check last updated timestamp at reimporting google events

app/src/main/kotlin/com/simplemobiletools/calendar/activities/EventActivity.kt

@@ -456,6 +456,8 @@ class EventActivity : SimpleActivity(), DBHelper.EventUpdateListener {
             eventType = mEventTypeId
             offset = getCurrentOffset()
             isDstIncluded = TimeZone.getDefault().inDaylightTime(Date())
+            lastUpdated = System.currentTimeMillis()
+            source = "Simple Calendar"
         }
 
         if (mEvent.id == 0) {

app/src/main/kotlin/com/simplemobiletools/calendar/asynctasks/FetchGoogleEventsTask.kt

@@ -86,10 +86,14 @@ class FetchGoogleEventsTask(val activity: Activity, credential: GoogleAccountCre
             if (googleEvent.status != CONFIRMED)
                 continue
 
+            val lastUpdate = DateTime(googleEvent.updated).millis
             val importId = googleEvent.iCalUID
             if (importIDs.contains(importId)) {
+                val oldEvent = dbHelper.getEventWithImportId(importId)
+                if (oldEvent != null && oldEvent.lastUpdated >= lastUpdate) {
                     continue
                 }
+            }
 
             val reminders = getReminder(googleEvent.reminders)
             val start = googleEvent.start
@@ -127,7 +131,7 @@ class FetchGoogleEventsTask(val activity: Activity, credential: GoogleAccountCre
 
             val event = Event(0, startTS, endTS, googleEvent.summary, googleEvent.description, reminders.getOrElse(0, { -1 }), reminders.getOrElse(1, { -1 }),
                     reminders.getOrElse(2, { -1 }), repeatRule.repeatInterval, importId, flags, repeatRule.repeatLimit, repeatRule.repeatRule,
-                    eventTypeId)
+                    eventTypeId, lastUpdated = lastUpdate)
 
             if (event.isAllDay && endTS > startTS) {
                 event.endTS -= DAY

app/src/main/kotlin/com/simplemobiletools/calendar/helpers/DBHelper.kt

@@ -226,7 +226,7 @@ class DBHelper private constructor(val context: Context) : SQLiteOpenHelper(cont
             put(COL_PARENT_EVENT_ID, event.parentId)
             put(COL_OFFSET, event.offset)
             put(COL_IS_DST_INCLUDED, if (event.isDstIncluded) 1 else 0)
-            put(COL_LAST_UPDATED, System.currentTimeMillis())
+            put(COL_LAST_UPDATED, event.lastUpdated)
             put(COL_SOURCE, event.source)
         }
     }
@@ -432,6 +432,17 @@ class DBHelper private constructor(val context: Context) : SQLiteOpenHelper(cont
         return ids.filter { it.trim().isNotEmpty() } as ArrayList<String>
     }
 
+    fun getEventWithImportId(importId: String): Event? {
+        val selection = "$MAIN_TABLE_NAME.$COL_IMPORT_ID = ?"
+        val selectionArgs = arrayOf(importId.toString())
+        val cursor = getEventsCursor(selection, selectionArgs)
+        val events = fillEvents(cursor)
+        return if (!events.isEmpty())
+            events[0]
+        else
+            null
+    }
+
     fun getEventWithId(id: Int): Event? {
         val selection = "$MAIN_TABLE_NAME.$COL_ID = ?"
         val selectionArgs = arrayOf(id.toString())

app/src/main/kotlin/com/simplemobiletools/calendar/models/GoogleEvent.kt

@@ -4,4 +4,4 @@ import com.google.gson.JsonArray
 import com.google.gson.JsonObject
 
 data class GoogleEvent(val summary: String, val description: String, val status: String, val start: GoogleEventDateTime, val end: GoogleEventDateTime,
-                       val reminders: JsonObject, val recurrence: JsonArray?, val iCalUID: String, val colorId: Int)
+                       val reminders: JsonObject, val recurrence: JsonArray?, val iCalUID: String, val colorId: Int, val updated: String)