fix(ics): export a series' deleted occurrences (#225)

Import learned to read EXDATE, but the export side never wrote it: an in-app
backup and restore brought back every occurrence the user had deleted. EXDATE
lives on the master row, so the export query's ORIGINAL_ID IS NULL filter never
hid it — it just wasn't in the projection.

An all-day series' exclusions are written VALUE=DATE, since RFC 5545 ties
EXDATE's value type to DTSTART's and a bare day code without it reads as a
malformed DATE-TIME. Sync adapters disagree on whether an all-day exclusion is
yyyyMMdd or a padded midnight stamp, so the time part is dropped on the way out.

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImpl.kt

@@ -308,7 +308,6 @@ class CalendarRepositoryImpl @Inject constructor(
         dataSource.deleteEventFromOccurrence(eventId, beginMillis)
     }
 
-
     private companion object {
         const val TAG = "CalendarRepository"
     }

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/IcsExportMapper.kt

@@ -56,6 +56,11 @@ internal fun ColumnReader.toIcsEvent(
         zoneId = getString(EventExportProjection.IDX_EVENT_TIMEZONE)?.takeIf { it.isNotBlank() }
             ?: "UTC",
         recurrenceRule = rrule,
+        exDates = if (rrule == null) {
+            emptyList()
+        } else {
+            exportExDates(getString(EventExportProjection.IDX_EXDATE), isAllDay)
+        },
         location = getString(EventExportProjection.IDX_LOCATION),
         description = getString(EventExportProjection.IDX_DESCRIPTION),
         reminderMinutes = if (isAllDay) {
@@ -72,3 +77,19 @@ internal fun ColumnReader.toIcsEvent(
     )
 }
 
+/**
+ * The row's `EXDATE` as the writer wants it: one stamp per entry, empties
+ * dropped.
+ *
+ * An all-day exclusion names a calendar day, and sync adapters are inconsistent
+ * about whether they write it as a bare `yyyyMMdd` or pad it to a midnight
+ * stamp; the time part is dropped so the exported value is the day either way.
+ * Calendula's own writes ([buildOccurrenceExdateValues]) are already bare.
+ */
+internal fun exportExDates(exdate: String?, isAllDay: Boolean): List<String> = exdate
+    ?.split(',')
+    ?.map { it.trim() }
+    ?.filter { it.isNotEmpty() }
+    ?.map { if (isAllDay) it.substringBefore('T') else it }
+    ?.distinct()
+    .orEmpty()

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/Projections.kt

@@ -121,10 +121,12 @@ internal object EventDetailProjection {
 /**
  * Master/one-off Events rows for a whole-calendar backup. Unlike
  * [EventDetailProjection] this reads `UID_2445` (to keep a row's identity across
- * backups) and `DURATION` (recurring rows carry it instead of DTEND). Modified-
+ * backups) and `DURATION` (recurring rows carry it instead of DTEND), plus
+ * `EXDATE` so a series exports the occurrences deleted from it. Modified-
  * occurrence and cancelled-exception rows are filtered out by the query
- * (`ORIGINAL_ID IS NULL`), so RECURRENCE-ID overrides and EXDATEs aren't
- * exported yet — a documented v1 limit (import skips them too).
+ * (`ORIGINAL_ID IS NULL`), so RECURRENCE-ID overrides aren't exported — a
+ * documented v1 limit (import skips them too). EXDATE is unaffected by that
+ * filter: it lives on the master row, not on an exception of its own.
  */
 internal object EventExportProjection {
     val COLUMNS: Array<String> = arrayOf(
@@ -137,6 +139,7 @@ internal object EventExportProjection {
         CalendarContract.Events.ALL_DAY,
         CalendarContract.Events.EVENT_TIMEZONE,
         CalendarContract.Events.RRULE,
+        CalendarContract.Events.EXDATE,
         CalendarContract.Events.EVENT_LOCATION,
         CalendarContract.Events.DESCRIPTION,
         CalendarContract.Events.STATUS,
@@ -153,11 +156,12 @@ internal object EventExportProjection {
     const val IDX_ALL_DAY = 6
     const val IDX_EVENT_TIMEZONE = 7
     const val IDX_RRULE = 8
-    const val IDX_LOCATION = 9
-    const val IDX_DESCRIPTION = 10
-    const val IDX_STATUS = 11
-    const val IDX_AVAILABILITY = 12
-    const val IDX_CALENDAR_ID = 13
+    const val IDX_EXDATE = 9
+    const val IDX_LOCATION = 10
+    const val IDX_DESCRIPTION = 11
+    const val IDX_STATUS = 12
+    const val IDX_AVAILABILITY = 13
+    const val IDX_CALENDAR_ID = 14
 }
 
 /**

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsEvent.kt

@@ -22,6 +22,12 @@ data class IcsEvent(
     val zoneId: String,
     /** Bare RRULE value (no `RRULE:` prefix), or null for a one-off event. */
     val recurrenceRule: String? = null,
+    /**
+     * Occurrences deleted from the series, in the provider's `EXDATE` shape —
+     * `yyyyMMdd` for an all-day series, a UTC `yyyyMMddTHHmmssZ` stamp
+     * otherwise. Empty for a one-off event.
+     */
+    val exDates: List<String> = emptyList(),
     val location: String? = null,
     val description: String? = null,
     /** Reminder lead times in minutes before start (raw provider offsets). */

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsWriter.kt

@@ -46,6 +46,7 @@ class IcsWriter(private val prodId: String = ICS_PROD_ID) {
         appendTimes(event)
         event.recurrenceRule?.takeIf { it.isNotBlank() }
             ?.let { add("RRULE:${it.removePrefix("RRULE:")}") }
+        appendExDates(event)
         event.location?.takeIf { it.isNotBlank() }
             ?.let { add("LOCATION:${escapeText(it)}") }
         event.description?.takeIf { it.isNotBlank() }
@@ -83,6 +84,20 @@ class IcsWriter(private val prodId: String = ICS_PROD_ID) {
         }
     }
 
+    /**
+     * The series' deleted occurrences. RFC 5545 ties `EXDATE`'s value type to
+     * `DTSTART`'s, so an all-day series needs the explicit `VALUE=DATE` — without
+     * it the bare day codes read as an invalid DATE-TIME. Only written for a
+     * recurring event: an exclusion names an occurrence, and a one-off has none.
+     */
+    private fun MutableList<String>.appendExDates(event: IcsEvent) {
+        if (event.recurrenceRule.isNullOrBlank()) return
+        val stamps = event.exDates.filter { it.isNotBlank() }.distinct()
+        if (stamps.isEmpty()) return
+        val prefix = if (event.isAllDay) "EXDATE;VALUE=DATE:" else "EXDATE:"
+        add(prefix + stamps.joinToString(","))
+    }
+
     private fun MutableList<String>.appendAlarm(minutes: Int, summary: String) {
         add("BEGIN:VALARM")
         add("ACTION:DISPLAY")