/*

  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/FunctionSpecializer.h>

#include <libyul/optimiser/ASTCopier.h>

#include <libyul/optimiser/CallGraphGenerator.h>

#include <libyul/optimiser/NameCollector.h>

#include <libyul/optimiser/NameDispenser.h>

#include <libyul/AST.h>

#include <libyul/YulName.h>

#include <libsolutil/CommonData.h>

#include <range/v3/algorithm/any_of.hpp>

#include <range/v3/view/enumerate.hpp>

#include <variant>

using namespace solidity::util;

using namespace solidity::yul;

FunctionSpecializer::LiteralArguments FunctionSpecializer::specializableArguments(

  FunctionCall const& _f

)

{

  auto heuristic = [&](Expression const& _e) -> std::optional<Expression>

  {

    if (std::holds_alternative<Literal>(_e))

      return ASTCopier{}.translate(_e);

    return std::nullopt;

  };

  return applyMap(_f.arguments, heuristic);

}

void FunctionSpecializer::operator()(FunctionCall& _f)

{

  ASTModifier::operator()(_f);

  // TODO When backtracking is implemented, the restriction of recursive functions can be lifted.

  if (

    isBuiltinFunctionCall(_f) ||

    (std::holds_alternative<Identifier>(_f.functionName) && m_recursiveFunctions.count(std::get<Identifier>(_f.functionName).name))

  )

    return;

  yulAssert(std::holds_alternative<Identifier>(_f.functionName));

  auto& identifier = std::get<Identifier>(_f.functionName);

  LiteralArguments arguments = specializableArguments(_f);

  if (ranges::any_of(arguments, [](auto& _a) { return _a.has_value(); }))

  {

    YulName oldName = std::move(identifier.name);

    auto newName = m_nameDispenser.newName(oldName);

    m_oldToNewMap[oldName].emplace_back(std::make_pair(newName, arguments));

    identifier.name = newName;

    _f.arguments = util::filter(

      _f.arguments,

      applyMap(arguments, [](auto& _a) { return !_a; })

    );

  }

}

FunctionDefinition FunctionSpecializer::specialize(

  FunctionDefinition const& _f,

  YulName _newName,

  FunctionSpecializer::LiteralArguments _arguments

)

{

  yulAssert(_arguments.size() == _f.parameters.size(), "");

  std::map<YulName, YulName> translatedNames = applyMap(

    NameCollector{_f, NameCollector::OnlyVariables}.names(),

    [&](auto& _name) -> std::pair<YulName, YulName>

    {

      return std::make_pair(_name, m_nameDispenser.newName(_name));

    },

    std::map<YulName, YulName>{}

  );

  FunctionDefinition newFunction = std::get<FunctionDefinition>(FunctionCopier{translatedNames}(_f));

  // Function parameters that will be specialized inside the body are converted into variable

  // declarations.

  std::vector<Statement> missingVariableDeclarations;

  for (auto&& [index, argument]: _arguments | ranges::views::enumerate)

    if (argument)

      missingVariableDeclarations.emplace_back(

        VariableDeclaration{

          _f.debugData,

          std::vector<NameWithDebugData>{newFunction.parameters[index]},

          std::make_unique<Expression>(std::move(*argument))

        }

      );

  newFunction.body.statements =

    std::move(missingVariableDeclarations) + std::move(newFunction.body.statements);

  // Only take those indices that cannot be specialized, i.e., whose value is `nullopt`.

  newFunction.parameters =

    util::filter(

      newFunction.parameters,

      applyMap(_arguments, [&](auto const& _v) { return !_v; })

    );

  newFunction.name = std::move(_newName);

  return newFunction;

}

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

{

  FunctionSpecializer f{

    CallGraphGenerator::callGraph(_ast).recursiveFunctions(),

    _context.dispenser

  };

  f(_ast);

  iterateReplacing(_ast.statements, [&](Statement& _s) -> std::optional<std::vector<Statement>>

  {

    if (std::holds_alternative<FunctionDefinition>(_s))

    {

      auto& functionDefinition = std::get<FunctionDefinition>(_s);

      if (f.m_oldToNewMap.count(functionDefinition.name))

      {

        std::vector<Statement> out = applyMap(

          f.m_oldToNewMap.at(functionDefinition.name),

          [&](auto& _p) -> Statement

          {

            return f.specialize(functionDefinition, std::move(_p.first), std::move(_p.second));

          }

        );

        return std::move(out) + make_vector<Statement>(std::move(functionDefinition));

      }

    }

    return std::nullopt;

  });

}