Improve error visibility and eliminate silent failures

- LocationProvider: close Flow with SecurityException when permission
  is missing (instead of silently completing), log trySend failures,
  handle lastLocation failure callback
- loadData(): wrap in top-level try-catch so database errors don't
  leave the app in a broken loading state
- Cache retry button: show "Waiting for GPS" toast when location is
  null instead of silently doing nothing
- selectShelterByData: use NaN for distance/bearing when no GPS fix
  yet, so UI shows "—" instead of misleading "0 m"
- DistanceUtils.formatDistance: handle NaN gracefully
- GeoJSON parser: require valid lokalId (primary key) — reject
  shelters with missing ID to prevent DB collisions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/main/java/no/naiv/tilfluktsrom/MainActivity.kt

@@ -193,18 +193,20 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
         }
 
         binding.cacheRetryButton.setOnClickListener {
-            currentLocation?.let { loc ->
-                if (isNetworkAvailable()) {
-                    startCaching(loc.latitude, loc.longitude)
-                } else {
+            val loc = currentLocation
+            if (loc == null) {
+                Toast.makeText(this, R.string.status_no_location, Toast.LENGTH_SHORT).show()
+            } else if (!isNetworkAvailable()) {
                 Toast.makeText(this, R.string.error_download_failed, Toast.LENGTH_SHORT).show()
-                }
+            } else {
+                startCaching(loc.latitude, loc.longitude)
             }
         }
     }
 
     private fun loadData() {
         lifecycleScope.launch {
+            try {
                 val hasData = repository.hasCachedData()
 
                 if (!hasData) {
@@ -253,6 +255,13 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
                         }
                     }
                 }
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Exception) {
+                Log.e(TAG, "Failed to initialize shelter data", e)
+                hideLoading()
+                binding.statusText.text = getString(R.string.error_download_failed)
+            }
         }
     }
 
@@ -384,7 +393,12 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
                 )
             )
         } else {
-            ShelterWithDistance(shelter = shelter, distanceMeters = 0.0, bearingDegrees = 0.0)
+            // No GPS yet — use NaN to signal "unknown distance"
+            ShelterWithDistance(
+                shelter = shelter,
+                distanceMeters = Double.NaN,
+                bearingDegrees = Double.NaN
+            )
         }
 
         userSelectedShelter = true

app/src/main/java/no/naiv/tilfluktsrom/data/ShelterGeoJsonParser.kt

@@ -91,6 +91,14 @@ object ShelterGeoJsonParser {
                     continue
                 }
 
+                // Require a valid primary key — without it shelters can collide in the DB
+                val lokalId = properties.optString("lokalId", null)
+                if (lokalId.isNullOrBlank()) {
+                    Log.w(TAG, "Skipping shelter at index $i: missing lokalId")
+                    skipped++
+                    continue
+                }
+
                 val plasser = properties.optInt("plasser", 0)
                 if (plasser < 0) {
                     Log.w(TAG, "Skipping shelter at index $i: negative capacity ($plasser)")
@@ -100,7 +108,7 @@ object ShelterGeoJsonParser {
 
                 shelters.add(
                     Shelter(
-                        lokalId = properties.optString("lokalId", "unknown-$i"),
+                        lokalId = lokalId,
                         romnr = properties.optInt("romnr", 0),
                         plasser = plasser,
                         adresse = properties.optString("adresse", ""),

app/src/main/java/no/naiv/tilfluktsrom/location/LocationProvider.kt

@@ -20,6 +20,9 @@ import kotlinx.coroutines.flow.callbackFlow
 /**
  * Provides GPS location updates using the Fused Location Provider.
  * Emits location updates as a Flow for reactive consumption.
+ *
+ * Closes the Flow with a SecurityException if location permission is not granted,
+ * so callers can detect and handle this failure explicitly.
  */
 class LocationProvider(private val context: Context) {
 
@@ -34,22 +37,28 @@ class LocationProvider(private val context: Context) {
 
     /**
      * Stream of location updates. Emits the last known location first (if available),
-     * then continuous updates.
+     * then continuous updates. Throws SecurityException if permission is not granted.
      */
     fun locationUpdates(): Flow<Location> = callbackFlow {
         if (!hasLocationPermission()) {
-            Log.w(TAG, "Location permission not granted")
-            close()
+            close(SecurityException("Location permission not granted"))
             return@callbackFlow
         }
 
         // Try to get last known location for immediate display
         try {
-            fusedClient.lastLocation.addOnSuccessListener { location ->
+            fusedClient.lastLocation
+                .addOnSuccessListener { location ->
                     if (location != null) {
-                    trySend(location)
+                        val result = trySend(location)
+                        if (result.isFailure) {
+                            Log.w(TAG, "Failed to emit last known location")
                         }
                     }
+                }
+                .addOnFailureListener { e ->
+                    Log.w(TAG, "Could not get last known location", e)
+                }
         } catch (e: SecurityException) {
             Log.e(TAG, "SecurityException getting last location", e)
         }
@@ -64,7 +73,12 @@ class LocationProvider(private val context: Context) {
 
         val callback = object : LocationCallback() {
             override fun onLocationResult(result: LocationResult) {
-                result.lastLocation?.let { trySend(it) }
+                result.lastLocation?.let { location ->
+                    val sendResult = trySend(location)
+                    if (sendResult.isFailure) {
+                        Log.w(TAG, "Failed to emit location update")
+                    }
+                }
             }
         }
 
@@ -76,7 +90,7 @@ class LocationProvider(private val context: Context) {
             )
         } catch (e: SecurityException) {
             Log.e(TAG, "SecurityException requesting location updates", e)
-            close()
+            close(e)
             return@callbackFlow
         }
 

app/src/main/java/no/naiv/tilfluktsrom/util/DistanceUtils.kt

@@ -38,6 +38,7 @@ object DistanceUtils {
      * Format distance for display: meters if <1km, otherwise km with one decimal.
      */
     fun formatDistance(meters: Double): String {
+        if (meters.isNaN()) return "—"
         return if (meters < 1000) {
             "${meters.toInt()} m"
         } else {