feat(fcm): Updated code for setting Notification Count parameter in AndroidNotification class (#309)

* Enforce positive integer for the notification count parameter

* Update code comments

Author: knocknarea

src/main/java/com/google/firebase/messaging/AndroidNotification.java

@@ -119,7 +119,7 @@ public class AndroidNotification {
           .put(Priority.HIGH, "PRIORITY_HIGH")
           .put(Priority.MAX, "PRIORITY_MAX")
           .build();
-
+  
   private AndroidNotification(Builder builder) {
     this.title = builder.title;
     this.body = builder.body;
@@ -150,7 +150,7 @@ private AndroidNotification(Builder builder) {
       this.titleLocArgs = null;
     }
     this.channelId = builder.channelId;
-    this.image = builder.image;
+    this.image = builder.image;    
     this.ticker = builder.ticker;
     this.sticky = builder.sticky;
     this.eventTime = builder.eventTime;
@@ -174,6 +174,10 @@ private AndroidNotification(Builder builder) {
     } else {
       this.visibility = null;
     }
+    if (builder.notificationCount != null) {
+      checkArgument(builder.notificationCount >= 0, 
+          "notificationCount if specified must be zero or positive valued");
+    }
     this.notificationCount = builder.notificationCount;
   }
 
@@ -220,6 +224,7 @@ public static class Builder {
     private List<String> titleLocArgs = new ArrayList<>();
     private String channelId;
     private String image;
+    private Integer notificationCount;
     private String ticker;
     private Boolean sticky;
     private String eventTime;
@@ -231,7 +236,6 @@ public static class Builder {
     private LightSettings lightSettings;
     private Boolean defaultLightSettings;
     private Visibility visibility;
-    private Integer notificationCount;
 
     private Builder() {}
 
@@ -580,13 +584,15 @@ public Builder setVisibility(Visibility visibility) {
 
     /**
      * Sets the number of items this notification represents. May be displayed as a badge 
-     * count for launchers that support badging. For example, this might be useful if you're 
-     * using just one notification to represent multiple new messages but you want the count 
-     * here to represent the number of total new messages. If zero or unspecified, systems 
-     * that support badging use the default, which is to increment a number displayed on 
+     * count for launchers that support badging. 
+     * If not invoked then notification count is left unchanged.
+     * For example, this might be useful if you're using just one notification to represent
+     * multiple new messages but you want the count here to represent the number of total
+     * new messages. If zero or unspecified, systems that support badging use the default, 
+     * which is to increment a number displayed on 
      * the long-press menu each time a new notification arrives.
      *
-     * @param notificationCount The notification count
+     * @param notificationCount Zero or positive value. Zero indicates leave unchanged.
      * @return This builder.
      */
     public Builder setNotificationCount(int notificationCount) {

src/test/java/com/google/firebase/messaging/MessageTest.java

@@ -167,6 +167,7 @@ public void testAndroidMessageWithNotification() throws IOException {
                 .addBodyLocalizationArg("body-arg1")
                 .addAllBodyLocalizationArgs(ImmutableList.of("body-arg2", "body-arg3"))
                 .setChannelId("channel-id")
+                .setNotificationCount(4)
                 .build())
             .build())
         .setTopic("test-topic")
@@ -184,6 +185,10 @@ public void testAndroidMessageWithNotification() throws IOException {
         .put("body_loc_key", "body-loc")
         .put("body_loc_args", ImmutableList.of("body-arg1", "body-arg2", "body-arg3"))
         .put("channel_id", "channel-id")
+        // There is a problem with the JsonParser assignment to BigDecimal takes priority over
+        // all other number types and so this integer value is interpreted as a BigDecimal 
+        // rather than an Integer.
+        .put("notification_count", BigDecimal.valueOf(4L))
         .build();
     Map<String, Object> data = ImmutableMap.of(
         "collapse_key", "test-key",
@@ -195,6 +200,11 @@ public void testAndroidMessageWithNotification() throws IOException {
     assertJsonEquals(ImmutableMap.of("topic", "test-topic", "android", data), message);
   }
 
+  @Test(expected = IllegalArgumentException.class)
+  public void testAndroidNotificationWithNegativeCount() throws IllegalArgumentException {
+    AndroidNotification.builder().setNotificationCount(-1).build();
+  }
+  
   @Test
   public void testAndroidMessageWithoutLocalization() throws IOException {
     Message message = Message.builder()