/*

  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/CircularReferencesPruner.h>

#include <libyul/optimiser/CallGraphGenerator.h>

#include <libyul/optimiser/FunctionGrouper.h>

#include <libyul/optimiser/OptimizerUtilities.h>

#include <libyul/AST.h>

#include <libsolutil/Algorithms.h>

using namespace std;

using namespace solidity::yul;

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

{

  CircularReferencesPruner{_context.reservedIdentifiers}(_ast);

  FunctionGrouper::run(_context, _ast);

}

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

{

  set<YulString> functionsToKeep =

    functionsCalledFromOutermostContext(CallGraphGenerator::callGraph(_block));

  for (auto&& statement: _block.statements)

    if (holds_alternative<FunctionDefinition>(statement))

    {

      FunctionDefinition const& funDef = std::get<FunctionDefinition>(statement);

      if (!functionsToKeep.count(funDef.name))

        statement = Block{};

    }

  removeEmptyBlocks(_block);

}

set<YulString> CircularReferencesPruner::functionsCalledFromOutermostContext(CallGraph const& _callGraph)

{

  set<YulString> verticesToTraverse = m_reservedIdentifiers;

  verticesToTraverse.insert(YulString(""));

  return util::BreadthFirstSearch<YulString>{{verticesToTraverse.begin(), verticesToTraverse.end()}}.run(

    [&_callGraph](YulString _function, auto&& _addChild) {

      if (_callGraph.functionCalls.count(_function))

        for (auto const& callee: _callGraph.functionCalls.at(_function))

          if (_callGraph.functionCalls.count(callee))

            _addChild(callee);

    }).visited;

}