text: // Copyright 2016 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_OFFLINE_PAGES_RECENT_TAB_HELPER_H_
  #define CHROME_BROWSER_OFFLINE_PAGES_RECENT_TAB_HELPER_H_
  
  #include <memory>
  #include <vector>
  
  #include "base/memory/weak_ptr.h"
  #include "components/offline_pages/core/offline_page_model.h"
  #include "components/offline_pages/core/snapshot_controller.h"
  #include "content/public/browser/web_contents_observer.h"
  #include "content/public/browser/web_contents_user_data.h"
  #include "url/gurl.h"
  
  namespace content {
  class NavigationHandle;
  }
  
  namespace offline_pages {
  
  // Attaches to every WebContent shown in a tab. Waits until the WebContent is
  // loaded to proper degree and then makes a snapshot of the page. Removes the
  // oldest snapshot in the 'ring buffer'. As a result, there is always up to N
  // snapshots of recent pages on the device.
  class RecentTabHelper
      : public content::WebContentsObserver,
        public content::WebContentsUserData<RecentTabHelper>,
        public SnapshotController::Client {
   public:
    ~RecentTabHelper() override;
  
    // content::WebContentsObserver
    void DidFinishNavigation(
        content::NavigationHandle* navigation_handle) override;
    void DocumentAvailableInMainFrame() override;
    void DocumentOnLoadCompletedInMainFrame() override;
    void WebContentsDestroyed() override;
    void OnVisibilityChanged(content::Visibility visibility) override;
  
    // Notifies that the tab of the associated WebContents will (most probably) be
    // closed. This call is expected to always happen before the one to WasHidden.
    void WillCloseTab();
  
    // SnapshotController::Client
    void StartSnapshot() override;
    void RunRenovations() override;
  
    // Delegate that is used by RecentTabHelper to get external dependencies.
    // Default implementation lives in .cc file, while tests provide an override.
    class Delegate {
     public:
      virtual ~Delegate() {}
      virtual std::unique_ptr<OfflinePageArchiver> CreatePageArchiver(
          content::WebContents* web_contents) = 0;
      // There is no expectations that tab_id is always present.
      virtual bool GetTabId(content::WebContents* web_contents, int* tab_id) = 0;
      virtual bool IsLowEndDevice() = 0;
      virtual bool IsCustomTab(content::WebContents* web_contents) = 0;
    };
    void SetDelegate(std::unique_ptr<RecentTabHelper::Delegate> delegate);
  
    // Creates a request to download the current page with a properly filled
    // |client_id| and valid |request_id| issued by RequestCoordinator from a
    // suspended request. This method might be called multiple times for the same
    // page at any point after its navigation commits. There are some important
    // points about how requests are handled:
    // a) While there is an ongoing request, new requests are ignored (no
    //    overlapping snapshots).
    // b) The page has to be sufficiently loaded to be considerer of minimum
    //    quality for the request to be started immediately.
    // c) Any calls made before the page is considered to have minimal quality
    //    will be scheduled to be executed once that happens. The scheduled
    //    request is considered "ongoing" for a) purposes.
    // d) If the save operation is successful the dormant request with
    //    RequestCoordinator is canceled; otherwise it is resumed. This logic is
    //    robust to crashes.
    // e) At the moment the page reaches high quality, if there was a successful
    //    snapshot saved at a lower quality then a new snapshot is automatically
    //    requested to replace it.
    // Note #1: Page quality is determined by SnapshotController and is based on
    // its assessment of "how much loaded" it is.
    // Note #2: Currently this method only accepts download requests from the
    // downloads namespace.
    void ObserveAndDownloadCurrentPage(const ClientId& client_id,
                                       int64_t request_id,
                                       const std::string& origin);
  
   private:
    struct SnapshotProgressInfo;
  
    explicit RecentTabHelper(content::WebContents* web_contents);
    friend class content::WebContentsUserData<RecentTabHelper>;
  
    void WebContentsWasHidden();
    void WebContentsWasShown();
  
    bool EnsureInitialized();
    void ContinueSnapshotWithIdsToPurge(SnapshotProgressInfo* snapshot_info,
                                        const std::vector<int64_t>& page_ids);
    void ContinueSnapshotAfterPurge(SnapshotProgressInfo* snapshot_info,
                                    OfflinePageModel::DeletePageResult result);
    void SavePageCallback(SnapshotProgressInfo* snapshot_info,
                          OfflinePageModel::SavePageResult result,
                          int64_t offline_id);
    void ReportSnapshotCompleted(SnapshotProgressInfo* snapshot_info,
                                 bool success);
    void ReportDownloadStatusToRequestCoordinator(
        SnapshotProgressInfo* snapshot_info,
        bool cancel_background_request);
    ClientId GetRecentPagesClientId() const;
    void SaveSnapshotForDownloads(bool replace_latest);
    void CancelInFlightSnapshots();
  
    // Page model is a service, no ownership. Can be null - for example, in
    // case when tab is in incognito profile.
    OfflinePageModel* page_model_ = nullptr;
  
    // If false, never make snapshots off the attached WebContents.
    // Not page-specific.
    bool snapshots_enabled_ = false;
  
    // Snapshot progress information for an ongoing snapshot requested by
    // downloads. Null if there's no ongoing request.
    std::unique_ptr<SnapshotProgressInfo> downloads_ongoing_snapshot_info_;
  
    // This is set to true if the ongoing snapshot for downloads is waiting on the
    // page to reach a minimal quality level to start.
    bool downloads_snapshot_on_hold_ = false;
  
    // Snapshot information for the last successful snapshot requested by
    // downloads. Null if no successful one has ever completed for the current
    // page.
    std::unique_ptr<SnapshotProgressInfo> downloads_latest_saved_snapshot_info_;
  
    // Snapshot progress information for a last_n triggered request. Null if
    // last_n is not currently capturing the current page. It is cleared upon non
    // ignored navigations.
    std::unique_ptr<SnapshotProgressInfo> last_n_ongoing_snapshot_info_;
  
    // Snapshot information for the last successful snapshot requested by
    // last_n. Null if no successful one has ever completed for the current page.
    // It is cleared when the referenced snapshot is deleted.
    std::unique_ptr<SnapshotProgressInfo> last_n_latest_saved_snapshot_info_;
  
    // If empty, the tab does not have AndroidId and can not capture pages.
    std::string tab_id_;
  
    // Monitors page loads and starts snapshots when a download request exist. It
    // is also used as an initialization flag for EnsureInitialized() to be run
    // only once.
    std::unique_ptr<SnapshotController> snapshot_controller_;
  
    std::unique_ptr<Delegate> delegate_;
  
    // Set at each navigation to control if last_n should save snapshots of the
    // current page being loaded.
    bool last_n_listen_to_tab_hidden_ = false;
  
    // Set to true when the tab containing the associated WebContents is in the
    // process of being closed.
    bool tab_is_closing_ = false;
  
    base::WeakPtrFactory<RecentTabHelper> weak_ptr_factory_;
  
    DISALLOW_COPY_AND_ASSIGN(RecentTabHelper);
  };
  
  }  // namespace offline_pages
  
  #endif  // CHROME_BROWSER_OFFLINE_PAGES_RECENT_TAB_HELPER_H_
  