// Data class (like Dart's model classes)
data class User(val id: Int, val name: String, val email: String)
// Null safety (similar to Dart)
val name: String = "Ali"       // Non-null
val nickname: String? = null   // Nullable
val length = nickname?.length ?: 0  // Safe call + elvis operator
// Extension functions (like Dart extensions)
fun String.isEmail(): Boolean =
    this.contains("@") && this.contains(".")
// Coroutines (like Dart Futures/Streams)
suspend fun fetchUsers(): List<User> {
    delay(1000) // Non-blocking delay
    return listOf(User(1, "Ali", "ali@example.com"))
}
// Sealed classes (like Dart sealed classes)
sealed class Result<out T> {
    data class Success<T>(val data: T) : Result<T>()
    data class Error(val message: String) : Result<Nothing>()
}

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Handle intent extras
        val userId = intent.getIntExtra("user_id", -1)

        // Load a fragment
        supportFragmentManager.beginTransaction()
            .replace(R.id.fragment_container, DetailFragment.newInstance(userId))
            .addToBackStack(null)
            .commit()
    }
}

class DetailFragment : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        return inflater.inflate(R.layout.fragment_detail, container, false)
    }
}

@Composable
fun UserCard(user: User, onClick: (Int) -> Unit) {
    Card(
        modifier = Modifier.fillMaxWidth().padding(8.dp).clickable { onClick(user.id) },
        elevation = CardDefaults.cardElevation(defaultElevation = 4.dp)
    ) {
        Row(modifier = Modifier.padding(16.dp)) {
            Icon(Icons.Default.Person, contentDescription = "User")
            Spacer(modifier = Modifier.width(12.dp))
            Column {
                Text(text = user.name, style = MaterialTheme.typography.titleMedium)
                Text(text = user.email, style = MaterialTheme.typography.bodySmall)
            }
        }
    }
}
@Preview(showBackground = true)
@Composable
fun PreviewUserCard() {
    UserCard(User(1, "Ali Najimi", "ali@example.com"), onClick = {})
}

class SyncWorker(appContext: Context, params: WorkerParameters) :
    CoroutineWorker(appContext, params) {

    override suspend fun doWork(): Result {
        return try {
            // Do background work
            val data = fetchRemoteData()
            saveToLocal(data)
            Result.success()
        } catch (e: Exception) {
            Result.retry() // or Result.failure()
        }
    }
}

val syncRequest = PeriodicWorkRequestBuilder<SyncWorker>(
    15, TimeUnit.MINUTES  // Minimum interval
).setConstraints(
    Constraints.Builder()
        .setRequiredNetworkType(NetworkType.CONNECTED)
        .setRequiresBatteryNotLow(true)
        .build()
).build()

WorkManager.getInstance(context).enqueueUniquePeriodicWork(
    "sync", ExistingPeriodicWorkPolicy.KEEP, syncRequest
)

// Request runtime permission
if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
    != PackageManager.PERMISSION_GRANTED
) {
    ActivityCompat.requestPermissions(
        this,
        arrayOf(Manifest.permission.CAMERA),
        REQUEST_CODE_CAMERA
    )
}
// Handle result
override fun onRequestPermissionsResult(
    requestCode: Int, permissions: Array<String>, grantResults: IntArray
) {
    if (requestCode == REQUEST_CODE_CAMERA &&
        grantResults.isNotEmpty() &&
        grantResults[0] == PackageManager.PERMISSION_GRANTED) {
        // Permission granted — open camera
    }
}

// Flutter side
const channel = MethodChannel('com.example/battery');

Future<int> getBatteryLevel() async {
  try {
    final level = await channel.invokeMethod<int>('getBatteryLevel');
    return level!;
  } on PlatformException catch (e) {
    print('Failed: ${e.message}');
    return -1;
  }
}

// MainActivity.kt
class MainActivity : FlutterActivity() {
    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger,
            "com.example/battery"
        ).setMethodCallHandler { call, result ->
            when (call.method) {
                "getBatteryLevel" -> {
                    val level = getBatteryLevel()
                    if (level != -1) {
                        result.success(level)
                    } else {
                        result.error("UNAVAILABLE", "Battery level not available", null)
                    }
                }
                else -> result.notImplemented()
            }
        }
    }
    private fun getBatteryLevel(): Int {
        val intent = IntentFilter(Intent.ACTION_BATTERY_CHANGED)
        val battery = registerReceiver(null, intent)
        val level = battery?.getIntExtra(BatteryManager.EXTRA_LEVEL, -1) ?: -1
        val scale = battery?.getIntExtra(BatteryManager.EXTRA_SCALE, -1) ?: -1
        return (level * 100) / scale
    }
}