// KILT Blockchain – https://botlabs.org
// Copyright (C) 2019-2024 BOTLabs GmbH

// The KILT Blockchain 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.

// The KILT Blockchain 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 this program.  If not, see <https://www.gnu.org/licenses/>.

// If you feel like getting in touch with us, you can do so at info@botlabs.org

// This code originally came from the purestake/moonbeam repo.
// see https://github.com/PureStake/moonbeam/blob/74324db0cfacaad555064c839f17072b57cb35e3/primitives/account/src/lib.rs for reference.

//! The Ethereum Signature implementation.
//!
//! It includes the Verify and IdentifyAccount traits for the AccountId20

use frame_support::crypto::ecdsa::ECDSAExt;
use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
use scale_info::TypeInfo;
use serde::{Deserialize, Serialize};
use sha3::{Digest, Keccak256};
use sp_core::{ecdsa, H160, H256};
use sp_runtime::RuntimeDebug;

/// The AccountId20 type.
/// It is a 20-byte Ethereum address.
#[derive(
	Eq,
	PartialEq,
	Copy,
	Clone,
	Encode,
	Decode,
	TypeInfo,
	MaxEncodedLen,
	Default,
	PartialOrd,
	Ord,
	RuntimeDebug,
	Serialize,
	Deserialize,
)]
pub struct AccountId20(pub [u8; 20]);

#[cfg(feature = "std")]
impl std::fmt::Display for AccountId20 {
	//TODO This is a pretty quck-n-dirty implementation. Perhaps we should add
	// checksum casing here? I bet there is a crate for that.
	// Maybe this one https://github.com/miguelmota/rust-eth-checksum
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		write!(f, "{:?}", self.0)
	}
}

impl From<[u8; 20]> for AccountId20 {
	fn from(bytes: [u8; 20]) -> Self {
		Self(bytes)
	}
}

impl From<AccountId20> for [u8; 20] {
	fn from(id: AccountId20) -> Self {
		id.0
	}
}

impl From<H160> for AccountId20 {
	fn from(h160: H160) -> Self {
		Self(h160.0)
	}
}

impl From<AccountId20> for H160 {
	fn from(id: AccountId20) -> Self {
		H160(id.0)
	}
}

#[cfg(feature = "std")]
impl std::str::FromStr for AccountId20 {
	type Err = &'static str;
	fn from_str(input: &str) -> Result<Self, Self::Err> {
		H160::from_str(input)
			.map(Into::into)
			.map_err(|_| "invalid hex address.")
	}
}

/// Public key for an Ethereum / Moonbeam compatible account
#[derive(Eq, PartialEq, Ord, PartialOrd, Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
pub struct EthereumSigner([u8; 20]);

impl sp_runtime::traits::IdentifyAccount for EthereumSigner {
	type AccountId = AccountId20;
	fn into_account(self) -> AccountId20 {
		AccountId20(self.0)
	}
}

impl From<[u8; 20]> for EthereumSigner {
	fn from(x: [u8; 20]) -> Self {
		EthereumSigner(x)
	}
}

impl TryFrom<ecdsa::Public> for EthereumSigner {
	type Error = &'static str;
	fn try_from(x: ecdsa::Public) -> Result<Self, Self::Error> {
		match x.to_eth_address() {
			Ok(x) => Ok(Self(x)),
			Err(_) => Err("invalid public key"),
		}
	}
}

impl From<libsecp256k1::PublicKey> for EthereumSigner {
	fn from(x: libsecp256k1::PublicKey) -> Self {
		let mut m = [0u8; 64];
		m.copy_from_slice(&x.serialize()[1..65]);
		let account = H160::from(H256::from_slice(Keccak256::digest(m).as_slice()));
		EthereumSigner(account.into())
	}
}

#[cfg(feature = "std")]
impl std::fmt::Display for EthereumSigner {
	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
		write!(fmt, "ethereum signature: {:?}", H160::from_slice(&self.0))
	}
}

#[derive(Eq, PartialEq, Clone, Encode, Decode, MaxEncodedLen, RuntimeDebug, TypeInfo)]
pub struct EthereumSignature(ecdsa::Signature);

impl From<ecdsa::Signature> for EthereumSignature {
	fn from(x: ecdsa::Signature) -> Self {
		EthereumSignature(x)
	}
}

impl sp_runtime::traits::Verify for EthereumSignature {
	type Signer = EthereumSigner;
	fn verify<L: sp_runtime::traits::Lazy<[u8]>>(&self, mut msg: L, signer: &AccountId20) -> bool {
		let mut hashed_message_buffer = [0u8; 32];
		hashed_message_buffer.copy_from_slice(Keccak256::digest(msg.get()).as_slice());
		match sp_io::crypto::secp256k1_ecdsa_recover(self.0.as_ref(), &hashed_message_buffer) {
			Ok(pubkey) => {
				// TODO This conversion could use a comment. Why H256 first, then H160?
				// TODO actually, there is probably just a better way to go from Keccak digest.
				AccountId20(H160::from(H256::from_slice(Keccak256::digest(pubkey).as_slice())).0) == *signer
			}
			Err(_) => {
				log::trace!("Error verifying signature");
				false
			}
		}
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use sp_core::{ecdsa, Pair};
	use sp_runtime::traits::IdentifyAccount;

	#[test]
	fn test_account_derivation_1() {
		// Test from https://asecuritysite.com/encryption/ethadd
		// This page generates a private ethereum key, a public key and computes an
		// address from it. We take those values as reference point to proof that our
		// implementation is correct.
		let secret_key = hex::decode("502f97299c472b88754accd412b7c9a6062ef3186fba0c0388365e1edec24875").unwrap();
		let mut expected_hex_account = [0u8; 20];
		hex::decode_to_slice("976f8456e4e2034179b284a23c0e0c8f6d3da50c", &mut expected_hex_account)
			.expect("example data is 20 bytes of valid hex");

		let public_key = ecdsa::Pair::from_seed_slice(&secret_key).unwrap().public();
		let account: EthereumSigner = public_key.try_into().unwrap();
		let expected_account = AccountId20::from(expected_hex_account);
		assert_eq!(account.into_account(), expected_account);
	}
	#[test]
	fn test_account_derivation_2() {
		// Test from https://asecuritysite.com/encryption/ethadd
		let secret_key = hex::decode("0f02ba4d7f83e59eaa32eae9c3c4d99b68ce76decade21cdab7ecce8f4aef81a").unwrap();
		let mut expected_hex_account = [0u8; 20];
		hex::decode_to_slice("420e9f260b40af7e49440cead3069f8e82a5230f", &mut expected_hex_account)
			.expect("example data is 20 bytes of valid hex");

		let public_key = ecdsa::Pair::from_seed_slice(&secret_key).unwrap().public();
		let account: EthereumSigner = public_key.try_into().unwrap();
		let expected_account = AccountId20::from(expected_hex_account);
		assert_eq!(account.into_account(), expected_account);
	}
}