/*
 * Copyright (C) 2010 Google Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "third_party/blink/renderer/core/fileapi/file_reader.h"

#include <utility>

#include "base/auto_reset.h"
#include "base/timer/elapsed_timer.h"
#include "third_party/blink/public/platform/task_type.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_union_arraybuffer_string.h"
#include "third_party/blink/renderer/core/event_target_names.h"
#include "third_party/blink/renderer/core/events/progress_event.h"
#include "third_party/blink/renderer/core/execution_context/execution_context.h"
#include "third_party/blink/renderer/core/fileapi/file.h"
#include "third_party/blink/renderer/core/fileapi/file_error.h"
#include "third_party/blink/renderer/core/frame/local_dom_window.h"
#include "third_party/blink/renderer/core/frame/web_feature.h"
#include "third_party/blink/renderer/core/probe/core_probes.h"
#include "third_party/blink/renderer/core/scheduler/task_attribution_util.h"
#include "third_party/blink/renderer/core/typed_arrays/dom_array_buffer.h"
#include "third_party/blink/renderer/platform/bindings/exception_state.h"
#include "third_party/blink/renderer/platform/instrumentation/use_counter.h"
#include "third_party/blink/renderer/platform/supplementable.h"
#include "third_party/blink/renderer/platform/wtf/deque.h"
#include "third_party/blink/renderer/platform/wtf/hash_set.h"

namespace blink {

namespace {

const std::string Utf8BlobUuid(Blob* blob) {
  return blob->Uuid().Utf8();
}

const std::string Utf8FilePath(Blob* blob) {
  return blob->HasBackingFile() ? To<File>(blob)->GetPath().Utf8() : "";
}

}  // namespace

// Embedders like chromium limit the number of simultaneous requests to avoid
// excessive IPC congestion. We limit this to 100 per thread to throttle the
// requests (the value is arbitrarily chosen).
static const size_t kMaxOutstandingRequestsPerThread = 100;
static const base::TimeDelta kProgressNotificationInterval =
    base::Milliseconds(50);

class FileReader::ThrottlingController final
    : public GarbageCollected<FileReader::ThrottlingController>,
      public Supplement<ExecutionContext> {
 public:
  static const char kSupplementName[];

  static ThrottlingController* From(ExecutionContext* context) {
    if (!context)
      return nullptr;

    ThrottlingController* controller =
        Supplement<ExecutionContext>::From<ThrottlingController>(*context);
    if (!controller) {
      controller = MakeGarbageCollected<ThrottlingController>(*context);
      ProvideTo(*context, controller);
    }
    return controller;
  }

  enum FinishReaderType { kDoNotRunPendingReaders, kRunPendingReaders };

  static void PushReader(ExecutionContext* context, FileReader* reader) {
    ThrottlingController* controller = From(context);
    if (!controller)
      return;

    reader->async_task_context()->Schedule(context, "FileReader");
    controller->PushReader(reader);
  }

  static FinishReaderType RemoveReader(ExecutionContext* context,
                                       FileReader* reader) {
    ThrottlingController* controller = From(context);
    if (!controller)
      return kDoNotRunPendingReaders;

    return controller->RemoveReader(reader);
  }

  static void FinishReader(ExecutionContext* context,
                           FileReader* reader,
                           FinishReaderType next_step) {
    ThrottlingController* controller = From(context);
    if (!controller)
      return;

    controller->FinishReader(reader, next_step);
    reader->async_task_context()->Cancel();
  }

  explicit ThrottlingController(ExecutionContext& context)
      : Supplement<ExecutionContext>(context),
        max_running_readers_(kMaxOutstandingRequestsPerThread) {}

  void Trace(Visitor* visitor) const override {
    visitor->Trace(pending_readers_);
    visitor->Trace(running_readers_);
    Supplement<ExecutionContext>::Trace(visitor);
  }

 private:
  void PushReader(FileReader* reader) {
    if (pending_readers_.empty() &&
        running_readers_.size() < max_running_readers_) {
      reader->ExecutePendingRead();
      DCHECK(!running_readers_.Contains(reader));
      running_readers_.insert(reader);
      return;
    }
    pending_readers_.push_back(reader);
    ExecuteReaders();
  }

  FinishReaderType RemoveReader(FileReader* reader) {
    FileReaderHashSet::const_iterator hash_iter = running_readers_.find(reader);
    if (hash_iter != running_readers_.end()) {
      running_readers_.erase(hash_iter);
      return kRunPendingReaders;
    }
    FileReaderDeque::const_iterator deque_end = pending_readers_.end();
    for (FileReaderDeque::const_iterator it = pending_readers_.begin();
         it != deque_end; ++it) {
      if (*it == reader) {
        pending_readers_.erase(it);
        break;
      }
    }
    return kDoNotRunPendingReaders;
  }

  void FinishReader(FileReader* reader, FinishReaderType next_step) {
    if (next_step == kRunPendingReaders)
      ExecuteReaders();
  }

  void ExecuteReaders() {
    // Dont execute more readers if the context is already destroyed (or in the
    // process of being destroyed).
    if (GetSupplementable()->IsContextDestroyed())
      return;
    while (running_readers_.size() < max_running_readers_) {
      if (pending_readers_.empty())
        return;
      FileReader* reader = pending_readers_.TakeFirst();
      reader->ExecutePendingRead();
      running_readers_.insert(reader);
    }
  }

  const size_t max_running_readers_;

  using FileReaderDeque = HeapDeque<Member<FileReader>>;
  using FileReaderHashSet = HeapHashSet<Member<FileReader>>;

  FileReaderDeque pending_readers_;
  FileReaderHashSet running_readers_;
};

// static
const char FileReader::ThrottlingController::kSupplementName[] =
    "FileReaderThrottlingController";

FileReader* FileReader::Create(ExecutionContext* context) {
  return MakeGarbageCollected<FileReader>(context);
}

FileReader::FileReader(ExecutionContext* context)
    : ActiveScriptWrappable<FileReader>({}),
      ExecutionContextLifecycleObserver(context),
      state_(kEmpty),
      loading_state_(kLoadingStateNone),
      still_firing_events_(false),
      read_type_(FileReadType::kReadAsBinaryString) {}

FileReader::~FileReader() = default;

const AtomicString& FileReader::InterfaceName() const {
  return event_target_names::kFileReader;
}

void FileReader::ContextDestroyed() {
  // The delayed abort task tidies up and advances to the DONE state.
  if (loading_state_ == kLoadingStateAborted)
    return;

  if (HasPendingActivity()) {
    ExecutionContext* destroyed_context = GetExecutionContext();
    ThrottlingController::FinishReader(
        destroyed_context, this,
        ThrottlingController::RemoveReader(destroyed_context, this));
  }
  task_state_ = nullptr;
  Terminate();
}

bool FileReader::HasPendingActivity() const {
  return state_ == kLoading || still_firing_events_;
}

void FileReader::readAsArrayBuffer(Blob* blob,
                                   ExceptionState& exception_state) {
  DCHECK(blob);
  DVLOG(1) << "reading as array buffer: " << Utf8BlobUuid(blob).data() << " "
           << Utf8FilePath(blob).data();

  ReadInternal(blob, FileReadType::kReadAsArrayBuffer, exception_state);
}

void FileReader::readAsBinaryString(Blob* blob,
                                    ExceptionState& exception_state) {
  DCHECK(blob);
  DVLOG(1) << "reading as binary: " << Utf8BlobUuid(blob).data() << " "
           << Utf8FilePath(blob).data();

  ReadInternal(blob, FileReadType::kReadAsBinaryString, exception_state);
}

void FileReader::readAsText(Blob* blob,
                            const String& encoding,
                            ExceptionState& exception_state) {
  DCHECK(blob);
  DVLOG(1) << "reading as text: " << Utf8BlobUuid(blob).data() << " "
           << Utf8FilePath(blob).data();

  encoding_ = encoding;
  ReadInternal(blob, FileReadType::kReadAsText, exception_state);
}

void FileReader::readAsText(Blob* blob, ExceptionState& exception_state) {
  readAsText(blob, String(), exception_state);
}

void FileReader::readAsDataURL(Blob* blob, ExceptionState& exception_state) {
  DCHECK(blob);
  DVLOG(1) << "reading as data URL: " << Utf8BlobUuid(blob).data() << " "
           << Utf8FilePath(blob).data();

  ReadInternal(blob, FileReadType::kReadAsDataURL, exception_state);
}

void FileReader::ReadInternal(Blob* blob,
                              FileReadType type,
                              ExceptionState& exception_state) {
  // If multiple concurrent read methods are called on the same FileReader,
  // InvalidStateError should be thrown when the state is kLoading.
  if (state_ == kLoading) {
    exception_state.ThrowDOMException(
        DOMExceptionCode::kInvalidStateError,
        "The object is already busy reading Blobs.");
    return;
  }

  ExecutionContext* context = GetExecutionContext();
  if (!context) {
    exception_state.ThrowDOMException(
        DOMExceptionCode::kAbortError,
        "Reading from a detached FileReader is not supported.");
    return;
  }

  // A document loader will not load new resources once the Document has
  // detached from its frame.
  LocalDOMWindow* window = DynamicTo<LocalDOMWindow>(context);
  if (window && !window->GetFrame()) {
    exception_state.ThrowDOMException(
        DOMExceptionCode::kAbortError,
        "Reading from a Document-detached FileReader is not supported.");
    return;
  }

  // "Snapshot" the Blob data rather than the Blob itself as ongoing
  // read operations should not be affected if close() is called on
  // the Blob being read.
  blob_data_handle_ = blob->GetBlobDataHandle();
  blob_type_ = blob->type();
  read_type_ = type;
  state_ = kLoading;
  loading_state_ = kLoadingStatePending;
  task_state_ = CaptureCurrentTaskState(context);
  error_ = nullptr;
  result_ = nullptr;
  DCHECK(ThrottlingController::From(context));
  ThrottlingController::PushReader(context, this);
}

void FileReader::ExecutePendingRead() {
  DCHECK_EQ(loading_state_, kLoadingStatePending);
  loading_state_ = kLoadingStateLoading;

  loader_ = MakeGarbageCollected<FileReaderLoader>(
      this, GetExecutionContext()->GetTaskRunner(TaskType::kFileReading));
  loader_->Start(blob_data_handle_);
  blob_data_handle_ = nullptr;
}

void FileReader::abort() {
  DVLOG(1) << "aborting";

  if (loading_state_ != kLoadingStateLoading &&
      loading_state_ != kLoadingStatePending) {
    return;
  }
  loading_state_ = kLoadingStateAborted;

  DCHECK_NE(kDone, state_);
  // Synchronously cancel the loader before dispatching events. This way we make
  // sure the FileReader internal state stays consistent even if another load
  // is started from one of the event handlers, or right after abort returns.
  Terminate();

  base::AutoReset<bool> firing_events(&still_firing_events_, true);

  // Setting error implicitly makes |result| return null.
  error_ = file_error::CreateDOMException(FileErrorCode::kAbortErr);

  // Unregister the reader.
  ThrottlingController::FinishReaderType final_step =
      ThrottlingController::RemoveReader(GetExecutionContext(), this);

  scheduler::TaskAttributionInfo* task_state =
      std::exchange(task_state_, nullptr);
  FireEvent(event_type_names::kAbort, task_state);
  // TODO(https://crbug.com/1204139): Only fire loadend event if no new load was
  // started from the abort event handler.
  FireEvent(event_type_names::kLoadend, task_state);

  // All possible events have fired and we're done, no more pending activity.
  ThrottlingController::FinishReader(GetExecutionContext(), this, final_step);
}

V8UnionArrayBufferOrString* FileReader::result() const {
  if (error_ || !loader_)
    return nullptr;

  // Only set the result after |loader_| has finished loading which means that
  // FileReader::DidFinishLoading() has also been called. This ensures that the
  // result is not available until just before the kLoad event is fired.
  if (!loader_->HasFinishedLoading() || state_ != ReadyState::kDone) {
    return nullptr;
  }

  return result_.Get();
}

void FileReader::Terminate() {
  if (loader_) {
    loader_->Cancel();
    loader_ = nullptr;
  }
  state_ = kDone;
  result_ = nullptr;
  loading_state_ = kLoadingStateNone;
}

FileErrorCode FileReader::DidStartLoading() {
  base::AutoReset<bool> firing_events(&still_firing_events_, true);
  FireEvent(event_type_names::kLoadstart, task_state_);
  return FileErrorCode::kOK;
}

FileErrorCode FileReader::DidReceiveData() {
  // Fire the progress event at least every 50ms.
  if (!last_progress_notification_time_) {
    last_progress_notification_time_ = base::ElapsedTimer();
  } else if (last_progress_notification_time_->Elapsed() >
             kProgressNotificationInterval) {
    base::AutoReset<bool> firing_events(&still_firing_events_, true);
    FireEvent(event_type_names::kProgress, task_state_);
    last_progress_notification_time_ = base::ElapsedTimer();
  }
  return FileErrorCode::kOK;
}

void FileReader::DidFinishLoading(FileReaderData contents) {
  if (loading_state_ == kLoadingStateAborted)
    return;
  DCHECK_EQ(loading_state_, kLoadingStateLoading);

  if (read_type_ == FileReadType::kReadAsArrayBuffer) {
    result_ = MakeGarbageCollected<V8UnionArrayBufferOrString>(
        std::move(contents).AsDOMArrayBuffer());
  } else {
    result_ = MakeGarbageCollected<V8UnionArrayBufferOrString>(
        std::move(contents).AsString(read_type_, encoding_, blob_type_));
  }
  // When we set m_state to DONE below, we still need to fire
  // the load and loadend events. To avoid GC to collect this FileReader, we
  // use this separate variable to keep the wrapper of this FileReader alive.
  // An alternative would be to keep any ActiveScriptWrappables alive that is on
  // the stack.
  base::AutoReset<bool> firing_events(&still_firing_events_, true);

  // It's important that we change m_loadingState before firing any events
  // since any of the events could call abort(), which internally checks
  // if we're still loading (therefore we need abort process) or not.
  loading_state_ = kLoadingStateNone;

  if (loader_->BytesLoaded() > 0) {
    FireEvent(event_type_names::kProgress, task_state_);
  }

  DCHECK_NE(kDone, state_);
  state_ = kDone;

  // Unregister the reader.
  ThrottlingController::FinishReaderType final_step =
      ThrottlingController::RemoveReader(GetExecutionContext(), this);

  scheduler::TaskAttributionInfo* task_state =
      std::exchange(task_state_, nullptr);
  FireEvent(event_type_names::kLoad, task_state);
  // TODO(https://crbug.com/1204139): Only fire loadend event if no new load was
  // started from the abort event handler.
  FireEvent(event_type_names::kLoadend, task_state);

  // All possible events have fired and we're done, no more pending activity.
  ThrottlingController::FinishReader(GetExecutionContext(), this, final_step);
}

void FileReader::DidFail(FileErrorCode error_code) {
  FileReaderAccumulator::DidFail(error_code);
  if (loading_state_ == kLoadingStateAborted)
    return;

  base::AutoReset<bool> firing_events(&still_firing_events_, true);

  DCHECK_EQ(kLoadingStateLoading, loading_state_);
  loading_state_ = kLoadingStateNone;

  DCHECK_NE(kDone, state_);
  state_ = kDone;

  error_ = file_error::CreateDOMException(error_code);

  // Unregister the reader.
  ThrottlingController::FinishReaderType final_step =
      ThrottlingController::RemoveReader(GetExecutionContext(), this);

  scheduler::TaskAttributionInfo* task_state =
      std::exchange(task_state_, nullptr);
  FireEvent(event_type_names::kError, task_state);
  FireEvent(event_type_names::kLoadend, task_state);

  // All possible events have fired and we're done, no more pending activity.
  ThrottlingController::FinishReader(GetExecutionContext(), this, final_step);
}

void FileReader::FireEvent(const AtomicString& type,
                           scheduler::TaskAttributionInfo* task_state) {
  probe::AsyncTask async_task(GetExecutionContext(), async_task_context(),
                              "event");
  std::optional<scheduler::TaskAttributionTracker::TaskScope> task_scope(
      SetCurrentTaskStateIfTopLevel(task_state, GetExecutionContext(),
                                    TaskScopeType::kMiscEvent));
  if (!loader_) {
    DispatchEvent(*ProgressEvent::Create(type, false, 0, 0));
    return;
  }

  if (loader_->TotalBytes()) {
    DispatchEvent(*ProgressEvent::Create(type, true, loader_->BytesLoaded(),
                                         *loader_->TotalBytes()));
  } else {
    DispatchEvent(
        *ProgressEvent::Create(type, false, loader_->BytesLoaded(), 0));
  }
}

void FileReader::Trace(Visitor* visitor) const {
  visitor->Trace(error_);
  visitor->Trace(loader_);
  visitor->Trace(result_);
  visitor->Trace(task_state_);
  EventTarget::Trace(visitor);
  ExecutionContextLifecycleObserver::Trace(visitor);
  FileReaderAccumulator::Trace(visitor);
}

}  // namespace blink