Append late URLs at the end of the nearby URL list

chrome/android/java/src/org/chromium/chrome/browser/physicalweb/UrlManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/physicalweb/UrlManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/UrlManager.java b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/UrlManager.java
index 07b4dc23f5896e19961e0efc3cd25b64f711b128..d99a59de9f15ad84c5f2cf4bae447ef2e5ba9feb 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/UrlManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/UrlManager.java
@@ -20,12 +20,14 @@ import android.os.SystemClock;
 import android.support.v4.app.NotificationCompat;
 
 import org.chromium.base.Log;
+import org.chromium.base.ObserverList;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.notifications.NotificationConstants;
 import org.chromium.chrome.browser.notifications.NotificationManagerProxy;
 import org.chromium.chrome.browser.notifications.NotificationManagerProxyImpl;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -57,6 +59,19 @@ class UrlManager {
     private final Context mContext;
     private NotificationManagerProxy mNotificationManager;
     private PwsClient mPwsClient;
+    private final ObserverList<Listener> mObservers;
+
+    /**
+     * Interface for observers that should be notified when the nearby URL list changes.
+     */
+    public interface Listener {
+        /**
+         * Callback called when one or more URLs are added to the URL list.
+         * @param urls A set of strings containing nearby URLs resolvable with our resolution
+         * service.
+         */
+        void onDisplayableUrlsAdded(Collection<String> urls);
+    }
 
     /**
      * Construct the UrlManager.
@@ -67,6 +82,7 @@ class UrlManager {
         mNotificationManager = new NotificationManagerProxyImpl(
                 (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE));
         mPwsClient = new PwsClientImpl();
+        mObservers = new ObserverList<Listener>();
         initSharedPreferences();
     }
 
@@ -83,6 +99,22 @@ class UrlManager {
     }
 
     /**
+     * Add an observer to be notified on changes to the nearby URL list.
+     * @param observer The observer to add.
+     */
+    public void addObserver(Listener observer) {
+        mObservers.addObserver(observer);
+    }
+
+    /**
+     * Remove an observer from the observer list.
+     * @param observer The observer to remove.
+     */
+    public void removeObserver(Listener observer) {
+        mObservers.removeObserver(observer);
+    }
+
+    /**
      * Add a URL to the store of URLs.
      * This method additionally updates the Physical Web notification.
      * @param url The URL to add.
@@ -93,8 +125,21 @@ class UrlManager {
         boolean isOnboarding = PhysicalWeb.isOnboarding(mContext);
         Set<String> nearbyUrls = getCachedNearbyUrls();
 
-        boolean isUrlListEmptyBefore = (isOnboarding && nearbyUrls.isEmpty())
-                || (!isOnboarding && getUrls().isEmpty());
+        // A URL is displayable if it is both nearby and resolved through our resolution service.
+        // When new displayable URLs are found we tell our observers. In onboarding mode we do not
+        // use our resolution service so the displayable list should always be empty. However, we
+        // still want to track the nearby URL count so we can show an opt-in notification.
+        // In normal operation, both the notification and observers are updated for changes to the
+        // displayable list.
+
+        int displayableUrlsBefore;
+        int notificationUrlsBefore;
+        if (isOnboarding) {
+            displayableUrlsBefore = 0;
+            notificationUrlsBefore = nearbyUrls.size();
+        } else {
+            displayableUrlsBefore = notificationUrlsBefore = getUrls().size();
+        }
 
         nearbyUrls.add(url);
         putCachedNearbyUrls(nearbyUrls);
@@ -103,8 +148,17 @@ class UrlManager {
             resolveUrl(url);
         }
 
-        boolean isUrlListEmptyAfter = !isOnboarding && getUrls().isEmpty();
-        updateNotification(isUrlListEmptyBefore, isUrlListEmptyAfter);
+        int displayableUrlsAfter;
+        int notificationUrlsAfter;
+        if (isOnboarding) {
+            displayableUrlsAfter = 0;
+            notificationUrlsAfter = nearbyUrls.size();
+        } else {
+            displayableUrlsAfter = notificationUrlsAfter = getUrls().size();
+        }
+
+        updateNotification(notificationUrlsBefore == 0, notificationUrlsAfter == 0);
+        notifyDisplayableUrlsChanged(displayableUrlsBefore, displayableUrlsAfter, url);
     }
 
     /**
@@ -120,9 +174,8 @@ class UrlManager {
         nearbyUrls.remove(url);
         putCachedNearbyUrls(nearbyUrls);
 
-        boolean isUrlListEmptyAfter = (isOnboarding && nearbyUrls.isEmpty())
-                || (!isOnboarding && getUrls().isEmpty());
-        updateNotification(false, isUrlListEmptyAfter);
+        int notificationUrlsAfter = isOnboarding ? nearbyUrls.size() : getUrls().size();
+        updateNotification(false, notificationUrlsAfter == 0);
     }
 
     /**
@@ -177,11 +230,14 @@ class UrlManager {
     private void addResolvedUrl(String url) {
         Log.d(TAG, "PWS resolved: %s", url);
         Set<String> resolvedUrls = getCachedResolvedUrls();
-        boolean isUrlListEmptyBefore = getUrls().isEmpty();
+        int displayableUrlsBefore = getUrls().size();
 
         resolvedUrls.add(url);
         putCachedResolvedUrls(resolvedUrls);
-        updateNotification(isUrlListEmptyBefore, getUrls().isEmpty());
+
+        int displayableUrlsAfter = getUrls().size();
+        updateNotification(displayableUrlsBefore == 0, displayableUrlsAfter == 0);
+        notifyDisplayableUrlsChanged(displayableUrlsBefore, displayableUrlsAfter, url);
     }
 
     private void removeResolvedUrl(String url) {
@@ -377,6 +433,18 @@ class UrlManager {
         alarmManager.cancel(pendingIntent);
     }
 
+    private void notifyDisplayableUrlsChanged(int displayCountBefore, int displayCountAfter,
+            String url) {
+        if (displayCountAfter > displayCountBefore) {
+            Collection<String> urls = new ArrayList<String>();
+            urls.add(url);
+            Collection<String> wrappedUrls = Collections.unmodifiableCollection(urls);
+            for (Listener observer : mObservers) {
+                observer.onDisplayableUrlsAdded(wrappedUrls);
+            }
+        }
+    }
+
     @VisibleForTesting
     void overridePwsClientForTesting(PwsClient pwsClient) {
         mPwsClient = pwsClient;