// This file is part of Substrate.

// Copyright (C) 2017-2021 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.

//! Hash utilities.

use codec::{Codec, MaxEncodedLen};
use sp_io::hashing::{blake2_128, blake2_256, twox_128, twox_256, twox_64};
use sp_std::prelude::Vec;

// This trait must be kept coherent with frame-support-procedural HasherKind usage
pub trait Hashable: Sized {
	fn blake2_128(&self) -> [u8; 16];
	fn blake2_256(&self) -> [u8; 32];
	fn blake2_128_concat(&self) -> Vec<u8>;
	fn twox_128(&self) -> [u8; 16];
	fn twox_256(&self) -> [u8; 32];
	fn twox_64_concat(&self) -> Vec<u8>;
	fn identity(&self) -> Vec<u8>;
}

impl<T: Codec> Hashable for T {
	fn blake2_128(&self) -> [u8; 16] {
		self.using_encoded(blake2_128)
	}
	fn blake2_256(&self) -> [u8; 32] {
		self.using_encoded(blake2_256)
	}
	fn blake2_128_concat(&self) -> Vec<u8> {
		self.using_encoded(Blake2_128Concat::hash)
	}
	fn twox_128(&self) -> [u8; 16] {
		self.using_encoded(twox_128)
	}
	fn twox_256(&self) -> [u8; 32] {
		self.using_encoded(twox_256)
	}
	fn twox_64_concat(&self) -> Vec<u8> {
		self.using_encoded(Twox64Concat::hash)
	}
	fn identity(&self) -> Vec<u8> {
		self.encode()
	}
}

/// Hasher to use to hash keys to insert to storage.
pub trait StorageHasher: 'static {
	const METADATA: frame_metadata::StorageHasher;
	type Output: AsRef<[u8]>;
	fn hash(x: &[u8]) -> Self::Output;

	/// The max length of the final hash, for the given key type.
	fn max_len<K: MaxEncodedLen>() -> usize;
}

/// Hasher to use to hash keys to insert to storage.
///
/// Reversible hasher store the encoded key after the hash part.
pub trait ReversibleStorageHasher: StorageHasher {
	/// Split the hash part out of the input.
	///
	/// I.e. for input `&[hash ++ key ++ some]` returns `&[key ++ some]`
	fn reverse(x: &[u8]) -> &[u8];
}

/// Store the key directly.
pub struct Identity;
impl StorageHasher for Identity {
	const METADATA: frame_metadata::StorageHasher = frame_metadata::StorageHasher::Identity;
	type Output = Vec<u8>;
	fn hash(x: &[u8]) -> Vec<u8> {
		x.to_vec()
	}
	fn max_len<K: MaxEncodedLen>() -> usize {
		K::max_encoded_len()
	}
}
impl ReversibleStorageHasher for Identity {
	fn reverse(x: &[u8]) -> &[u8] {
		x
	}
}

/// Hash storage keys with `concat(twox64(key), key)`
pub struct Twox64Concat;
impl StorageHasher for Twox64Concat {
	const METADATA: frame_metadata::StorageHasher = frame_metadata::StorageHasher::Twox64Concat;
	type Output = Vec<u8>;
	fn hash(x: &[u8]) -> Vec<u8> {
		twox_64(x).iter().chain(x.into_iter()).cloned().collect::<Vec<_>>()
	}
	fn max_len<K: MaxEncodedLen>() -> usize {
		K::max_encoded_len().saturating_add(8)
	}
}
impl ReversibleStorageHasher for Twox64Concat {
	fn reverse(x: &[u8]) -> &[u8] {
		if x.len() < 8 {
			log::error!("Invalid reverse: hash length too short");
			return &[]
		}
		&x[8..]
	}
}

/// Hash storage keys with `concat(blake2_128(key), key)`
pub struct Blake2_128Concat;
impl StorageHasher for Blake2_128Concat {
	const METADATA: frame_metadata::StorageHasher = frame_metadata::StorageHasher::Blake2_128Concat;
	type Output = Vec<u8>;
	fn hash(x: &[u8]) -> Vec<u8> {
		blake2_128(x).iter().chain(x.into_iter()).cloned().collect::<Vec<_>>()
	}
	fn max_len<K: MaxEncodedLen>() -> usize {
		K::max_encoded_len().saturating_add(16)
	}
}
impl ReversibleStorageHasher for Blake2_128Concat {
	fn reverse(x: &[u8]) -> &[u8] {
		if x.len() < 16 {
			log::error!("Invalid reverse: hash length too short");
			return &[]
		}
		&x[16..]
	}
}

/// Hash storage keys with blake2 128
pub struct Blake2_128;
impl StorageHasher for Blake2_128 {
	const METADATA: frame_metadata::StorageHasher = frame_metadata::StorageHasher::Blake2_128;
	type Output = [u8; 16];
	fn hash(x: &[u8]) -> [u8; 16] {
		blake2_128(x)
	}
	fn max_len<K: MaxEncodedLen>() -> usize {
		16
	}
}

/// Hash storage keys with blake2 256
pub struct Blake2_256;
impl StorageHasher for Blake2_256 {
	const METADATA: frame_metadata::StorageHasher = frame_metadata::StorageHasher::Blake2_256;
	type Output = [u8; 32];
	fn hash(x: &[u8]) -> [u8; 32] {
		blake2_256(x)
	}
	fn max_len<K: MaxEncodedLen>() -> usize {
		32
	}
}

/// Hash storage keys with twox 128
pub struct Twox128;
impl StorageHasher for Twox128 {
	const METADATA: frame_metadata::StorageHasher = frame_metadata::StorageHasher::Twox128;
	type Output = [u8; 16];
	fn hash(x: &[u8]) -> [u8; 16] {
		twox_128(x)
	}
	fn max_len<K: MaxEncodedLen>() -> usize {
		16
	}
}

/// Hash storage keys with twox 256
pub struct Twox256;
impl StorageHasher for Twox256 {
	const METADATA: frame_metadata::StorageHasher = frame_metadata::StorageHasher::Twox256;
	type Output = [u8; 32];
	fn hash(x: &[u8]) -> [u8; 32] {
		twox_256(x)
	}
	fn max_len<K: MaxEncodedLen>() -> usize {
		32
	}
}

#[cfg(test)]
mod tests {
	use super::*;

	#[test]
	fn test_twox_64_concat() {
		let r = Twox64Concat::hash(b"foo");
		assert_eq!(r.split_at(8), (&twox_128(b"foo")[..8], &b"foo"[..]))
	}

	#[test]
	fn test_blake2_128_concat() {
		let r = Blake2_128Concat::hash(b"foo");
		assert_eq!(r.split_at(16), (&blake2_128(b"foo")[..], &b"foo"[..]))
	}

	#[test]
	fn max_lengths() {
		use codec::Encode;
		let encoded_0u32 = &0u32.encode()[..];
		assert_eq!(Twox64Concat::hash(encoded_0u32).len(), Twox64Concat::max_len::<u32>());
		assert_eq!(Twox128::hash(encoded_0u32).len(), Twox128::max_len::<u32>());
		assert_eq!(Twox256::hash(encoded_0u32).len(), Twox256::max_len::<u32>());
		assert_eq!(Blake2_128::hash(encoded_0u32).len(), Blake2_128::max_len::<u32>());
		assert_eq!(Blake2_128Concat::hash(encoded_0u32).len(), Blake2_128Concat::max_len::<u32>());
		assert_eq!(Blake2_256::hash(encoded_0u32).len(), Blake2_256::max_len::<u32>());
		assert_eq!(Identity::hash(encoded_0u32).len(), Identity::max_len::<u32>());
	}
}