Demo: preselect the featured trip on a clean URL

/api/config now carries featured_sel (a new Store method; empty for
real databases), and the app applies it once on first feed load when
the URL has no ?sel=. Opening the demo at / lands directly in
presentation view on the featured road trip — no query string needed.
A shared ?sel= link still wins over the featured selection.

Author: Greg

src/db.go

@@ -398,6 +398,9 @@ func classifyCharge(fast bool, geofence, addrName, city *string) (category, titl
 	}
 }
 
+// Featured preselection is a demo-mode concept; real data has none.
+func (d *DB) Featured() []string { return nil }
+
 // ---- detail -------------------------------------------------------------------
 
 func (d *DB) Detail(ctx context.Context, id string) (*Detail, error) {

src/demo.go

@@ -14,9 +14,10 @@ import (
 // demoStore generates deterministic synthetic data around a fictional area so
 // the app runs and renders with no database. No real locations are used.
 type demoStore struct {
-	drives  []demoDrive
-	charges []demoCharge
-	units   string
+	drives   []demoDrive
+	charges  []demoCharge
+	units    string
+	featured []string
 }
 
 type demoDrive struct {
@@ -191,6 +192,7 @@ func (s *demoStore) addFeaturedTrip(now time.Time) {
 			km: d.Km, durMin: d.DurMin, speedMax: d.SpeedMax,
 			from: d.From, to: d.To, s0: d.S0, s1: d.S1, kwh: d.KWh, coords: d.Coords,
 		})
+		s.featured = append(s.featured, "d"+strconv.Itoa(1500+i))
 	}
 	for i, c := range trip.Charges {
 		s.charges = append(s.charges, demoCharge{
@@ -199,9 +201,12 @@ func (s *demoStore) addFeaturedTrip(now time.Time) {
 			category: "supercharger", title: c.Name,
 			pt: []float64{c.Lng, c.Lat}, curve: c.Curve,
 		})
+		s.featured = append(s.featured, "c"+strconv.Itoa(2500+i))
 	}
 }
 
+func (s *demoStore) Featured() []string { return s.featured }
+
 func (s *demoStore) Cars(ctx context.Context) ([]Car, error) {
 	return []Car{{ID: 1, Name: "Demo", Model: "Model Y"}}, nil
 }

src/handlers.go

@@ -24,6 +24,7 @@ func registerAPI(mux *http.ServeMux, s Store, cfg Config) {
 			"units":         cfg.Units,
 			"map_style_url": cfg.MapStyleURL,
 			"demo":          cfg.Demo,
+			"featured_sel":  s.Featured(),
 		})
 	})
 

src/model.go

@@ -34,6 +34,9 @@ type Store interface {
 	// Detail returns the panel payload for one activity id ("d123" / "c45"),
 	// or nil when the id doesn't exist.
 	Detail(ctx context.Context, id string) (*Detail, error)
+	// Featured returns activity ids the UI should preselect on a fresh load
+	// (no ?sel= in the URL). Empty outside demo mode.
+	Featured() []string
 }
 
 type Car struct {

src/web/src/App.tsx

@@ -52,6 +52,9 @@ export default function App() {
   const pendingShareRef = useRef<string[] | null>(
     new URLSearchParams(location.search).get('sel')?.split(',').filter(Boolean) ?? null,
   )
+  // Without a shared link, the server's featured selection (demo mode's
+  // showcase trip) is preselected once on the first feed load.
+  const featuredDoneRef = useRef(false)
 
   const [summary, setSummary] = useState<Summary | null>(null)
   const [activities, setActivities] = useState<Activity[]>([])
@@ -101,6 +104,10 @@ export default function App() {
         if (pendingShareRef.current) {
           setSelected(pendingShareRef.current)
           pendingShareRef.current = null
+          featuredDoneRef.current = true
+        } else if (!featuredDoneRef.current) {
+          featuredDoneRef.current = true
+          if (config.featured_sel?.length) setSelected(config.featured_sel)
         }
 
         let all = first

src/web/src/api.ts

@@ -3,6 +3,7 @@ export type AppConfig = {
   units: 'km' | 'mi'
   map_style_url: string
   demo: boolean
+  featured_sel?: string[] | null
 }
 
 export type Car = { id: number; name: string; model?: string }