redefine logic to try and get a stable price with unstable timeline

src/lib/mastodon.ts

@@ -70,14 +70,27 @@ export async function getPostsPerHour(tag: string): Promise<number> {
  * Returns posts-per-hour AND a sorted list of co-occurring tag names
  * (lowercased, excluding the queried tag itself).
  *
- * Strategy:
- *   - Paginate until we have at least one post older than 1 hour (a complete picture),
- *     OR we exhaust the timeline, OR we hit MAX_PAGES_PER_HASHTAG.
- *   - Oldest post >= 1 hour old: count posts in the last hour directly (full window).
- *   - Hit the page cap (burst): more posts exist beyond what we fetched — extrapolate from
- *     the covered span (postsPerHour = count / coveredHours).
- *   - Timeline exhausted (sparse): these are all the posts that exist — use the raw count.
- *     Extrapolating would artificially inflate a tag with 3 posts clustered in 10 minutes.
+ * Pagination strategy:
+ *   - Fetch pages until the oldest post in a batch falls before the 1-hour cutoff
+ *     (the horizon), OR the timeline is exhausted, OR MAX_PAGES_PER_HASHTAG is reached.
+ *   - When we first cross the horizon, keep fetching additional pages as long as each
+ *     new page contributes at least one post within the cutoff. Only stop when a page
+ *     adds nothing new to the in-window count — at that point the window is stable.
+ *     This handles out-of-order federation: Mastodon timelines are ordered by post ID
+ *     (local receive time), not created_at. A post authored at 10:45 on a remote server
+ *     may arrive at 11:05, get a recent ID and appear near the top of the stream — but
+ *     its created_at is in the past/out of order. Continuing until the count stabilises
+ *     ensures all such late-arriving posts are captured regardless of how many pages
+ *     they span.
+ *   - After collecting all pages, sort by created_at and filter to the last hour for an
+ *     accurate count regardless of any remaining ordering noise.
+ *
+ * PPH calculation:
+ *   - Crossed horizon (direct): we have a full window — count posts with created_at >= cutoff.
+ *   - Hit page cap without crossing (burst): more posts exist beyond what we fetched —
+ *     extrapolate from the covered time span (count / coveredHours).
+ *   - Timeline exhausted without crossing (sparse): all posts in the last hour are accounted
+ *     for — use the raw count directly (no extrapolation).
  */
 export async function getPostsData(
   tag: string,
@@ -91,8 +104,15 @@ export async function getPostsData(
   let allPosts: MastodonPost[] = []
   let maxId: string | undefined
   let hitPageCap = false
+  let crossedHorizon = false
 
   for (let page = 0; page < maxPages; page++) {
+    // Once we've crossed the horizon, snapshot the in-window count before this fetch
+    // so we can detect whether the page contributed anything new.
+    const inWindowBefore = crossedHorizon
+      ? allPosts.filter((p) => new Date(p.created_at).getTime() >= cutoff).length
+      : 0
+
     const { posts, nextMaxId } = await fetchPage(tag, maxId, postLimit)
 
     if (posts.length === 0) break
@@ -101,21 +121,30 @@ export async function getPostsData(
     // End of timeline or no more pages
     if (posts.length < postLimit || !nextMaxId) break
 
-    // If the oldest post in this batch is already beyond 1 hour, we have a full window
+    if (crossedHorizon) {
+      // Keep fetching while this page added new in-window posts; stop when count stabilises
+      const inWindowAfter = allPosts.filter((p) => new Date(p.created_at).getTime() >= cutoff).length
+      if (inWindowAfter === inWindowBefore) break
+    }
+
+    // Check if this batch first crosses the 1-hour horizon
     const oldestInBatch = Math.min(...posts.map((p) => new Date(p.created_at).getTime()))
-    if (oldestInBatch < cutoff) break
+    if (oldestInBatch < cutoff) crossedHorizon = true
 
     maxId = nextMaxId
 
-    // Mark if we completed the final allowed page without breaking
-    if (page === maxPages - 1) hitPageCap = true
+    // Only mark as hit-cap when we never found old enough data (true burst scenario)
+    if (page === maxPages - 1 && !crossedHorizon) hitPageCap = true
   }
 
   if (allPosts.length === 0) return { postsPerHour: 0, relatedTags: [], hasAnyPosts: false }
 
+  // Sort globally by created_at so the window filter is accurate regardless of federation order
+  allPosts.sort((a, b) => new Date(b.created_at).getTime() - new Date(a.created_at).getTime())
+
   const times = allPosts.map((p) => new Date(p.created_at).getTime())
-  const newestMs = Math.max(...times)
-  const oldestMs = Math.min(...times)
+  const newestMs = times[0]
+  const oldestMs = times[times.length - 1]
 
   let postsPerHour: number
   if (oldestMs < cutoff) {