Introduce the PlatformNotificationContext class.

content/browser/notifications/platform_notification_context.cc

+// Copyright 2015 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 "content/browser/notifications/platform_notification_context.h"
+
+#include "base/threading/sequenced_worker_pool.h"
+#include "content/browser/notifications/notification_database.h"
+#include "content/browser/notifications/notification_database_data.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+// Name of the directory in the user's profile directory where the notification
+// database files should be stored.
+const base::FilePath::CharType kPlatformNotificationsDirectory[] =
+    FILE_PATH_LITERAL("Platform Notifications");
+
+PlatformNotificationContext::PlatformNotificationContext(
+    const base::FilePath& path)
+    : path_(path),
+      next_notification_id_(0) {
+}
+
+PlatformNotificationContext::~PlatformNotificationContext() {
+  // If the database has been initialized, it must be deleted on the task runner
+  // thread as closing it may cause file I/O.
+  if (database_) {
+    DCHECK(task_runner_);
+    task_runner_->DeleteSoon(FROM_HERE, database_.release());
+  }
+}
+
+void PlatformNotificationContext::ReadNotificationData(
+    int64_t notification_id,
+    const GURL& origin,
+    const ReadResultCallback& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  LazyInitialize(
+       base::Bind(&PlatformNotificationContext::DoReadNotificationData,
+                  this, notification_id, origin, callback),
+       base::Bind(callback, false /* success */, NotificationDatabaseData()));
+}
+
+void PlatformNotificationContext::DoReadNotificationData(
+    int64_t notification_id,
+    const GURL& origin,
+    const ReadResultCallback& callback) {
+  NotificationDatabaseData database_data;

[Bernhard Bauer, 2015/03/13 16:51:18]

DCHECK you're on the right thread? (Also below)

[Peter Beverloo, 2015/03/13 16:57:07]

All the public methods in database_ have the appropriate DCHECKs as the very
first line in their implementation.

[Bernhard Bauer, 2015/03/13 17:24:01]

Those do, but there are also methods like LazyInitialize, and in general DCHECKs
also serve as documentation about which method runs on which thread (which you
diligently explain in the header, but that's distant as well).

[Peter Beverloo, 2015/03/13 20:43:30]

Done.

+  NotificationDatabase::Status status =
+      database_->ReadNotificationData(notification_id,
+                                      origin,
+                                      &database_data);
+
+  if (status == NotificationDatabase::STATUS_OK) {
+    BrowserThread::PostTask(BrowserThread::IO,
+                            FROM_HERE,
+                            base::Bind(callback,
+                                       true /* success */,
+                                       database_data));
+    return;
+  }
+
+  // TODO(peter): Record UMA on |status| for reading from the database.
+  // TODO(peter): Do the DeleteAndStartOver dance for STATUS_ERROR_CORRUPTED.
+
+  BrowserThread::PostTask(
+      BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(callback, false /* success */, NotificationDatabaseData()));
+}
+
+void PlatformNotificationContext::WriteNotificationData(
+    const GURL& origin,
+    const NotificationDatabaseData& database_data,
+    const WriteResultCallback& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  LazyInitialize(
+       base::Bind(&PlatformNotificationContext::DoWriteNotificationData,
+                  this, origin, database_data, callback),
+       base::Bind(callback, false /* success */, 0 /* notification_id */));
+}
+
+void PlatformNotificationContext::DoWriteNotificationData(
+    const GURL& origin,
+    const NotificationDatabaseData& database_data,
+    const WriteResultCallback& callback) {
+  int64_t notification_id = next_notification_id_++;
+  NotificationDatabase::Status status =
+      database_->WriteNotificationData(notification_id,
+                                       origin,
+                                       database_data);
+
+  if (status == NotificationDatabase::STATUS_OK) {
+    BrowserThread::PostTask(BrowserThread::IO,
+                            FROM_HERE,
+                            base::Bind(callback,
+                                       true /* success */,
+                                       notification_id));
+    return;
+  }
+
+  // TODO(peter): Record UMA on |status| for reading from the database.
+  // TODO(peter): Do the DeleteAndStartOver dance for STATUS_ERROR_CORRUPTED.
+
+  BrowserThread::PostTask(
+      BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(callback, false /* success */, 0 /* notification_id */));
+}
+
+void PlatformNotificationContext::LazyInitialize(
+    const base::Closure& success_closure,
+    const base::Closure& failure_closure) {
+  if (!task_runner_) {
+    base::SequencedWorkerPool* pool = BrowserThread::GetBlockingPool();
+    base::SequencedWorkerPool::SequenceToken token = pool->GetSequenceToken();
+
+    task_runner_ = pool->GetSequencedTaskRunner(token);
+  }
+
+  if (!database_) {
+    database_.reset(new NotificationDatabase(GetDatabasePath()));
+
+    task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&PlatformNotificationContext::OpenDatabase,
+                   this, success_closure, failure_closure));
+    return;
+  }
+
+  task_runner_->PostTask(FROM_HERE, success_closure);
+}
+
+void PlatformNotificationContext::OpenDatabase(
+    const base::Closure& success_closure,
+    const base::Closure& failure_closure) {
+  DCHECK(database_);
+
+  // TODO(peter): Record UMA on |status| for opening the database.
+  NotificationDatabase::Status status =
+      database_->Open(true /* create_if_missing */);
+
+  if (status == NotificationDatabase::STATUS_OK) {
+    status = database_->GetNextNotificationId(&next_notification_id_);
+    if (status == NotificationDatabase::STATUS_OK) {
+      success_closure.Run();
+      return;
+    }
+  }
+
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE, failure_closure);
+}
+
+base::FilePath PlatformNotificationContext::GetDatabasePath() const {
+  if (path_.empty())
+    return path_;
+
+  return path_.Append(kPlatformNotificationsDirectory);
+}
+
+void PlatformNotificationContext::SetTaskRunnerForTesting(
+    scoped_refptr<base::SequencedTaskRunner> task_runner) {
+  task_runner_ = task_runner;
+}
+
+}  // namespace content