BayernMessenger/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/session/room/RoomSummaryObserver.kt

package im.vector.matrix.android.internal.session.room

import com.zhuinden.monarchy.Monarchy
import im.vector.matrix.android.api.session.events.model.EventType
import im.vector.matrix.android.api.session.room.model.RoomNameContent
import im.vector.matrix.android.api.session.room.model.RoomTopicContent
import im.vector.matrix.android.internal.database.mapper.asDomain
import im.vector.matrix.android.internal.database.model.EventEntity
import im.vector.matrix.android.internal.database.model.RoomEntity
import im.vector.matrix.android.internal.database.model.RoomSummaryEntity
import im.vector.matrix.android.internal.database.query.last
import im.vector.matrix.android.internal.database.query.where
import io.realm.RealmResults
import java.util.concurrent.atomic.AtomicBoolean

internal class RoomSummaryObserver(private val monarchy: Monarchy) {

    private lateinit var roomResults: RealmResults<RoomEntity>
    private var isStarted = AtomicBoolean(false)

    fun start() {
        if (isStarted.compareAndSet(false, true)) {
            monarchy.doWithRealm {
                roomResults = RoomEntity.where(it).findAllAsync()
                roomResults.addChangeListener { rooms, changeSet ->
                    manageRoomResults(rooms, changeSet.changes)
                    manageRoomResults(rooms, changeSet.insertions)
                }
            }
        }
    }

    fun dispose() {
        if (isStarted.compareAndSet(true, false)) {
            roomResults.removeAllChangeListeners()
        }
    }

    // PRIVATE

    private fun manageRoomResults(rooms: RealmResults<RoomEntity>, indexes: IntArray) {
        indexes.forEach {
            val room = rooms[it]
            if (room != null) {
                manageRoom(room.roomId)
            }
        }
    }

    private fun manageRoom(roomId: String) {
        monarchy.writeAsync { realm ->
            val lastNameEvent = EventEntity.where(realm, roomId, EventType.STATE_ROOM_NAME).last()?.asDomain()
            val lastTopicEvent = EventEntity.where(realm, roomId, EventType.STATE_ROOM_TOPIC).last()?.asDomain()
            val lastMessageEvent = EventEntity.where(realm, roomId, EventType.MESSAGE).last()

            val roomSummary = realm.copyToRealmOrUpdate(RoomSummaryEntity(roomId))
            roomSummary.displayName = lastNameEvent?.content<RoomNameContent>()?.name
            roomSummary.topic = lastTopicEvent?.content<RoomTopicContent>()?.topic
            roomSummary.lastMessage = lastMessageEvent
        }
    }

}