/* 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_dom_FetchStreamReader_h
#define mozilla_dom_FetchStreamReader_h

#include "js/RootingAPI.h"
#include "js/TypeDecls.h"
#include "mozilla/Attributes.h"
#include "mozilla/GlobalTeardownObserver.h"
#include "mozilla/WeakPtr.h"
#include "mozilla/dom/AbortFollower.h"
#include "mozilla/dom/FetchBinding.h"
#include "mozilla/dom/PromiseNativeHandler.h"
#include "nsIAsyncOutputStream.h"
#include "nsIGlobalObject.h"

namespace mozilla::dom {

class AbortSignalImpl;
class ReadableStream;
class ReadableStreamDefaultReader;
class StrongWorkerRef;

class FetchStreamReader;

// Tiny helper that follows an AbortSignalImpl and closes a FetchStreamReader
// on abort, propagating the abort reason to the underlying ReadableStream's
// cancel callback.
class FetchStreamReaderAbortFollower final : public AbortFollower {
 public:
  NS_DECL_ISUPPORTS

  explicit FetchStreamReaderAbortFollower(FetchStreamReader* aReader);

  void RunAbortAlgorithm() override;

 private:
  ~FetchStreamReaderAbortFollower() = default;

  WeakPtr<FetchStreamReader> mReader;
};

class OutputStreamHolder final : public nsIOutputStreamCallback {
 public:
  NS_DECL_ISUPPORTS
  NS_DECL_NSIOUTPUTSTREAMCALLBACK

  OutputStreamHolder(FetchStreamReader* aReader, nsIAsyncOutputStream* aOutput);

  nsresult Init(JSContext* aCx);

  void Shutdown();

  // These just proxy the calls to the nsIAsyncOutputStream
  nsresult AsyncWait(uint32_t aFlags, uint32_t aRequestedCount,
                     nsIEventTarget* aEventTarget);
  nsresult Write(char* aBuffer, uint32_t aLength, uint32_t* aWritten) {
    return mOutput->Write(aBuffer, aLength, aWritten);
  }
  nsresult CloseWithStatus(nsresult aStatus) {
    return mOutput->CloseWithStatus(aStatus);
  }
  nsresult StreamStatus() { return mOutput->StreamStatus(); }

  nsIAsyncOutputStream* GetOutputStream() { return mOutput; }

 private:
  ~OutputStreamHolder();

  RefPtr<FetchStreamReader> mAsyncWaitReader;
  // WeakPtr to avoid cycles
  WeakPtr<FetchStreamReader> mReader;
  // To ensure the worker sticks around
  RefPtr<StrongWorkerRef> mAsyncWaitWorkerRef;
  RefPtr<StrongWorkerRef> mWorkerRef;
  nsCOMPtr<nsIAsyncOutputStream> mOutput;
};

class FetchStreamReader final : public GlobalTeardownObserver,
                                public SupportsWeakPtr {
 public:
  NS_DECL_CYCLE_COLLECTING_ISUPPORTS_FINAL
  NS_DECL_CYCLE_COLLECTION_CLASS(FetchStreamReader)

  // This creates a nsIInputStream able to retrieve data from the ReadableStream
  // object. The reading starts when StartConsuming() is called.
  static nsresult Create(JSContext* aCx, nsIGlobalObject* aGlobal,
                         FetchStreamReader** aStreamReader,
                         nsIInputStream** aInputStream);

  bool OnOutputStreamReady();

  MOZ_CAN_RUN_SCRIPT
  void ChunkSteps(JSContext* aCx, JS::Handle<JS::Value> aChunk,
                  ErrorResult& aRv);
  MOZ_CAN_RUN_SCRIPT
  void CloseSteps(JSContext* aCx, ErrorResult& aRv);
  MOZ_CAN_RUN_SCRIPT
  void ErrorSteps(JSContext* aCx, JS::Handle<JS::Value> aError,
                  ErrorResult& aRv);

  // Idempotently close the output stream and null out all state. If aCx is
  // provided, the reader will also be canceled.  aStatus must be a DOM error
  // as understood by DOMException because it will be provided as the
  // cancellation reason.
  //
  // This is a script boundary minimize annotation changes required while
  // we figure out how to handle some more tricky annotation cases (for
  // example, the destructor of this class. Tracking under Bug 1750656)
  MOZ_CAN_RUN_SCRIPT_BOUNDARY
  void CloseAndRelease(JSContext* aCx, nsresult aStatus);

  void StartConsuming(JSContext* aCx, ReadableStream* aStream,
                      ErrorResult& aRv);

  // True once StartConsuming() has acquired a reader on the JS stream.
  bool IsConsuming() const { return !!mReader; }

  // Have this FetchStreamReader follow aSignal so that the underlying
  // ReadableStream's cancel algorithm fires (with the signal's reason) when
  // the fetch is aborted. aSignal must not have aborted already: Follow()
  // ignores such a signal, and fetch() cancels the body itself in that case.
  MOZ_CAN_RUN_SCRIPT_BOUNDARY
  void FollowSignal(AbortSignalImpl* aSignal);

  MOZ_CAN_RUN_SCRIPT_BOUNDARY
  void RunAbortAlgorithm(AbortSignalImpl* aSignal);

  // Cancel the underlying reader with aReason, then close the output stream
  // and release internal state. Equivalent to CloseAndRelease for cleanup,
  // but uses an explicit JS reason for the cancel rather than synthesizing
  // one from an nsresult.
  MOZ_CAN_RUN_SCRIPT_BOUNDARY
  void CancelAndRelease(JSContext* aCx, JS::Handle<JS::Value> aReason);

  // Nothing will consume the pipe once the global is gone, so close it while
  // the owning thread can still run the pipe's notifications.
  void DisconnectFromOwner() override;

 private:
  explicit FetchStreamReader(nsIGlobalObject* aGlobal);
  ~FetchStreamReader();

  nsresult WriteBuffer();

  // Cancel mReader with aReason. Cleanup must not propagate exceptions, so the
  // result is ignored and the returned promise marked handled.
  MOZ_CAN_RUN_SCRIPT_BOUNDARY
  void CancelReader(JSContext* aCx, JS::Handle<JS::Value> aReason);

  // Close the pipe with aStatus and drop everything the reader holds.
  void ReleaseState(nsresult aStatus);

  // Attempt to copy data from mBuffer into mPipeOut. Returns `true` if data was
  // written, and AsyncWait callbacks or FetchReadRequest calls have been set up
  // to write more data in the future, and `false` otherwise.
  MOZ_CAN_RUN_SCRIPT
  bool Process(JSContext* aCx);

  void ReportErrorToConsole(JSContext* aCx, JS::Handle<JS::Value> aValue);

  nsCOMPtr<nsIGlobalObject> mGlobal;
  nsCOMPtr<nsIEventTarget> mOwningEventTarget;

  RefPtr<OutputStreamHolder> mOutput;

  RefPtr<ReadableStreamDefaultReader> mReader;

  nsTArray<uint8_t> mBuffer;
  uint32_t mBufferRemaining = 0;
  uint32_t mBufferOffset = 0;

  bool mHasOutstandingReadRequest = false;
  bool mStreamClosed = false;

  RefPtr<FetchStreamReaderAbortFollower> mAbortFollower;
};

}  // namespace mozilla::dom

#endif  // mozilla_dom_FetchStreamReader_h