// This file is part of Substrate.

// Copyright (C) 2021 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.

#![cfg_attr(not(feature = "std"), no_std)]
#![warn(missing_docs)]

//! A BEEFY+MMR pallet combo.
//!
//! While both BEEFY and Merkle Mountain Range (MMR) can be used separately,
//! these tools were designed to work together in unison.
//!
//! The pallet provides a standardized MMR Leaf format that is can be used
//! to bridge BEEFY+MMR-based networks (both standalone and polkadot-like).
//!
//! The MMR leaf contains:
//! 1. Block number and parent block hash.
//! 2. Merkle Tree Root Hash of next BEEFY validator set.
//! 3. Merkle Tree Root Hash of current parachain heads state.
//!
//! and thanks to versioning can be easily updated in the future.

use sp_runtime::traits::{Convert, Hash};
use sp_std::prelude::*;

use beefy_primitives::mmr::{BeefyNextAuthoritySet, MmrLeaf, MmrLeafVersion};
use pallet_mmr::primitives::LeafDataProvider;

use codec::Encode;
use frame_support::traits::Get;

pub use pallet::*;

#[cfg(test)]
mod mock;
#[cfg(test)]
mod tests;

/// A BEEFY consensus digest item with MMR root hash.
pub struct DepositBeefyDigest<T>(sp_std::marker::PhantomData<T>);

impl<T> pallet_mmr::primitives::OnNewRoot<beefy_primitives::MmrRootHash> for DepositBeefyDigest<T>
where
	T: pallet_mmr::Config<Hash = beefy_primitives::MmrRootHash>,
	T: pallet_beefy::Config,
{
	fn on_new_root(root: &<T as pallet_mmr::Config>::Hash) {
		let digest = sp_runtime::generic::DigestItem::Consensus(
			beefy_primitives::BEEFY_ENGINE_ID,
			codec::Encode::encode(&beefy_primitives::ConsensusLog::<
				<T as pallet_beefy::Config>::BeefyId,
			>::MmrRoot(*root)),
		);
		<frame_system::Pallet<T>>::deposit_log(digest);
	}
}

/// Convert BEEFY secp256k1 public keys into Ethereum addresses
pub struct BeefyEcdsaToEthereum;
impl Convert<beefy_primitives::crypto::AuthorityId, Vec<u8>> for BeefyEcdsaToEthereum {
	fn convert(a: beefy_primitives::crypto::AuthorityId) -> Vec<u8> {
		use sp_core::crypto::Public;
		let compressed_key = a.as_slice();

		libsecp256k1::PublicKey::parse_slice(
			compressed_key,
			Some(libsecp256k1::PublicKeyFormat::Compressed),
		)
		// uncompress the key
		.map(|pub_key| pub_key.serialize().to_vec())
		// now convert to ETH address
		.map(|uncompressed| sp_io::hashing::keccak_256(&uncompressed[1..])[12..].to_vec())
		.map_err(|_| {
			log::error!(target: "runtime::beefy", "Invalid BEEFY PublicKey format!");
		})
		.unwrap_or_default()
	}
}

type MerkleRootOf<T> = <T as pallet_mmr::Config>::Hash;
type ParaId = u32;
type ParaHead = Vec<u8>;

/// A type that is able to return current list of parachain heads that end up in the MMR leaf.
pub trait ParachainHeadsProvider {
	/// Return a list of tuples containing a `ParaId` and Parachain Header data (ParaHead).
	///
	/// The returned data does not have to be sorted.
	fn parachain_heads() -> Vec<(ParaId, ParaHead)>;
}

/// A default implementation for runtimes without parachains.
impl ParachainHeadsProvider for () {
	fn parachain_heads() -> Vec<(ParaId, ParaHead)> {
		Default::default()
	}
}

#[frame_support::pallet]
pub mod pallet {
	#![allow(missing_docs)]

	use super::*;
	use frame_support::pallet_prelude::*;

	/// BEEFY-MMR pallet.
	#[pallet::pallet]
	#[pallet::generate_store(pub(super) trait Store)]
	pub struct Pallet<T>(_);

	/// The module's configuration trait.
	#[pallet::config]
	#[pallet::disable_frame_system_supertrait_check]
	pub trait Config: pallet_mmr::Config + pallet_beefy::Config {
		/// Current leaf version.
		///
		/// Specifies the version number added to every leaf that get's appended to the MMR.
		/// Read more in [`MmrLeafVersion`] docs about versioning leaves.
		type LeafVersion: Get<MmrLeafVersion>;

		/// Convert BEEFY AuthorityId to a form that would end up in the Merkle Tree.
		///
		/// For instance for ECDSA (secp256k1) we want to store uncompressed public keys (65 bytes)
		/// and later to Ethereum Addresses (160 bits) to simplify using them on Ethereum chain,
		/// but the rest of the Substrate codebase is storing them compressed (33 bytes) for
		/// efficiency reasons.
		type BeefyAuthorityToMerkleLeaf: Convert<<Self as pallet_beefy::Config>::BeefyId, Vec<u8>>;

		/// Retrieve a list of current parachain heads.
		///
		/// The trait is implemented for `paras` module, but since not all chains might have
		/// parachains, and we want to keep the MMR leaf structure uniform, it's possible to use
		/// `()` as well to simply put dummy data to the leaf.
		type ParachainHeads: ParachainHeadsProvider;
	}

	/// Details of next BEEFY authority set.
	///
	/// This storage entry is used as cache for calls to `update_beefy_next_authority_set`.
	#[pallet::storage]
	#[pallet::getter(fn beefy_next_authorities)]
	pub type BeefyNextAuthorities<T: Config> =
		StorageValue<_, BeefyNextAuthoritySet<MerkleRootOf<T>>, ValueQuery>;
}

impl<T: Config> LeafDataProvider for Pallet<T>
where
	MerkleRootOf<T>: From<beefy_merkle_tree::Hash> + Into<beefy_merkle_tree::Hash>,
{
	type LeafData = MmrLeaf<
		<T as frame_system::Config>::BlockNumber,
		<T as frame_system::Config>::Hash,
		MerkleRootOf<T>,
	>;

	fn leaf_data() -> Self::LeafData {
		MmrLeaf {
			version: T::LeafVersion::get(),
			parent_number_and_hash: frame_system::Pallet::<T>::leaf_data(),
			parachain_heads: Pallet::<T>::parachain_heads_merkle_root(),
			beefy_next_authority_set: Pallet::<T>::update_beefy_next_authority_set(),
		}
	}
}

impl<T: Config> beefy_merkle_tree::Hasher for Pallet<T>
where
	MerkleRootOf<T>: Into<beefy_merkle_tree::Hash>,
{
	fn hash(data: &[u8]) -> beefy_merkle_tree::Hash {
		<T as pallet_mmr::Config>::Hashing::hash(data).into()
	}
}

impl<T: Config> Pallet<T>
where
	MerkleRootOf<T>: From<beefy_merkle_tree::Hash> + Into<beefy_merkle_tree::Hash>,
{
	/// Returns latest root hash of a merkle tree constructed from all active parachain headers.
	///
	/// The leafs are sorted by `ParaId` to allow more efficient lookups and non-existence proofs.
	///
	/// NOTE this does not include parathreads - only parachains are part of the merkle tree.
	///
	/// NOTE This is an initial and inefficient implementation, which re-constructs
	/// the merkle tree every block. Instead we should update the merkle root in
	/// [Self::on_initialize] call of this pallet and update the merkle tree efficiently (use
	/// on-chain storage to persist inner nodes).
	fn parachain_heads_merkle_root() -> MerkleRootOf<T> {
		let mut para_heads = T::ParachainHeads::parachain_heads();
		para_heads.sort();
		let para_heads = para_heads.into_iter().map(|pair| pair.encode());
		beefy_merkle_tree::merkle_root::<Self, _, _>(para_heads).into()
	}

	/// Returns details of the next BEEFY authority set.
	///
	/// Details contain authority set id, authority set length and a merkle root,
	/// constructed from uncompressed secp256k1 public keys converted to Ethereum addresses
	/// of the next BEEFY authority set.
	///
	/// This function will use a storage-cached entry in case the set didn't change, or compute and
	/// cache new one in case it did.
	fn update_beefy_next_authority_set() -> BeefyNextAuthoritySet<MerkleRootOf<T>> {
		let id = pallet_beefy::Pallet::<T>::validator_set_id() + 1;
		let current_next = Self::beefy_next_authorities();
		// avoid computing the merkle tree if validator set id didn't change.
		if id == current_next.id {
			return current_next
		}

		let beefy_addresses = pallet_beefy::Pallet::<T>::next_authorities()
			.into_iter()
			.map(T::BeefyAuthorityToMerkleLeaf::convert)
			.collect::<Vec<_>>();
		let len = beefy_addresses.len() as u32;
		let root = beefy_merkle_tree::merkle_root::<Self, _, _>(beefy_addresses).into();
		let next_set = BeefyNextAuthoritySet { id, len, root };
		// cache the result
		BeefyNextAuthorities::<T>::put(&next_set);
		next_set
	}
}