Modularize Compact Language Detector 2 (CLD2) data sources

components/translate/content/renderer/renderer_cld_data_provider.h

+// Copyright 2014 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_TRANSLATE_CONTENT_RENDERER_RENDERER_CLD_DATA_PROVIDER_H_
+#define COMPONENTS_TRANSLATE_CONTENT_RENDERER_RENDERER_CLD_DATA_PROVIDER_H_
+
+#include "base/callback.h"
+#include "ipc/ipc_listener.h"
+
+namespace IPC {
+class Message;
+}
+
+namespace content {
+class RenderViewObserver;
+}
+
+namespace translate {
+
+// Renderer-side interface responsible for providing CLD data.
+// The implementation must be paired with a browser-side implementation of
+// the BrowserCldDataProvider class:
+//
+//   components/translate/content/browser/browser_cld_data_provider.h
+//
+// ... and the glue between them is typically a pair of request/response IPC
+// messages using the CldDataProviderMsgStart IPCMessageStart enumerated
+// constant from ipc_message_start.h
+class RendererCldDataProvider : public IPC::Listener {
+ public:
+  virtual ~RendererCldDataProvider() {}
+
+  // (Inherited from IPC::Listener)
+  // If the specified message is a response for CLD data, attempts to
+  // initialize CLD2 and returns true in all cases. If initialization is
+  // successful and a callback has been configured via
+  // SetCldAvailableCallback(...), that callback is invoked from the message
+  // loop thread.
+  // This method is defined as virtual in order to force the implementation to
+  // define the specific IPC message(s) that it handles.
+  virtual bool OnMessageReceived(const IPC::Message&) = 0;
+
+  // Invoked by the renderer process to request that CLD data be obtained and
+  // that CLD be initialized with it. The implementation is expected to
+  // communicate with the paired BrowserCldDataProvider implementation on the
+  // browser side.
+  // This method must be invoked on the message loop thread.
+  virtual void SendCldDataRequest() = 0;
+
+  // Convenience method that tracks whether or not CLD data is available.
+  // This method can be used in the absence of a callback (i.e., if the caller
+  // wants a simple way to check the state of CLD data availability without
+  // keeping a separate boolean flag tripped by a callback).
+  virtual bool IsCldDataAvailable() = 0;
+
+  // Sets a callback that will be invoked when CLD data is successfully
+  // obtained from the paired BrowserCldDataProvider implementation on the
+  // browser side, after CLD has been successfully initialized.
+  // Both the initialization of CLD2 as well as the invocation of the callback
+  // must happen on the message loop thread.
+  virtual void SetCldAvailableCallback(base::Callback<void(void)>) = 0;
+};
+
+// Static factory function defined by the implementation that produces a new
+// provider for the specified render view host.
+RendererCldDataProvider* CreateRendererCldDataProviderFor(
+    content::RenderViewObserver*);
+
+}  // namespace translate
+
+#endif  // COMPONENTS_TRANSLATE_CONTENT_RENDERER_RENDERER_CLD_DATAP_PROVIDER_H_