/*

  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

/**

 * Class that can answer questions about values of variables and their relations.

 */

#pragma once

#include <libyul/ASTForward.h>

#include <libyul/YulString.h>

#include <libsolutil/Common.h>

#include <libsolutil/Numeric.h>

#include <map>

#include <functional>

namespace solidity::yul

{

struct Dialect;

struct AssignedValue;

/**

 * Class that can answer questions about values of variables and their relations.

 */

class KnowledgeBase

{

public:

  KnowledgeBase(

    Dialect const& _dialect,

    std::function<AssignedValue const*(YulString)> _variableValues

  ):

    m_dialect(_dialect),

    m_variableValues(std::move(_variableValues))

  {}

  bool knownToBeDifferent(YulString _a, YulString _b);

  std::optional<u256> differenceIfKnownConstant(YulString _a, YulString _b);

  bool knownToBeDifferentByAtLeast32(YulString _a, YulString _b);

  bool knownToBeEqual(YulString _a, YulString _b) const { return _a == _b; }

  bool knownToBeZero(YulString _a);

  std::optional<u256> valueIfKnownConstant(YulString _a);

private:

  Expression simplify(Expression _expression);

  Expression simplifyRecursively(Expression _expression);

  Dialect const& m_dialect;

  std::function<AssignedValue const*(YulString)> m_variableValues;

  size_t m_counter = 0;

};

}