Cache walk-on NR fares by day of week for instant display

Store GWR walk-on fares keyed by timetable period + weekday
(weekday_gwr_fares_{direction}_{crs}_{period}_{day}), mirroring
the existing NR timetable weekday cache strategy.

On page load the server embeds any cached weekday fares in the page
as WALKON_CACHED_FARES so JS can populate prices immediately without
waiting for the GWR API. The live API call still runs afterwards to
verify and update any changed fares; the spinner label changes to
"Verifying fares" when cached prices are already shown.

The weekday cache is written whenever exact-date fares are fetched
from GWR, keeping it fresh, and populated lazily from the exact-date
cache on first access.

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

app.py

@@ -129,6 +129,13 @@ def _nr_weekday_cache_key(direction: str, station_crs: str, section_date: str) -
     )
 
 
+def _walkon_weekday_cache_key(direction: str, station_crs: str, section_date: str) -> str:
+    return (
+        f"weekday_gwr_fares_{direction}_{station_crs}_"
+        f"{_nr_timetable_period_key(section_date)}_{_weekday_for(section_date)}"
+    )
+
+
 def _eurostar_exact_cache_key(direction: str, section_date: str, destination: str) -> str:
     return f"eurostar_{direction}_{section_date}_{destination}"
 
@@ -517,6 +524,9 @@ def _results(station_crs, slug, travel_date, journey_type, return_date):
         fare_direction = "to_paddington" if direction == "outbound" else "from_paddington"
         gwr_fares = {}
         cached_advance = get_cached(advance_cache_key, ttl=24 * 3600)
+        walkon_weekday_key = _walkon_weekday_cache_key(rtt_direction, station_crs, section_date)
+        exact_walkon = get_cached(gwr_cache_key, ttl=30 * 24 * 3600)
+        cached_walkon = exact_walkon if exact_walkon is not None else get_cached(walkon_weekday_key)
 
         if direction == "outbound":
             trips = combine_trips(
@@ -603,6 +613,7 @@ def _results(station_crs, slug, travel_date, journey_type, return_date):
             "max_connection": section_max_connection,
             "provisional_timetable": nr_provisional or es_provisional,
             "advance_fares": cached_advance,
+            "cached_walkon_fares": cached_walkon,
             "walkon_api_url": url_for(
                 "api_walkon_fares",
                 station_crs=station_crs,
@@ -755,11 +766,13 @@ def _results(station_crs, slug, travel_date, journey_type, return_date):
 
     trip_fares = {}
     advance_fares = {}
+    walkon_cached_fares = {}
     walkon_api_urls = {}
     advance_api_urls = {}
     advance_stream_urls = {}
     for section in sections:
         advance_fares[section["id"]] = section["advance_fares"]
+        walkon_cached_fares[section["id"]] = section.get("cached_walkon_fares")
         walkon_api_urls[section["id"]] = section["walkon_api_url"]
         advance_api_urls[section["id"]] = section["advance_api_url"]
         advance_stream_urls[section["id"]] = section["advance_stream_url"]
@@ -860,6 +873,7 @@ def _results(station_crs, slug, travel_date, journey_type, return_date):
         section_directions_json=json.dumps(section_directions),
         trip_fares_json=json.dumps(trip_fares),
         advance_fares_json=json.dumps(advance_fares),
+        walkon_cached_fares_json=json.dumps(walkon_cached_fares),
         walkon_api_urls_json=json.dumps(walkon_api_urls),
         advance_api_urls_json=json.dumps(advance_api_urls),
         advance_stream_urls_json=json.dumps(advance_stream_urls),
@@ -918,8 +932,11 @@ def api_walkon_fares(station_crs, travel_date):
     if direction not in {"to_paddington", "from_paddington"}:
         direction = "to_paddington"
     cache_key = f"gwr_fares_{direction}_{station_crs}_{travel_date}"
+    weekday_key = _walkon_weekday_cache_key(direction, station_crs, travel_date)
     cached = get_cached(cache_key, ttl=30 * 24 * 3600)
     if cached is not None:
+        if get_cached(weekday_key) is None:
+            set_cached(weekday_key, cached)
         return jsonify(cached)
     try:
         fares = (
@@ -928,6 +945,7 @@ def api_walkon_fares(station_crs, travel_date):
             else gwr_fares_scraper.fetch(station_crs, travel_date, direction=direction)
         )
         set_cached(cache_key, fares)
+        set_cached(weekday_key, fares)
         return jsonify(fares)
     except Exception as e:
         return jsonify({"error": str(e)}), 500

templates/results.html

@@ -142,6 +142,7 @@
     const DEFAULT_MIN_CONN_IN = {{ default_inbound_min_connection }};
     let TRIP_FARES = {{ trip_fares_json | safe }};
     let ADVANCE_FARES = {{ advance_fares_json | safe }};
+    const WALKON_CACHED_FARES = {{ walkon_cached_fares_json | safe }};
     let WALKON_API_URLS = {{ walkon_api_urls_json | safe }};
     let ADVANCE_API_URLS = {{ advance_api_urls_json | safe }};
     let ADVANCE_STREAM_URLS = {{ advance_stream_urls_json | safe }};
@@ -566,8 +567,17 @@
         return c === 'advance_std' || c === 'advance_1st';
       });
       if (needsAdvance) loadMissingAdvanceFares();
+      /* Pre-populate walk-on fares from weekday cache so prices show immediately */
+      var hasPreloaded = false;
+      for (var sid in WALKON_CACHED_FARES) {
+        if (WALKON_CACHED_FARES[sid]) { mergeWalkonFares(sid, WALKON_CACHED_FARES[sid]); hasPreloaded = true; }
+      }
       updateDisplay();
       updateRowHighlights();
+      if (hasPreloaded) {
+        var loadingEl = document.getElementById('walkon-loading');
+        if (loadingEl) loadingEl.innerHTML = '<span class="spinner spinner-inline" aria-hidden="true"></span>Verifying fares';
+      }
       loadWalkonFares();
       startTimetableRefresh();
     }