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// This file is part of Substrate.

// Copyright (C) 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.

//! Simple ECDSA secp256k1 API.
//!
//! Provides an extension trait for [`sp_core::ecdsa::Public`] to do certain operations.

use sp_core::{crypto::ByteArray, ecdsa::Public};

/// Extension trait for [`Public`] to be used from inside the runtime.
///
/// # Note
///
/// This is needed because host functions cannot be called from within
/// `sp_core` due to cyclic dependencies  on `sp_io`.
pub trait ECDSAExt {
	/// Returns Ethereum address calculated from this ECDSA public key.
	fn to_eth_address(&self) -> Result<[u8; 20], ()>;
}

impl ECDSAExt for Public {
	fn to_eth_address(&self) -> Result<[u8; 20], ()> {
		use k256::{elliptic_curve::sec1::ToEncodedPoint, PublicKey};

		PublicKey::from_sec1_bytes(self.as_slice()).map_err(drop).and_then(|pub_key| {
			// uncompress the key
			let uncompressed = pub_key.to_encoded_point(false);
			// convert to ETH address
			<[u8; 20]>::try_from(
				sp_io::hashing::keccak_256(&uncompressed.as_bytes()[1..])[12..].as_ref(),
			)
			.map_err(drop)
		})
	}
}

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

	#[test]
	fn to_eth_address_works() {
		let pair = ecdsa::Pair::from_string("//Alice//password", None).unwrap();
		let eth_address = pair.public().to_eth_address().unwrap();
		assert_eq!(
			array_bytes::bytes2hex("0x", &eth_address),
			"0xdc1cce4263956850a3c8eb349dc6fc3f7792cb27"
		);
	}
}