/*

  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

#include <libyul/optimiser/ConditionalUnsimplifier.h>

#include <libyul/optimiser/Semantics.h>

#include <libyul/AST.h>

#include <libyul/Utilities.h>

#include <libyul/optimiser/NameCollector.h>

#include <libyul/ControlFlowSideEffectsCollector.h>

#include <libsolutil/CommonData.h>

using namespace std;

using namespace solidity;

using namespace solidity::yul;

using namespace solidity::util;

void ConditionalUnsimplifier::run(OptimiserStepContext& _context, Block& _ast)

{

  ConditionalUnsimplifier{

    _context.dialect,

    ControlFlowSideEffectsCollector{_context.dialect, _ast}.functionSideEffectsNamed()

  }(_ast);

}

void ConditionalUnsimplifier::operator()(Switch& _switch)

{

  visit(*_switch.expression);

  if (!holds_alternative<Identifier>(*_switch.expression))

  {

    ASTModifier::operator()(_switch);

    return;

  }

  YulString expr = std::get<Identifier>(*_switch.expression).name;

  for (auto& _case: _switch.cases)

  {

    if (_case.value)

    {

      (*this)(*_case.value);

      if (

        !_case.body.statements.empty() &&

        holds_alternative<Assignment>(_case.body.statements.front())

      )

      {

        Assignment const& assignment = std::get<Assignment>(_case.body.statements.front());

        if (

          assignment.variableNames.size() == 1 &&

          assignment.variableNames.front().name == expr &&

          holds_alternative<Literal>(*assignment.value) &&

          valueOfLiteral(std::get<Literal>(*assignment.value)) == valueOfLiteral(*_case.value)

        )

          _case.body.statements.erase(_case.body.statements.begin());

      }

    }

    (*this)(_case.body);

  }

}

void ConditionalUnsimplifier::operator()(Block& _block)

{

  walkVector(_block.statements);

  iterateReplacingWindow<2>(

    _block.statements,

    [&](Statement& _stmt1, Statement& _stmt2) -> std::optional<vector<Statement>>

    {

      if (holds_alternative<If>(_stmt1))

      {

        If& _if = std::get<If>(_stmt1);

        if (

          holds_alternative<Identifier>(*_if.condition) &&

          !_if.body.statements.empty()

        )

        {

          YulString condition = std::get<Identifier>(*_if.condition).name;

          if (

            holds_alternative<Assignment>(_stmt2) &&

            TerminationFinder(m_dialect, &m_functionSideEffects).controlFlowKind(_if.body.statements.back()) !=

              TerminationFinder::ControlFlow::FlowOut

          )

          {

            Assignment const& assignment = std::get<Assignment>(_stmt2);

            if (

              assignment.variableNames.size() == 1 &&

              assignment.variableNames.front().name == condition &&

              holds_alternative<Literal>(*assignment.value) &&

              valueOfLiteral(std::get<Literal>(*assignment.value)) == 0

            )

              return {make_vector<Statement>(std::move(_stmt1))};

          }

        }

      }

      return {};

    }

  );

}