Narrow to last message read when narrow is performed from streams drawer.

Author: Sam1301

app/src/main/java/com/zulip/android/activities/RecyclerMessageAdapter.java

@@ -422,7 +422,8 @@ public void onClick(View view) {
     @Override
     public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
         super.onViewRecycled(holder);
-        if (holder.getItemViewType() == VIEWTYPE_MESSAGE && !startedFromFilter)
+        if (holder.getItemViewType() == VIEWTYPE_MESSAGE)
+            // mark fields as read in homeview and streams narrow
             markThisMessageAsRead((Message) getItem(holder.getAdapterPosition()));
     }
 
@@ -434,7 +435,7 @@ public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
     private void markThisMessageAsRead(Message message) {
         try {
             int mID = message.getID();
-            if (zulipApp.getPointer() < mID) {
+            if (!startedFromFilter && zulipApp.getPointer() < mID) {
                 zulipApp.syncPointer(mID);
             }
 

app/src/main/java/com/zulip/android/activities/ZulipActivity.java

@@ -1203,7 +1203,7 @@ public boolean onChildClick(ExpandableListView parent, View v, int groupPosition
             public boolean onGroupClick(ExpandableListView expandableListView, View view, int position, long l) {
                 resetStreamSearch();
                 String streamName = ((TextView) view.findViewById(R.id.name)).getText().toString();
-                doNarrow(new NarrowFilterStream(streamName, null));
+                doNarrowToLastRead(streamName);
                 drawerLayout.openDrawer(GravityCompat.START);
                 if (previousClick != -1 && expandableListView.getCount() > previousClick) {
                     expandableListView.collapseGroup(previousClick);
@@ -1232,7 +1232,7 @@ public boolean setViewValue(View view, Cursor cursor, int columnIndex) {
                             @Override
                             public void onClick(View v) {
                                 resetStreamSearch();
-                                onNarrow(new NarrowFilterStream(streamName, null));
+                                doNarrowToLastRead(streamName);
                                 onNarrowFillSendBoxStream(streamName, "", false);
                             }
                         });
@@ -1277,6 +1277,24 @@ public void onClick(View v) {
         streamsDrawer.setAdapter(streamsDrawerAdapter);
     }
 
+    /**
+     * Helper function used to call {@link ZulipActivity#onNarrow(NarrowFilter, int)} or
+     * {@link ZulipActivity#onNarrow(NarrowFilter)} based on last message read in {@param streamName} stream.
+     *
+     * @param streamName stream name
+     */
+    private void doNarrowToLastRead(String streamName) {
+        // get last message read in stream
+        Message message = Stream.getLastMessageRead(app, streamName);
+        if (message != null) {
+            // fetch results around the last message read
+            onNarrow(new NarrowFilterStream(streamName, null), message.getId());
+        } else {
+            // new stream
+            onNarrow(new NarrowFilterStream(streamName, null));
+        }
+    }
+
     /**
      * Change streamsDrawerAdapter cursor to default
      * Clear text of etSearchStream
@@ -1878,7 +1896,7 @@ public void onNarrowFillSendBoxStream(String stream, String subject, boolean ope
     }
 
     public void onNarrow(NarrowFilter narrowFilter) {
-        // TODO: check if already narrowed to this particular stream/subject
+        if (narrowedList == null || narrowFilter != narrowedList.filter)
         doNarrow(narrowFilter);
     }
 

app/src/main/java/com/zulip/android/models/Stream.java

@@ -218,5 +218,25 @@ public void setFetchColor(String fetchedColor) {
 
     public void setInHomeView(boolean inHomeView) {
         this.inHomeView = inHomeView;
+
+    /**
+     * This function returns the last message read in {@param streamName} stream.
+     *
+     * @param app {@link ZulipApp}
+     * @param streamName name of stream
+     * @return last message {@link Message} read
+     */
+    public static Message getLastMessageRead(ZulipApp app, String streamName) {
+        try {
+            Dao<Message, Integer> messageDao = app.getDatabaseHelper().getDao(Message.class);
+
+            // query for message in given stream and orderby timestamp decreasingly
+            return messageDao.queryBuilder().orderBy(Message.TIMESTAMP_FIELD, false)
+                    .where().eq(Message.RECIPIENTS_FIELD, new SelectArg(Message.RECIPIENTS_FIELD, streamName))
+                    .queryForFirst();
+        } catch (SQLException e) {
+            ZLog.logException(e);
+        }
+        return null;
     }
 }