Runtime Permissions

<!-- AndroidManifest.xml -->
<uses-permission android:name="android.permission.INTERNET" />            <!-- normal -->
<uses-permission android:name="android.permission.CAMERA" />              <!-- dangerous -->
<uses-permission android:name="android.permission.POST_NOTIFICATIONS" />  <!-- dangerous, API 33+ -->
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

class ScanActivity : AppCompatActivity() {

    // 1. register BEFORE the activity is started (as a property)
    private val cameraPermission = registerForActivityResult(ActivityResultContracts.RequestPermission()) { granted ->
        if (granted) openCamera()
        else Snackbar.make(binding.root, "Camera permission is needed to scan", Snackbar.LENGTH_LONG).show()
    }

    private fun onScanClicked() {
        when {
            // 2. already granted?
            ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) ==
                PackageManager.PERMISSION_GRANTED -> openCamera()

            // 3. user denied once → explain why first
            shouldShowRequestPermissionRationale(Manifest.permission.CAMERA) -> showRationale()

            // 4. ask
            else -> cameraPermission.launch(Manifest.permission.CAMERA)
        }
    }
}

private fun showRationale() {
    MaterialAlertDialogBuilder(this)
        .setTitle("Allow camera?")
        .setMessage("We use the camera only to scan your ID card. Photos stay on your phone.")
        .setNegativeButton("Not now", null)
        .setPositiveButton("Continue") { _, _ -> cameraPermission.launch(Manifest.permission.CAMERA) }
        .show()
}

// Permanently denied → open the app's settings page
private fun openAppSettings() {
    startActivity(Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS,
        Uri.fromParts("package", packageName, null)))
}

private val locationPermissions = registerForActivityResult(
    ActivityResultContracts.RequestMultiplePermissions()
) { result ->
    val fine = result[Manifest.permission.ACCESS_FINE_LOCATION] == true
    val coarse = result[Manifest.permission.ACCESS_COARSE_LOCATION] == true
    when {
        fine -> startPreciseLocation()
        coarse -> startApproximateLocation()
        else -> showNoLocationMessage()
    }
}

locationPermissions.launch(arrayOf(
    Manifest.permission.ACCESS_FINE_LOCATION,
    Manifest.permission.ACCESS_COARSE_LOCATION
))

// Student Diary – MainActivity
private val notificationPermission =
    registerForActivityResult(ActivityResultContracts.RequestPermission()) { granted ->
        if (!granted) {
            Snackbar.make(binding.root, R.string.notifications_off, Snackbar.LENGTH_LONG).show()
        }
    }

private fun askNotificationPermission() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU && !NotificationHelper.canNotify(this)) {
        notificationPermission.launch(Manifest.permission.POST_NOTIFICATIONS)
    }
}

// NotificationHelper
fun canNotify(context: Context): Boolean =
    Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU ||
        ContextCompat.checkSelfPermission(context, Manifest.permission.POST_NOTIFICATIONS) ==
        PackageManager.PERMISSION_GRANTED