Revert "LobstersApp: replace with a BackgroundScaffold"

This reverts commit be58017cac.

app/src/main/java/dev/msfjarvis/lobsters/ui/main/LobstersApp.kt

@@ -1,75 +1,114 @@
 package dev.msfjarvis.lobsters.ui.main
 
-import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.lazy.rememberLazyListState
-import androidx.compose.material.BackdropScaffold
+import androidx.compose.material.BottomNavigation
-import androidx.compose.material.BackdropScaffoldDefaults
+import androidx.compose.material.BottomNavigationItem
-import androidx.compose.material.BackdropValue
+import androidx.compose.material.Scaffold
 import androidx.compose.material.Text
-import androidx.compose.material.rememberBackdropScaffoldState
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.res.stringResource
-import androidx.compose.ui.text.font.FontWeight
-import androidx.compose.ui.text.style.TextAlign
-import androidx.compose.ui.unit.sp
 import androidx.lifecycle.viewmodel.compose.viewModel
+import androidx.navigation.compose.KEY_ROUTE
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.currentBackStackEntryAsState
+import androidx.navigation.compose.navigate
+import androidx.navigation.compose.rememberNavController
 import androidx.paging.compose.collectAsLazyPagingItems
-import dev.msfjarvis.lobsters.R
+import dev.msfjarvis.lobsters.ui.navigation.Destination
 import dev.msfjarvis.lobsters.ui.posts.HottestPosts
 import dev.msfjarvis.lobsters.ui.posts.SavedPosts
 import dev.msfjarvis.lobsters.ui.viewmodel.LobstersViewModel
+import dev.msfjarvis.lobsters.util.IconResource
+import kotlinx.coroutines.launch
 
 @Composable
 fun LobstersApp() {
   val viewModel: LobstersViewModel = viewModel()
-  val scaffoldState = rememberBackdropScaffoldState(initialValue = BackdropValue.Concealed)
+  val coroutineScope = rememberCoroutineScope()
-  BackdropScaffold(
+  val navController = rememberNavController()
-    scaffoldState = scaffoldState,
-    gesturesEnabled = false,
-    appBar = {
-      Spacer(modifier = Modifier.height(BackdropScaffoldDefaults.PeekHeight.times(0.3f)))
-      Text(
-        text = stringResource(id = R.string.app_name),
-        textAlign = TextAlign.Center,
-        fontSize = 18.sp,
-        fontWeight = FontWeight.Bold,
-        modifier = Modifier.fillMaxWidth(),
-      )
-      Spacer(modifier = Modifier.height(BackdropScaffoldDefaults.PeekHeight.times(0.3f)))
-    },
-    backLayerContent = { BackgroundLayerContent(viewModel) },
-  ) {
-    ForegroundLayerContent(viewModel)
-  }
-}
-
-@Composable
-fun ForegroundLayerContent(
-  viewModel: LobstersViewModel,
-) {
   val hottestPosts = viewModel.posts.collectAsLazyPagingItems()
+  val savedPosts by viewModel.savedPosts.collectAsState()
   val hottestPostsListState = rememberLazyListState()
 
+  val navBackStackEntry by navController.currentBackStackEntryAsState()
+  val currentRoute =
+    navBackStackEntry?.arguments?.getString(KEY_ROUTE) ?: Destination.startDestination.route
+  val currentDestination = Destination.getDestinationFromRoute(currentRoute)
+  val navigateToDestination: (destination: Destination) -> Unit = { destination ->
+    navController.navigate(destination.route) {
+      launchSingleTop = true
+      popUpTo(navController.graph.startDestination) { inclusive = false }
+    }
+  }
+  val jumpToIndex: (Int) -> Unit = {
+    coroutineScope.launch {
+      hottestPostsListState.snapToItemIndex(it)
+    }
+  }
+
+  Scaffold(
+    bottomBar = {
+      LobstersBottomNav(
+        currentDestination,
+        navigateToDestination,
+        jumpToIndex,
+      )
+    },
+  ) { innerPadding ->
+    NavHost(navController, startDestination = Destination.startDestination.route) {
+      composable(Destination.Hottest.route) {
         HottestPosts(
           posts = hottestPosts,
           listState = hottestPostsListState,
           isPostSaved = viewModel::isPostSaved,
           saveAction = viewModel::toggleSave,
+          modifier = Modifier.padding(bottom = innerPadding.calculateBottomPadding()),
         )
-}
+      }
-
+      composable(Destination.Saved.route) {
-@Composable
-fun BackgroundLayerContent(
-  viewModel: LobstersViewModel,
-) {
-  val savedPosts by viewModel.savedPosts.collectAsState()
         SavedPosts(
           posts = savedPosts,
           saveAction = viewModel::toggleSave,
+          modifier = Modifier.padding(bottom = innerPadding.calculateBottomPadding()),
         )
+      }
+    }
+  }
+}
+
+@Composable
+fun LobstersBottomNav(
+  currentDestination: Destination,
+  navigateToDestination: (destination: Destination) -> Unit,
+  jumpToIndex: (index: Int) -> Unit,
+) {
+  BottomNavigation(modifier = Modifier.testTag("LobstersBottomNav")) {
+    Destination.values().forEach { screen ->
+      BottomNavigationItem(
+        icon = {
+          IconResource(
+            resourceId = screen.badgeRes,
+            contentDescription = stringResource(screen.labelRes),
+          )
+        },
+        label = { Text(stringResource(id = screen.labelRes)) },
+        selected = currentDestination == screen,
+        alwaysShowLabels = false,
+        onClick = {
+          if (screen != currentDestination) {
+            navigateToDestination(screen)
+          } else if (screen.route == Destination.Hottest.route) {
+            jumpToIndex(0)
+          }
+        }
+      )
+    }
+  }
 }