// Compose: Dynamic color theme
@Composable
fun AppTheme(
    darkTheme: Boolean = isSystemInDarkTheme(),
    dynamicColor: Boolean = true,
    content: @Composable () -> Unit
) {
    val colorScheme = when {
        dynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
            val context = LocalContext.current
            if (darkTheme) dynamicDarkColorScheme(context)
            else dynamicLightColorScheme(context)
        }
        darkTheme -> darkColorScheme()
        else -> lightColorScheme()
    }
    MaterialTheme(
        colorScheme = colorScheme,
        typography = AppTypography,
        content = content
    )
}

<!-- XML: Dynamic color in themes.xml -->
<style name="Theme.App" parent="Theme.Material3.DayNight.NoActionBar">
    <item name="dynamicColorThemeOverlay">@style/ThemeOverlay.Material3.DynamicColors.DayNight</item>
</style>

// Correct: semantic color roles
Text(
    text = "Error message",
    color = MaterialTheme.colorScheme.error
)
Surface(color = MaterialTheme.colorScheme.errorContainer) {
    Text(text = "Error detail", color = MaterialTheme.colorScheme.onErrorContainer)
}

// WRONG: hardcoded colors
Text(text = "Error", color = Color(0xFFB00020)) // Anti-pattern

// Compose: Detect system theme
val darkTheme = isSystemInDarkTheme()

// Custom color scheme with brand seed
private val BrandLightColorScheme = lightColorScheme(
    primary = Color(0xFF1B6D2F),
    onPrimary = Color(0xFFFFFFFF),
    primaryContainer = Color(0xFFA4F6A8),
    onPrimaryContainer = Color(0xFF002107),
    // ... generate full palette from seed
)

// Compose: Navigation Bar
NavigationBar {
    items.forEachIndexed { index, item ->
        NavigationBarItem(
            icon = {
                Icon(
                    imageVector = if (selectedItem == index) item.filledIcon else item.outlinedIcon,
                    contentDescription = item.label
                )
            },
            label = { Text(item.label) },
            selected = selectedItem == index,
            onClick = { selectedItem = index }
        )
    }
}

// Compose: Navigation Rail for larger screens
NavigationRail(
    header = {
        FloatingActionButton(
            onClick = { /* primary action */ },
            containerColor = MaterialTheme.colorScheme.tertiaryContainer
        ) {
            Icon(Icons.Default.Add, contentDescription = "Create")
        }
    }
) {
    items.forEachIndexed { index, item ->
        NavigationRailItem(
            icon = { Icon(item.icon, contentDescription = item.label) },
            label = { Text(item.label) },
            selected = selectedItem == index,
            onClick = { selectedItem = index }
        )
    }
}

// Compose: Permanent Navigation Drawer for large screens
PermanentNavigationDrawer(
    drawerContent = {
        PermanentDrawerSheet {
            Text("App Name", modifier = Modifier.padding(16.dp),
                 style = MaterialTheme.typography.titleMedium)
            HorizontalDivider()
            items.forEach { item ->
                NavigationDrawerItem(
                    label = { Text(item.label) },
                    selected = item == selectedItem,
                    onClick = { selectedItem = item },
                    icon = { Icon(item.icon, contentDescription = null) }
                )
            }
        }
    }
) {
    Scaffold { /* page content */ }
}

// Compose: Predictive back handling
val predictiveBackHandler = remember { PredictiveBackHandler(enabled = true) { progress ->
    // Animate based on progress (0.0 to 1.0)
}}

<!-- AndroidManifest.xml: opt in to predictive back -->
<application android:enableOnBackInvokedCallback="true">

// Compose: Window size classes
val windowSizeClass = calculateWindowSizeClass(this)
when (windowSizeClass.widthSizeClass) {
    WindowWidthSizeClass.Compact -> CompactLayout()
    WindowWidthSizeClass.Medium -> MediumLayout()
    WindowWidthSizeClass.Expanded -> ExpandedLayout()
}

// Compose: Edge-to-edge setup
class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        enableEdgeToEdge()
        super.onCreate(savedInstanceState)
        setContent {
            Scaffold(
                modifier = Modifier.fillMaxSize(),
                // Scaffold handles insets for top/bottom bars automatically
            ) { innerPadding ->
                Content(modifier = Modifier.padding(innerPadding))
            }
        }
    }
}

// Compose: Detect fold posture
val foldingFeatures = WindowInfoTracker.getOrCreate(context)
    .windowLayoutInfo(context)
    .collectAsState(initial = WindowLayoutInfo(emptyList()))

// Compose: Custom typography
val AppTypography = Typography(
    displayLarge = TextStyle(
        fontFamily = FontFamily(Font(R.font.brand_regular)),
        fontWeight = FontWeight.Normal,
        fontSize = 57.sp,
        lineHeight = 64.sp,
        letterSpacing = (-0.25).sp
    ),
    bodyLarge = TextStyle(
        fontFamily = FontFamily(Font(R.font.brand_regular)),
        fontWeight = FontWeight.Normal,
        fontSize = 16.sp,
        lineHeight = 24.sp,
        letterSpacing = 0.5.sp
    )
    // ... define all 15 roles
)

// Compose: FAB variants
// Standard FAB
FloatingActionButton(onClick = { /* action */ }) {
    Icon(Icons.Default.Add, contentDescription = "Create new item")
}

// Extended FAB (with label - preferred for clarity)
ExtendedFloatingActionButton(
    onClick = { /* action */ },
    icon = { Icon(Icons.Default.Edit, contentDescription = null) },
    text = { Text("Compose") }
)

// Large FAB
LargeFloatingActionButton(onClick = { /* action */ }) {
    Icon(Icons.Default.Add, contentDescription = "Create", modifier = Modifier.size(36.dp))
}

// Compose: Top app bar variants
// Small (default)
TopAppBar(
    title = { Text("Page Title") },
    navigationIcon = {
        IconButton(onClick = { /* navigate up */ }) {
            Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back")
        }
    },
    actions = {
        IconButton(onClick = { /* search */ }) {
            Icon(Icons.Default.Search, contentDescription = "Search")
        }
    }
)

// Medium — expands title area
MediumTopAppBar(
    title = { Text("Section Title") },
    scrollBehavior = TopAppBarDefaults.enterAlwaysScrollBehavior()
)

// Large — for prominent titles
LargeTopAppBar(
    title = { Text("Screen Title") },
    scrollBehavior = TopAppBarDefaults.exitUntilCollapsedScrollBehavior()
)

// Compose: Modal bottom sheet
ModalBottomSheet(
    onDismissRequest = { showSheet = false },
    sheetState = rememberModalBottomSheetState()
) {
    Column(modifier = Modifier.padding(16.dp)) {
        Text("Sheet Title", style = MaterialTheme.typography.titleLarge)
        Spacer(modifier = Modifier.height(16.dp))
        // Sheet content
    }
}

// Compose: Alert dialog
AlertDialog(
    onDismissRequest = { showDialog = false },
    title = { Text("Discard draft?") },
    text = { Text("Your unsaved changes will be lost.") },
    confirmButton = {
        TextButton(onClick = { /* confirm */ }) { Text("Discard") }
    },
    dismissButton = {
        TextButton(onClick = { showDialog = false }) { Text("Cancel") }
    }
)

// Compose: Snackbar with action
val snackbarHostState = remember { SnackbarHostState() }
Scaffold(snackbarHost = { SnackbarHost(snackbarHostState) }) {
    // trigger snackbar
    LaunchedEffect(key) {
        val result = snackbarHostState.showSnackbar(
            message = "Item archived",
            actionLabel = "Undo",
            duration = SnackbarDuration.Short
        )
        if (result == SnackbarResult.ActionPerformed) { /* undo */ }
    }
}

// Filter Chip
FilterChip(
    selected = isSelected,
    onClick = { isSelected = !isSelected },
    label = { Text("Filter") },
    leadingIcon = if (isSelected) {
        { Icon(Icons.Default.Check, contentDescription = null, modifier = Modifier.size(18.dp)) }
    } else null
)

// Assist Chip
AssistChip(
    onClick = { /* action */ },
    label = { Text("Add to calendar") },
    leadingIcon = { Icon(Icons.Default.CalendarToday, contentDescription = null) }
)

// Compose: Accessible components
Icon(
    Icons.Default.Favorite,
    contentDescription = "Add to favorites" // Descriptive, not "heart icon"
)

// Decorative elements
Icon(
    Icons.Default.Star,
    contentDescription = null // null for purely decorative
)

// Merge semantics for compound elements
Row(modifier = Modifier.semantics(mergeDescendants = true) {}) {
    Icon(Icons.Default.Event, contentDescription = null)
    Text("March 15, 2026")
}

// Custom actions
Box(modifier = Modifier.semantics {
    customActions = listOf(
        CustomAccessibilityAction("Archive") { /* archive */ true },
        CustomAccessibilityAction("Delete") { /* delete */ true }
    )
})

// Compose: Ensure minimum touch target
IconButton(onClick = { /* action */ }) {
    // IconButton already provides 48dp minimum touch target
    Icon(Icons.Default.Close, contentDescription = "Close")
}

// Manual minimum touch target
Box(
    modifier = Modifier
        .sizeIn(minWidth = 48.dp, minHeight = 48.dp)
        .clickable { /* action */ },
    contentAlignment = Alignment.Center
) {
    Icon(Icons.Default.Info, contentDescription = "Info", modifier = Modifier.size(24.dp))
}

// Compose: Custom focus order
Column {
    var focusRequester = remember { FocusRequester() }
    TextField(
        modifier = Modifier.focusRequester(focusRequester),
        value = text,
        onValueChange = { text = it }
    )
    LaunchedEffect(Unit) {
        focusRequester.requestFocus() // Auto-focus on screen load
    }
}

// Compose: Pull to refresh
PullToRefreshBox(
    isRefreshing = isRefreshing,
    onRefresh = { viewModel.refresh() }
) {
    LazyColumn { /* content */ }
}

// Compose: Swipe to dismiss
SwipeToDismissBox(
    state = rememberSwipeToDismissBoxState(),
    backgroundContent = {
        Box(
            modifier = Modifier.fillMaxSize().background(MaterialTheme.colorScheme.error),
            contentAlignment = Alignment.CenterEnd
        ) {
            Icon(Icons.Default.Delete, contentDescription = "Delete",
                 tint = MaterialTheme.colorScheme.onError)
        }
    }
) {
    ListItem(headlineContent = { Text("Swipeable item") })
}

// Create notification channel (required for Android 8+)
val channel = NotificationChannel(
    "messages",
    "Messages",
    NotificationManager.IMPORTANCE_HIGH
).apply {
    description = "New message notifications"
    enableLights(true)
    lightColor = Color.BLUE
}
notificationManager.createNotificationChannel(channel)

// Compose: Permission request
val permissionState = rememberPermissionState(Manifest.permission.CAMERA)

if (permissionState.status.isGranted) {
    CameraPreview()
} else {
    Column {
        Text("Camera access is needed to scan QR codes.")
        Button(onClick = { permissionState.launchPermissionRequest() }) {
            Text("Grant Camera Access")
        }
    }
}

// Photo picker: no permission needed
val pickMedia = rememberLauncherForActivityResult(
    ActivityResultContracts.PickVisualMedia()
) { uri ->
    uri?.let { /* handle selected media */ }
}
pickMedia.launch(PickVisualMediaRequest(ActivityResultContracts.PickVisualMedia.ImageOnly))

// Compose Glance API widget
class TaskWidget : GlanceAppWidget() {
    override suspend fun provideGlance(context: Context, id: GlanceId) {
        provideContent {
            GlanceTheme {
                Column(
                    modifier = GlanceModifier
                        .fillMaxSize()
                        .background(GlanceTheme.colors.widgetBackground)
                        .padding(16.dp)
                ) {
                    Text(
                        text = "Tasks",
                        style = TextStyle(fontWeight = FontWeight.Bold,
                                         color = GlanceTheme.colors.onSurface)
                    )
                    // Widget content
                }
            }
        }
    }
}