feat(feeds): add old and best sort

src/stores/feeds/feed-sorter.test.ts

@@ -149,4 +149,52 @@ describe('feedSorter', () => {
  {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub2', cid: '11'},
  ])
  })
+
+ test('sort by old', async () => {
+ const sorted = feedSorter.sort('old', feed)
+ expect(sorted).toEqual([
+ {timestamp: day(1), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', pinned: true, cid: '16'},
+ {timestamp: day(0), upvoteCount: 1000, downvoteCount: 1, subplebbitAddress: 'sub1', pinned: true, cid: '17'},
+ {timestamp: day(0), upvoteCount: 10001, downvoteCount: 1000, subplebbitAddress: 'sub1', cid: '2'},
+ {timestamp: day(0), upvoteCount: 10000, downvoteCount: 1000, subplebbitAddress: 'sub2', cid: '10'},
+ {timestamp: day(0), upvoteCount: 1000, downvoteCount: 1, subplebbitAddress: 'sub1', cid: '1'},
+ {timestamp: day(0), upvoteCount: 1000, downvoteCount: 1, subplebbitAddress: 'sub2', cid: '9'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '0'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '3'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 100, subplebbitAddress: 'sub1', cid: '7'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub2', cid: '8'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub2', cid: '11'},
+ {timestamp: day(0), lastReplyTimestamp: day(4) + 2, upvoteCount: 100, downvoteCount: 100, subplebbitAddress: 'sub3', cid: '15'},
+ {timestamp: day(1), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '6'},
+ {timestamp: day(1), lastReplyTimestamp: day(4) + 1, upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub3', cid: '14'},
+ {timestamp: day(2), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '5'},
+ {timestamp: day(2), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub3', cid: '13'},
+ {timestamp: day(3), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '4'},
+ {timestamp: day(3), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub2', cid: '12'},
+ ])
+ })
+
+ test('sort by best', async () => {
+ const sorted = feedSorter.sort('best', feed)
+ expect(sorted).toEqual([
+ {timestamp: day(1), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', pinned: true, cid: '16'},
+ {timestamp: day(0), upvoteCount: 1000, downvoteCount: 1, subplebbitAddress: 'sub1', pinned: true, cid: '17'},
+ {timestamp: day(0), upvoteCount: 1000, downvoteCount: 1, subplebbitAddress: 'sub1', cid: '1'},
+ {timestamp: day(0), upvoteCount: 1000, downvoteCount: 1, subplebbitAddress: 'sub2', cid: '9'},
+ {timestamp: day(0), upvoteCount: 10001, downvoteCount: 1000, subplebbitAddress: 'sub1', cid: '2'},
+ {timestamp: day(0), upvoteCount: 10000, downvoteCount: 1000, subplebbitAddress: 'sub2', cid: '10'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '0'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '3'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub2', cid: '8'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub2', cid: '11'},
+ {timestamp: day(1), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '6'},
+ {timestamp: day(1), lastReplyTimestamp: day(4) + 1, upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub3', cid: '14'},
+ {timestamp: day(2), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '5'},
+ {timestamp: day(2), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub3', cid: '13'},
+ {timestamp: day(3), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub1', cid: '4'},
+ {timestamp: day(3), upvoteCount: 100, downvoteCount: 10, subplebbitAddress: 'sub2', cid: '12'},
+ {timestamp: day(0), upvoteCount: 100, downvoteCount: 100, subplebbitAddress: 'sub1', cid: '7'},
+ {timestamp: day(0), lastReplyTimestamp: day(4) + 2, upvoteCount: 100, downvoteCount: 100, subplebbitAddress: 'sub3', cid: '15'},
+ ])
+ })
 })

src/stores/feeds/feed-sorter.ts

@@ -85,6 +85,46 @@ const sortByActive = (feed: any[]) => {
  .sort((a, b) => (b.lastReplyTimestamp || b.timestamp || 0) - (a.lastReplyTimestamp || a.timestamp || 0))
 }
 
+const sortByOld = (feed: any[]) => {
+ // sort by upvoteCount first for tiebreaker, then timestamp
+ return feed.sort((a, b) => (b.upvoteCount || 0) - (a.upvoteCount || 0)).sort((a, b) => (a.timestamp || 0) - (b.timestamp || 0))
+}
+
+// "best" sort from reddit replies
+// https://web.archive.org/web/20100305052116/http://blog.reddit.com/2009/10/reddits-new-comment-sorting-system.html
+// https://medium.com/hacking-and-gonzo/how-reddit-ranking-algorithms-work-ef111e33d0d9
+// http://www.evanmiller.org/how-not-to-sort-by-average-rating.html
+// https://github.com/reddit-archive/reddit/blob/753b17407e9a9dca09558526805922de24133d53/r2/r2/lib/db/_sorts.pyx#L70
+const sortByBest = (feed: any[]) => {
+ const postScores: {[key: string]: number} = {}
+ for (const post of feed) {
+ let upvoteCount = post.upvoteCount || 0
+ upvoteCount++ // reddit initial upvotes is 1, plebbit is 0
+ const downvoteCount = post.downvoteCount || 0
+
+ // n is the total number of ratings
+ const n = upvoteCount + downvoteCount
+ if (n === 0) {
+ postScores[post.cid] = 0
+ continue
+ }
+
+ // zα/2 is the (1-α/2) quantile of the standard normal distribution
+ const z = 1.281551565545
+
+ // p is the observed fraction of positive ratings
+ const p = upvoteCount / n
+
+ const left = p + (1 / (2 * n)) * z * z
+ const right = z * Math.sqrt((p * (1 - p)) / n + (z * z) / (4 * n * n))
+ const under = 1 + (1 / n) * z * z
+ postScores[post.cid] = (left - right) / under
+ }
+
+ // sort by old first for tiebreaker (like reddit does)
+ return feed.sort((a, b) => (a.timestamp || 0) - (b.timestamp || 0)).sort((a, b) => (postScores[b.cid] || 0) - (postScores[a.cid] || 0))
+}
+
 export const sort = (sortType: string, feed: any[]) => {
  // pinned posts are not sorted, maybe in a future version we can sort them based on something
  const pinnedPosts = feed.filter((post) => post.pinned)
@@ -105,6 +145,12 @@ export const sort = (sortType: string, feed: any[]) => {
  if (sortType.match('active')) {
  return [...pinnedPosts, ...sortByActive(feed)]
  }
+ if (sortType.match('old')) {
+ return [...pinnedPosts, ...sortByOld(feed)]
+ }
+ if (sortType.match('best')) {
+ return [...pinnedPosts, ...sortByBest(feed)]
+ }
  throw Error(`feedsStore feedSorter sort type '${sortType}' doesn't exist`)
 }