/*

  This file is part of solidity.

  solidity 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.

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

*/

// SPDX-License-Identifier: GPL-3.0

/**

 * Module providing metrics for the optimizer.

 */

#pragma once

#include <libyul/optimiser/ASTWalker.h>

#include <liblangutil/EVMVersion.h>

#include <libsolutil/Numeric.h>

#include <libevmasm/Instruction.h>

namespace solidity::yul

{

class EVMDialect;

/**

 * Gas meter for expressions only involving literals, identifiers and

 * EVM instructions.

 *

 * Assumes that EXP is not used with exponents larger than a single byte.

 * Is not particularly exact for anything apart from arithmetic.

 *

 * Assumes that Keccak-256 is computed on a single word (rounded up).

 */

class GasMeter

{

public:

  GasMeter(EVMDialect const& _dialect, bool _isCreation, bigint _runs):

    m_dialect(_dialect),

    m_isCreation{_isCreation},

    m_runs(_isCreation? 1 : _runs)

  {}

  /// @returns the full combined costs of deploying and evaluating the expression.

  bigint costs(Expression const& _expression) const;

  /// @returns the combined costs of deploying and running the instruction, not including

  /// the costs for its arguments.

  bigint instructionCosts(evmasm::Instruction _instruction) const;

private:

  bigint combineCosts(std::pair<bigint, bigint> _costs) const;

  EVMDialect const& m_dialect;

  bool m_isCreation = false;

  bigint m_runs;

};

class GasMeterVisitor: public ASTWalker

{

public:

  static std::pair<bigint, bigint> costs(

    Expression const& _expression,

    EVMDialect const& _dialect,

    bool _isCreation

  );

  static std::pair<bigint, bigint> instructionCosts(

    evmasm::Instruction _instruction,

    EVMDialect const& _dialect,

    bool _isCreation = false

  );

public:

  GasMeterVisitor(EVMDialect const& _dialect, bool _isCreation):

    m_dialect(_dialect),

    m_isCreation{_isCreation}

  {}

  void operator()(FunctionCall const& _funCall) override;

  void operator()(Literal const& _literal) override;

  void operator()(Identifier const& _identifier) override;

private:

  bigint singleByteDataGas() const;

  /// Computes the cost of storing and executing the single instruction (excluding its arguments).

  /// For EXP, it assumes that the exponent is at most 255.

  /// Does not work particularly exact for anything apart from arithmetic.

  void instructionCostsInternal(evmasm::Instruction _instruction);

  EVMDialect const& m_dialect;

  bool m_isCreation = false;

  bigint m_runGas = 0;

  bigint m_dataGas = 0;

};

}