Kotlin-Android-Open-Source/solivagant

allprojects {
  repositories {
    [...]
    mavenCentral()
  }
}

implementation("io..hoc081098:solivagant-navigation:0.0.1-alpha01")

@Immutable
@Parcelize
data object StartScreenRoute : NavRoute, NavRoot

@Immutable
@Parcelize
data object SearchProductScreenRoute : NavRoute

@JvmField
val StartScreenDestination: NavDestination =
  ScreenDestination<StartScreenRoute> { StartScreen() }

@Composable
internal fun StartScreen(
  modifier: Modifier = Modifier,
  viewModel: StartViewModel = koinKmpViewModel(),
) {
  // UI Composable
}

class StartViewModel(
  // used to trigger navigation actions from outside the view layer (e.g. from a ViewModel).
  // Usually, it is singleton object, or the host Activity retained scope.
  private val navigator: NavEventNavigator,
) : ViewModel() {
  internal fun navigateToProductsScreen() = navigator.navigateTo(ProductsScreenRoute)
  internal fun navigateToSearchProductScreen() = navigator.navigateTo(SearchProductScreenRoute)
}

@JvmField
val SearchProductScreenDestination: NavDestination =
  ScreenDestination<SearchProductScreenRoute> { SearchProductsScreen() }

@Composable
fun SearchProductsScreen(
  modifier: Modifier = Modifier,
  viewModel: SearchProductsViewModel = koinKmpViewModel<SearchProductsViewModel>(),
) {
  // UI Composable
}

class SearchProductsViewModel(
  private val searchProducts: SearchProducts,
  private val savedStateHandle: SavedStateHandle,
  // used to trigger navigation actions from outside the view layer (e.g. from a ViewModel).
  // Usually, it is singleton object, or the host Activity retained scope.
  private val navigator: NavEventNavigator,
) : ViewModel() {
  fun navigateToProductDetail(id: Int) {
    navigator.navigateTo(ProductDetailScreenRoute(id))
  }
}

@Stable
private val AllDestinations: ImmutableSet<NavDestination> = persistentSetOf(
  StartScreenDestination,
  SearchProductScreenDestination,
  // and more ...
)

@Composable
fun MyAwesomeApp(
  // used to trigger navigation actions from outside the view layer (e.g. from a ViewModel).
  // Usually, it is singleton object, or the host Activity retained scope.
  navigator: NavEventNavigator,
  modifier: Modifier = Modifier,
) {
  var currentRoute: BaseRoute? by remember { mutableStateOf(null) }

  NavHost(
    modifier = modifier,
    // route to the screen that should be shown initially
    startRoute = StartScreenRoute,
    // should contain all destinations that can be navigated to
    destinations = AllDestinations,
    navEventNavigator = navigator,
    destinationChangedCallback = { currentRoute = it },
  )
}

class MainActivity : ComponentActivity() {
  override fun onCreate(savedInstanceState: Bundle) {
    super.onCreate()

    // navigator can be retrieved from the DI container, such as Koin, Dagger Hilt, etc.

    setContent {
      MyAwesomeApp(
        navigator = navigator
      )
    }
  }
}

// navigate to the destination that the given route leads to
navigator.navigateTo(DetailScreenRoute("some-id"))
// navigate up in the hierarchy
navigator.navigateUp()
// navigate to the previous destination in the backstack
navigator.navigateBack()
// navigate back to the destination belonging to the referenced route and remove all destinations
// in between from the back stack, depending on inclusive the destination
navigator.navigateBackTo<MainScreenRoute>(inclusive = false)