[iOS Clean] Created OverlayService.

ios/clean/chrome/browser/ui/overlays/overlay_scheduler.h

+// Copyright 2017 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 IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_OVERLAY_SCHEDULER_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_OVERLAY_SCHEDULER_H_
+
+#include <Foundation/Foundation.h>
+#include <list>
+
+#import "ios/chrome/browser/web_state_list/web_state_list_observer.h"
+#import "ios/clean/chrome/browser/ui/overlays/overlay_queue_observer.h"
+#import "ios/shared/chrome/browser/ui/browser_list/browser_user_data.h"
+
+@class BrowserCoordinator;
+@protocol OverlayPresentationCommands;
+@protocol TabGridCommands;
+
+namespace web {
+class WebState;
+}
+
+// An object that manages scheduling when overlays from various OverlayQueues
+// can be started.  If an OverlayQueue requires a WebState's content area to be
+// visible, this class will update the WebStateLists's active WebState.
+class OverlayScheduler : public BrowserUserData<OverlayScheduler>,
+                         public OverlayQueueObserver,
+                         public WebStateListObserver {
+ public:
+  ~OverlayScheduler() override;
+
+  // Starts or stops observing |browser_|'s WebStateList and OverlayQueues.
+  void StartObservingBrowser();
+  void StopObservingBrowser();
+
+  // Whether a scheduled overlay is currently being shown.
+  bool IsShowingOverlay() const;
+
+  // Replaces the currently visible overlay with |overlay_coordinator|.
+  void ReplaceVisibleOverlay(BrowserCoordinator* overlay_coordinator);
+
+  // Cancels all scheduled overlays and empties overlay queues.
+  void CancelOverlays();
+
+ private:
+  friend class BrowserUserData<OverlayScheduler>;
+  // The Browser for which this object is scheduling overlays.
+  Browser* browser_;
+  // Whether the sheduler is currently observing |browser_|'s WebStateList and
+  // OverlayQueues.
+  bool observing_;
+  // The OverlayQueues that have queued overlays.  After an overlay is stopped,
+  // the first queue is popped and the first ovelay in the next queue is
+  // started.
+  std::list<OverlayQueue*> overlay_queues_;
+
+  // Private constructor used by factory method.
+  explicit OverlayScheduler(Browser* browser);
+
+  // OverlayQueueObserver:
+  void OverlayQueueDidAddOverlay(OverlayQueue* queue) override;
+  void OverlayQueueWillReplaceVisibleOverlay(OverlayQueue* queue) override;
+  void OverlayQueueDidStopVisibleOverlay(OverlayQueue* queue) override;
+  void OverlayQueueDidCancelOverlays(OverlayQueue* queue) override;
+
+  // WebStateListObserver:
+  void WebStateInsertedAt(WebStateList* web_state_list,
+                          web::WebState* web_state,
+                          int index) override;
+  void WebStateDetachedAt(WebStateList* web_state_list,
+                          web::WebState* web_state,
+                          int index) override;
+
+  // Attempts to show the next queued overlay.
+  void TryToStartNextOverlay();
+  // Starts observing |web_state_list|.  Also starts observing the OverlayQueue
+  // for each WebState in the list.
+  void StartObservingWebStateList(WebStateList* web_state_list);
+  // Stops observing |web_state_list| and the OverlayQueues for each WebState in
+  // the list.  Also cancels any queues overlays.
+  void StopObservingWebStateList(WebStateList* web_state_list);
+  // Lazily creates an OverlayQueue for |web_state| and starts observing it.
+  void StartObservingQueueForWebState(web::WebState* web_state);
+  // Cancels the overlays in |web_state|'s OverlayQueue and stops observing it.
+  void StopObservingQueueForWebState(web::WebState* web_state);
+};
+
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_OVERLAY_SCHEDULER_H_