// 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.

#ifndef SRC_PROGRAM_ID_H_
#define SRC_PROGRAM_ID_H_

#include <stdint.h>
#include <iostream>
#include <utility>

#include "src/debug.h"

namespace tint {

/// If 1 then checks are enabled that AST nodes are not leaked from one program
/// to another.
/// TODO(bclayton): We'll want to disable this in production builds. For now we
/// always check.
#define TINT_CHECK_FOR_CROSS_PROGRAM_LEAKS 1

/// A ProgramID is a unique identifier of a Program.
/// ProgramID can be used to ensure that objects referenced by the Program are
/// owned exclusively by that Program and have accidentally not leaked from
/// another Program.
class ProgramID {
 public:
  /// Constructor
  ProgramID();

  /// @returns a new. globally unique ProgramID
  static ProgramID New();

  /// Equality operator
  /// @param rhs the other ProgramID
  /// @returns true if the ProgramIDs are equal
  bool operator==(const ProgramID& rhs) const { return val == rhs.val; }

  /// Inequality operator
  /// @param rhs the other ProgramID
  /// @returns true if the ProgramIDs are not equal
  bool operator!=(const ProgramID& rhs) const { return val != rhs.val; }

  /// @returns the numerical identifier value
  uint32_t Value() const { return val; }

  /// @returns true if this ProgramID is valid
  operator bool() const { return val != 0; }

 private:
  explicit ProgramID(uint32_t);

  uint32_t val = 0;
};

/// A simple pass-through function for ProgramID. Intended to be overloaded for
/// other types.
/// @param id a ProgramID
/// @returns id. Simple pass-through function
inline ProgramID ProgramIDOf(ProgramID id) {
  return id;
}

/// Writes the ProgramID to the std::ostream.
/// @param out the std::ostream to write to
/// @param id the program identifier to write
/// @returns out so calls can be chained
inline std::ostream& operator<<(std::ostream& out, ProgramID id) {
  out << "Program<" << id.Value() << ">";
  return out;
}

namespace detail {

/// AssertProgramIDsEqual is called by TINT_ASSERT_PROGRAM_IDS_EQUAL() and
/// TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID() to assert that the ProgramIDs of
/// `a` and `b` are equal.
template <typename A, typename B>
void AssertProgramIDsEqual(A&& a,
                           B&& b,
                           bool if_valid,
                           const char* msg,
                           const char* file,
                           size_t line) {
  auto a_id = ProgramIDOf(std::forward<A>(a));
  auto b_id = ProgramIDOf(std::forward<B>(b));
  if (a_id == b_id) {
    return;  // matched
  }
  if (if_valid && (!a_id || !b_id)) {
    return;  //  a or b were not valid
  }
  diag::List diagnostics;
  tint::InternalCompilerError(file, line, diagnostics) << msg;
}

}  // namespace detail

/// TINT_ASSERT_PROGRAM_IDS_EQUAL(A, B) is a macro that asserts that the program
/// identifiers for A and B are equal.
///
/// TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(A, B) is a macro that asserts that
/// the program identifiers for A and B are equal, if both A and B have valid
/// program identifiers.
#if TINT_CHECK_FOR_CROSS_PROGRAM_LEAKS
#define TINT_ASSERT_PROGRAM_IDS_EQUAL(a, b)                                   \
  detail::AssertProgramIDsEqual(                                              \
      a, b, false, "TINT_ASSERT_PROGRAM_IDS_EQUAL(" #a ", " #b ")", __FILE__, \
      __LINE__)
#define TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(a, b)                        \
  detail::AssertProgramIDsEqual(                                            \
      a, b, true, "TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(" #a ", " #b ")", \
      __FILE__, __LINE__)
#else
#define TINT_ASSERT_PROGRAM_IDS_EQUAL(a, b) \
  do {                                      \
  } while (false)
#define TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(a, b) \
  do {                                               \
  } while (false)
#endif

}  // namespace tint

#endif  // SRC_PROGRAM_ID_H_