class ScheduleRepository(
    private val service: ScheduleService,
    private val lessonsDAO: LessonsDAO
) {

    val schedule: ScheduleResponse? get() = scheduleLiveData.value

    private val scheduleLiveData = MutableLiveData<ScheduleResponse>()

    private var observer: Observer<ScheduleResponse>? = null

    fun subscribe(callback: (ScheduleResponse) -> Unit) {
        observer = Observer(callback).also {
            scheduleLiveData.observeForever(callback)
        }
    }

    fun unsubscribe() = observer?.let(scheduleLiveData::removeObserver)

    suspend fun initSchedule(group: String?) {
        val lessons = lessonsDAO.getLessons()
        scheduleLiveData.postValue(ScheduleResponse(null, ArrayList(lessons)))
        loadSchedule(group)
    }

    suspend fun loadSchedule(group: String?) {
        service.getSchedule(group?.toHttpQueryFormat()).also {
            scheduleLiveData.postValue(it)
            saveSchedule(it.schedule)
        }
    }

    private suspend fun saveSchedule(lessons: ArrayList<Lesson>) {
        lessonsDAO.deleteAll()
        lessonsDAO.insertAll(lessons)
    }
}