AndroidEventProcessor: also update SEQUENCE

Author: rfc2822

lib/src/main/kotlin/at/bitfire/synctools/mapping/calendar/AndroidEventProcessor.kt

@@ -7,6 +7,7 @@
 package at.bitfire.synctools.mapping.calendar
 
 import android.content.Entity
+import android.provider.CalendarContract
 import android.provider.CalendarContract.Events
 import android.provider.CalendarContract.ExtendedProperties
 import at.bitfire.synctools.icalendar.AssociatedEvents
@@ -90,21 +91,27 @@ class AndroidEventProcessor(
     /**
      * Result of the [mapToVEvents] operation.
      *
-     * @param uid               UID of the generated iCalendar
-     * @param generatedUid      whether [uid] was generated by [mapToVEvents] (*false*: UID was already present before mapping)
      * @param associatedEvents  mapped events
+     * @param uid               UID of the mapped events
+     * @param generatedUid      whether [uid] was generated by [mapToVEvents] (*false*: `UID` was already present before mapping)
+     * @param updatedSequence   the new increased `SEQUENCE` of the main event (*null* if sequence was not increased by [mapToVEvents])
      */
     class MappingResult(
+        val associatedEvents: AssociatedEvents,
         val uid: String,
         val generatedUid: Boolean,
-        val associatedEvents: AssociatedEvents
+        val updatedSequence: Int?
     )
 
     /**
      * Maps an Android event with its exceptions to VEVENTs.
      *
-     * VEVENTs must have a valid UID, so this method (or better so say, the [UidProcessor] that it calls)
-     * generates an UID, if necessary.
+     * VEVENTs must have a valid `UID`, so this method (or better so say, the [UidProcessor] that it calls)
+     * generates an UID, if necessary. If an `UID` was generated, it is noted in the result.
+     *
+     * This method also increases the `SEQUENCE`, if necessary, so that the mapped `SEQUENCE`
+     * can be different than the original `SEQUENCE` in [eventAndExceptions]. If the `SEQUENCE` was
+     * increased, it is noted in the result.
      */
     fun mapToVEvents(eventAndExceptions: EventAndExceptions): MappingResult {
         // make sure that main event has a UID
@@ -114,6 +121,8 @@ class AndroidEventProcessor(
             UUID.randomUUID().toString()
         }
 
+        val updatedSequence = increaseSequence(eventAndExceptions.main)
+
         // map main event
         val main = populateEvent(
             entity = eventAndExceptions.main,
@@ -149,9 +158,10 @@ class AndroidEventProcessor(
             prodId = generateProdId(eventAndExceptions.main)
         )
         return MappingResult(
+            associatedEvents = mappedEvents,
             uid = uid,
             generatedUid = generatedUid,
-            associatedEvents = mappedEvents
+            updatedSequence = updatedSequence
         )
     }
 
@@ -179,6 +189,47 @@ class AndroidEventProcessor(
         return prodIdGenerator.generateProdId(packages)
     }
 
+    /**
+     * Increases the event's SEQUENCE, if necessary.
+     *
+     * @param main  event to be checked (**will be modified** when SEQUENCE needs to be increased)
+     *
+     * @return updated sequence (or *null* if sequence was not increased/modified)
+     */
+    private fun increaseSequence(main: Entity): Int? {
+        val mainValues = main.entityValues
+
+        val weAreOrganizer: Boolean by lazy {
+            mainValues.getAsInteger(Events.IS_ORGANIZER) == 1
+        }
+        val groupScheduled: Boolean by lazy {
+            main.subValues.any { it.uri == CalendarContract.Attendees.CONTENT_URI }
+        }
+
+        val currentSeq = mainValues.getAsInteger(EventsContract.COLUMN_SEQUENCE)
+        return when {
+            currentSeq == null -> {
+                /* First upload, request to set to 0 in calendar provider after upload.
+                We can let it empty in the Entity because then no SEQUENCE property will be generated,
+                which is equal to SEQUENCE:0. */
+                0
+            }
+            // currentSequence != null for the following branches
+            groupScheduled && weAreOrganizer -> {
+                /* Upload of a group-scheduled event and we are the organizer, so we increase the SEQUENCE.
+                We also have to store it into the Entity so that it the new value will be mapped. */
+                (currentSeq + 1).also { newSeq ->
+                    mainValues.put(EventsContract.COLUMN_SEQUENCE, newSeq)
+                }
+            }
+            else -> {
+                /* Standard upload (either not group-scheduled or we are not the organizer). We don't
+                increase the SEQUENCE and so we don't have to modify the Entity, too. */
+                null
+            }
+        }
+    }
+
     /**
      * Reads data of an event from the calendar provider, i.e. converts the [entity] values into a [VEvent].
      *
@@ -198,23 +249,23 @@ class AndroidEventProcessor(
      * Makes sure that the event has a UID ([Events.UID_2445] in the main event row).
      *
      * If the event doesn't have a UID, a new one is generated using [uidGenerator] and
-     * put into [entity].
+     * put into [main].
      *
-     * @param entity    event to be checked (**will be modified** if it doesn't already have a UID)
+     * @param main  event to be checked (**will be modified** if it doesn't already have a UID)
      */
     private fun provideUid(
-        entity: Entity,
+        main: Entity,
         generateUid: () -> String
     ): String {
-        val mainValues = entity.entityValues
+        val mainValues = main.entityValues
         val existingUid = mainValues.getAsString(Events.UID_2445)
         if (existingUid != null) {
             // UID already present, nothing to do
             return existingUid
         }
 
         // have a look at extended properties (Google Calendar)
-        val googleCalendarUid = entity.subValues.firstOrNull {
+        val googleCalendarUid = main.subValues.firstOrNull {
             it.uri == ExtendedProperties.CONTENT_URI &&
             it.values.getAsString(ExtendedProperties.NAME) == EventsContract.EXTNAME_GOOGLE_CALENDAR_UID
         }?.values?.getAsString(ExtendedProperties.VALUE)

lib/src/main/kotlin/at/bitfire/synctools/storage/calendar/EventsContract.kt

@@ -19,21 +19,29 @@ object EventsContract {
 
     /**
      * Custom sync column to store the last known ETag of an event.
+     *
+     * Type: [String]
      */
     const val COLUMN_ETAG = CalendarContract.Events.SYNC_DATA1
 
     /**
      * Custom sync column to store sync flags of an event.
+     *
+     * Type: [Int]
      */
     const val COLUMN_FLAGS = CalendarContract.Events.SYNC_DATA2
 
     /**
      * Custom sync column to store the SEQUENCE of an event.
+     *
+     * Type: [Int]
      */
     const val COLUMN_SEQUENCE = CalendarContract.Events.SYNC_DATA3
 
     /**
      * Custom sync column to store the Schedule-Tag of an event.
+     *
+     * Type: [String]
      */
     const val COLUMN_SCHEDULE_TAG = CalendarContract.Events.SYNC_DATA4