Completed Tutorial :)

app/src/main/java/com/example/cupcake/CupcakeScreen.kt

@@ -15,39 +15,59 @@
  */
 package com.example.cupcake
 
+import android.content.Context
+import android.content.Intent
+import androidx.annotation.StringRes
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.ArrowBack
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
-import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
 import androidx.compose.material3.TopAppBar
-import androidx.compose.material3.TopAppBarDefaults
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.dimensionResource
 import androidx.compose.ui.res.stringResource
 import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.navigation.NavHostController
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.currentBackStackEntryAsState
 import androidx.navigation.compose.rememberNavController
+import com.example.cupcake.data.DataSource
+import com.example.cupcake.ui.OrderSummaryScreen
 import com.example.cupcake.ui.OrderViewModel
+import com.example.cupcake.ui.SelectOptionScreen
+import com.example.cupcake.ui.StartOrderScreen
+
+
+enum class CupcakeScreen(@StringRes val title: Int) {
+    Start(title = R.string.app_name),
+    Flavor(title = R.string.choose_flavor),
+    Pickup(title = R.string.choose_pickup_date),
+    Summary(title = R.string.order_summary)
+}
+
 
 /**
  * Composable that displays the topBar and displays back button if back navigation is possible.
  */
 @Composable
 fun CupcakeAppBar(
+    currentScreen: CupcakeScreen,
     canNavigateBack: Boolean,
-    navigateUp: () -> Unit,
+    navigateUp: () -> Unit = {},
     modifier: Modifier = Modifier
 ) {
     TopAppBar(
-        title = { Text(stringResource(id = R.string.app_name)) },
+        title = { Text(stringResource(currentScreen.title)) },
-        colors = TopAppBarDefaults.mediumTopAppBarColors(
-            containerColor = MaterialTheme.colorScheme.primaryContainer
-        ),
         modifier = modifier,
         navigationIcon = {
             if (canNavigateBack) {
@@ -60,6 +80,7 @@ fun CupcakeAppBar(
             }
         }
     )
+
 }
 
 @Composable
@@ -67,16 +88,111 @@ fun CupcakeApp(
     viewModel: OrderViewModel = viewModel(),
     navController: NavHostController = rememberNavController()
 ) {
+    val backStackEntry by navController.currentBackStackEntryAsState()
+    val currentScreen = CupcakeScreen.valueOf(
+        backStackEntry?.destination?.route ?: CupcakeScreen.Start.name
+    )
 
     Scaffold(
         topBar = {
             CupcakeAppBar(
-                canNavigateBack = false,
+                currentScreen = currentScreen,
-                navigateUp = { /* TODO: implement back navigation */ }
+                canNavigateBack = navController.previousBackStackEntry != null,
+                navigateUp = { navController.navigateUp() }
             )
+
         }
     ) { innerPadding ->
         val uiState by viewModel.uiState.collectAsState()
 
+
+        NavHost(
+            navController = navController,
+            startDestination = CupcakeScreen.Start.name,
+            modifier = Modifier.padding(innerPadding)
+        ) {
+            composable(route = CupcakeScreen.Start.name) {
+                StartOrderScreen(
+                    quantityOptions = DataSource.quantityOptions,
+                    onNextButtonClicked = {
+                        viewModel.setQuantity(it)
+                        navController.navigate(CupcakeScreen.Flavor.name)
+                    },
+                    modifier = Modifier
+                        .fillMaxSize()
+                        .padding(dimensionResource(R.dimen.padding_medium))
+                )
+            }
+
+            composable(route = CupcakeScreen.Flavor.name) {
+                val context = LocalContext.current
+                SelectOptionScreen(
+                    subtotal = uiState.price,
+                    onNextButtonClicked = { navController.navigate(CupcakeScreen.Pickup.name) },
+                    onCancelButtonClicked = {
+                        cancelOrderAndNavigateToStart(viewModel, navController)
+                    },
+                    options = DataSource.flavors.map { id -> context.resources.getString(id) },
+                    onSelectionChanged = { viewModel.setFlavor(it) },
+                    modifier = Modifier.fillMaxHeight()
+                )
+            }
+
+            composable(route = CupcakeScreen.Pickup.name) {
+                SelectOptionScreen(
+                    subtotal = uiState.price,
+                    onNextButtonClicked = { navController.navigate(CupcakeScreen.Summary.name) },
+                    onCancelButtonClicked = {
+                        cancelOrderAndNavigateToStart(viewModel, navController)
+                    },
+                    options = uiState.pickupOptions,
+                    onSelectionChanged = { viewModel.setDate(it) },
+                    modifier = Modifier.fillMaxHeight()
+                )
+            }
+
+            composable(route = CupcakeScreen.Summary.name) {
+                val context = LocalContext.current
+                OrderSummaryScreen(
+                    orderUiState = uiState,
+                    onCancelButtonClicked = {
+                        cancelOrderAndNavigateToStart(viewModel, navController)
+                    },
+                    onSendButtonClicked = { subject: String, summary: String ->
+                        shareOrder(context, subject = subject, summary = summary)
+                    },
+
+                    modifier = Modifier.fillMaxHeight()
+                )
+            }
+
+
+        }
     }
 }
+
+private fun shareOrder(context: Context, subject: String, summary: String) {
+    val intent = Intent(Intent.ACTION_SEND).apply {
+        type = "text/plain"
+        putExtra(Intent.EXTRA_SUBJECT, subject)
+        putExtra(Intent.EXTRA_TEXT, summary)
+    }
+
+    context.startActivity(
+        Intent.createChooser(
+            intent,
+            context.getString(R.string.new_cupcake_order)
+        )
+    )
+
+}
+
+
+private fun cancelOrderAndNavigateToStart(
+    viewModel: OrderViewModel,
+    navController: NavHostController
+) {
+    viewModel.resetOrder()
+    navController.popBackStack(CupcakeScreen.Start.name, inclusive = false)
+}
+

app/src/main/java/com/example/cupcake/ui/SelectOptionScreen.kt

@@ -52,6 +52,8 @@ fun SelectOptionScreen(
     subtotal: String,
     options: List<String>,
     onSelectionChanged: (String) -> Unit = {},
+    onCancelButtonClicked: () -> Unit = {},
+    onNextButtonClicked: () -> Unit = {},
     modifier: Modifier = Modifier
 ) {
     var selectedValue by rememberSaveable { mutableStateOf("") }
@@ -105,7 +107,7 @@ fun SelectOptionScreen(
         ) {
             OutlinedButton(
                 modifier = Modifier.weight(1f),
-                onClick = {}
+                onClick = onCancelButtonClicked
             ) {
                 Text(stringResource(R.string.cancel))
             }
@@ -113,7 +115,7 @@ fun SelectOptionScreen(
                 modifier = Modifier.weight(1f),
                 // the button is enabled when the user makes a selection
                 enabled = selectedValue.isNotEmpty(),
-                onClick = {}
+                onClick = onNextButtonClicked
             ) {
                 Text(stringResource(R.string.next))
             }

app/src/main/java/com/example/cupcake/ui/StartOrderScreen.kt

@@ -49,6 +49,8 @@ import com.example.cupcake.ui.theme.CupcakeTheme
 @Composable
 fun StartOrderScreen(
     quantityOptions: List<Pair<Int, Int>>,
+    onNextButtonClicked: (Int) -> Unit,
+
     modifier: Modifier = Modifier
 ) {
     Column(
@@ -83,7 +85,7 @@ fun StartOrderScreen(
             quantityOptions.forEach { item ->
                 SelectQuantityButton(
                     labelResourceId = item.first,
-                    onClick = {}
+                    onClick = { onNextButtonClicked(item.second) }
                 )
             }
         }
@@ -114,9 +116,11 @@ fun StartOrderPreview() {
     CupcakeTheme {
         StartOrderScreen(
             quantityOptions = DataSource.quantityOptions,
+            onNextButtonClicked = {},
             modifier = Modifier
                 .fillMaxSize()
                 .padding(dimensionResource(R.dimen.padding_medium))
         )
     }
 }
+

app/src/main/java/com/example/cupcake/ui/SummaryScreen.kt

@@ -48,6 +48,9 @@ import com.example.cupcake.ui.theme.CupcakeTheme
 @Composable
 fun OrderSummaryScreen(
     orderUiState: OrderUiState,
+        onCancelButtonClicked: () -> Unit,
+    onSendButtonClicked: (String, String) -> Unit,
+
     modifier: Modifier = Modifier
 ) {
     val resources = LocalContext.current.resources
@@ -103,13 +106,13 @@ fun OrderSummaryScreen(
             ) {
                 Button(
                     modifier = Modifier.fillMaxWidth(),
-                    onClick = {}
+    onClick = { onSendButtonClicked(newOrder, orderSummary) }
                 ) {
                     Text(stringResource(R.string.send))
                 }
                 OutlinedButton(
                     modifier = Modifier.fillMaxWidth(),
-                    onClick = {}
+                    onClick = onCancelButtonClicked
                 ) {
                     Text(stringResource(R.string.cancel))
                 }
@@ -121,10 +124,13 @@ fun OrderSummaryScreen(
 @Preview
 @Composable
 fun OrderSummaryPreview() {
-    CupcakeTheme {
+   CupcakeTheme {
-        OrderSummaryScreen(
+       OrderSummaryScreen(
-            orderUiState = OrderUiState(0, "Test", "Test", "$300.00"),
+           orderUiState = OrderUiState(0, "Test", "Test", "$300.00"),
-            modifier = Modifier.fillMaxHeight()
+           onSendButtonClicked = { subject: String, summary: String -> },
-        )
+           onCancelButtonClicked = {},
-    }
+           modifier = Modifier.fillMaxHeight()
+       )
+   }
 }
+