fix: #9954, get next post timestamp

fixes topic events being inserted in after first page but at the wrong spot

public/src/modules/helpers.js

@@ -212,7 +212,7 @@
 
 	function renderTopicEvents(index) {
 		const start = this.posts[index].timestamp;
-		const end = this.posts[index + 1] ? this.posts[index + 1].timestamp : Date.now();
+		const end = this.posts[index].nextPostTimestamp;
 		const events = this.events.filter(event => event.timestamp >= start && event.timestamp < end);
 		if (!events.length) {
 			return '';

src/topics/index.js

@@ -240,9 +240,26 @@ async function getMainPostAndReplies(topic, set, uid, start, stop, reverse) {
 
 	Topics.calculatePostIndices(replies, repliesStart);
 
+	await Topics.addNextPostTimestamp(postData, set, reverse);
 	return await Topics.addPostData(postData, uid);
 }
 
+Topics.addNextPostTimestamp = async function (postData, set, reverse) {
+	if (!postData.length) {
+		return;
+	}
+	postData.forEach((p, index) => {
+		if (p && postData[index + 1]) {
+			p.nextPostTimestamp = postData[index + 1].timestamp;
+		}
+	});
+	const lastPost = postData[postData.length - 1];
+	if (lastPost && lastPost.index) {
+		const data = await db[reverse ? 'getSortedSetRevRangeWithScores' : 'getSortedSetRangeWithScores'](set, lastPost.index, lastPost.index);
+		lastPost.nextPostTimestamp = data.length ? data[0].score : Date.now();
+	}
+};
+
 async function getDeleter(topicData) {
 	if (!parseInt(topicData.deleterUid, 10)) {
 		return null;

src/topics/posts.js

@@ -24,6 +24,7 @@ module.exports = function (Topics) {
 		const postData = await posts.getPostsFromSet(set, start, stop, uid, reverse);
 		Topics.calculatePostIndices(postData, start);
 
+		await Topics.addNextPostTimestamp(postData, set, reverse);
 		return await Topics.addPostData(postData, uid);
 	};