice: &[u8]) -> Result<Pair, SecretStringError> {
		let secret = SecretKey::parse_slice(seed_slice)
			.map_err(|_| SecretStringError::InvalidSeedLength)?;
		let public = PublicKey::from_secret_key(&secret);
		Ok(Pair{ secret, public })
	}

	/// Derive a child key from a series of given junctions.
	fn derive<Iter: Iterator<Item=DeriveJunction>>(&self,
		path: Iter,
		_seed: Option<Seed>
	) -> Result<(Pair, Option<Seed>), DeriveError> {
		let mut acc = self.secret.serialize();
		for j in path {
			match j {
				DeriveJunction::Soft(_cc) => return Err(DeriveError::SoftKeyInPath),
				DeriveJunction::Hard(cc) => acc = derive_hard_junction(&acc, &cc),
			}
		}
		Ok((Self::from_seed(&acc), Some(acc)))
	}

	/// Get the public key.
	fn public(&self) -> Public {
		Public(self.public.serialize_compressed())
	}

	/// Sign a message.
	fn sign(&self, message: &[u8]) -> Signature {
		let message = secp256k1::Message::parse(&blake2_256(message));
		secp256k1::sign(&message, &self.secret).into()
	}

	/// Verify a signature on a message. Returns true if the signature is good.
	fn verify<M: AsRef<[u8]>>(sig: &Self::Signature, message: M, pubkey: &Self::Public) -> bool {
		let message = secp256k1::Message::parse(&blake2_256(message.as_ref()));
		let sig: (_, _) = match sig.try_into() { Ok(x) => x, _ => return false };
		match secp256k1::recover(&message, &sig.0, &sig.1) {
			Ok(actual) => &pubkey.0[..] == &actual.serialize_compressed()[..],
			_ => false,
		}
	}

	/// Verify a signature on a message. Returns true if the signature is good.
	///
	/// This doesn't use the type system to ensure that `sig` and `pubkey` are the correct
	/// size. Use it only if you're coming from byte buffers and need the speed.
	fn verify_weak<P: AsRef<[u8]>, M: AsRef<[u8]>>(sig: &[u8], message: M, pubkey: P) -> bool {
		let message = secp256k1::Message::parse(&blake2_256(message.as_ref()));
		if sig.len() != 65 { return false }
		let ri = match secp256k1::RecoveryId::parse(sig[64]) { Ok(x) => x, _ => return false };
		let sig = match secp256k1::Signature::parse_slice(&sig[0..64]) { Ok(x) => x, _ => return false };
		match secp256k1::recover(&message, &sig, &ri) {
			Ok(actual) => pubkey.as_ref() == &actual.serialize_compressed()[..],
			_ => false,
		}
	}

	/// Return a vec filled with raw data.
	fn to_raw_vec(&self) -> Vec<u8> {
		self.seed().to_vec()
	}
}

#[cfg(feature = "full_crypto")]
impl Pair {
	/// Get the seed for this key.
	pub fn seed(&self) -> Seed {
		self.secret.serialize()
	}

	/// Exactly as `from_string` except that if no matches are found then, the the first 32
	/// characters are taken (padded with spaces as necessary) and used as the MiniSecretKey.
	#[cfg(feature = "std")]
	pub fn from_legacy_string(s: &str, password_override: Option<&str>) -> Pair {
		Self::from_string(s, password_override).unwrap_or_else(|_| {
			let mut padded_seed: Seed = [' ' as u8; 32];
			let len = s.len().min(32);
			padded_seed[..len].copy_from_slice(&s.as_bytes()[..len]);
			Self::from_seed(&padded_seed)
		})
	}
}

impl CryptoType for Public {
	#[cfg(feature="full_crypto")]
	type Pair = Pair;
}

impl CryptoType for Signature {
	#[cfg(feature="full_crypto")]
	type Pair = Pair;
}

#[cfg(feature="full_crypto")]
impl CryptoType for Pair {
	type Pair = Pair;
}

#[cfg(test)]
mod test {
	use super::*;
	use hex_literal::hex;
	use crate::crypto::DEV_PHRASE;

	#[test]
	fn default_phrase_should_be_used() {
		assert_eq!(
			Pair::from_string("//Alice///password", None).unwrap().public(),
			Pair::from_string(&format!("{}//Alice", DEV_PHRASE), Some("password")).unwrap().public(),
		);
	}

	#[test]
	fn seed_and_derive_should_work() {
		let seed = hex!("9d61b19deffd5a60ba844af492ec2cc44449c5697b326919703bac031cae7f60");
		let pair = Pair::from_seed(&seed);
		assert_eq!(pair.seed(), seed);
		let path = vec![DeriveJunction::Hard([0u8; 32])];
		let derived = pair.derive(path.into_iter(), None).ok().unwrap();
		assert_eq!(
			derived.0.seed(),
			hex!("b8eefc4937200a8382d00050e050ced2d4ab72cc2ef1b061477afb51564fdd61")
		);
	}

	#[test]
	fn test_vector_should_work() {
		let pair = Pair::from_seed(
			&hex!("9d61b19deffd5a60ba844af492ec2cc44449c5697b326919703bac031cae7f60")
		);
		let public = pair.public();
		assert_eq!(public, Public::from_raw(
			hex!("028db55b05db86c0b1786ca49f095d76344c9e6056b2f02701a7e7f3c20aabfd91")
		));
		let message = b"";
		let signature = hex!("3dde91174bd9359027be59a428b8146513df80a2a3c7eda2194f64de04a69ab97b753169e94db6ffd50921a2668a48b94ca11e3d32c1ff19cfe88890aa7e8f3c00");
		let signature = Signature::from_raw(signature);
		assert!(&pair.sign(&message[..]) == &signature);
		assert!(Pair::verify(&signature, &message[..], &public));
	}

	#[test]
	fn test_vector_by_string_should_work() {
		let pair = Pair::from_string(
			"0x9d61b19deffd5a60ba844af492ec2cc44449c5697b326919703bac031cae7f60",
			None
		).unwrap();
		let public = pair.public();
		assert_eq!(public, Public::from_raw(
			hex!("028db55b05db86c0b1786ca49f095d76344c9e6056b2f02701a7e7f3c20aabfd91")
		));
		let message = b"";
		let signature = hex!("3dde91174bd9359027be59a428b8146513df80a2a3c7eda2194f64de04a69ab97b753169e94db6ffd50921a2668a48b94ca11e3d32c1ff19cfe88890aa7e8f3c00");
		let signature = Signature::from_raw(signature);
		assert!(&pair.sign(&message[..]) == &signature);
		assert!(Pair::verify(&signature, &message[..], &public));
	}

	#[test]
	fn generated_pair_should_work() {
		let (pair, _) = Pair::generate();
		let public = pair.public();
		let message = b"Something important";
		let signature = pair.sign(&message[..]);
		assert!(Pair::verify(&signature, &message[..], &public));
		assert!(!Pair::verify(&signature, b"Something else", &public));
	}

	#[test]
	fn seeded_pair_should_work() {
		let pair = Pair::from_seed(b"12345678901234567890123456789012");
		let public = pair.public();
		assert_eq!(public, Public::from_raw(
			hex!("035676109c54b9a16d271abeb4954316a40a32bcce023ac14c8e26e958aa68fba9")
		));
		let message = hex!("2f8c6129d816cf51c374bc7f08c3e63ed156cf78aefb4a6550d97b87997977ee00000000000000000200d75a980182b10ab7d54bfed3c964073a0ee172f3daa62325af021a68f707511a4500000000000000");
		let signature = pair.sign(&message[..]);
		println!("Correct signature: {:?}", signature);
		assert!(Pair::verify(&signature, &message[..], &public));
		assert!(!Pair::verify(&signature, "Other message", &public));
	}

	#[test]
	fn generate_with_phrase_recovery_possible() {
		let (pair1, phrase, _) = Pair::generate_with_phrase(None);
		let (pair2, _) = Pair::from_phrase(&phrase, None).unwrap();

		assert_eq!(pair1.public(), pair2.public());
	}

	#[test]
	fn generate_with_password_phrase_recovery_possible() {
		let (pair1, phrase, _) = Pair::generate_with_phrase(Some("password"));
		let (pair2, _) = Pair::from_phrase(&phrase, Some("password")).unwrap();

		assert_eq!(pair1.public(), pair2.public());
	}

	#[test]
	fn password_does_something() {
		let (pair1, phrase, _) = Pair::generate_with_phrase(Some("password"));
		let (pair2, _) = Pair::from_phrase(&phrase, None).unwrap();

		assert_ne!(pair1.public(), pair2.public());
	}

	#[test]
	fn ss58check_roundtrip_works() {
		let pair = Pair::from_seed(b"12345678901234567890123456789012");
		let public = pair.public();
		let s = public.to_ss58check();
		println!("Correct: {}", s);
		let cmp = Public::from_ss58check(&s).unwrap();
		assert_eq!(cmp, public);
	}
}