// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/file_system_access/file_system_access_local_path_watcher.h"

#include "base/files/file_path.h"
#include "base/task/bind_post_task.h"
#include "base/task/thread_pool.h"
#include "content/browser/file_system_access/file_path_watcher/file_path_watcher.h"
#include "content/browser/file_system_access/file_system_access_error.h"
#include "content/browser/file_system_access/file_system_access_watcher_manager.h"
#include "storage/browser/file_system/file_system_url.h"
#include "third_party/blink/public/mojom/file_system_access/file_system_access_error.mojom-shared.h"

namespace content {

namespace {

// Creates a task runner suitable for file path watching.
scoped_refptr<base::SequencedTaskRunner> CreateFilePathWatcherTaskRunner() {
  return base::ThreadPool::CreateSequencedTaskRunner({
      // Needed for file I/O.
      base::MayBlock(),

      // File path watching is likely not user visible.
      base::TaskPriority::BEST_EFFORT,

      // File path watching should not block shutdown.
      base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN,
  });
}

}  // namespace

FileSystemAccessLocalPathWatcher::FileSystemAccessLocalPathWatcher(
    FileSystemAccessWatchScope scope,
    scoped_refptr<storage::FileSystemContext> file_system_context,
    base::PassKey<FileSystemAccessWatcherManager> /*pass_key*/)
    : FileSystemAccessChangeSource(std::move(scope),
                                   std::move(file_system_context)),
      watcher_(CreateFilePathWatcherTaskRunner()) {}

FileSystemAccessLocalPathWatcher::~FileSystemAccessLocalPathWatcher() = default;

void FileSystemAccessLocalPathWatcher::Initialize(
    base::OnceCallback<void(blink::mojom::FileSystemAccessErrorPtr)>
        on_source_initialized) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (scope().IsRecursive() && !FilePathWatcher::RecursiveWatchAvailable()) {
    std::move(on_source_initialized)
        .Run(file_system_access_error::FromStatus(
            blink::mojom::FileSystemAccessStatus::kNotSupportedError));
    return;
  }

  FilePathWatcher::CallbackWithChangeInfo on_change_callback =
      base::BindRepeating(&FileSystemAccessLocalPathWatcher::OnFilePathChanged,
                          weak_factory_.GetWeakPtr());

  FilePathWatcher::UsageChangeCallback on_usage_change_callback =
      base::BindRepeating(&FileSystemAccessLocalPathWatcher::OnUsageChange,
                          weak_factory_.GetWeakPtr());

  FilePathWatcher::WatchOptions watch_options{
      .type = scope().IsRecursive() ? FilePathWatcher::Type::kRecursive
                                    : FilePathWatcher::Type::kNonRecursive,
#if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_WIN) || \
    BUILDFLAG(IS_MAC)
      // Note: `report_modified_path` is also present on Android
      // and Fuchsia. Update this switch if support for watching
      // the local file system is added on those platforms.
      //
      // TODO(crbug.com/40260973): Report the affected
      // path on more platforms.
      .report_modified_path = true,
#endif  // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_WIN) ||
        // BUILDFLAG(IS_MAC)
  };

  watch_path_ = scope().root_url().path();
  // For file observations, we watch the parent directory so we can report file
  // deletes when the parent directory is deleted. This also helps prevent the
  // crswap move to its target file showing up as an appeared event.
  // Additionally, the watcher manager needs to know this info to be able to
  // convert that event to a modify.
  if (scope().GetWatchType() == FileSystemAccessWatchScope::WatchType::kFile) {
    watch_path_ = watch_path_.DirName();
  }
  watcher_.AsyncCall(&FilePathWatcher::WatchWithChangeInfo)
      .WithArgs(
          watch_path_, std::move(watch_options),
          base::BindPostTaskToCurrentDefault(std::move(on_change_callback)),
          base::BindPostTaskToCurrentDefault(
              std::move(on_usage_change_callback)))
      .Then(base::BindOnce(
          [](base::WeakPtr<FileSystemAccessLocalPathWatcher> self,
             base::OnceCallback<void(blink::mojom::FileSystemAccessErrorPtr)>
                 callback,
             std::optional<size_t> current_usage) {
            if (!current_usage.has_value()) {
              std::move(callback).Run(file_system_access_error::FromStatus(
                  blink::mojom::FileSystemAccessStatus::kOperationFailed));
              return;
            }

            self->current_usage_ = current_usage.value();
            std::move(callback).Run(file_system_access_error::Ok());
          },
          weak_factory_.GetWeakPtr(), std::move(on_source_initialized)));
}

size_t FileSystemAccessLocalPathWatcher::current_usage() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return current_usage_;
}

void FileSystemAccessLocalPathWatcher::OnFilePathChanged(
    const FilePathWatcher::ChangeInfo& change_info,
    const base::FilePath& changed_path,
    bool error) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // Notify if any error occurs without further processing.
  if (error) {
    NotifyOfChange(base::FilePath(), error, change_info);
    return;
  }

  const base::FilePath& root_path = scope().root_url().path();
  // File observations result in the parent directory being watched.
  if (scope().GetWatchType() == FileSystemAccessWatchScope::WatchType::kFile &&
      changed_path != root_path) {
    // This logic is a backup for when we don't get a delete event for the
    // `root_path`. When the parent is deleted, so is the file. We updated the
    // `change_info.modified_path` to the file's path and the
    // `change_info.file_path_type` to `kFile`. After reporting the file
    // deletion, we report an error because the parent directory has been
    // deleted. Eg. On macOS, we only receive a single deleted event, at the
    // parent directory level.
    if (changed_path == watch_path_ &&
        change_info.change_type == FilePathWatcher::ChangeType::kDeleted) {
      FilePathWatcher::ChangeInfo file_change_info = {
          FilePathWatcher::FilePathType::kFile,
          FilePathWatcher::ChangeType::kDeleted, root_path};
      NotifyOfChange(base::FilePath(), error, file_change_info);
    } else if (change_info.moved_from_path == root_path) {
      // If the file is renamed, we report a kDeleted event for the `root_path`.
      // If we were directly watching the file, this would be handled in the
      // FilePathWatcher which would convert the event to a kDeleted since
      // renaming a watched file is a move out of scope.
      FilePathWatcher::ChangeInfo file_change_info = {
          FilePathWatcher::FilePathType::kFile,
          FilePathWatcher::ChangeType::kDeleted, root_path};
      NotifyOfChange(base::FilePath(), error, file_change_info);
    }

    return;
  }

  base::FilePath relative_path;
  if (root_path.empty()) {
    relative_path = changed_path;
  } else if (root_path.IsParent(changed_path)) {
    CHECK(root_path.AppendRelativePath(changed_path, &relative_path));
  } else {
    // It is illegal for a source to notify of a change outside of its scope.
    CHECK_EQ(root_path, changed_path);
  }

  NotifyOfChange(relative_path, error, change_info);
}

void FileSystemAccessLocalPathWatcher::OnUsageChange(size_t old_usage,
                                                     size_t new_usage) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  CHECK_EQ(current_usage_, old_usage);
  if (new_usage == current_usage_) {
    return;
  }

  current_usage_ = new_usage;
  NotifyOfUsageChange(old_usage, new_usage);
}

}  // namespace content