[iOS Clean] Created OverlayService.

ios/clean/chrome/browser/ui/overlay_service/internal/overlay_queue.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_INTERNAL_OVERLAY_QUEUE_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_INTERNAL_OVERLAY_QUEUE_H_
+
+#import <Foundation/Foundation.h>
+
+#include "base/observer_list.h"
+#import "ios/clean/chrome/browser/ui/overlay_service/browser_coordinator+overlay_support.h"
+#import "ios/clean/chrome/browser/ui/overlay_service/internal/overlay_queue_observer.h"
+
+namespace web {
+class WebState;
+}
+
+// Class used to enqueue BrowserCoordinators.  It uses OverlayQueueObservers to
+// communicate changes in the queue.
+class OverlayQueue {
+ public:
+  virtual ~OverlayQueue();
+
+  // Adds and removes OverlayQueueObservers.
+  void AddObserver(OverlayQueueObserver* observer);
+  void RemoveObserver(OverlayQueueObserver* observer);
+
+  // Starts the next overlay in the queue.  If GetWebState() returns non-null,
+  // it is expected that its content area is visible before this is called.
+  virtual void StartNextOverlay() = 0;
+  // Called to notify the OverlayQueue that |overlay_coordinator| was stopped.
+  virtual void OverlayWasStopped(BrowserCoordinator* overlay_coordinator);
+  // Removes the currently displayed overlay and adds |overlay_coordinator| to
+  // the front of the queue to be displayed immediately.
+  virtual void ReplaceVisibleOverlay(BrowserCoordinator* overlay_coordinator);
+  // Returns whether there are any queued overlays.
+  bool HasQueuedOverlays() const;
+  // Returns whether an overlay is curently started.
+  bool IsShowingOverlay() const;
+  // Cancels all queued overlays for this queue.  If one is being displayed, it
+  // will also be stopped
+  void CancelOverlays();
+
+  // Some OverlayQueues require that a particular WebState's content area is
+  // visible before its queued BrowserCoordinators can be started.  If this
+  // queue's overlays require showing a WebState, this function will return that
+  // WebState.
+  virtual web::WebState* GetWebState() const;
+
+ protected:
+  // Adds |overlay_coordinator| to the queue and schedules its presentation.
+  void AddOverlay(BrowserCoordinator* overlay_coordinator);
+  // Returns the number of overlays in the queue.
+  NSUInteger GetCount() const;
+  // Returns the first BrowserCoordinator in the queue.
+  BrowserCoordinator* GetFirstOverlay();
+  // Called when the first overlay in the queue is started.
+  void OverlayWasStarted();
+  // Default constructor.
+  OverlayQueue();
+
+ private:
+  // The observers for this queue.
+  base::ObserverList<OverlayQueueObserver> observers_;
+  // The queue of overlays that were added for this WebState.
+  __strong NSMutableArray<BrowserCoordinator*>* overlays_;
+  // Whether an overlay is currently started.  If this is true, the first
+  // BrowserCoordinator in |overlays_| has been started.
+  bool showing_overlay_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverlayQueue);
+};
+
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_INTERNAL_OVERLAY_QUEUE_H_