[Offline] Adding archiver interface

components/offline_pages/offline_page_archiver.h

+// 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.
+
+#ifndef COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ARCHIVER_H_
+#define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ARCHIVER_H_
+
+#include "base/files/file_path.h"
+#include "url/gurl.h"
+
+namespace offline_pages {
+
+// Interface of a class responsible for creation of the archive for offline use.
+//
+// Archiver will be implemented by embedder and may have additional methods that
+// are not interesting from the perspective of OfflinePageModel. Example of such
+// extra information or capability is a way to enumerate available WebContents
+// to find the one that needs to be used to create archive (or to map it to the
+// URL passed in CreateArchive in some other way).
+//
+// Archiver will be responsible for naming the file that is being save (it has

[Dmitry Titov, 2015/06/15 21:55:42]

save -> saved

[fgorski, 2015/06/16 15:18:38]

Done.

+// URL, title and the whole page content at it's disposal). For that it should
+// be also configured with the path where the archives are stored.
+//
+// Archiver should be able archive multiple pages in parallel, as these are

[Dmitry Titov, 2015/06/15 21:55:42]

able -> able to

[fgorski, 2015/06/16 15:18:38]

Done.

+// asynchronous calls carried out by some other component.
+//
+// If archiver get two consecutive requests to archive the same page (may be run

[Dmitry Titov, 2015/06/15 21:55:42]

get -> gets

[fgorski, 2015/06/16 15:18:38]

Done.

+// in parallel) it can generate 2 different names for files and save the same
+// page separately, as if these were 2 completely unrelated pages. It is up to
+// the caller (e.g. OfflinePageModel) to make sure that situation like that does
+// not happen.
+//
+// If the page is not completely loaded, it is up to the implemetnation of the

[Dmitry Titov, 2015/06/15 21:55:42]

type: implemetnation

[fgorski, 2015/06/16 15:18:38]

Done.

+// archiver whether to respond with ERROR_CONTENT_UNAVAILBLE, wait longer to
+// actually snapshot a complete page, or snapshot whatever is available at that
+// point in time (what the uses sees).

[Dmitry Titov, 2015/06/15 21:55:42]

uses -> user

[fgorski, 2015/06/16 15:18:38]

Done.

+//
+// TODO(fgorski): Add ability to delete archive.
+// TODO(fgorski): Add ability to check that archive exists.
+// TODO(fgorski): Add ability to refresh an existing archive in one step.
+// TODO(fgorski): Add ability to identify all of the archives in the directory,
+// to enable to model to reconcile the archives.
+class OfflinePageArchiver {
+ public:
+  // Represents an in progress request to archive a page.
+  class Request {
+   public:
+    virtual ~Request() {}
+
+    // Cancels an in progress request to archive a page.
+    virtual void Cancel() = 0;
+    virtual const GURL& url() const = 0;
+  };
+
+  // Errors that will be reported when archive creation fails.
+  enum ArchiveError {
+    ERROR_UNKNOWN,              // Don't know what went wrong.
+    ERROR_DEVICE_FULL,          // Cannot save the archive - device is full.
+    ERROR_CANCELLED,            // Caller cancelled the request.
+    ERROR_CONTENT_UNAVAILABLE,  // Content to archive is not available.
+  };
+
+  // Interface of the clients that requests to archive pages.
+  class Client {
+   public:
+    virtual ~Client() {}
+
+    // Callback called by the archiver upon successful creation of the archive.
+    virtual void OnCreateArchiveSuccess(Request* request,

[Dmitry Titov, 2015/06/15 22:30:03]

Additional comment: consider merging both callbacks and adding a new value to
ArchiveError (SUCCESSFULLY_CREATED?) and renaming ArchiveError into
ArchiveResult...

[fgorski, 2015/06/16 15:18:38]

Done.

+                                        const base::FilePath& file_path) = 0;
+    // Callback called by the archiver when it fails to create the archive.
+    virtual void OnCreateArchiveFailure(Request* request,
+                                        ArchiveError error) = 0;
+  };
+
+  virtual ~OfflinePageArchiver() {}
+
+  // Starts creating the archive. Will pass result by calling methods on the
+  // passed in client. Caller owns the returned request object.
+  // If request is deleted during the archiving, the callback will not be
+  // invoked. The archive might however be created.
+  virtual scoped_ptr<Request> CreateArchive(const GURL& url,
+                                            Client* client) = 0;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ARCHIVER_H_