/*

  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

/**

 * Specific AST walkers that collect semantical facts.

 */

#pragma once

#include <libyul/optimiser/ASTWalker.h>

#include <libyul/SideEffects.h>

#include <libyul/optimiser/CallGraphGenerator.h>

#include <libyul/AST.h>

#include <set>

namespace solidity::yul

{

struct Dialect;

/**

 * Specific AST walker that determines side-effect free-ness and movability of code.

 * Enters into function definitions.

 */

class SideEffectsCollector: public ASTWalker

{

public:

  explicit SideEffectsCollector(

    Dialect const& _dialect,

    std::map<YulString, SideEffects> const* _functionSideEffects = nullptr

  ): m_dialect(_dialect), m_functionSideEffects(_functionSideEffects) {}

  SideEffectsCollector(

    Dialect const& _dialect,

    Expression const& _expression,

    std::map<YulString, SideEffects> const* _functionSideEffects = nullptr

  );

  SideEffectsCollector(Dialect const& _dialect, Statement const& _statement);

  SideEffectsCollector(

    Dialect const& _dialect,

    Block const& _ast,

    std::map<YulString, SideEffects> const* _functionSideEffects = nullptr

  );

  SideEffectsCollector(

    Dialect const& _dialect,

    ForLoop const& _ast,

    std::map<YulString, SideEffects> const* _functionSideEffects = nullptr

  );

  using ASTWalker::operator();

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

  bool movable() const { return m_sideEffects.movable; }

  bool movableRelativeTo(SideEffects const& _other, bool _codeContainsMSize)

  {

    if (!m_sideEffects.cannotLoop)

      return false;

    if (m_sideEffects.movable)

      return true;

    if (

      !m_sideEffects.movableApartFromEffects ||

      m_sideEffects.storage == SideEffects::Write ||

      m_sideEffects.otherState == SideEffects::Write ||

      m_sideEffects.memory == SideEffects::Write

    )

      return false;

    if (m_sideEffects.otherState == SideEffects::Read)

      if (_other.otherState == SideEffects::Write)

        return false;

    if (m_sideEffects.storage == SideEffects::Read)

      if (_other.storage == SideEffects::Write)

        return false;

    if (m_sideEffects.memory == SideEffects::Read)

      if (_codeContainsMSize || _other.memory == SideEffects::Write)

        return false;

    return true;

  }

  bool canBeRemoved(bool _allowMSizeModification = false) const

  {

    if (_allowMSizeModification)

      return m_sideEffects.canBeRemovedIfNoMSize;

    else

      return m_sideEffects.canBeRemoved;

  }

  bool cannotLoop() const { return m_sideEffects.cannotLoop; }

  bool invalidatesStorage() const { return m_sideEffects.storage == SideEffects::Write; }

  bool invalidatesMemory() const { return m_sideEffects.memory == SideEffects::Write; }

  SideEffects sideEffects() { return m_sideEffects; }

private:

  Dialect const& m_dialect;

  std::map<YulString, SideEffects> const* m_functionSideEffects = nullptr;

  SideEffects m_sideEffects;

};

/**

 * This class can be used to determine the side-effects of user-defined functions.

 *

 * It is given a dialect and a mapping that represents the direct calls from user-defined

 * functions to other user-defined functions and built-in functions.

 */

class SideEffectsPropagator

{

public:

  static std::map<YulString, SideEffects> sideEffects(

    Dialect const& _dialect,

    CallGraph const& _directCallGraph

  );

};

/**

 * Class that can be used to find out if certain code contains the MSize instruction

 * or a verbatim bytecode builtin (which is always assumed that it could contain MSize).

 *

 * Note that this is a purely syntactic property meaning that even if this is false,

 * the code can still contain calls to functions that contain the msize instruction.

 *

 * The only safe way to determine this is by passing the full AST.

 */

class MSizeFinder: public ASTWalker

{

public:

  static bool containsMSize(Dialect const& _dialect, Block const& _ast);

  using ASTWalker::operator();

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

private:

  MSizeFinder(Dialect const& _dialect): m_dialect(_dialect) {}

  Dialect const& m_dialect;

  bool m_msizeFound = false;

};

/**

 * Class that can be used to find out if the given function contains the ``leave`` statement.

 *

 * Returns true even in the case where the function definition contains another function definition

 * that contains the leave statement.

 */

class LeaveFinder: public ASTWalker

{

public:

  static bool containsLeave(FunctionDefinition const& _fun)

  {

    LeaveFinder f;

    f(_fun);

    return f.m_leaveFound;

  }

  using ASTWalker::operator();

  void operator()(Leave const&) override { m_leaveFound = true; }

private:

  LeaveFinder() = default;

  bool m_leaveFound = false;

};

/**

 * Specific AST walker that determines whether an expression is movable

 * and collects the referenced variables.

 * Can only be used on expressions.

 */

class MovableChecker: public SideEffectsCollector

{

public:

  explicit MovableChecker(

    Dialect const& _dialect,

    std::map<YulString, SideEffects> const* _functionSideEffects = nullptr

  ): SideEffectsCollector(_dialect, _functionSideEffects) {}

  MovableChecker(Dialect const& _dialect, Expression const& _expression);

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

  /// Disallow visiting anything apart from Expressions (this throws).

  void visit(Statement const&) override;

  using ASTWalker::visit;

  std::set<YulString> const& referencedVariables() const { return m_variableReferences; }

private:

  /// Which variables the current expression references.

  std::set<YulString> m_variableReferences;

};

struct ControlFlowSideEffects;

/**

 * Helper class to find "irregular" control flow.

 * This includes termination, break, continue and leave.

 * In general, it is applied only to "simple" statements. The control-flow

 * of loops, switches and if statements is always "FlowOut" with the assumption

 * that the caller will descend into them.

 */

class TerminationFinder

{

public:

  /// "Terminate" here means that there is no continuing control-flow.

  /// If this is applied to a function that can revert or stop, but can also

  /// exit regularly, the property is set to "FlowOut".

  enum class ControlFlow { FlowOut, Break, Continue, Terminate, Leave };

  TerminationFinder(

    Dialect const& _dialect,

    std::map<YulString, ControlFlowSideEffects> const* _functionSideEffects = nullptr

  ): m_dialect(_dialect), m_functionSideEffects(_functionSideEffects) {}

  /// @returns the index of the first statement in the provided sequence

  /// that is an unconditional ``break``, ``continue``, ``leave`` or a

  /// call to a terminating function.

  /// If control flow can continue at the end of the list,

  /// returns `FlowOut` and ``size_t(-1)``.

  /// The function might return ``FlowOut`` even though control

  /// flow cannot actually continue.

  std::pair<ControlFlow, size_t> firstUnconditionalControlFlowChange(

    std::vector<Statement> const& _statements

  );

  /// @returns the control flow type of the given statement.

  /// This function could return FlowOut even if control flow never continues.

  ControlFlow controlFlowKind(Statement const& _statement);

  /// @returns true if the expression contains a

  /// call to a terminating function, i.e. a function that does not have

  /// a regular "flow out" control-flow (it might also be recursive).

  bool containsNonContinuingFunctionCall(Expression const& _expr);

private:

  Dialect const& m_dialect;

  std::map<YulString, ControlFlowSideEffects> const* m_functionSideEffects;

};

}