Add R5 validation

r5-java/src/main/java/propertymap/App.java

@@ -54,6 +54,7 @@ public class App {
 
         LocalDate today = LocalDate.now();
         TransportNetwork network = Router.loadNetwork(requiredEnv("DATA_DIR"), requiredEnv("NETWORK_CACHE_DIR"));
+        Router.validateTransitServices(network, today);
 
         System.err.println("Loading postcodes (England only)...");
         Parquet.Postcodes postcodes = Parquet.loadEnglandPostcodes(

r5-java/src/main/java/propertymap/Router.java

@@ -22,6 +22,7 @@ import java.io.File;
 import java.time.LocalDate;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.BitSet;
 import java.util.EnumSet;
 import java.util.List;
 
@@ -78,12 +79,42 @@ public class Router {
             System.err.println("  Cached to " + cacheFile);
         }
 
+        validateTransitNetwork(network, cacheFile, dataDir);
+
         System.err.println("  Building distance tables...");
         network.transitLayer.buildDistanceTables(null);
         System.err.println("  Network ready");
         return network;
     }
 
+    private static void validateTransitNetwork(TransportNetwork network, File cacheFile, String dataDir) {
+        TransitLayer transitLayer = network.transitLayer;
+        int stops = transitLayer == null ? 0 : transitLayer.getStopCount();
+        int routes = transitLayer == null || transitLayer.routes == null ? 0 : transitLayer.routes.size();
+        int patterns = transitLayer == null || transitLayer.tripPatterns == null ? 0 : transitLayer.tripPatterns.size();
+        int services = transitLayer == null || transitLayer.services == null ? 0 : transitLayer.services.size();
+
+        if (stops == 0 || routes == 0 || patterns == 0) {
+            throw new IllegalStateException(String.format(
+                "R5 network has no usable transit data (stops=%d, routes=%d, patterns=%d). "
+                    + "The cache at %s was likely built without GTFS. Ensure %s contains GTFS .zip files, "
+                    + "then delete %s and rerun.",
+                stops, routes, patterns, cacheFile.getPath(), dataDir, cacheFile.getPath()));
+        }
+
+        System.err.printf("  Transit: %,d stops, %,d routes, %,d patterns, %,d services%n",
+            stops, routes, patterns, services);
+    }
+
+    static void validateTransitServices(TransportNetwork network, LocalDate date) {
+        BitSet activeServices = network.transitLayer.getActiveServicesForDate(date);
+        if (activeServices.cardinality() == 0) {
+            throw new IllegalStateException("R5 network has transit data, but no active services on "
+                + date + ". Rebuild property-data/transit from current feeds or choose a date covered by GTFS.");
+        }
+        System.err.printf("  Active transit services on %s: %,d%n", date, activeServices.cardinality());
+    }
+
     /**
      * Filter destinations by distance, build chunks, compute travel times for one origin.
      * Returns only the filtered subset indices and their travel times.