import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.flow.MutableSharedFlow
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.flow.update
import kotlinx.coroutines.launch

abstract class StateAndEventViewModel<UiState, Event>(initialState: UiState) : ViewModel() {

    private val events = MutableSharedFlow<Event>(replay = 0)
    private val _uiState: MutableStateFlow<UiState> = MutableStateFlow(initialState)
    val uiState: StateFlow<UiState> = _uiState.asStateFlow()

    init {
        viewModelScope.launch {
            events.collect { event ->
                handleEvent(event)
            }
        }
    }

    protected abstract suspend fun handleEvent(event: Event)

    protected fun updateUiState(update: UiState.() -> UiState) {
        _uiState.update { _uiState.value.update() }
    }

    fun onEvent(event: Event) {
        viewModelScope.launch {
            events.emit(event)
        }
    }
}






@HiltViewModel
class DetailViewModel @Inject constructor(
    private val getItemDetail: GetItemDetailUseCase,
    private val navigator: NavigationService,
) : StateAndEventViewModel<DetailUIState, DetailUIEvent>(DetailUIState(null)) {

    private fun loadItemDetail() {
        viewModelScope.launch {
            getItemDetail.getDetail()
                .onStart {
                    updateUiState { copy(isLoading = true) }
                }
                .catch { exception ->
                    updateUiState { copy(error = exception) }
                }
                .collect {
                    updateUiState { copy(itemData = it, isLoading = false) }
                }
        }
    }

    private fun handleBack() {
        navigator.goBack()
    }

    private fun handleSearchDetailClick() {
        navigator.navigateTo("detail/search")
    }

    override suspend fun handleEvent(event: DetailUIEvent) {
        when (event) {
            is DetailUIEvent.Dismiss -> handleBack()
            is DetailUIEvent.LoadItemDetail -> loadItemDetail()
            is DetailUIEvent.SearchDetailClick -> handleSearchDetailClick()
        }
    }

}