Initial commit.

app/src/main/java/com/pixelized/biblib/ui/viewmodel/NavigationViewModel.kt

@@ -0,0 +1,61 @@
+package com.pixelized.biblib.ui.viewmodel
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.pixelized.biblib.data.ui.BookUio
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import java.util.*
+
+class NavigationViewModel : ViewModel() {
+
+    private val stack = Stack<Page>()
+
+    private val _screen = MutableLiveData<Screen>()
+    val screen: LiveData<Screen> get() = _screen
+
+    private val _page = MutableLiveData<Page>()
+    val page: LiveData<Page> get() = _page
+
+    init {
+        _screen.value = Screen.SplashScreen
+        viewModelScope.launch {
+            delay(3000)
+            navigateTo(Page.HomePage)
+            navigateTo(Screen.MainScreen)
+        }
+    }
+
+    fun navigateTo(screen: Screen): Boolean {
+        _screen.postValue(screen)
+        return true
+    }
+
+    fun navigateTo(page: Page): Boolean {
+        _page.postValue(page)
+        stack.push(page)
+        return true
+    }
+
+    fun navigateBack() : Boolean {
+        stack.pop()
+        return if (stack.empty()) {
+            false
+        } else {
+            _page.postValue(stack.peek())
+            true
+        }
+    }
+
+    sealed class Screen {
+        object SplashScreen : Screen()
+        object MainScreen : Screen()
+    }
+
+    sealed class Page {
+        object HomePage : Page()
+        data class Detail(val book: BookUio) : Page()
+    }
+}