[Offline] Adding archiver interface

components/offline_pages/offline_page_archiver.h

Index: components/offline_pages/offline_page_archiver.h
diff --git a/components/offline_pages/offline_page_archiver.h b/components/offline_pages/offline_page_archiver.h
new file mode 100644
index 0000000000000000000000000000000000000000..c12bef8c2a9b5619e95cef2d8f3559e666f3f4c8
--- /dev/null
+++ b/components/offline_pages/offline_page_archiver.h
@@ -0,0 +1,64 @@
+// 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.
+class OfflinePageArchiver {
+ public:
+  // Represents an in progress request to archive a page.
+  class Request {
+   public:
+    explicit Request(const GURL& url);

[Dmitry Titov, 2015/06/12 18:09:11]

It's better to leave just an interface here, without ctor, all abstract, no data
members. Then, implement actual Request as static class in a corresponding .cc
file that will define OfflinePageArchiverImpl.
This way, details of implementation of Request are hidden and there is no
question about who can create one etc. For example, it might have a pointer to
some internal data structure of Archiver and pull url form there, etc.

[fgorski, 2015/06/12 20:37:34]

Done.

+    virtual ~Request();
+
+    // Cancels an in progress request to archive a page.
+    virtual void Cancel() = 0;
+    const GURL& url() const { return url_; }
+
+   private:
+    GURL url_;
+  };
+
+  // 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, because device is full.
+    ERROR_CANCELLED,    // Caller cancelled the request.
+  };
+
+  // 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,
+                                        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;
+
+   protected:

[Dmitry Titov, 2015/06/12 18:09:11]

No need to have this ctor here. It is only needed if you also add DISALLO..
macro here, since defining a private copy ctor (by macros) will prevent compiler
from generating a default ctor.
In general, doing all that in a pure abstract class does not make a lot of sense
- it's better to keep the interface clean.

[fgorski, 2015/06/12 20:37:34]

Done.

+    Client();
+  };
+
+  OfflinePageArchiver();

[Dmitry Titov, 2015/06/12 18:09:11]

This ctor can be omitted.

[fgorski, 2015/06/12 20:37:34]

Done.

+  virtual ~OfflinePageArchiver();
+
+  // Starts creating the archive. Will pass result by calling methods on the
+  // passed in client. Caller owns the returned request object.

[Dmitry Titov, 2015/06/12 18:09:11]

This needs to say what happens to ongoing archiving operation if the Request is
deleted by the caller. Archiver impl will need a test for it.

[fgorski, 2015/06/12 20:37:34]

Done.

+  virtual scoped_ptr<Request> CreateArchive(const GURL& url,

[Dmitry Titov, 2015/06/12 18:09:11]

Need a comment of what happens if the same URL is used when:
- archive already exists on disk because of previously finished operation
- there is another archiving operation still in progress
- there is no currently open WebContents with specified url
- there is a WebContents but the tab with it was killed by OS (as discovered by
Archiver when this call is received)
- the WebContent exists but it is still loading (main or other resources)

[fgorski, 2015/06/12 20:37:34]

Archiver comes up with a name for the archive that is valid and not used.
Archiver should be capable to start multiple requests in parallel.
Model should make a proper request. This is outside of scope of archiver.
Added ArchiverError::ERROR_CONTENT_UNAVAILABLE
Same error as above
Operation will take long. On success we proceed, on canceled navigation, see
above.

+                                            Client* client) = 0;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ARCHIVER_H_