android notif: Parse pm_users in the "crunchy shell".

When we pass this on to our JS code after the user opens a
notification, that code will go and try to parse it.  Ensure up front,
here in our crunchy shell, that it will actually parse successfully.

A further good step would be to actually pass JS a list of ints,
rather than re-encode as a string.  That can be separate, though.

Author: gnprice

android/app/src/main/java/com/zulipmobile/notifications/FcmMessage.kt

@@ -49,10 +49,11 @@ internal sealed class Recipient {
     /**
      * A group PM.
      *
-     * pmUsers: the user IDs of all users in the conversation, sorted,
-     *     in ASCII decimal, comma-separated.
+     * pmUsers: the user IDs of all users in the conversation.
      */
-    data class GroupPm(val pmUsers: String) : Recipient()
+    data class GroupPm(val pmUsers: Set<Int>) : Recipient() {
+        fun getPmUsersString() = pmUsers.sorted().joinToString { toString() }
+    }
 
     /** A stream message. */
     data class Stream(val stream: String, val topic: String) : Recipient()
@@ -120,7 +121,7 @@ internal data class MessageFcmMessage(
             }
             is Recipient.GroupPm -> {
                 bundle.putString("recipient_type", "private")
-                bundle.putString("pm_users", recipient.pmUsers)
+                bundle.putString("pm_users", recipient.getPmUsersString())
             }
             is Recipient.Pm -> {
                 bundle.putString("recipient_type", "private")
@@ -157,8 +158,8 @@ internal data class MessageFcmMessage(
                         data.require("stream"),
                         data.require("topic"))
                 "private" ->
-                    data["pm_users"]?.let {
-                        Recipient.GroupPm(it)
+                    data["pm_users"]?.parseCommaSeparatedInts("pm_users")?.let {
+                        Recipient.GroupPm(it.toSet())
                     } ?: Recipient.Pm
                 else -> throw FcmMessageParseException("unexpected recipient_type: $recipientType")
             }

android/app/src/main/java/com/zulipmobile/notifications/NotificationHelper.java

@@ -96,7 +96,7 @@ private static String buildKeyString(MessageFcmMessage fcmMessage) {
                     ((Recipient.Stream) recipient).getStream());
         else if (recipient instanceof Recipient.GroupPm) {
             return String.format("%s:%s:group", fcmMessage.getSender().getFullName(),
-                    ((Recipient.GroupPm) recipient).getPmUsers());
+                    ((Recipient.GroupPm) recipient).getPmUsersString());
         } else {
             return String.format("%s:%s:private", fcmMessage.getSender().getFullName(),
                     fcmMessage.getSender().getEmail());

android/app/src/test/java/com/zulipmobile/notifications/FcmMessageTest.kt

@@ -121,7 +121,7 @@ class MessageFcmMessageTest : FcmMessageTestBase() {
             )
         )
         expect.that(parse(Example.groupPm).recipient).isEqualTo(
-            Recipient.GroupPm(pmUsers = Example.groupPm["pm_users"]!!)
+            Recipient.GroupPm(pmUsers = setOf(123, 234, 345))
         )
         expect.that(parse(Example.pm).recipient).isEqualTo(
             Recipient.Pm
@@ -151,6 +151,9 @@ class MessageFcmMessageTest : FcmMessageTestBase() {
         assertParseFails(Example.stream.minus("stream"))
         assertParseFails(Example.stream.minus("topic"))
         assertParseFails(Example.groupPm.minus("recipient_type"))
+        assertParseFails(Example.groupPm.plus("pm_users" to "abc,34"))
+        assertParseFails(Example.groupPm.plus("pm_users" to "12,abc"))
+        assertParseFails(Example.groupPm.plus("pm_users" to "12,"))
         assertParseFails(Example.pm.minus("recipient_type"))
         assertParseFails(Example.pm.plus("recipient_type" to "nonsense"))