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// Copyright 2019-2022 PureStake Inc.
// This file is part Utils package, originally developed by PureStake

// Utils 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.

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

//! Cost calculations.
//! TODO: PR EVM to make those cost calculations public.

use crate::EvmResult;
use pallet_3vm_evm_primitives::{ExitError, PrecompileFailure};
use sp_core::U256;

pub fn log_costs(topics: usize, data_len: usize) -> EvmResult<u64> {
    // Cost calculation is copied from EVM code that is not publicly exposed by the crates.
    // https://github.com/rust-blockchain/evm/blob/master/gasometer/src/costs.rs#L148

    const G_LOG: u64 = 375;
    const G_LOGDATA: u64 = 8;
    const G_LOGTOPIC: u64 = 375;

    let topic_cost = G_LOGTOPIC
        .checked_mul(topics as u64)
        .ok_or(PrecompileFailure::Error {
            exit_status: ExitError::OutOfGas,
        })?;

    let data_cost = G_LOGDATA
        .checked_mul(data_len as u64)
        .ok_or(PrecompileFailure::Error {
            exit_status: ExitError::OutOfGas,
        })?;

    G_LOG
        .checked_add(topic_cost)
        .ok_or(PrecompileFailure::Error {
            exit_status: ExitError::OutOfGas,
        })?
        .checked_add(data_cost)
        .ok_or(PrecompileFailure::Error {
            exit_status: ExitError::OutOfGas,
        })
}

// Compute the cost of doing a subcall.
// Some parameters cannot be known in advance, so we estimate the worst possible cost.
pub fn call_cost(value: U256, config: &evm::Config) -> u64 {
    // Copied from EVM code since not public.
    pub const G_CALLVALUE: u64 = 9000;
    pub const G_NEWACCOUNT: u64 = 25000;

    fn address_access_cost(is_cold: bool, regular_value: u64, config: &evm::Config) -> u64 {
        if config.increase_state_access_gas {
            if is_cold {
                config.gas_account_access_cold
            } else {
                config.gas_storage_read_warm
            }
        } else {
            regular_value
        }
    }

    fn xfer_cost(is_call_or_callcode: bool, transfers_value: bool) -> u64 {
        if is_call_or_callcode && transfers_value {
            G_CALLVALUE
        } else {
            0
        }
    }

    fn new_cost(
        is_call_or_staticcall: bool,
        new_account: bool,
        transfers_value: bool,
        config: &evm::Config,
    ) -> u64 {
        let eip161 = !config.empty_considered_exists;
        if is_call_or_staticcall {
            if eip161 {
                if transfers_value && new_account {
                    G_NEWACCOUNT
                } else {
                    0
                }
            } else if new_account {
                G_NEWACCOUNT
            } else {
                0
            }
        } else {
            0
        }
    }

    let transfers_value = value != U256::default();
    let is_cold = true;
    let is_call_or_callcode = true;
    let is_call_or_staticcall = true;
    let new_account = true;

    address_access_cost(is_cold, config.gas_call, config)
        + xfer_cost(is_call_or_callcode, transfers_value)
        + new_cost(is_call_or_staticcall, new_account, transfers_value, config)
}