// Copyright 2021 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// This file contains temporary code to help implement the new `ast::Type`s.
// Once complete, this file should be completely removed.
// Bug: crbug.com/tint/724

#ifndef SRC_TYPEPAIR_H_
#define SRC_TYPEPAIR_H_

#include <cstddef>
#include <type_traits>
#include <utility>

// X11 likes to #define Bool leading to confusing error messages.
// If its defined, undefine it.
#ifdef Bool
#undef Bool
#endif

namespace tint {

namespace ast {
class AccessControl;
class Array;
class Bool;
class DepthTexture;
class ExternalTexture;
class F32;
class I32;
class Matrix;
class MultisampledTexture;
class Pointer;
class Sampler;
class SampledTexture;
class StorageTexture;
class Struct;
class Texture;
class Type;
class U32;
class Vector;
class Void;
}  // namespace ast

namespace sem {
class AccessControl;
class Array;
class Bool;
class DepthTexture;
class ExternalTexture;
class F32;
class I32;
class Matrix;
class MultisampledTexture;
class Pointer;
class Sampler;
class SampledTexture;
class StorageTexture;
class Struct;
class Texture;
class Type;
class U32;
class Vector;
class Void;
}  // namespace sem

namespace typ {  //  type-pair

/// A simple wrapper around a raw pointer. Used to prevent a whole bunch of
/// warnings about `auto` needing to be declared as `auto*` while we're
/// migrating code.
template <typename T>
struct Ptr {
  /// The raw pointer
  T* const ptr;

  /// Constructor
  Ptr() = default;

  /// Copy constructor
  /// @param other the Ptr to copy
  template <typename OTHER>
  Ptr(const Ptr<OTHER>& other) : ptr(static_cast<T*>(other.ptr)) {}

  /// Constructor
  /// @param p the pointer to wrap in a Ptr
  template <typename U>
  Ptr(U* p) : ptr(p) {}  // NOLINT: explicit

  /// @returns the pointer
  operator T*() { return ptr; }

  /// @returns the pointer
  operator const T*() const { return ptr; }

  /// @returns the pointer
  T* operator->() { return ptr; }

  /// @returns the pointer
  const T* operator->() const { return ptr; }
};

/// TypePair is a pair of ast::Type and sem::Type pointers used to simplify
/// migration to the new ast::Type nodes.
///
/// Type attempts to behave as either an ast::Type or sem::Type:
/// * Type has constructors that take either an ast::Type and sem::Type pointer
///   pair, and single-parameter implicit constructors for either a single
///   ast::Type or sem::Type pointer.
/// * Type also has user-defined conversion functions for returning either an
///   ast::Type or sem::Type pointer.
/// * operator->() returns the sem::Type pointer. Later in the migration this
///   will switch to returning the ast::Type pointer.
template <typename AST, typename SEM>
struct TypePair {
  /// Alias of the `AST` template type parameter
  using AST_TYPE = AST;
  /// Alias of the `SEM` template type parameter
  using SEM_TYPE = SEM;

  /// The ast::Type pointer
  AST const* ast = nullptr;
  /// The sem::Type pointer
  SEM const* sem = nullptr;

  /// Constructor
  TypePair() = default;
  /// Copy constructor
  /// @param other the TypePair to copy
  template <typename OTHER_AST, typename OTHER_SEM>
  TypePair(const TypePair<OTHER_AST, OTHER_SEM>& other)
      : ast(static_cast<const AST*>(other.ast)),
        sem(static_cast<const SEM*>(other.sem)) {}
  /// Constructor
  /// @param a the ast::Type pointer
  TypePair(const AST* a) : ast(a) {}  // NOLINT: explicit
  /// Constructor
  /// @param s the sem::Type pointer
  TypePair(const SEM* s) : sem(s) {}  // NOLINT: explicit
  /// Constructor
  /// @param a the ast::Type pointer
  /// @param s the sem::Type pointer
  TypePair(const AST* a, const SEM* s) : ast(a), sem(s) {}
  /// Constructor
  /// @param ptr the Ptr<T>
  template <typename T>
  TypePair(Ptr<T> ptr) : TypePair(ptr.ptr) {}  // NOLINT: explicit
  /// Constructor
  TypePair(std::nullptr_t) {}  // NOLINT: explicit

  /// @returns the ast::Type pointer
  operator AST*() const { return const_cast<AST*>(ast); }
  /// @returns the sem::Type pointer
  operator SEM*() const { return const_cast<SEM*>(sem); }
  /// @returns the sem::Type pointer
  SEM* operator->() const { return const_cast<SEM*>(sem); }

  /// @returns true if sem is valid
  explicit operator bool() const { return sem != nullptr; }

  /// @param ty the semantic type to compare against
  /// @returns true if the semantic type is equal to `ty`
  bool operator==(sem::Type* ty) const { return sem == ty; }

  /// @param ty the semantic type to compare against
  /// @returns true if the semantic type is not equal to `ty`
  bool operator!=(sem::Type* ty) const { return !((*this) == ty); }

  /// @param other the TypePair to compare against
  /// @returns true if this TypePair is less than `other`
  template <typename OTHER_AST, typename OTHER_SEM>
  bool operator<(const TypePair<OTHER_AST, OTHER_SEM>& other) const {
    if (sem < other.sem) {
      return true;
    }
    if (sem > other.sem) {
      return false;
    }
    return ast < other.ast;
  }
};

/// @param lhs LHS value to compare
/// @param rhs RHS value to compare
/// @returns true if values compare equal
template <typename AST, typename SEM>
bool operator==(const TypePair<AST, SEM>& lhs, const TypePair<AST, SEM>& rhs) {
  return lhs.sem == rhs.sem;
}

/// @param lhs LHS value to compare
/// @param rhs RHS value to compare
/// @returns true if values compare not equal
template <typename AST, typename SEM>
bool operator!=(const TypePair<AST, SEM>& lhs, const TypePair<AST, SEM>& rhs) {
  return !(lhs == rhs);
}

/// @param lhs LHS value to compare
/// @returns true if `lhs` is nullptr
template <typename AST, typename SEM>
bool operator==(const TypePair<AST, SEM>& lhs, std::nullptr_t) {
  return lhs.sem == nullptr;
}

/// @param lhs LHS value to compare
/// @returns true if `lhs` is not nullptr
template <typename AST, typename SEM>
bool operator!=(const TypePair<AST, SEM>& lhs, std::nullptr_t) {
  return !(lhs == nullptr);
}

/// @param rhs RHS value to compare
/// @returns true if `rhs` is nullptr
template <typename AST, typename SEM>
bool operator==(std::nullptr_t, const TypePair<AST, SEM>& rhs) {
  return nullptr == rhs.sem;
}

/// @param rhs RHS value to compare
/// @returns true if `rhs` is not nullptr
template <typename AST, typename SEM>
bool operator!=(std::nullptr_t, const TypePair<AST, SEM>& rhs) {
  return !(nullptr == rhs);
}

using Type = TypePair<ast::Type, sem::Type>;

using Array = TypePair<ast::Array, sem::Array>;
using Bool = TypePair<ast::Bool, sem::Bool>;
using DepthTexture = TypePair<ast::DepthTexture, sem::DepthTexture>;
using ExternalTexture = TypePair<ast::ExternalTexture, sem::ExternalTexture>;
using F32 = TypePair<ast::F32, sem::F32>;
using I32 = TypePair<ast::I32, sem::I32>;
using Matrix = TypePair<ast::Matrix, sem::Matrix>;
using MultisampledTexture =
    TypePair<ast::MultisampledTexture, sem::MultisampledTexture>;
using Pointer = TypePair<ast::Pointer, sem::Pointer>;
using Sampler = TypePair<ast::Sampler, sem::Sampler>;
using SampledTexture = TypePair<ast::SampledTexture, sem::SampledTexture>;
using StorageTexture = TypePair<ast::StorageTexture, sem::StorageTexture>;
using Struct = TypePair<ast::Struct, sem::Struct>;
using Texture = TypePair<ast::Texture, sem::Texture>;
using U32 = TypePair<ast::U32, sem::U32>;
using Vector = TypePair<ast::Vector, sem::Vector>;
using Void = TypePair<ast::Void, sem::Void>;

// Helpers

/// Makes a type pair, deducing the return type from input args
/// @parm ast the ast node
/// @param sem the sem node
/// @returns a type pair
template <typename AST, typename SEM>
inline auto MakeTypePair(AST* ast, SEM* sem) {
  return TypePair<AST, SEM>{ast, sem};
}

}  // namespace typ

}  // namespace tint

#endif  // SRC_TYPEPAIR_H_