// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/chromeos/drive/file_system.h"

#include "base/bind.h"
#include "base/file_util.h"
#include "base/platform_file.h"
#include "base/prefs/pref_service.h"
#include "chrome/browser/browser_process.h"
#include "chrome/browser/chromeos/drive/change_list_loader.h"
#include "chrome/browser/chromeos/drive/change_list_processor.h"
#include "chrome/browser/chromeos/drive/drive.pb.h"
#include "chrome/browser/chromeos/drive/file_cache.h"
#include "chrome/browser/chromeos/drive/file_system/copy_operation.h"
#include "chrome/browser/chromeos/drive/file_system/create_directory_operation.h"
#include "chrome/browser/chromeos/drive/file_system/create_file_operation.h"
#include "chrome/browser/chromeos/drive/file_system/download_operation.h"
#include "chrome/browser/chromeos/drive/file_system/get_file_for_saving_operation.h"
#include "chrome/browser/chromeos/drive/file_system/move_operation.h"
#include "chrome/browser/chromeos/drive/file_system/open_file_operation.h"
#include "chrome/browser/chromeos/drive/file_system/remove_operation.h"
#include "chrome/browser/chromeos/drive/file_system/search_operation.h"
#include "chrome/browser/chromeos/drive/file_system/touch_operation.h"
#include "chrome/browser/chromeos/drive/file_system/truncate_operation.h"
#include "chrome/browser/chromeos/drive/file_system/update_operation.h"
#include "chrome/browser/chromeos/drive/file_system_observer.h"
#include "chrome/browser/chromeos/drive/file_system_util.h"
#include "chrome/browser/chromeos/drive/job_scheduler.h"
#include "chrome/browser/chromeos/drive/logging.h"
#include "chrome/browser/chromeos/drive/remove_stale_cache_files.h"
#include "chrome/browser/chromeos/drive/resource_entry_conversion.h"
#include "chrome/browser/chromeos/drive/search_metadata.h"
#include "chrome/browser/chromeos/drive/sync_client.h"
#include "chrome/browser/drive/drive_service_interface.h"
#include "chrome/common/pref_names.h"
#include "content/public/browser/browser_thread.h"
#include "google_apis/drive/drive_api_parser.h"

using content::BrowserThread;

namespace drive {
namespace {

// Gets a ResourceEntry from the metadata, and overwrites its file info when the
// cached file is dirty.
FileError GetLocallyStoredResourceEntry(
    internal::ResourceMetadata* resource_metadata,
    internal::FileCache* cache,
    const base::FilePath& file_path,
    ResourceEntry* entry) {
  std::string local_id;
  FileError error = resource_metadata->GetIdByPath(file_path, &local_id);
  if (error != FILE_ERROR_OK)
    return error;

  error = resource_metadata->GetResourceEntryById(local_id, entry);
  if (error != FILE_ERROR_OK)
    return error;

  // For entries that will never be cached, use the original resource entry
  // as is.
  if (!entry->has_file_specific_info() ||
      entry->file_specific_info().is_hosted_document())
    return FILE_ERROR_OK;

  // When no dirty cache is found, use the original resource entry as is.
  FileCacheEntry cache_entry;
  if (!cache->GetCacheEntry(local_id, &cache_entry) || !cache_entry.is_dirty())
    return FILE_ERROR_OK;

  // If the cache is dirty, obtain the file info from the cache file itself.
  base::FilePath local_cache_path;
  error = cache->GetFile(local_id, &local_cache_path);
  if (error != FILE_ERROR_OK)
    return error;

  base::PlatformFileInfo file_info;
  if (!base::GetFileInfo(local_cache_path, &file_info))
    return FILE_ERROR_NOT_FOUND;

  SetPlatformFileInfoToResourceEntry(file_info, entry);
  return FILE_ERROR_OK;
}

// Runs the callback with parameters.
void RunGetResourceEntryCallback(const GetResourceEntryCallback& callback,
                                 scoped_ptr<ResourceEntry> entry,
                                 FileError error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error != FILE_ERROR_OK)
    entry.reset();
  callback.Run(error, entry.Pass());
}

// Used to implement Pin().
FileError PinInternal(internal::ResourceMetadata* resource_metadata,
                      internal::FileCache* cache,
                      const base::FilePath& file_path,
                      std::string* local_id) {
  FileError error = resource_metadata->GetIdByPath(file_path, local_id);
  if (error != FILE_ERROR_OK)
    return error;

  ResourceEntry entry;
  error = resource_metadata->GetResourceEntryById(*local_id, &entry);
  if (error != FILE_ERROR_OK)
    return error;

  // TODO(hashimoto): Support pinning directories. crbug.com/127831
  if (entry.file_info().is_directory())
    return FILE_ERROR_NOT_A_FILE;

  return cache->Pin(*local_id);
}

// Used to implement Unpin().
FileError UnpinInternal(internal::ResourceMetadata* resource_metadata,
                        internal::FileCache* cache,
                        const base::FilePath& file_path,
                        std::string* local_id) {
  FileError error = resource_metadata->GetIdByPath(file_path, local_id);
  if (error != FILE_ERROR_OK)
    return error;

  return cache->Unpin(*local_id);
}

// Used to implement MarkCacheFileAsMounted().
FileError MarkCacheFileAsMountedInternal(
    internal::ResourceMetadata* resource_metadata,
    internal::FileCache* cache,
    const base::FilePath& drive_file_path,
    base::FilePath* cache_file_path) {
  std::string local_id;
  FileError error = resource_metadata->GetIdByPath(drive_file_path, &local_id);
  if (error != FILE_ERROR_OK)
    return error;

  return cache->MarkAsMounted(local_id, cache_file_path);
}

// Runs the callback with arguments.
void RunMarkMountedCallback(const MarkMountedCallback& callback,
                            base::FilePath* cache_file_path,
                            FileError error) {
  DCHECK(!callback.is_null());
  callback.Run(error, *cache_file_path);
}

// Used to implement GetCacheEntry.
bool GetCacheEntryInternal(internal::ResourceMetadata* resource_metadata,
                                 internal::FileCache* cache,
                                 const base::FilePath& drive_file_path,
                                 FileCacheEntry* cache_entry) {
  std::string id;
  if (resource_metadata->GetIdByPath(drive_file_path, &id) != FILE_ERROR_OK)
    return false;

  return cache->GetCacheEntry(id, cache_entry);
}

// Runs the callback with arguments.
void RunGetCacheEntryCallback(const GetCacheEntryCallback& callback,
                              const FileCacheEntry* cache_entry,
                              bool success) {
  DCHECK(!callback.is_null());
  callback.Run(success, *cache_entry);
}

// Callback for ResourceMetadata::GetLargestChangestamp.
// |callback| must not be null.
void OnGetLargestChangestamp(
    FileSystemMetadata metadata,  // Will be modified.
    const GetFilesystemMetadataCallback& callback,
    int64 largest_changestamp) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  metadata.largest_changestamp = largest_changestamp;
  callback.Run(metadata);
}

// Thin adapter to map GetFileCallback to FileOperationCallback.
void GetFileCallbackToFileOperationCallbackAdapter(
    const FileOperationCallback& callback,
    FileError error,
    const base::FilePath& unused_file_path,
    scoped_ptr<ResourceEntry> unused_entry) {
  callback.Run(error);
}

// Clears |resource_metadata| and |cache|.
FileError ResetOnBlockingPool(internal::ResourceMetadata* resource_metadata,
                              internal::FileCache* cache) {
  FileError error = resource_metadata->Reset();
  if (error != FILE_ERROR_OK)
    return error;
 return cache->ClearAll() ? FILE_ERROR_OK : FILE_ERROR_FAILED;
}

}  // namespace

FileSystem::FileSystem(
    PrefService* pref_service,
    internal::FileCache* cache,
    DriveServiceInterface* drive_service,
    JobScheduler* scheduler,
    internal::ResourceMetadata* resource_metadata,
    base::SequencedTaskRunner* blocking_task_runner,
    const base::FilePath& temporary_file_directory)
    : pref_service_(pref_service),
      cache_(cache),
      drive_service_(drive_service),
      scheduler_(scheduler),
      resource_metadata_(resource_metadata),
      last_update_check_error_(FILE_ERROR_OK),
      blocking_task_runner_(blocking_task_runner),
      temporary_file_directory_(temporary_file_directory),
      weak_ptr_factory_(this) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  ResetComponents();
}

FileSystem::~FileSystem() {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  change_list_loader_->RemoveObserver(this);
}

void FileSystem::Reload(const FileOperationCallback& callback) {
  // Discard the current loader and operation objects and renew them. This is to
  // avoid that changes initiated before the metadata reset is applied after the
  // reset, which may cause an inconsistent state.
  // TODO(kinaba): callbacks held in the subcomponents are discarded. We might
  // want to have a way to abort and flush callbacks in in-flight operations.
  ResetComponents();

  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&ResetOnBlockingPool, resource_metadata_, cache_),
      base::Bind(&FileSystem::ReloadAfterReset,
                 weak_ptr_factory_.GetWeakPtr(),
                 callback));
}

void FileSystem::ReloadAfterReset(const FileOperationCallback& callback,
                                  FileError error) {
  if (error != FILE_ERROR_OK) {
    LOG(ERROR) << "Failed to reload Drive file system: "
               << FileErrorToString(error);
    callback.Run(error);
    return;
  }

  change_list_loader_->LoadIfNeeded(
      internal::DirectoryFetchInfo(),
      base::Bind(&FileSystem::OnUpdateChecked, weak_ptr_factory_.GetWeakPtr()));
  callback.Run(error);
}

void FileSystem::ResetComponents() {
  file_system::OperationObserver* observer = this;
  copy_operation_.reset(
      new file_system::CopyOperation(
          blocking_task_runner_.get(),
          observer,
          scheduler_,
          resource_metadata_,
          cache_,
          drive_service_->GetResourceIdCanonicalizer()));
  create_directory_operation_.reset(new file_system::CreateDirectoryOperation(
      blocking_task_runner_.get(), observer, scheduler_, resource_metadata_));
  create_file_operation_.reset(
      new file_system::CreateFileOperation(blocking_task_runner_.get(),
                                           observer,
                                           scheduler_,
                                           resource_metadata_,
                                           cache_));
  move_operation_.reset(
      new file_system::MoveOperation(blocking_task_runner_.get(),
                                     observer,
                                     resource_metadata_));
  open_file_operation_.reset(
      new file_system::OpenFileOperation(blocking_task_runner_.get(),
                                         observer,
                                         scheduler_,
                                         resource_metadata_,
                                         cache_,
                                         temporary_file_directory_));
  remove_operation_.reset(
      new file_system::RemoveOperation(blocking_task_runner_.get(),
                                       observer,
                                       resource_metadata_,
                                       cache_));
  touch_operation_.reset(new file_system::TouchOperation(
      blocking_task_runner_.get(), observer, resource_metadata_));
  truncate_operation_.reset(
      new file_system::TruncateOperation(blocking_task_runner_.get(),
                                         observer,
                                         scheduler_,
                                         resource_metadata_,
                                         cache_,
                                         temporary_file_directory_));
  download_operation_.reset(
      new file_system::DownloadOperation(blocking_task_runner_.get(),
                                         observer,
                                         scheduler_,
                                         resource_metadata_,
                                         cache_,
                                         temporary_file_directory_));
  update_operation_.reset(
      new file_system::UpdateOperation(blocking_task_runner_.get(),
                                       observer,
                                       scheduler_,
                                       resource_metadata_,
                                       cache_));
  search_operation_.reset(new file_system::SearchOperation(
      blocking_task_runner_.get(), scheduler_, resource_metadata_));
  get_file_for_saving_operation_.reset(
      new file_system::GetFileForSavingOperation(blocking_task_runner_.get(),
                                                 observer,
                                                 scheduler_,
                                                 resource_metadata_,
                                                 cache_,
                                                 temporary_file_directory_));

  sync_client_.reset(new internal::SyncClient(blocking_task_runner_.get(),
                                              observer,
                                              scheduler_,
                                              resource_metadata_,
                                              cache_,
                                              temporary_file_directory_));

  change_list_loader_.reset(new internal::ChangeListLoader(
      blocking_task_runner_.get(),
      resource_metadata_,
      scheduler_,
      drive_service_));
  change_list_loader_->AddObserver(this);
}

void FileSystem::CheckForUpdates() {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DVLOG(1) << "CheckForUpdates";

  change_list_loader_->CheckForUpdates(
      base::Bind(&FileSystem::OnUpdateChecked, weak_ptr_factory_.GetWeakPtr()));
}

void FileSystem::OnUpdateChecked(FileError error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DVLOG(1) << "CheckForUpdates finished: " << FileErrorToString(error);
  last_update_check_time_ = base::Time::Now();
  last_update_check_error_ = error;
}

void FileSystem::AddObserver(FileSystemObserver* observer) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  observers_.AddObserver(observer);
}

void FileSystem::RemoveObserver(FileSystemObserver* observer) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  observers_.RemoveObserver(observer);
}

void FileSystem::TransferFileFromLocalToRemote(
    const base::FilePath& local_src_file_path,
    const base::FilePath& remote_dest_file_path,
    const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());
  copy_operation_->TransferFileFromLocalToRemote(local_src_file_path,
                                                 remote_dest_file_path,
                                                 callback);
}

void FileSystem::Copy(const base::FilePath& src_file_path,
                      const base::FilePath& dest_file_path,
                      bool preserve_last_modified,
                      const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());
  copy_operation_->Copy(
      src_file_path, dest_file_path, preserve_last_modified, callback);
}

void FileSystem::Move(const base::FilePath& src_file_path,
                      const base::FilePath& dest_file_path,
                      bool preserve_last_modified,
                      const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());
  move_operation_->Move(
      src_file_path, dest_file_path, preserve_last_modified, callback);
}

void FileSystem::Remove(const base::FilePath& file_path,
                        bool is_recursive,
                        const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());
  remove_operation_->Remove(file_path, is_recursive, callback);
}

void FileSystem::CreateDirectory(
    const base::FilePath& directory_path,
    bool is_exclusive,
    bool is_recursive,
    const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  // Ensure its parent directory is loaded to the local metadata.
  LoadDirectoryIfNeeded(
      directory_path.DirName(),
      base::Bind(&FileSystem::CreateDirectoryAfterLoad,
                 weak_ptr_factory_.GetWeakPtr(),
                 directory_path, is_exclusive, is_recursive, callback));
}

void FileSystem::CreateDirectoryAfterLoad(
    const base::FilePath& directory_path,
    bool is_exclusive,
    bool is_recursive,
    const FileOperationCallback& callback,
    FileError load_error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  switch (load_error) {
    case FILE_ERROR_OK:
    case FILE_ERROR_NOT_FOUND:
      create_directory_operation_->CreateDirectory(
          directory_path, is_exclusive, is_recursive, callback);
      break;
    default:
      callback.Run(load_error);
  }
}

void FileSystem::CreateFile(const base::FilePath& file_path,
                            bool is_exclusive,
                            const std::string& mime_type,
                            const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());
  create_file_operation_->CreateFile(
      file_path, is_exclusive, mime_type, callback);
}

void FileSystem::TouchFile(const base::FilePath& file_path,
                           const base::Time& last_access_time,
                           const base::Time& last_modified_time,
                           const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!last_access_time.is_null());
  DCHECK(!last_modified_time.is_null());
  DCHECK(!callback.is_null());
  touch_operation_->TouchFile(
      file_path, last_access_time, last_modified_time, callback);
}

void FileSystem::TruncateFile(const base::FilePath& file_path,
                              int64 length,
                              const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());
  truncate_operation_->Truncate(file_path, length, callback);
}

void FileSystem::Pin(const base::FilePath& file_path,
                     const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  std::string* local_id = new std::string;
  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&PinInternal, resource_metadata_, cache_, file_path, local_id),
      base::Bind(&FileSystem::FinishPin,
                 weak_ptr_factory_.GetWeakPtr(),
                 callback,
                 base::Owned(local_id)));
}

void FileSystem::FinishPin(const FileOperationCallback& callback,
                           const std::string* local_id,
                           FileError error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error == FILE_ERROR_OK)
    sync_client_->AddFetchTask(*local_id);
  callback.Run(error);
}

void FileSystem::Unpin(const base::FilePath& file_path,
                       const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  std::string* local_id = new std::string;
  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&UnpinInternal,
                 resource_metadata_,
                 cache_,
                 file_path,
                 local_id),
      base::Bind(&FileSystem::FinishUnpin,
                 weak_ptr_factory_.GetWeakPtr(),
                 callback,
                 base::Owned(local_id)));
}

void FileSystem::FinishUnpin(const FileOperationCallback& callback,
                             const std::string* local_id,
                             FileError error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error == FILE_ERROR_OK)
    sync_client_->RemoveFetchTask(*local_id);
  callback.Run(error);
}

void FileSystem::GetFile(const base::FilePath& file_path,
                         const GetFileCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  download_operation_->EnsureFileDownloadedByPath(
      file_path,
      ClientContext(USER_INITIATED),
      GetFileContentInitializedCallback(),
      google_apis::GetContentCallback(),
      callback);
}

void FileSystem::GetFileForSaving(const base::FilePath& file_path,
                                  const GetFileCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  get_file_for_saving_operation_->GetFileForSaving(file_path, callback);
}

void FileSystem::GetFileContent(
    const base::FilePath& file_path,
    const GetFileContentInitializedCallback& initialized_callback,
    const google_apis::GetContentCallback& get_content_callback,
    const FileOperationCallback& completion_callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!initialized_callback.is_null());
  DCHECK(!get_content_callback.is_null());
  DCHECK(!completion_callback.is_null());

  download_operation_->EnsureFileDownloadedByPath(
      file_path,
      ClientContext(USER_INITIATED),
      initialized_callback,
      get_content_callback,
      base::Bind(&GetFileCallbackToFileOperationCallbackAdapter,
                 completion_callback));
}

void FileSystem::GetResourceEntry(
    const base::FilePath& file_path,
    const GetResourceEntryCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  scoped_ptr<ResourceEntry> entry(new ResourceEntry);
  ResourceEntry* entry_ptr = entry.get();
  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&GetLocallyStoredResourceEntry,
                 resource_metadata_,
                 cache_,
                 file_path,
                 entry_ptr),
      base::Bind(&FileSystem::GetResourceEntryAfterGetEntry,
                 weak_ptr_factory_.GetWeakPtr(),
                 file_path,
                 callback,
                 base::Passed(&entry)));
}

void FileSystem::GetResourceEntryAfterGetEntry(
    const base::FilePath& file_path,
    const GetResourceEntryCallback& callback,
    scoped_ptr<ResourceEntry> entry,
    FileError error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error == FILE_ERROR_NOT_FOUND) {
    // If the information about the path is not in the local ResourceMetadata,
    // try fetching information of the directory and retry.
    //
    // Note: this forms mutual recursion between GetResourceEntry and
    // LoadDirectoryIfNeeded, because directory loading requires the existence
    // of directory entry itself. The recursion terminates because we always go
    // up the hierarchy by .DirName() bounded under the Drive root path.
    if (util::GetDriveGrandRootPath().IsParent(file_path)) {
      LoadDirectoryIfNeeded(
          file_path.DirName(),
          base::Bind(&FileSystem::GetResourceEntryAfterLoad,
                     weak_ptr_factory_.GetWeakPtr(),
                     file_path,
                     callback));
      return;
    }
  }

  callback.Run(error, entry.Pass());
}

void FileSystem::GetResourceEntryAfterLoad(
    const base::FilePath& file_path,
    const GetResourceEntryCallback& callback,
    FileError error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error != FILE_ERROR_OK) {
    callback.Run(error, scoped_ptr<ResourceEntry>());
    return;
  }

  scoped_ptr<ResourceEntry> entry(new ResourceEntry);
  ResourceEntry* entry_ptr = entry.get();
  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&GetLocallyStoredResourceEntry,
                 resource_metadata_,
                 cache_,
                 file_path,
                 entry_ptr),
      base::Bind(&RunGetResourceEntryCallback,
                 callback,
                 base::Passed(&entry)));
}

void FileSystem::ReadDirectory(
    const base::FilePath& directory_path,
    const ReadDirectoryCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  LoadDirectoryIfNeeded(
      directory_path,
      base::Bind(&FileSystem::ReadDirectoryAfterLoad,
                 weak_ptr_factory_.GetWeakPtr(),
                 directory_path,
                 callback));
}

void FileSystem::LoadDirectoryIfNeeded(const base::FilePath& directory_path,
                                       const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  GetResourceEntry(
      directory_path,
      base::Bind(&FileSystem::LoadDirectoryIfNeededAfterGetEntry,
                 weak_ptr_factory_.GetWeakPtr(),
                 directory_path,
                 callback));
}

void FileSystem::LoadDirectoryIfNeededAfterGetEntry(
    const base::FilePath& directory_path,
    const FileOperationCallback& callback,
    FileError error,
    scoped_ptr<ResourceEntry> entry) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error != FILE_ERROR_OK) {
    callback.Run(error);
    return;
  }

  if (!entry->file_info().is_directory()) {
    callback.Run(FILE_ERROR_NOT_A_DIRECTORY);
    return;
  }

  // drive/other does not exist on the server.
  if (entry->local_id() == util::kDriveOtherDirLocalId) {
    callback.Run(FILE_ERROR_OK);
    return;
  }

  // Pass the directory fetch info so we can fetch the contents of the
  // directory before loading change lists.
  internal::DirectoryFetchInfo directory_fetch_info(
      entry->resource_id(),
      entry->directory_specific_info().changestamp());
  change_list_loader_->LoadIfNeeded(directory_fetch_info, callback);
}

void FileSystem::ReadDirectoryAfterLoad(
    const base::FilePath& directory_path,
    const ReadDirectoryCallback& callback,
    FileError error) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  DVLOG_IF(1, error != FILE_ERROR_OK) << "LoadIfNeeded failed. "
                                      << FileErrorToString(error);

  resource_metadata_->ReadDirectoryByPathOnUIThread(
      directory_path,
      base::Bind(&FileSystem::ReadDirectoryAfterRead,
                 weak_ptr_factory_.GetWeakPtr(),
                 directory_path,
                 callback));
}

void FileSystem::ReadDirectoryAfterRead(
    const base::FilePath& directory_path,
    const ReadDirectoryCallback& callback,
    FileError error,
    scoped_ptr<ResourceEntryVector> entries) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error != FILE_ERROR_OK) {
    callback.Run(error,
                 scoped_ptr<ResourceEntryVector>());
    return;
  }
  DCHECK(entries.get());  // This is valid for empty directories too.

  // TODO(satorux): Stop handling hide_hosted_docs here. crbug.com/256520.
  const bool hide_hosted_docs =
      pref_service_->GetBoolean(prefs::kDisableDriveHostedFiles);
  scoped_ptr<ResourceEntryVector> filtered(new ResourceEntryVector);
  for (size_t i = 0; i < entries->size(); ++i) {
    if (hide_hosted_docs &&
        entries->at(i).file_specific_info().is_hosted_document()) {
      continue;
    }
    filtered->push_back(entries->at(i));
  }

  callback.Run(FILE_ERROR_OK, filtered.Pass());
}

void FileSystem::GetAvailableSpace(
    const GetAvailableSpaceCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  change_list_loader_->GetAboutResource(
      base::Bind(&FileSystem::OnGetAboutResource,
                 weak_ptr_factory_.GetWeakPtr(),
                 callback));
}

void FileSystem::OnGetAboutResource(
    const GetAvailableSpaceCallback& callback,
    google_apis::GDataErrorCode status,
    scoped_ptr<google_apis::AboutResource> about_resource) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  FileError error = GDataToFileError(status);
  if (error != FILE_ERROR_OK) {
    callback.Run(error, -1, -1);
    return;
  }
  DCHECK(about_resource);

  callback.Run(FILE_ERROR_OK,
               about_resource->quota_bytes_total(),
               about_resource->quota_bytes_used());
}

void FileSystem::GetShareUrl(
    const base::FilePath& file_path,
    const GURL& embed_origin,
    const GetShareUrlCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  // Resolve the resource id.
  resource_metadata_->GetResourceEntryByPathOnUIThread(
      file_path,
      base::Bind(&FileSystem::GetShareUrlAfterGetResourceEntry,
                 weak_ptr_factory_.GetWeakPtr(),
                 file_path,
                 embed_origin,
                 callback));
}

void FileSystem::GetShareUrlAfterGetResourceEntry(
    const base::FilePath& file_path,
    const GURL& embed_origin,
    const GetShareUrlCallback& callback,
    FileError error,
    scoped_ptr<ResourceEntry> entry) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (error != FILE_ERROR_OK) {
    callback.Run(error, GURL());
    return;
  }
  if (util::IsSpecialResourceId(entry->resource_id())) {
    // Do not load special directories. Just return.
    callback.Run(FILE_ERROR_FAILED, GURL());
    return;
  }

  scheduler_->GetShareUrl(
      entry->resource_id(),
      embed_origin,
      ClientContext(USER_INITIATED),
      base::Bind(&FileSystem::OnGetResourceEntryForGetShareUrl,
                 weak_ptr_factory_.GetWeakPtr(),
                 callback));
}

void FileSystem::OnGetResourceEntryForGetShareUrl(
    const GetShareUrlCallback& callback,
    google_apis::GDataErrorCode status,
    const GURL& share_url) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  FileError error = GDataToFileError(status);
  if (error != FILE_ERROR_OK) {
    callback.Run(error, GURL());
    return;
  }

  if (share_url.is_empty()) {
    callback.Run(FILE_ERROR_FAILED, GURL());
    return;
  }

  callback.Run(FILE_ERROR_OK, share_url);
}

void FileSystem::Search(const std::string& search_query,
                        const GURL& next_link,
                        const SearchCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());
  search_operation_->Search(search_query, next_link, callback);
}

void FileSystem::SearchMetadata(const std::string& query,
                                int options,
                                int at_most_num_matches,
                                const SearchMetadataCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  // TODO(satorux): Stop handling hide_hosted_docs here. crbug.com/256520.
  if (pref_service_->GetBoolean(prefs::kDisableDriveHostedFiles))
    options |= SEARCH_METADATA_EXCLUDE_HOSTED_DOCUMENTS;

  drive::internal::SearchMetadata(blocking_task_runner_,
                                  resource_metadata_,
                                  query,
                                  options,
                                  at_most_num_matches,
                                  callback);
}

void FileSystem::OnDirectoryChangedByOperation(
    const base::FilePath& directory_path) {
  OnDirectoryChanged(directory_path);
}

void FileSystem::OnCacheFileUploadNeededByOperation(
    const std::string& local_id) {
  sync_client_->AddUploadTask(ClientContext(USER_INITIATED), local_id);
}

void FileSystem::OnEntryUpdatedByOperation(const std::string& local_id) {
  sync_client_->AddUpdateTask(local_id);
}

void FileSystem::OnDirectoryChanged(const base::FilePath& directory_path) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  FOR_EACH_OBSERVER(FileSystemObserver, observers_,
                    OnDirectoryChanged(directory_path));
}

void FileSystem::OnLoadFromServerComplete() {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  sync_client_->StartCheckingExistingPinnedFiles();
}

void FileSystem::OnInitialLoadComplete() {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  blocking_task_runner_->PostTask(FROM_HERE,
                                  base::Bind(&internal::RemoveStaleCacheFiles,
                                             cache_,
                                             resource_metadata_));
  sync_client_->StartProcessingBacklog();
}

void FileSystem::GetMetadata(
    const GetFilesystemMetadataCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  FileSystemMetadata metadata;
  metadata.refreshing = change_list_loader_->IsRefreshing();

  // Metadata related to delta update.
  metadata.last_update_check_time = last_update_check_time_;
  metadata.last_update_check_error = last_update_check_error_;

  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&internal::ResourceMetadata::GetLargestChangestamp,
                 base::Unretained(resource_metadata_)),
      base::Bind(&OnGetLargestChangestamp, metadata, callback));
}

void FileSystem::MarkCacheFileAsMounted(
    const base::FilePath& drive_file_path,
    const MarkMountedCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  base::FilePath* cache_file_path = new base::FilePath;
  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&MarkCacheFileAsMountedInternal,
                 resource_metadata_,
                 cache_,
                 drive_file_path,
                 cache_file_path),
      base::Bind(&RunMarkMountedCallback,
                 callback,
                 base::Owned(cache_file_path)));
}

void FileSystem::MarkCacheFileAsUnmounted(
    const base::FilePath& cache_file_path,
    const FileOperationCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  if (!cache_->IsUnderFileCacheDirectory(cache_file_path)) {
    callback.Run(FILE_ERROR_FAILED);
    return;
  }

  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&internal::FileCache::MarkAsUnmounted,
                 base::Unretained(cache_),
                 cache_file_path),
      callback);
}

void FileSystem::GetCacheEntry(
    const base::FilePath& drive_file_path,
    const GetCacheEntryCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  FileCacheEntry* cache_entry = new FileCacheEntry;
  base::PostTaskAndReplyWithResult(
      blocking_task_runner_,
      FROM_HERE,
      base::Bind(&GetCacheEntryInternal,
                 resource_metadata_,
                 cache_,
                 drive_file_path,
                 cache_entry),
      base::Bind(&RunGetCacheEntryCallback,
                 callback,
                 base::Owned(cache_entry)));
}

void FileSystem::OpenFile(const base::FilePath& file_path,
                          OpenMode open_mode,
                          const std::string& mime_type,
                          const OpenFileCallback& callback) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  DCHECK(!callback.is_null());

  open_file_operation_->OpenFile(file_path, open_mode, mime_type, callback);
}

}  // namespace drive