/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 mozilla_RemoteLazyInputStreamStorage_h
#define mozilla_RemoteLazyInputStreamStorage_h

#include "mozilla/RefPtr.h"
#include "nsClassHashtable.h"
#include "nsIObserver.h"

class nsIInputStream;
struct nsID;

namespace mozilla {

class NS_NO_VTABLE RemoteLazyInputStreamParentCallback {
 public:
  virtual void ActorDestroyed(const nsID& aID) = 0;

  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING

 protected:
  virtual ~RemoteLazyInputStreamParentCallback() = default;
};

class RemoteLazyInputStreamStorage final : public nsIObserver {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIOBSERVER

  // This initializes the singleton and it must be called on the main-thread.
  static void Initialize();

  static Result<RefPtr<RemoteLazyInputStreamStorage>, nsresult> Get();

  nsISerialEventTarget* TaskQueue() { return mTaskQueue; }

  void AddStream(nsIInputStream* aInputStream, const nsID& aID);

  // Removes and returns the stream corresponding to the nsID. May return a
  // nullptr if there's no stream stored for the nsID.
  nsCOMPtr<nsIInputStream> ForgetStream(const nsID& aID);

  bool HasStream(const nsID& aID);

  void GetStream(const nsID& aID, uint64_t aStart, uint64_t aLength,
                 nsIInputStream** aInputStream);

  void StoreCallback(const nsID& aID,
                     RemoteLazyInputStreamParentCallback* aCallback);

  already_AddRefed<RemoteLazyInputStreamParentCallback> TakeCallback(
      const nsID& aID);

  void ActorCreated(const nsID& aID);
  void ActorDestroyed(const nsID& aID);

 private:
  RemoteLazyInputStreamStorage() = default;
  ~RemoteLazyInputStreamStorage() = default;

  nsCOMPtr<nsISerialEventTarget> mTaskQueue;

  struct StreamData {
    nsCOMPtr<nsIInputStream> mInputStream;
    RefPtr<RemoteLazyInputStreamParentCallback> mCallback;
    size_t mActorCount = 0;
  };

  nsClassHashtable<nsIDHashKey, StreamData> mStorage;
};

}  // namespace mozilla

#endif  // mozilla_RemoteLazyInputStreamStorage_h