// This file is part of Substrate.

// Copyright (C) 2017-2020 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

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

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

use sp_std::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, CryptoTypePublicPair, UncheckedFrom, CryptoType, Derive, CryptoTypeId};
use sp_runtime_interface::pass_by::PassByInner;
#[cfg(feature = "full_crypto")]
use secp256k1::{PublicKey, SecretKey};

/// An identifier used to match public keys against ecdsa keys
pub const CRYPTO_ID: CryptoTypeId = CryptoTypeId(*b"ecds");

/// 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 compressed public key.
#[derive(Clone, Encode, Decode, PassByInner)]
pub struct Public([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.as_ref().cmp(&other.as_ref())
	}
}

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

impl Eq for Public {}

/// 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 {
		Self(data)
	}

	/// Create a new instance from the given full public key.
	///
	/// This will convert the full public key into the compressed format.
	#[cfg(feature = "std")]
	pub fn from_full(full: &[u8]) -> Result<Self, ()> {
		secp256k1::PublicKey::parse_slice(full, None)
			.map(|k| k.serialize_compressed())
			.map(Self)
			.map_err(|_| ())
	}
}

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);
		Self(r)
	}

	fn to_public_crypto_pair(&self) -> CryptoTypePublicPair {
		CryptoTypePublicPair(CRYPTO_ID, self.to_raw_vec())
	}
}

impl From<Public> for CryptoTypePublicPair {
	fn from(key: Public) -> Self {
		(&key).into()
	}
}

impl From<&Public> for CryptoTypePublicPair {
	fn from(key: &Public) -> Self {
		CryptoTypePublicPair(CRYPTO_ID, key.to_raw_vec())
	}
}

impl Derive for Public {}

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

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

	fn try_from(data: &[u8]) -> Result<Self, Self::Error> {
		if data.len() == 33 {
			Ok(Self::from_slice(data))
		} else {

			Err(())
		}
	}
}

#[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())
	}
}

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

	#[cfg(not(feature = "std"))]
	fn fmt(&self, _: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
		Ok(())
	}
}

#[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 sp_std::hash::Hash for Public {
	fn hash<H: sp_std::hash::Hasher>(&self, state: &mut H) {
		self.as_ref().hash(state);
	}
}

/// A signature (a 512-bit value, plus 8 bits for recovery ID).
#[derive(Encode, Decode, PassByInner)]
pub struct Signature([u8; 65]);

impl sp_std::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(())
		}
	}
}

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

#[cfg(feature = "std")]
impl<'de> Deserialize<'de> for Signature {
	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where D: Deserializer<'de> {
		let signature_hex = hex::decode(&String::deserialize(deserializer)?)
			.map_err(|e| de::Error::custom(format!("{:?}", e)))?;
		Ok(Signature::try_from(signature_hex.as_ref())
			.map_err(|e| de::Error::custom(format!("{:?}", e)))?)
	}
}

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[..]
	}
}

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

	#[cfg(not(feature = "std"))]
	fn fmt(&self, _: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
		Ok(())
	}
}

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

	/// A new instance from the given slice that should be 65 bytes long.
	///
	/// 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_slice(data: &[u8]) -> Self {
		let mut r = [0u8; 65];
		r.copy_from_slice(data);
		Signature(r)
	}

	/// 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(|_| ())?,
		))
	}
}

/// 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,
}

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

#[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()[1..],
			_ => 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, set_default_ss58_version};
	use serde_json;

	#[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_full(
				&hex!("8db55b05db86c0b1786ca49f095d76344c9e6056b2f02701a7e7f3c20aabfd913ebbe148dd17c56551a52952371071a6c604b3f3abe8f2c8fa742158ea6dd7d4")[..],
			).unwrap(),
		);
		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_full(
				&hex!("8db55b05db86c0b1786ca49f095d76344c9e6056b2f02701a7e7f3c20aabfd913ebbe148dd17c56551a52952371071a6c604b3f3abe8f2c8fa742158ea6dd7d4")[..],
			).unwrap(),
		);
		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_full(
				&hex!("5676109c54b9a16d271abeb4954316a40a32bcce023ac14c8e26e958aa68fba995840f3de562156558efbfdac3f16af0065e5f66795f4dd8262a228ef8c6d813")[..],
			).unwrap(),
		);
		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);
	}

	#[test]
	fn ss58check_custom_format_works() {
		use crate::crypto::Ss58AddressFormat;
		// temp save default format version
		let default_format = Ss58AddressFormat::default();
		// set current ss58 version is custom "200" `Ss58AddressFormat::Custom(200)`
		set_default_ss58_version(Ss58AddressFormat::Custom(200));
		// custom addr encoded by version 200
		let addr = "2X64kMNEWAW5KLZMSKcGKEc96MyuaRsRUku7vomuYxKgqjVCRj";
		Public::from_ss58check(&addr).unwrap();
		set_default_ss58_version(default_format);
		// set  current ss58 version to default version
		let addr = "KWAfgC2aRG5UVD6CpbPQXCx4YZZUhvWqqAJE6qcYc9Rtr6g5C";
		Public::from_ss58check(&addr).unwrap();
	}

	#[test]
	fn signature_serialization_works() {
		let pair = Pair::from_seed(b"12345678901234567890123456789012");
		let message = b"Something important";
		let signature = pair.sign(&message[..]);
		let serialized_signature = serde_json::to_string(&signature).unwrap();
		// Signature is 65 bytes, so 130 chars + 2 quote chars
		assert_eq!(serialized_signature.len(), 132);
		let signature = serde_json::from_str(&serialized_signature).unwrap();
		assert!(Pair::verify(&signature, &message[..], &pair.public()));
	}

	#[test]
	fn signature_serialization_doesnt_panic() {
		fn deserialize_signature(text: &str) -> Result<Signature, serde_json::error::Error> {
			Ok(serde_json::from_str(text)?)
		}
		assert!(deserialize_signature("Not valid json.").is_err());
		assert!(deserialize_signature("\"Not an actual signature.\"").is_err());
		// Poorly-sized
		assert!(deserialize_signature("\"abc123\"").is_err());
	}
}