Fix recurring event duplication bug

When a recurring event has a modified occurrence, the calendar was showing both the original and modified versions. This happened because the code didn't properly handle RECURRENCE-ID exceptions in iCal data.

Changes:
- Modified extractScheduleEventsInRange() to collect exception events first and filter them from recurring patterns
- Updated expandEventOccurrences() to skip dates that have exceptions
- Applied same fix to extractScheduleEvents() for proper date range filtering

Fixes issue where modified recurring events appeared twice in the UI.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/pages/calendar/Schedule.tsx

@@ -28,7 +28,39 @@ const extractScheduleEventsInRange = (
   rangeEnd: ICAL.Time,
 ): ScheduleEvent[] => {
   const vevents = icalComp.getAllSubcomponents("vevent")
-  return vevents
+
+  // First, collect all exception events (events with RECURRENCE-ID)
+  const exceptions = new Map<string, Set<string>>() // uid -> set of recurrence-id strings
+  const exceptionEvents: ScheduleEvent[] = []
+
+  vevents.forEach((vevent) => {
+    const recurrenceId = vevent.getFirstPropertyValue("recurrence-id")
+    if (recurrenceId) {
+      const uid = vevent.getFirstPropertyValue("uid")
+      const event = new ICAL.Event(vevent)
+
+      // Check if exception is in range
+      if (event.startDate.compare(rangeEnd) <= 0 && event.endDate.compare(rangeStart) >= 0) {
+        exceptionEvents.push({
+          start: event.startDate.toJSDate(),
+          end: event.endDate.toJSDate(),
+          summary: event.summary,
+          description: event.description,
+          recurrenceId: recurrenceId.toString(),
+        })
+      }
+
+      // Track exception for filtering recurring events
+      if (!exceptions.has(uid)) {
+        exceptions.set(uid, new Set())
+      }
+      exceptions.get(uid)!.add(recurrenceId.toString())
+    }
+  })
+
+  // Process regular and recurring events
+  const regularEvents = vevents
+    .filter(vevent => !vevent.getFirstPropertyValue("recurrence-id"))
     .flatMap<ScheduleEvent>((vevent) => {
       const event = new ICAL.Event(vevent)
       if (!event.isRecurring()) {
@@ -41,8 +73,11 @@ const extractScheduleEventsInRange = (
           recurrenceId: undefined,
         }]
       }
-      return expandEventOccurrences(event, rangeStart, rangeEnd)
+      const eventExceptions = exceptions.get(event.uid) || new Set()
+      return expandEventOccurrences(event, rangeStart, rangeEnd, eventExceptions)
     })
+
+  return [...regularEvents, ...exceptionEvents]
     .sort((a, b) => b.start.getTime() - a.start.getTime())
 }
 
@@ -50,6 +85,7 @@ const expandEventOccurrences = (
   event: ICAL.Event,
   rangeStart: ICAL.Time,
   rangeEnd: ICAL.Time,
+  exceptions?: Set<string>,
 ): ScheduleEvent[] => {
   const occurrences: ScheduleEvent[] = []
   const iterator = event.iterator()
@@ -58,6 +94,10 @@ const expandEventOccurrences = (
     if (!next) break
     if (next.compare(rangeEnd) > 0) break
     if (next.compare(rangeStart) < 0) continue
+
+    // Skip this occurrence if it has an exception
+    if (exceptions && exceptions.has(next.toString())) continue
+
     const details = event.getOccurrenceDetails(next)
     occurrences.push({
       start: details.startDate.toJSDate(),
@@ -73,8 +113,40 @@ const expandEventOccurrences = (
 const extractScheduleEvents = (icalComp: ICAL.Component): ScheduleEvent[] => {
   const vevents = icalComp.getAllSubcomponents("vevent")
   const rangeEnd = ICAL.Time.fromDateString("2026-01-01")
+  const rangeStart = ICAL.Time.fromDateString("2020-01-01")
 
-  return vevents
+  // First, collect all exception events (events with RECURRENCE-ID)
+  const exceptions = new Map<string, Set<string>>() // uid -> set of recurrence-id strings
+  const exceptionEvents: ScheduleEvent[] = []
+
+  vevents.forEach((vevent) => {
+    const recurrenceId = vevent.getFirstPropertyValue("recurrence-id")
+    if (recurrenceId) {
+      const uid = vevent.getFirstPropertyValue("uid")
+      const event = new ICAL.Event(vevent)
+
+      // Check if exception is in range
+      if (event.startDate.compare(rangeEnd) <= 0 && event.endDate.compare(rangeStart) >= 0) {
+        exceptionEvents.push({
+          start: event.startDate.toJSDate(),
+          end: event.endDate.toJSDate(),
+          summary: event.summary,
+          description: event.description,
+          recurrenceId: recurrenceId.toString(),
+        })
+      }
+
+      // Track exception for filtering recurring events
+      if (!exceptions.has(uid)) {
+        exceptions.set(uid, new Set())
+      }
+      exceptions.get(uid)!.add(recurrenceId.toString())
+    }
+  })
+
+  // Process regular and recurring events
+  const regularEvents = vevents
+    .filter(vevent => !vevent.getFirstPropertyValue("recurrence-id"))
     .flatMap<ScheduleEvent>((vevent) => {
       const event = new ICAL.Event(vevent)
       if (event.iterator().complete) {
@@ -84,11 +156,13 @@ const extractScheduleEvents = (icalComp: ICAL.Component): ScheduleEvent[] => {
           summary: event.summary,
           description: event.description,
           recurrenceId: event.uid || event.startDate.toString(),
-
         }]
       }
-      return expandEventOccurrences(event, rangeEnd)
+      const eventExceptions = exceptions.get(event.uid) || new Set()
+      return expandEventOccurrences(event, rangeStart, rangeEnd, eventExceptions)
     })
+
+  return [...regularEvents, ...exceptionEvents]
     .sort((a, b) => b.start.getTime() - a.start.getTime())
 }