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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.

pub use evm::{
    executor::stack::{
        IsPrecompileResult, PrecompileFailure, PrecompileHandle, PrecompileOutput, PrecompileSet,
    },
    Context, ExitError, ExitRevert, ExitSucceed, Transfer,
};
use sp_std::vec::Vec;

pub type PrecompileResult = Result<PrecompileOutput, PrecompileFailure>;

/// One single precompile used by EVM engine.
pub trait Precompile {
    /// Try to execute the precompile with given `handle` which provides all call data
    /// and allow to register costs and logs.
    fn execute(handle: &mut impl PrecompileHandle) -> PrecompileResult;
}

pub trait LinearCostPrecompile {
    const BASE: u64;
    const WORD: u64;

    fn execute(
        input: &[u8],
        cost: u64,
    ) -> core::result::Result<(ExitSucceed, Vec<u8>), PrecompileFailure>;
}

impl<T: LinearCostPrecompile> Precompile for T {
    fn execute(handle: &mut impl PrecompileHandle) -> PrecompileResult {
        let target_gas = handle.gas_limit();
        let cost = ensure_linear_cost(target_gas, handle.input().len() as u64, T::BASE, T::WORD)?;

        handle.record_cost(cost)?;
        let (exit_status, output) = T::execute(handle.input(), cost)?;
        Ok(PrecompileOutput {
            exit_status,
            output,
        })
    }
}

/// Linear gas cost
fn ensure_linear_cost(
    target_gas: Option<u64>,
    len: u64,
    base: u64,
    word: u64,
) -> Result<u64, PrecompileFailure> {
    let cost = base
        .checked_add(word.checked_mul(len.saturating_add(31) / 32).ok_or(
            PrecompileFailure::Error {
                exit_status: ExitError::OutOfGas,
            },
        )?)
        .ok_or(PrecompileFailure::Error {
            exit_status: ExitError::OutOfGas,
        })?;

    if let Some(target_gas) = target_gas {
        if cost > target_gas {
            return Err(PrecompileFailure::Error {
                exit_status: ExitError::OutOfGas,
            })
        }
    }

    Ok(cost)
}