enabling infinite post loader (re: issue #42), fixes #42

public/src/forum/topic.js

@@ -8,7 +8,8 @@
 			deleted: templates.get('deleted'),
 			pinned: templates.get('pinned')
 		},
-		topic_name = templates.get('topic_name');
+		topic_name = templates.get('topic_name'),
+		infiniteLoaderActive = false;
 
 	function addCommasToNumbers() {
 		$('.formatted-number').each(function(index, element) {
@@ -204,6 +205,20 @@
 		followEl[0].addEventListener('click', function() {
 			socket.emit('api:topic.follow', tid);
 		}, false);
+
+		// Infinite scrolling of posts
+		window.addEventListener('scroll', function() {
+			var	windowHeight = document.body.offsetHeight - $(window).height(),
+				half = windowHeight / 2;
+
+			if (document.body.scrollTop > half && !infiniteLoaderActive) {
+				infiniteLoaderActive = true;
+				socket.emit('api:topic.loadMore', {
+					tid: tid,
+					after: document.querySelectorAll('#post-container li[data-pid]').length
+				});
+			}
+		});
 	});
 
 
@@ -304,18 +319,20 @@
 	socket.on('event:new_post', function(data) {
 		data.posts[0].display_moderator_tools = 'none';
 		var html = templates.prepare(templates['topic'].blocks['posts']).parse(data),
-			uniqueid = new Date().getTime();
-
-		jQuery('<div id="' + uniqueid + '"></div>')
-			.appendTo("#post-container")
-			.hide()
-			.append(html)
-			.fadeIn('slow');
+			uniqueid = new Date().getTime(),
+			tempContainer = jQuery('<div id="' + uniqueid + '"></div>')
+				.appendTo("#post-container")
+				.hide()
+				.append(html)
+				.fadeIn('slow');
 
 		for(var x=0,numPosts=data.posts.length;x<numPosts;x++) {
 			socket.emit('api:post.privileges', data.posts[x].pid);
 		}
 
+		tempContainer.replaceWith(tempContainer.contents());
+		infiniteLoaderActive = false;
+
 		set_up_posts(uniqueid);
 		
 		addCommasToNumbers();

src/posts.js

@@ -17,16 +17,17 @@ marked.setOptions({
 	Posts.getPostsByTid = function(tid, current_user, start, end, callback) {
 		RDB.lrange('tid:' + tid + ':posts', start, end, function(err, pids) {
 			RDB.handle(err);
-			
-			if (pids.length === 0 ) {
-				throw new Error('Topic should never have 0 posts. tid: ' + tid);
-			}
-			
 			topics.markAsRead(tid, current_user);
 
-			Posts.getPostsByPids(pids, current_user, function(posts) {
-				callback(posts);
-			});
+			if (pids.length) {
+				Posts.getPostsByPids(pids, current_user, function(posts) {
+					callback(posts);
+				});
+			} else {
+				callback({
+					error: 'no-posts'
+				});
+			}
 		});
 	}
 

src/websockets.js

@@ -410,11 +410,13 @@ var SocketIO = require('socket.io').listen(global.server, { log:false }),
 				end = start + 10;
 
 			posts.getPostsByTid(data.tid, uid, start, end, function(posts){
-				postTools.constructPostObject(posts, data.tid, uid, null, function(postObj) {
-					io.sockets.in('topic_' + data.tid).emit('event:new_post', {
-						posts: postObj
+				if (!posts.error) {
+					postTools.constructPostObject(posts, data.tid, uid, null, function(postObj) {
+						io.sockets.in('topic_' + data.tid).emit('event:new_post', {
+							posts: postObj
+						});
 					});
-				});
+				}
 			});
 		});