// Copyright (c) 2011 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 CHROME_BROWSER_UI_WEBUI_NTP_MOST_VISITED_HANDLER_H_
#define CHROME_BROWSER_UI_WEBUI_NTP_MOST_VISITED_HANDLER_H_
#pragma once

#include <string>
#include <vector>

#include "chrome/browser/history/history_types.h"
#include "content/browser/cancelable_request.h"
#include "content/browser/webui/web_ui.h"
#include "content/common/notification_observer.h"
#include "content/common/notification_registrar.h"

class GURL;
class PageUsageData;
class PrefService;

namespace base {
class ListValue;
class Value;
}

// The handler for Javascript messages related to the "most visited" view.
//
// This class manages two preferences:
// - The URL blacklist: URLs we do not want to show in the thumbnails list.  It
//   is a dictionary for quick access (it associates a dummy boolean to the URL
//   string).
// - Pinned URLs: This is a dictionary for the pinned URLs for the the most
//   visited part of the new tab page. The key of the dictionary is a hash of
//   the URL and the value is a dictionary with title, url and index.  This is
//   owned by the PrefService.
class MostVisitedHandler : public WebUIMessageHandler,
                           public NotificationObserver {
 public:

  MostVisitedHandler();
  virtual ~MostVisitedHandler();

  // WebUIMessageHandler override and implementation.
  virtual WebUIMessageHandler* Attach(WebUI* web_ui) OVERRIDE;
  virtual void RegisterMessages() OVERRIDE;

  // Callback for the "getMostVisited" message.
  void HandleGetMostVisited(const base::ListValue* args);

  // Callback for the "blacklistURLFromMostVisited" message.
  void HandleBlacklistURL(const base::ListValue* args);

  // Callback for the "removeURLsFromMostVisitedBlacklist" message.
  void HandleRemoveURLsFromBlacklist(const base::ListValue* args);

  // Callback for the "clearMostVisitedURLsBlacklist" message.
  void HandleClearBlacklist(const base::ListValue* args);

  // Callback for the "addPinnedURL" message.
  void HandleAddPinnedURL(const base::ListValue* args);

  // Callback for the "removePinnedURL" message.
  void HandleRemovePinnedURL(const base::ListValue* args);

  // NotificationObserver implementation.
  virtual void Observe(int type,
                       const NotificationSource& source,
                       const NotificationDetails& details) OVERRIDE;

  const std::vector<GURL>& most_visited_urls() const {
    return most_visited_urls_;
  }

  static void RegisterUserPrefs(PrefService* prefs);

 private:
  struct MostVisitedPage;

  // Send a request to the HistoryService to get the most visited pages.
  void StartQueryForMostVisited();

  // Sets pages_value_ from a format produced by TopSites.
  void SetPagesValueFromTopSites(const history::MostVisitedURLList& data);

  // Callback for TopSites.
  void OnMostVisitedURLsAvailable(const history::MostVisitedURLList& data);

  // Puts the passed URL in the blacklist (so it does not show as a thumbnail).
  void BlacklistURL(const GURL& url);

  // Returns the key used in url_blacklist_ and pinned_urls_ for the passed
  // |url|.
  std::string GetDictionaryKeyForURL(const std::string& url);

  // Gets the page data for a pinned URL at a given index. This returns
  // true if found.
  bool GetPinnedURLAtIndex(int index, MostVisitedPage* page);

  void AddPinnedURL(const MostVisitedPage& page, int index);
  void RemovePinnedURL(const GURL& url);

  // Sends pages_value_ to the javascript side to and resets page_value_.
  void SendPagesValue();

  NotificationRegistrar registrar_;

  // Our consumer for the history service.
  CancelableRequestConsumerTSimple<PageUsageData*> cancelable_consumer_;
  CancelableRequestConsumer topsites_consumer_;

  // The most visited URLs, in priority order.
  // Only used for matching up clicks on the page to which most visited entry
  // was clicked on for metrics purposes.
  std::vector<GURL> most_visited_urls_;

  // We pre-fetch the first set of result pages.  This variable is false until
  // we get the first getMostVisited() call.
  bool got_first_most_visited_request_;

  // Keep the results of the db query here.
  scoped_ptr<base::ListValue> pages_value_;

  DISALLOW_COPY_AND_ASSIGN(MostVisitedHandler);
};

#endif  // CHROME_BROWSER_UI_WEBUI_NTP_MOST_VISITED_HANDLER_H_