// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of Open Ethereum.

// Open Ethereum 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.

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

//! Environment information for transaction execution.

use std::cmp;
use std::sync::Arc;
use hash::keccak;
use ethereum_types::{U256, H256, Address};
use ethjson;

type BlockNumber = u64;

/// Simple vector of hashes, should be at most 256 items large, can be smaller if being used
/// for a block whose number is less than 257.
pub type LastHashes = Vec<H256>;

/// Information concerning the execution environment for a message-call/contract-creation.
#[derive(Debug, Clone)]
pub struct EnvInfo {
	/// The block number.
	pub number: BlockNumber,
	/// The block author.
	pub author: Address,
	/// The block timestamp.
	pub timestamp: u64,
	/// The block difficulty.
	pub difficulty: U256,
	/// The block gas limit.
	pub gas_limit: U256,
	/// The last 256 block hashes.
	pub last_hashes: Arc<LastHashes>,
	/// The gas used.
	pub gas_used: U256,
}

impl Default for EnvInfo {
	fn default() -> Self {
		EnvInfo {
			number: 0,
			author: Address::zero(),
			timestamp: 0,
			difficulty: 0.into(),
			gas_limit: 0.into(),
			last_hashes: Arc::new(vec![]),
			gas_used: 0.into(),
		}
	}
}

impl From<ethjson::vm::Env> for EnvInfo {
	fn from(e: ethjson::vm::Env) -> Self {
		let number = e.number.into();
		EnvInfo {
			number,
			author: e.author.into(),
			difficulty: e.difficulty.into(),
			gas_limit: e.gas_limit.into(),
			timestamp: e.timestamp.into(),
			last_hashes: Arc::new((1..cmp::min(number + 1, 257)).map(|i| keccak(format!("{}", number - i).as_bytes())).collect()),
			gas_used: U256::default(),
		}
	}
}

#[cfg(test)]
mod tests {
	use std::str::FromStr;
	use super::*;
	use ethereum_types::{U256, Address};
	use ethjson;

	#[test]
	fn it_serializes_from_json() {
		let env_info = EnvInfo::from(ethjson::vm::Env {
			author: ethjson::hash::Address(Address::from_str("000000f00000000f000000000000f00000000f00").unwrap()),
			number: ethjson::uint::Uint(U256::from(1_112_339)),
			difficulty: ethjson::uint::Uint(U256::from(50_000)),
			gas_limit: ethjson::uint::Uint(U256::from(40_000)),
			timestamp: ethjson::uint::Uint(U256::from(1_100))
		});

		assert_eq!(env_info.number, 1112339);
		assert_eq!(env_info.author, Address::from_str("000000f00000000f000000000000f00000000f00").unwrap());
		assert_eq!(env_info.gas_limit, 40000.into());
		assert_eq!(env_info.difficulty, 50000.into());
		assert_eq!(env_info.gas_used, 0.into());
	}

	#[test]
	fn it_can_be_created_as_default() {
		let default_env_info = EnvInfo::default();

		assert_eq!(default_env_info.difficulty, 0.into());
	}
}
