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// This file is part of Substrate.

// Copyright (C) 2017-2020 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.

use codec::{Encode, Decode};
use crate::{Trait, Module};
use sp_runtime::{
	traits::{SignedExtension, Zero},
	transaction_validity::TransactionValidityError,
};

/// Genesis hash check to provide replay protection between different networks.
#[derive(Encode, Decode, Clone, Eq, PartialEq)]
pub struct CheckGenesis<T: Trait + Send + Sync>(sp_std::marker::PhantomData<T>);

impl<T: Trait + Send + Sync> sp_std::fmt::Debug for CheckGenesis<T> {
	#[cfg(feature = "std")]
	fn fmt(&self, f: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
		write!(f, "CheckGenesis")
	}

	#[cfg(not(feature = "std"))]
	fn fmt(&self, _: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
		Ok(())
	}
}

impl<T: Trait + Send + Sync> CheckGenesis<T> {
	/// Creates new `SignedExtension` to check genesis hash.
	pub fn new() -> Self {
		Self(sp_std::marker::PhantomData)
	}
}

impl<T: Trait + Send + Sync> SignedExtension for CheckGenesis<T> {
	type AccountId = T::AccountId;
	type Call = <T as Trait>::Call;
	type AdditionalSigned = T::Hash;
	type Pre = ();
	const IDENTIFIER: &'static str = "CheckGenesis";

	fn additional_signed(&self) -> Result<Self::AdditionalSigned, TransactionValidityError> {
		Ok(<Module<T>>::block_hash(T::BlockNumber::zero()))
	}
}