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// SPDX-License-Identifier: Apache-2.0
// This file is part of Frontier.
//
// Copyright (c) 2020-2022 Parity Technologies (UK) Ltd.
//
// 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.

#![cfg_attr(not(feature = "std"), no_std)]
#![allow(clippy::large_enum_variant)]
#![warn(unused_crate_dependencies)]

use scale_codec::{Decode, Encode};
use sp_core::H256;
use sp_runtime::{
	generic::{Digest, OpaqueDigestItemId},
	ConsensusEngineId,
};
use sp_std::vec::Vec;

pub const FRONTIER_ENGINE_ID: ConsensusEngineId = [b'f', b'r', b'o', b'n'];

#[derive(Clone, PartialEq, Eq)]
pub enum Log {
	Pre(PreLog),
	Post(PostLog),
}

#[derive(Decode, Encode, Clone, PartialEq, Eq)]
pub enum PreLog {
	#[codec(index = 3)]
	Block(ethereum::BlockV2),
}

#[derive(Decode, Encode, Clone, PartialEq, Eq)]
pub enum PostLog {
	/// Ethereum block hash and txn hashes.
	#[codec(index = 1)]
	Hashes(Hashes),
	/// Ethereum block.
	#[codec(index = 2)]
	Block(ethereum::BlockV2),
	/// Ethereum block hash.
	#[codec(index = 3)]
	BlockHash(H256),
}

#[derive(Decode, Encode, Clone, PartialEq, Eq)]
pub struct Hashes {
	/// Ethereum block hash.
	pub block_hash: H256,
	/// Transaction hashes of the Ethereum block.
	pub transaction_hashes: Vec<H256>,
}

impl Hashes {
	pub fn from_block(block: ethereum::BlockV2) -> Self {
		Hashes {
			block_hash: block.header.hash(),
			transaction_hashes: block
				.transactions
				.into_iter()
				.map(|txn| txn.hash())
				.collect(),
		}
	}
}

#[derive(Clone, Debug)]
pub enum FindLogError {
	NotFound,
	MultipleLogs,
}

pub fn find_pre_log(digest: &Digest) -> Result<PreLog, FindLogError> {
	_find_log(digest, OpaqueDigestItemId::PreRuntime(&FRONTIER_ENGINE_ID))
}

pub fn find_post_log(digest: &Digest) -> Result<PostLog, FindLogError> {
	_find_log(digest, OpaqueDigestItemId::Consensus(&FRONTIER_ENGINE_ID))
}

fn _find_log<Log: Decode>(
	digest: &Digest,
	digest_item_id: OpaqueDigestItemId,
) -> Result<Log, FindLogError> {
	let mut found = None;

	for log in digest.logs() {
		let log = log.try_to::<Log>(digest_item_id);
		match (log, found.is_some()) {
			(Some(_), true) => return Err(FindLogError::MultipleLogs),
			(Some(log), false) => found = Some(log),
			(None, _) => (),
		}
	}

	found.ok_or(FindLogError::NotFound)
}

pub fn find_log(digest: &Digest) -> Result<Log, FindLogError> {
	let mut found = None;

	for log in digest.logs() {
		let pre_log = log.try_to::<PreLog>(OpaqueDigestItemId::PreRuntime(&FRONTIER_ENGINE_ID));
		match (pre_log, found.is_some()) {
			(Some(_), true) => return Err(FindLogError::MultipleLogs),
			(Some(pre_log), false) => found = Some(Log::Pre(pre_log)),
			(None, _) => (),
		}

		let post_log = log.try_to::<PostLog>(OpaqueDigestItemId::Consensus(&FRONTIER_ENGINE_ID));
		match (post_log, found.is_some()) {
			(Some(_), true) => return Err(FindLogError::MultipleLogs),
			(Some(post_log), false) => found = Some(Log::Post(post_log)),
			(None, _) => (),
		}
	}

	found.ok_or(FindLogError::NotFound)
}

pub fn ensure_log(digest: &Digest) -> Result<(), FindLogError> {
	find_log(digest).map(|_log| ())
}