/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef js_TraceableFifo_h
#define js_TraceableFifo_h

#include "ds/Fifo.h"
#include "js/GCVector.h"
#include "js/RootingAPI.h"
#include "js/TracingAPI.h"

namespace js {

// A TraceableFifo is a Fifo with an additional trace method that knows how to
// visit all of the items stored in the Fifo. For Fifos that contain GC things,
// this is usually more convenient than manually iterating and marking the
// contents.
//
// Most types of GC pointers as keys and values can be traced with no extra
// infrastructure. For structs and non-gc-pointer members, ensure that there is
// a specialization of GCPolicy<T> with an appropriate trace method available
// to handle the custom type. Generic helpers can be found in
// js/public/TracingAPI.h. Generic helpers can be found in
// js/public/TracingAPI.h.
//
// Note that although this Fifo's trace will deal correctly with moved items, it
// does not itself know when to barrier or trace items. To function properly it
// must either be used with Rooted, or barriered and traced manually.
template <typename T, size_t MinInlineCapacity = 0,
          typename AllocPolicy = TempAllocPolicy>
class TraceableFifo
    : public js::Fifo<T, MinInlineCapacity, AllocPolicy, JS::GCVector> {
  using Base = js::Fifo<T, MinInlineCapacity, AllocPolicy, JS::GCVector>;

 public:
  explicit TraceableFifo(AllocPolicy alloc = AllocPolicy())
      : Base(std::move(alloc)) {}

  TraceableFifo(TraceableFifo&& rhs) : Base(std::move(rhs)) {}
  TraceableFifo& operator=(TraceableFifo&& rhs) = default;

  TraceableFifo(const TraceableFifo&) = delete;
  TraceableFifo& operator=(const TraceableFifo&) = delete;

  void trace(JSTracer* trc) {
    this->front_.trace(trc);
    this->rear_.trace(trc);
  }
};

template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
class WrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>, Wrapper> {
  using TF = TraceableFifo<T, Capacity, AllocPolicy>;
  const TF& fifo() const { return static_cast<const Wrapper*>(this)->get(); }

 public:
  size_t length() const { return fifo().length(); }
  bool empty() const { return fifo().empty(); }
  const T& front() const { return fifo().front(); }
};

template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
class MutableWrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>,
                                  Wrapper>
    : public WrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>,
                                  Wrapper> {
  using TF = TraceableFifo<T, Capacity, AllocPolicy>;
  TF& fifo() { return static_cast<Wrapper*>(this)->get(); }

 public:
  T& front() { return fifo().front(); }

  template <typename U>
  bool pushBack(U&& u) {
    return fifo().pushBack(std::forward<U>(u));
  }
  template <typename... Args>
  bool emplaceBack(Args&&... args) {
    return fifo().emplaceBack(std::forward<Args...>(args...));
  }

  void popFront() { fifo().popFront(); }
  void clear() { fifo().clear(); }
};

}  // namespace js

#endif  // js_TraceableFifo_h