Merge pull request 'fix(events): decrement the live like count on un-like' (#112) from fix/events-like-count-unlike into dev

Reviewed-on: #112

src/modules/events/composables/useEventLikes.ts

@@ -7,52 +7,77 @@ import { tryInjectService, SERVICE_TOKENS } from '@/core/di-container'
  * user's NIP-51 bookmark list (kind 10003) — the same action the heart
  * performs (and what the Favorites page reads).
  *
- * One batched subscription covers every event coordinate that a mounted
- * heart has registered, filtered by `#a`. It stays open after EOSE, so
- * when anyone publishes/updates a bookmark list referencing a tracked
- * event the relay pushes it live and the count increments for everyone
- * in real time (Alice likes → Bob's count ticks up).
+ * Counting bookmark lists by `#a` alone can't see un-likes: when someone
+ * removes an event their new (replaceable) list no longer contains the
+ * coord, so it stops matching the `#a` filter and never arrives. To make
+ * decrements real-time too we ALSO watch every known liker by `authors`,
+ * and track each author's current set of liked coords — so a list that
+ * drops a coord is delivered and we remove that author from the count.
  *
- * Caveats (inherent to counting replaceable bookmark lists via `#a`):
- *  - An un-like by ANOTHER user only reflects on next load: their new
- *    list no longer contains the coord, so it no longer matches the
- *    filter and we never receive the update. Counts are correct on a
- *    fresh load (the un-liker is simply absent from the results).
- *  - The current user's own like/un-like updates instantly via setSelf(),
- *    driven by the optimistic heart state.
+ *  - `#a` filter      → discovers NEW likers (lists containing a tracked coord).
+ *  - `authors` filter → catches updates (add AND remove) from anyone we've
+ *                       already counted, including their last un-like.
+ *
+ * Both feed one handler that diffs the author's previous vs current liked
+ * coords. The current user's own like/un-like also updates instantly via
+ * setSelf(), kept consistent with the same per-author bookkeeping.
  */
 
 const BOOKMARK_KIND = 10003
 
-// coord ("kind:pubkey:dTag") -> set of pubkeys who bookmarked it.
-const authorsByCoord = new Map<string, Set<string>>() // plain map, for dedup
-const counts = reactive(new Map<string, number>())     // reactive mirror for the UI
+const counts = reactive(new Map<string, number>())     // coord -> count (reactive, for the UI)
+const authorsByCoord = new Map<string, Set<string>>()  // coord -> pubkeys who like it (count source)
+const authorCoords = new Map<string, Set<string>>()    // pubkey -> tracked coords in their latest list
+const authorSeenAt = new Map<string, number>()         // pubkey -> created_at of latest processed list
+const knownAuthors = new Set<string>()                 // everyone we've seen like a tracked coord
 const tracked = new Set<string>()
 
 let unsubscribe: (() => void) | null = null
 let resubTimer: ReturnType<typeof setTimeout> | null = null
 
-function setCount(coord: string, pubkey: string, present: boolean) {
+function addAuthor(coord: string, pubkey: string) {
   let set = authorsByCoord.get(coord)
   if (!set) {
     set = new Set()
     authorsByCoord.set(coord, set)
   }
-  const had = set.has(pubkey)
-  if (present && !had) {
+  if (!set.has(pubkey)) {
     set.add(pubkey)
     counts.set(coord, set.size)
-  } else if (!present && had) {
-    set.delete(pubkey)
-    counts.set(coord, set.size)
   }
 }
 
-function ingest(event: NostrEvent) {
-  // A bookmark list references many events via 'a' tags; credit the
-  // author to every coord we're tracking.
+function removeAuthor(coord: string, pubkey: string) {
+  const set = authorsByCoord.get(coord)
+  if (set && set.delete(pubkey)) counts.set(coord, set.size)
+}
+
+function handleEvent(event: NostrEvent) {
+  const pk = event.pubkey
+  const seenAt = authorSeenAt.get(pk) ?? -1
+  // Ignore strictly-older replaceable lists; reprocess same/newer (so a
+  // re-delivery after we start tracking a new coord still credits it).
+  if (event.created_at < seenAt) return
+  authorSeenAt.set(pk, Math.max(seenAt, event.created_at))
+
+  // Tracked coords this list currently references.
+  const next = new Set<string>()
   for (const tag of event.tags) {
-    if (tag[0] === 'a' && tracked.has(tag[1])) setCount(tag[1], event.pubkey, true)
+    if (tag[0] === 'a' && tracked.has(tag[1])) next.add(tag[1])
+  }
+  const prev = authorCoords.get(pk) ?? new Set<string>()
+
+  // Removals (un-likes): present before, gone now.
+  for (const coord of prev) if (!next.has(coord)) removeAuthor(coord, pk)
+  // Additions (likes): new this time.
+  for (const coord of next) if (!prev.has(coord)) addAuthor(coord, pk)
+  authorCoords.set(pk, next)
+
+  // Watch this liker by author from now on so their future un-like (which
+  // wouldn't match the #a filter) still reaches us.
+  if (next.size && !knownAuthors.has(pk)) {
+    knownAuthors.add(pk)
+    scheduleResubscribe()
   }
 }
 
@@ -68,17 +93,22 @@ function resubscribe() {
   }
   const coords = [...tracked]
   if (coords.length === 0) return
+  const filters: Record<string, unknown>[] = [{ kinds: [BOOKMARK_KIND], '#a': coords }]
+  // Also watch known likers by author, so an un-like (a list that drops
+  // the coord, no longer matching #a) is still delivered and decrements.
+  if (knownAuthors.size) filters.push({ kinds: [BOOKMARK_KIND], authors: [...knownAuthors] })
   unsubscribe = relayHub.subscribe({
     id: 'event-likes-aggregate',
-    filters: [{ kinds: [BOOKMARK_KIND], '#a': coords }],
-    onEvent: (event: NostrEvent) => ingest(event),
+    filters,
+    onEvent: (event: NostrEvent) => handleEvent(event),
   })
 }
 
 function scheduleResubscribe() {
   if (resubTimer) clearTimeout(resubTimer)
-  // Debounced so a burst of mounting hearts results in one (re)subscribe.
-  resubTimer = setTimeout(resubscribe, 250)
+  // Debounced so a burst of mounting hearts / discovered likers results
+  // in one (re)subscribe.
+  resubTimer = setTimeout(resubscribe, 300)
 }
 
 export function useEventLikes() {
@@ -96,12 +126,22 @@ export function useEventLikes() {
 
   /**
    * Reflect the current user's own like state immediately (optimistic),
-   * so their count matches the instant heart fill and their un-like
-   * decrements right away.
+   * kept consistent with the per-author bookkeeping so the real event
+   * round-tripping back reconciles to a no-op.
    */
   function setSelf(coord: string, pubkey: string, liked: boolean) {
     if (!coord || !pubkey) return
-    setCount(coord, pubkey, liked)
+    const set = authorCoords.get(pubkey) ?? new Set<string>()
+    const had = set.has(coord)
+    if (liked && !had) {
+      set.add(coord)
+      authorCoords.set(pubkey, set)
+      addAuthor(coord, pubkey)
+    } else if (!liked && had) {
+      set.delete(coord)
+      authorCoords.set(pubkey, set)
+      removeAuthor(coord, pubkey)
+    }
   }
 
   return { track, likeCount, setSelf }