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// Copyright 2019-2022 PureStake Inc.
// This file is part of Moonbeam.

// Moonbeam 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.

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

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

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

use core::marker::PhantomData;
use fp_evm::{ExitError, IsPrecompileResult, PrecompileFailure};
use precompile_utils::{
	precompile_set::{is_precompile_or_fail, IsActivePrecompile},
	prelude::*,
};
use sp_core::Get;

const DUMMY_CODE: [u8; 5] = [0x60, 0x00, 0x60, 0x00, 0xfd];

pub struct PrecompileRegistry<Runtime>(PhantomData<Runtime>);

#[precompile_utils::precompile]
impl<Runtime> PrecompileRegistry<Runtime>
where
	Runtime: pallet_evm::Config,
	Runtime::PrecompilesType: IsActivePrecompile,
{
	#[precompile::public("isPrecompile(address)")]
	#[precompile::view]
	fn is_precompile(handle: &mut impl PrecompileHandle, address: Address) -> EvmResult<bool> {
		// We consider the precompile set is optimized to do at most one storage read.
		// In the case of moonbeam, the storage item that can be read is pallet_asset::Asset
		// (TODO make it more generic, maybe add a const generic on PrecompileRegistry type)
		// Storage item: Asset:
		// Blake2_128(16) + AssetId(16) + AssetDetails((4 * AccountId(20)) + (3 * Balance(16)) + 15)
		handle.record_db_read::<Runtime>(175)?;
		is_precompile_or_fail::<Runtime>(address.0, handle.remaining_gas())
	}

	#[precompile::public("isActivePrecompile(address)")]
	#[precompile::view]
	fn is_active_precompile(
		handle: &mut impl PrecompileHandle,
		address: Address,
	) -> EvmResult<bool> {
		// We consider the precompile set is optimized to do at most one storage read.
		// In the case of moonbeam, the storage item that can be read is pallet_asset::Asset
		// (TODO make it more generic, maybe add a const generic on PrecompileRegistry type)
		// Storage item: Asset:
		// Blake2_128(16) + AssetId(16) + AssetDetails((4 * AccountId(20)) + (3 * Balance(16)) + 15)
		handle.record_db_read::<Runtime>(175)?;
		match <Runtime::PrecompilesValue>::get()
			.is_active_precompile(address.0, handle.remaining_gas())
		{
			IsPrecompileResult::Answer { is_precompile, .. } => Ok(is_precompile),
			IsPrecompileResult::OutOfGas => Err(PrecompileFailure::Error {
				exit_status: ExitError::OutOfGas,
			}),
		}
	}

	#[precompile::public("updateAccountCode(address)")]
	fn update_account_code(handle: &mut impl PrecompileHandle, address: Address) -> EvmResult<()> {
		// Prevent touching addresses that are not precompiles.
		//
		// We consider the precompile set is optimized to do at most one storage read.
		// In the case of moonbeam, the storage item that can be read is pallet_asset::Asset
		// (TODO make it more generic, maybe add a const generic on PrecompileRegistry type)
		// Storage item: Asset:
		// Blake2_128(16) + AssetId(16) + AssetDetails((4 * AccountId(20)) + (3 * Balance(16)) + 15)
		handle.record_db_read::<Runtime>(175)?;
		if !is_precompile_or_fail::<Runtime>(address.0, handle.remaining_gas())? {
			return Err(revert("provided address is not a precompile"));
		}

		// pallet_evm::create_account read storage item pallet_evm::AccountCodes
		//
		// AccountCodes: Blake2128(16) + H160(20) + Vec(5)
		// We asume an existing precompile can hold at most 5 bytes worth of dummy code.
		handle.record_db_read::<Runtime>(41)?;
		pallet_evm::Pallet::<Runtime>::create_account(address.0, DUMMY_CODE.to_vec());

		Ok(())
	}
}