recent_senders: Update data structures for stream/topic edits.

* Remove old topic and reprocess both old and new topic to ensure
that we are correctly storing the last_msg_id of users in the
topic. Also, Handle topic's stream (& topic) edit updates.
* Add function to get all messages in a topic in message_utils.js.
* Send topic edit event to recent_senders.
* Add func get sorted list of recent_senders to topic.
The function will be useful to handle topic edits in Recent Topic UI.

frontend_tests/node_tests/recent_senders.js

@@ -1,6 +1,16 @@
 const rs = zrequire('recent_senders');
 
 let next_id = 0;
+const messages = [];
+
+set_global('message_util', {
+    get_messages_in_topic: (stream_id, topic) => {
+        return messages.filter(x => {
+            return x.stream_id === stream_id &&
+                   x.topic.toLowerCase() === topic.toLowerCase();
+        });
+    },
+});
 
 run_test('process_message_for_senders', () => {
     const stream1 = 1;
@@ -10,10 +20,13 @@ run_test('process_message_for_senders', () => {
     const topic1 = "topic-1";
     const topic2 = "topic-2";
     const topic3 = "topic-3";
+    const topic4 = "topic-4";
 
     const sender1 = 1;
     const sender2 = 2;
     const sender3 = 3;
+    const stream4 = 4;
+    const stream5 = 5;
 
     // New stream
     const message1 = {
@@ -28,6 +41,8 @@ run_test('process_message_for_senders', () => {
         topic: topic1,
         sender_id: sender2,
     };
+    messages.push(message1, message2);
+
     rs.process_message_for_senders(message1);
     rs.process_message_for_senders(message2);
 
@@ -51,6 +66,8 @@ run_test('process_message_for_senders', () => {
         topic: topic2,
         sender_id: sender3,
     };
+    messages.push(message3);
+
     rs.process_message_for_senders(message3);
     assert.equal(
         rs.compare_by_recency({user_id: sender3}, {user_id: sender2}, stream1, topic2) < 0,
@@ -63,6 +80,8 @@ run_test('process_message_for_senders', () => {
         topic: topic1,
         sender_id: sender2,
     };
+    messages.push(message4);
+
     rs.process_message_for_senders(message4);
     assert.equal(
         rs.compare_by_recency({user_id: sender1}, {user_id: sender2}, stream1, topic1) > 0,
@@ -75,6 +94,8 @@ run_test('process_message_for_senders', () => {
         topic: topic1,
         sender_id: sender1,
     };
+    messages.push(message5);
+
     rs.process_message_for_senders(message5);
     assert.equal(
         rs.compare_by_recency({user_id: sender1}, {user_id: sender2}, stream1, topic1) < 0,
@@ -99,6 +120,7 @@ run_test('process_message_for_senders', () => {
         topic: topic3,
         sender_id: sender3,
     };
+    messages.push(message6, message7, message8);
 
     rs.process_message_for_senders(message6);
     rs.process_message_for_senders(message7);
@@ -113,4 +135,72 @@ run_test('process_message_for_senders', () => {
         true);
 
     assert.equal(rs.compare_by_recency({}, {}, next_id += 1, ''), 0);
+
+    // new message in topic2
+    const message9 = {
+        stream_id: stream3,
+        id: next_id += 1,
+        topic: topic2,
+        sender_id: sender3,
+    };
+    messages.push(message9);
+
+    rs.process_message_for_senders(message9);
+
+    // Test topic change
+    assert.equal(
+        rs.get_topic_recent_senders(stream3, topic3).toString(), '3'
+    );
+    assert.equal(
+        rs.get_topic_recent_senders(stream3, topic2).toString(), '2,3'
+    );
+
+    // message7's topic was changed by user
+    messages[6].topic = topic3;
+
+    rs.process_topic_edit(stream3, topic2, topic3);
+    assert.equal(
+        rs.get_topic_recent_senders(stream3, topic3).toString(), '2,3'
+    );
+    assert.equal(
+        rs.get_topic_recent_senders(stream3, topic2).toString(), '3'
+    );
+
+    // Test stream change
+    assert.equal(
+        rs.get_topic_recent_senders(stream3, topic3).toString(), '2,3'
+    );
+    assert.equal(
+        rs.get_topic_recent_senders(stream4, topic3).toString(), ''
+    );
+    // stream of topic3 was changed to stream4.
+    messages[6].stream_id = stream4; // message7's topic is topic3
+    messages[7].stream_id = stream4;
+    rs.process_topic_edit(stream3, topic3, topic3, stream4);
+    assert.equal(
+        rs.get_topic_recent_senders(stream3, topic3).toString(), ''
+    );
+    assert.equal(
+        rs.get_topic_recent_senders(stream4, topic3).toString(), '2,3'
+    );
+
+    // Test stream & topic change
+    assert.equal(
+        rs.get_topic_recent_senders(stream4, topic3).toString(), '2,3'
+    );
+    assert.equal(
+        rs.get_topic_recent_senders(stream5, topic4).toString(), ''
+    );
+    // stream of topic3 was changed to stream5 and topic was changed to topic4.
+    messages[6].stream_id = stream5;
+    messages[7].stream_id = stream5;
+    messages[6].topic = topic4;
+    messages[7].topic = topic4;
+    rs.process_topic_edit(stream4, topic3, topic4, stream5);
+    assert.equal(
+        rs.get_topic_recent_senders(stream4, topic3).toString(), ''
+    );
+    assert.equal(
+        rs.get_topic_recent_senders(stream5, topic4).toString(), '2,3'
+    );
 });