Second try at splitting WebDataService (minus ownership changes)

chrome/browser/webdata/web_database_service.cc

Index: chrome/browser/webdata/web_database_service.cc
diff --git a/chrome/browser/webdata/web_database_service.cc b/chrome/browser/webdata/web_database_service.cc
new file mode 100644
index 0000000000000000000000000000000000000000..543d9ba05fa40f25b06bd159b801af713a11a04e
--- /dev/null
+++ b/chrome/browser/webdata/web_database_service.cc
@@ -0,0 +1,262 @@
+// Copyright 2013 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/webdata/web_database_service.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "chrome/browser/api/webdata/web_data_results.h"
+#include "chrome/browser/api/webdata/web_data_service_consumer.h"
+#include "chrome/browser/webdata/web_data_request_manager.h"
+#include "chrome/browser/webdata/web_data_service.h"
+// TODO(caitkp): Remove this autofill dependency.
+#include "components/autofill/browser/autofill_country.h"
+
+using base::Bind;
+using base::FilePath;
+using content::BrowserThread;
+
+
+////////////////////////////////////////////////////////////////////////////////
+//
+// WebDataServiceBackend implementation.
+//
+////////////////////////////////////////////////////////////////////////////////
+
+// Refcounted to allow asynchronous destruction on the DB thread.
+class WebDataServiceBackend
+    : public base::RefCountedThreadSafe<WebDataServiceBackend,
+                                        BrowserThread::DeleteOnDBThread> {
+ public:
+  explicit WebDataServiceBackend(const FilePath& path);
+
+  // Initializes the database and notifies caller via callback when complete.
+  // Callback is called synchronously.
+  void InitDatabaseWithCallback(
+      const WebDatabaseService::InitCallback& callback);
+
+  // Opens the database file from the profile path if an init has not yet been
+  // attempted. Separated from the constructor to ease construction/destruction
+  // of this object on one thread but database access on the DB thread. Returns
+  // the status of the database.
+  sql::InitStatus LoadDatabaseIfNecessary();
+
+  // Shuts down database. |should_reinit| tells us whether or not it should be
+  // possible to re-initialize the DB after the shutdown.
+  void ShutdownDatabase(bool should_reinit);
+
+  // Task wrappers to run database tasks.
+  void DBWriteTaskWrapper(
+      const WebDatabaseService::WriteTask& task,
+      scoped_ptr<WebDataRequest> request);
+  void DBReadTaskWrapper(
+      const WebDatabaseService::ReadTask& task,
+      scoped_ptr<WebDataRequest> request);
+
+  const scoped_refptr<WebDataRequestManager>& request_manager() {
+    return request_manager_;
+  }
+
+  WebDatabase* database() { return db_.get(); }
+
+ private:
+  friend struct BrowserThread::DeleteOnThread<BrowserThread::DB>;
+  friend class base::DeleteHelper<WebDataServiceBackend>;
+
+  virtual ~WebDataServiceBackend();
+
+  // Commit the current transaction.
+  void Commit();
+
+  // Path to database file.
+  FilePath db_path_;
+
+  scoped_ptr<WebDatabase> db_;
+
+  // Keeps track of all pending requests made to the db.
+  scoped_refptr<WebDataRequestManager> request_manager_;
+
+  // State of database initialization. Used to prevent the executing of tasks
+  // before the db is ready.
+  sql::InitStatus init_status_;
+
+  // True if an attempt has been made to load the database (even if the attempt
+  // fails), used to avoid continually trying to reinit if the db init fails.
+  bool init_complete_;
+
+  // The application locale.  The locale is needed for some database migrations,
+  // and must be read on the UI thread.  It's cached here so that we can pass it
+  // to the migration code on the DB thread.
+  const std::string app_locale_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebDataServiceBackend);
+};
+
+WebDataServiceBackend::WebDataServiceBackend(const FilePath& path)
+    : db_path_(path),
+      request_manager_(new WebDataRequestManager()),
+      init_status_(sql::INIT_FAILURE),
+      init_complete_(false),
+      app_locale_(AutofillCountry::ApplicationLocale()) {
+}
+
+void WebDataServiceBackend::InitDatabaseWithCallback(
+    const WebDatabaseService::InitCallback& callback) {
+  if (!callback.is_null()) {
+    callback.Run(LoadDatabaseIfNecessary());
+  }
+}
+
+sql::InitStatus WebDataServiceBackend::LoadDatabaseIfNecessary() {
+  if (init_complete_ || db_path_.empty()) {
+    return init_status_;
+  }
+  init_complete_ = true;
+  db_.reset(new WebDatabase());
+  init_status_ = db_->Init(db_path_, app_locale_);
+  if (init_status_ != sql::INIT_OK) {
+    LOG(ERROR) << "Cannot initialize the web database: " << init_status_;
+    db_.reset(NULL);
+    return init_status_;
+  }
+
+  db_->BeginTransaction();
+  return init_status_;
+}
+
+void WebDataServiceBackend::ShutdownDatabase(bool should_reinit) {
+  if (db_ && init_status_ == sql::INIT_OK)
+    db_->CommitTransaction();
+  db_.reset(NULL);
+  init_complete_ = !should_reinit; // Setting init_complete_ to true will ensure
+  // that the init sequence is not re-run.
+
+  init_status_ = sql::INIT_FAILURE;
+}
+
+void WebDataServiceBackend::DBWriteTaskWrapper(
+    const WebDatabaseService::WriteTask& task,
+    scoped_ptr<WebDataRequest> request) {
+  LoadDatabaseIfNecessary();
+  if (db_ && init_status_ == sql::INIT_OK && !request->IsCancelled()) {
+    WebDatabase::State state = task.Run(db_.get());
+    if (state == WebDatabase::COMMIT_NEEDED)
+      Commit();
+  }
+  request_manager_->RequestCompleted(request.Pass());
+}
+
+void WebDataServiceBackend::DBReadTaskWrapper(
+    const WebDatabaseService::ReadTask& task,
+    scoped_ptr<WebDataRequest> request) {
+  LoadDatabaseIfNecessary();
+  if (db_ && init_status_ == sql::INIT_OK && !request->IsCancelled()) {
+    request->SetResult(task.Run(db_.get()).Pass());
+  }
+  request_manager_->RequestCompleted(request.Pass());
+}
+
+WebDataServiceBackend::~WebDataServiceBackend() {
+  ShutdownDatabase(false);
+}
+
+void WebDataServiceBackend::Commit() {
+  if (db_ && init_status_ == sql::INIT_OK) {
+    db_->CommitTransaction();
+    db_->BeginTransaction();
+  } else {
+    NOTREACHED() << "Commit scheduled after Shutdown()";
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+WebDatabaseService::WebDatabaseService(const base::FilePath& path)
+    : path_(path) {
+  // WebDatabaseService should be instantiated on UI thread.
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  // WebDatabaseService requires DB thread if instantiated.
+  DCHECK(BrowserThread::IsWellKnownThread(BrowserThread::DB));
+}
+
+WebDatabaseService::~WebDatabaseService() {
+}
+
+void WebDatabaseService::LoadDatabase(const InitCallback& callback) {
+  if (!wds_backend_)
+    wds_backend_ = new WebDataServiceBackend(path_);
+
+  BrowserThread::PostTask(
+      BrowserThread::DB,
+      FROM_HERE,
+      Bind(&WebDataServiceBackend::InitDatabaseWithCallback,
+           wds_backend_, callback));
+}
+
+void WebDatabaseService::UnloadDatabase() {
+  if (!wds_backend_)
+    return;
+  BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
+      Bind(&WebDataServiceBackend::ShutdownDatabase,
+           wds_backend_, true));
+}
+
+void WebDatabaseService::ShutdownDatabase() {
+  if (!wds_backend_)
+    return;
+  BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
+      Bind(&WebDataServiceBackend::ShutdownDatabase,
+           wds_backend_, false));
+}
+
+WebDatabase* WebDatabaseService::GetDatabaseOnDB() const {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::DB));
+  if (!wds_backend_)
+    return NULL;
+  return wds_backend_->database();
+}
+
+void WebDatabaseService::ScheduleDBTask(
+    const tracked_objects::Location& from_here,
+    const WriteTask& task) {
+  if (!wds_backend_) {
+    NOTREACHED() << "Task scheduled after Shutdown()";
+    return;
+  }
+
+  scoped_ptr<WebDataRequest> request(
+      new WebDataRequest(NULL, wds_backend_->request_manager()));
+
+  BrowserThread::PostTask(BrowserThread::DB, from_here,
+      Bind(&WebDataServiceBackend::DBWriteTaskWrapper, wds_backend_,
+           task, base::Passed(&request)));
+}
+
+WebDataService::Handle WebDatabaseService::ScheduleDBTaskWithResult(
+    const tracked_objects::Location& from_here,
+    const ReadTask& task,
+    WebDataServiceConsumer* consumer) {
+  DCHECK(consumer);
+  WebDataService::Handle handle = 0;
+
+  if (!wds_backend_) {
+    NOTREACHED() << "Task scheduled after Shutdown()";
+    return handle;
+  }
+
+  scoped_ptr<WebDataRequest> request(
+      new WebDataRequest(consumer, wds_backend_->request_manager()));
+  handle = request->GetHandle();
+
+  BrowserThread::PostTask(BrowserThread::DB, from_here,
+      Bind(&WebDataServiceBackend::DBReadTaskWrapper, wds_backend_,
+           task, base::Passed(&request)));
+
+  return handle;
+}
+
+void WebDatabaseService::CancelRequest(WebDataServiceBase::Handle h) {
+  if (!wds_backend_)
+    return;
+  wds_backend_->request_manager()->CancelRequest(h);
+}