fix: mode

src/jobs/generateEventOccurrences.ts

@@ -10,24 +10,31 @@ import {
  * Materializes each Event's recurrence rule into `eventOccurrence` rows for
  * a rolling window.
  *
- * Per event we wipe every future occurrence and regenerate from the current
- * rule. Occurrences are derivative pointers to the parent event, so there
- * is no editor-edited state to preserve — rule edits and recurring→once
- * transitions stay trivially correct.
+ * Two modes:
+ *  - `replace` (default): wipe every future occurrence and regenerate from
+ *    the current rule. Used by the Events `afterChange` hook, where the rule
+ *    or date may have changed — wiping keeps rule edits and recurring→once
+ *    transitions trivially correct.
+ *  - `append`: never delete; only create occurrences whose slot doesn't yet
+ *    exist. Used by the periodic backfill job, where the rule hasn't changed
+ *    and we only want to extend the window forward without churning (and
+ *    re-id'ing) occurrences that are already correct.
  *
  * Weekday and time-of-day come directly from `event.date`. Calendar-date
  * generation lives in scheduleOccurrences.ts (DST-safe by construction:
  * dates are built at local midnight and then stitched with the event's
  * HH:mm).
  *
- * Exposed both as a Payload Jobs Queue task (weekly cron backfill) and as a
- * direct function called from the Events `afterChange` hook so edits are
- * reflected immediately without waiting for a queue worker.
+ * Exposed both as a Payload Jobs Queue task (cron backfill) and as a direct
+ * function called from the Events `afterChange` hook so edits are reflected
+ * immediately without waiting for a queue worker.
  */
 
 const DEFAULT_WEEKS_AHEAD = 8
 const MS_PER_WEEK = 7 * 24 * 60 * 60 * 1000
 
+type RegenerateMode = 'replace' | 'append'
+
 type GenerateEventOccurrencesInput = {
   weeksAhead?: number
   eventId?: string
@@ -60,19 +67,22 @@ export const regenerateOccurrencesForEvent = async ({
   req,
   weeksAhead = DEFAULT_WEEKS_AHEAD,
   now = new Date(),
+  mode = 'replace',
 }: {
   event: EventLike
   payload: Payload
   req?: PayloadRequest
   weeksAhead?: number
   now?: Date
+  mode?: RegenerateMode
 }): Promise<GenerateEventOccurrencesOutput> => {
   const horizon = new Date(now.getTime() + weeksAhead * MS_PER_WEEK)
 
-  // Snapshot cancelled dates so manual cancellations survive the wipe/regen.
-  // Matching by ISO date works because regen derives timestamps from the same
-  // event.date stepped by whole calendar days — shi)fts in event.date
-  // intentionally drop stale cancellations.
+  // Existing future occurrences. Used to (replace) snapshot cancellations so
+  // they survive the wipe, and (append) dedup so we don't recreate slots that
+  // already exist. Matching by ISO date works because regen derives
+  // timestamps from the same event.date stepped by whole calendar days —
+  // shifts in event.date intentionally drop stale cancellations.
   const existing = await payload.find({
     collection: 'eventOccurrence',
     where: {
@@ -91,21 +101,32 @@ export const regenerateOccurrencesForEvent = async ({
       .filter((occ) => occ.cancelled === true && typeof occ.date === 'string')
       .map((occ) => new Date(occ.date as string).toISOString()),
   )
+  const existingSlots = new Set(
+    existing.docs
+      .filter((occ) => typeof occ.date === 'string')
+      .map((occ) => new Date(occ.date as string).toISOString()),
+  )
 
-  const wipe = await payload.delete({
-    collection: 'eventOccurrence',
-    where: {
-      and: [
-        { event: { equals: event.id } },
-        { date: { greater_than_equal: now.toISOString() } },
-      ],
-    },
-    req,
-  })
-  let deleted = wipe.docs.length
+  let deleted = 0
   let created = 0
   let skipped = 0
 
+  if (mode === 'replace') {
+    // Wipe future occurrences and rebuild from the current rule. Used by the
+    // Event hook, where the rule/date may have changed.
+    const wipe = await payload.delete({
+      collection: 'eventOccurrence',
+      where: {
+        and: [
+          { event: { equals: event.id } },
+          { date: { greater_than_equal: now.toISOString() } },
+        ],
+      },
+      req,
+    })
+    deleted = wipe.docs.length
+  }
+
   if (!event.date) {
     return { created, deleted, skipped: skipped + 1 }
   }
@@ -128,16 +149,21 @@ export const regenerateOccurrencesForEvent = async ({
   const recurrenceType = event.recurrenceType ?? 'none'
 
   if (recurrenceType === 'none') {
+    const iso = eventDate.toISOString()
     if (eventDate.getTime() < now.getTime()) {
       return { created, deleted, skipped: skipped + 1 }
     }
+    // In append mode the slot may already exist (not wiped) — leave it alone.
+    if (mode === 'append' && existingSlots.has(iso)) {
+      return { created, deleted, skipped: skipped + 1 }
+    }
     await payload.create({
       collection: 'eventOccurrence',
       data: {
         event: event.id,
-        date: eventDate.toISOString(),
+        date: iso,
         endDateTime: endFor(eventDate),
-        cancelled: cancelledDates.has(eventDate.toISOString()),
+        cancelled: cancelledDates.has(iso),
         generated: true,
       },
       req,
@@ -152,6 +178,12 @@ export const regenerateOccurrencesForEvent = async ({
   const dates = expandEventOccurrences(event, { now, horizon: effectiveEnd })
   for (const date of dates) {
     const iso = date.toISOString()
+    // In append mode the future occurrences were never wiped, so leave any
+    // slot that already has an occurrence alone.
+    if (mode === 'append' && existingSlots.has(iso)) {
+      skipped += 1
+      continue
+    }
     await payload.create({
       collection: 'eventOccurrence',
       data: {
@@ -163,6 +195,7 @@ export const regenerateOccurrencesForEvent = async ({
       },
       req,
     })
+    existingSlots.add(iso)
     created += 1
   }
 
@@ -214,6 +247,10 @@ export const generateEventOccurrencesTask: TaskConfig<{
         payload,
         weeksAhead,
         now,
+        // Periodic backfill: only extend the window forward. The rule hasn't
+        // changed here, so don't wipe/recreate occurrences that are already
+        // correct (that only happens via the Event hook on an actual edit).
+        mode: 'append',
       })
       created += result.created
       deleted += result.deleted