[Android O] Refactor channel definitions into new class

chrome/android/java/src/org/chromium/chrome/browser/notifications/ChannelDefinitions.java

 // 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.
 
 package org.chromium.chrome.browser.notifications;
 
 import android.annotation.TargetApi;
 import android.app.NotificationManager;
 import android.os.Build;
 import android.support.annotation.StringDef;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Set;
 
 /**
- * Initializes our notification channels.
+ * Defines the properties of all notification channels we post notifications to in Android O+.
+ *
+ * PLEASE NOTE, notification channels appear in system UI and are persisted forever by Android,
+ * so should not be added or removed lightly, and the proper deprecation and versioning steps must
+ * be taken when doing so. Please read the comments and speak to one of this file's OWNERs when
+ * adding/removing a channel.
  */
-public class ChannelsInitializer {
+public class ChannelDefinitions {
+    public static final String CHANNEL_ID_BROWSER = "browser";
+    public static final String CHANNEL_ID_DOWNLOADS = "downloads";
+    public static final String CHANNEL_ID_INCOGNITO = "incognito";
+    public static final String CHANNEL_ID_MEDIA = "media";
+    public static final String CHANNEL_ID_SITES = "sites";
+    static final String CHANNEL_GROUP_ID_GENERAL = "general";
     /**
      * Version number identifying the current set of channels. This must be incremented whenever
      * any channels are added or removed from the set of channels created in
-     * {@link ChannelsInitializer#initializeStartupChannels()}
+     * {@link ChannelsInitializer#initializeStartupChannels()}.
      */
     static final int CHANNELS_VERSION = 0;
 
     // To define a new channel, add the channel ID to this StringDef and add a new entry to
     // PredefinedChannels.MAP below with the appropriate channel parameters.
     @StringDef({CHANNEL_ID_BROWSER, CHANNEL_ID_DOWNLOADS, CHANNEL_ID_INCOGNITO, CHANNEL_ID_MEDIA,
             CHANNEL_ID_SITES})
     @Retention(RetentionPolicy.SOURCE)
     public @interface ChannelId {}
-    public static final String CHANNEL_ID_BROWSER = "browser";
-    public static final String CHANNEL_ID_DOWNLOADS = "downloads";
-    public static final String CHANNEL_ID_INCOGNITO = "incognito";
-    public static final String CHANNEL_ID_MEDIA = "media";
-    public static final String CHANNEL_ID_SITES = "sites";
 
     @StringDef({CHANNEL_GROUP_ID_GENERAL})
     @Retention(RetentionPolicy.SOURCE)
-    private @interface ChannelGroupId {}
-    static final String CHANNEL_GROUP_ID_GENERAL = "general";
+    @interface ChannelGroupId {}
 
     // Map defined in static inner class so it's only initialized lazily.
     @TargetApi(Build.VERSION_CODES.N) // for NotificationManager.IMPORTANCE_* constants
     private static class PredefinedChannels {
         /**
          * The set of predefined channels to be initialized on startup. CHANNELS_VERSION must be
          * incremented every time an entry is modified, removed or added to this map.
          */
-        private static final Map<String, Channel> MAP;
+        static final Map<String, Channel> MAP;
         static {
             Map<String, Channel> map = new HashMap<>();
             map.put(CHANNEL_ID_BROWSER,
                     new Channel(CHANNEL_ID_BROWSER,
                             org.chromium.chrome.R.string.notification_category_browser,
                             NotificationManager.IMPORTANCE_LOW, CHANNEL_GROUP_ID_GENERAL));
             map.put(CHANNEL_ID_DOWNLOADS,
                     new Channel(CHANNEL_ID_DOWNLOADS,
                             org.chromium.chrome.R.string.notification_category_downloads,
                             NotificationManager.IMPORTANCE_LOW, CHANNEL_GROUP_ID_GENERAL));
             map.put(CHANNEL_ID_INCOGNITO,
                     new Channel(CHANNEL_ID_INCOGNITO,
                             org.chromium.chrome.R.string.notification_category_incognito,
                             NotificationManager.IMPORTANCE_LOW, CHANNEL_GROUP_ID_GENERAL));
             map.put(CHANNEL_ID_MEDIA,
                     new Channel(CHANNEL_ID_MEDIA,
                             org.chromium.chrome.R.string.notification_category_media,
                             NotificationManager.IMPORTANCE_LOW, CHANNEL_GROUP_ID_GENERAL));
             map.put(CHANNEL_ID_SITES,
                     new Channel(CHANNEL_ID_SITES,
                             org.chromium.chrome.R.string.notification_category_sites,
                             NotificationManager.IMPORTANCE_DEFAULT, CHANNEL_GROUP_ID_GENERAL));
             MAP = Collections.unmodifiableMap(map);
         }
     }
 
     // Map defined in static inner class so it's only initialized lazily.
     private static class PredefinedChannelGroups {
-        private static final Map<String, ChannelGroup> MAP;
+        static final Map<String, ChannelGroup> MAP;
         static {
             Map<String, ChannelGroup> map = new HashMap<>();
             map.put(CHANNEL_GROUP_ID_GENERAL,
                     new ChannelGroup(CHANNEL_GROUP_ID_GENERAL,
                             org.chromium.chrome.R.string.notification_category_group_general));
             MAP = Collections.unmodifiableMap(map);
         }
     }
 
-    private final NotificationManagerProxy mNotificationManager;
-
-    public ChannelsInitializer(NotificationManagerProxy notificationManagerProxy) {
-        mNotificationManager = notificationManagerProxy;
+    Set<String> getStartupChannelIds() {
+        // CHANNELS_VERSION must be incremented if the set of channels returned here changes.
+        return PredefinedChannels.MAP.keySet();
     }
 
-    public void initializeStartupChannels() {
-        // CHANNELS_VERSION must be incremented if the set of channels initialized here changes.
-        for (@ChannelId String channelId : PredefinedChannels.MAP.keySet()) {
-            ensureInitialized(channelId);
-        }
+    ChannelGroup getChannelGroupFromId(Channel channel) {
+        return PredefinedChannelGroups.MAP.get(channel.mGroupId);
     }
 
-    void deleteAllChannels() {
-        for (String channelId : mNotificationManager.getNotificationChannelIds()) {
-            mNotificationManager.deleteNotificationChannel(channelId);
-        }
+    Channel getChannelFromId(@ChannelId String channelId) {
+        return PredefinedChannels.MAP.get(channelId);
     }
 
     /**
-     * Ensures the given channel has been created on the notification manager so a notification
-     * can be safely posted to it. This should only be used for channels that are predefined in
-     * ChannelsInitializer.
-     *
-     * Calling this is a (potentially lengthy) no-op if the channel has already been created.
-     *
-     * @param channelId The ID of the channel to be initialized.
-     */
-    public void ensureInitialized(@ChannelId String channelId) {
-        if (!PredefinedChannels.MAP.containsKey(channelId)) {
-            throw new IllegalStateException("Could not initialize channel: " + channelId);
-        }
-        Channel channel = PredefinedChannels.MAP.get(channelId);
-        // Channel group must be created before the channel.
-        mNotificationManager.createNotificationChannelGroup(
-                PredefinedChannelGroups.MAP.get(channel.mGroupId));
-        mNotificationManager.createNotificationChannel(channel);
-    }
-
-    /**
      * Helper class containing notification channel properties.
      */
     public static class Channel {
         @ChannelId
         public final String mId;
         final int mNameResId;
         final int mImportance;
         @ChannelGroupId
         final String mGroupId;
 
@@ skipping 13 matching lines @@
         @ChannelGroupId
         final String mId;
         final int mNameResId;
 
         ChannelGroup(@ChannelGroupId String id, int nameResId) {
             this.mId = id;
             this.mNameResId = nameResId;
         }
     }
 }