Add one change & crime

frontend/src/hooks/useTravelTime.ts

@@ -66,6 +66,9 @@ export interface TravelTimeEntry {
   useBest: boolean;
   /** Restrict transit to walk-transit-walk (0 changes). Optional; defaults to false. */
   noChange?: boolean;
+  /** Restrict transit to at most one change. Optional; defaults to false.
+   *  Mutually exclusive with noChange (the UI never sets both). */
+  oneChange?: boolean;
   /** Drop buses from the allowed transit modes. Optional; defaults to false. */
   noBuses?: boolean;
 }
@@ -77,42 +80,44 @@ export interface TravelTimeEntry {
  *
  * For non-transit modes the entry.mode passes through unchanged.
  *
- * Note: the transit-one-change* variants exist server-side but are not reachable
- * from the UI toggles (only no-change + no-buses are exposed). They're available
- * via direct API access for callers that want them.
+ * noChange and oneChange are mutually exclusive (the UI never sets both); if
+ * they ever were, noChange wins here.
  */
 export function resolveTransitVariant(entry: TravelTimeEntry): string {
   if (entry.mode !== 'transit') return entry.mode;
   const nc = entry.noChange ?? false;
+  const oc = entry.oneChange ?? false;
   const nb = entry.noBuses ?? false;
-  if (nc && nb) return 'transit-no-change-no-bus';
-  if (nc) return 'transit-no-change';
-  if (nb) return 'transit-no-bus';
-  return 'transit';
+  if (nc) return nb ? 'transit-no-change-no-bus' : 'transit-no-change';
+  if (oc) return nb ? 'transit-one-change-no-bus' : 'transit-one-change';
+  return nb ? 'transit-no-bus' : 'transit';
 }
 
 /**
  * Parse a server-side mode string (incl. transit variants) back into a base
  * TransportMode + UI toggle booleans. Returns null for mode strings the UI
- * cannot represent (currently: transit-one-change, transit-one-change-no-bus).
- * Callers should skip entries that parse to null rather than silently
- * normalising to a different variant.
+ * cannot represent. Callers should skip entries that parse to null rather than
+ * silently normalising to a different variant.
  */
 export function parseServerMode(
   modeStr: string
-): { mode: TransportMode; noChange: boolean; noBuses: boolean } | null {
+): { mode: TransportMode; noChange: boolean; oneChange: boolean; noBuses: boolean } | null {
   if (modeStr === 'car' || modeStr === 'bicycle' || modeStr === 'walking') {
-    return { mode: modeStr, noChange: false, noBuses: false };
+    return { mode: modeStr, noChange: false, oneChange: false, noBuses: false };
   }
   switch (modeStr) {
     case 'transit':
-      return { mode: 'transit', noChange: false, noBuses: false };
+      return { mode: 'transit', noChange: false, oneChange: false, noBuses: false };
     case 'transit-no-bus':
-      return { mode: 'transit', noChange: false, noBuses: true };
+      return { mode: 'transit', noChange: false, oneChange: false, noBuses: true };
     case 'transit-no-change':
-      return { mode: 'transit', noChange: true, noBuses: false };
+      return { mode: 'transit', noChange: true, oneChange: false, noBuses: false };
     case 'transit-no-change-no-bus':
-      return { mode: 'transit', noChange: true, noBuses: true };
+      return { mode: 'transit', noChange: true, oneChange: false, noBuses: true };
+    case 'transit-one-change':
+      return { mode: 'transit', noChange: false, oneChange: true, noBuses: false };
+    case 'transit-one-change-no-bus':
+      return { mode: 'transit', noChange: false, oneChange: true, noBuses: true };
     default:
       return null;
   }
@@ -145,6 +150,7 @@ export function useTravelTime(initial?: TravelTimeInitial) {
         timeRange: null,
         useBest: false,
         noChange: false,
+        oneChange: false,
         noBuses: false,
       },
     ]);
@@ -182,11 +188,27 @@ export function useTravelTime(initial?: TravelTimeInitial) {
     );
   }, []);
 
+  // noChange and oneChange are mutually exclusive: enabling one clears the
+  // other so the resolved server variant is never ambiguous.
   const handleToggleNoChange = useCallback((index: number) => {
     setEntries((prev) =>
       dedupeTravelTimeEntries(
         prev.map((entry, i) =>
-          i === index ? { ...entry, noChange: !(entry.noChange ?? false) } : entry
+          i === index
+            ? { ...entry, noChange: !(entry.noChange ?? false), oneChange: false }
+            : entry
+        )
+      )
+    );
+  }, []);
+
+  const handleToggleOneChange = useCallback((index: number) => {
+    setEntries((prev) =>
+      dedupeTravelTimeEntries(
+        prev.map((entry, i) =>
+          i === index
+            ? { ...entry, oneChange: !(entry.oneChange ?? false), noChange: false }
+            : entry
         )
       )
     );
@@ -219,6 +241,7 @@ export function useTravelTime(initial?: TravelTimeInitial) {
     handleTimeRangeChange,
     handleToggleBest,
     handleToggleNoChange,
+    handleToggleOneChange,
     handleToggleNoBuses,
   };
 }