Add Eurostar Plus prices and NR advance fare support

- Eurostar scraper now fetches both Standard and Plus (PLUS class code)
  prices/seats in a single API call; each service dict gains plus_price
  and plus_seats fields
- GWR fares scraper gains fetch_advance() which makes two sets of
  paginated calls (standard advance + first-class advance) and returns
  cheapest per departure; shared _run_pages() generator reduces
  duplication in fetch()
- New /api/advance_fares/<station_crs>/<travel_date> endpoint returns
  advance fares as JSON, cached for 24 hours
- Results page gains NR ticket selector (Walk-on / Std Advance / 1st
  Advance) and Eurostar selector (Standard / Plus); total column is
  JS-computed from the selected combination with cheapest/priciest
  highlighting
- Load advance prices button fetches the API lazily; if advance fares
  are already cached they are embedded in the page and applied on load
  so the button is hidden automatically

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

scraper/gwr_fares.py

@@ -12,7 +12,7 @@ _API_URL = "https://api.gwr.com/api/shopping/journeysearch"
 # API key is embedded in the GWR web app (appvalues.prod.json)
 _API_KEY = "OgovGqAlLp4gWAhL7DQLo7pMCt8GHi2U4SPFiZgG"
 _PAD_CODE = "GBQQP"  # London Paddington cluster code as used by GWR website
-_WANTED_CODES = {"SSS", "SVS", "SDS", "CDS"}
+_WALKON_CODES = {"SSS", "SVS", "SDS", "CDS"}
 _MAX_PAGES = 20
 
 
@@ -67,59 +67,128 @@ def _request_body(
     }
 
 
-def fetch(station_crs: str, travel_date: str) -> dict[str, dict]:
+def _run_pages(station_crs: str, travel_date: str, first_class: bool = False):
     """
-    Fetch GWR single fares from station_crs to London Paddington on travel_date.
+    Iterate all pages of GWR journey search results.
 
-    Returns {departure_time: {'ticket': name, 'price': float, 'code': code}}
-    where price is in £ and only the cheapest available standard-class ticket
-    per departure (with restrictions already applied by GWR) is kept.
+    Yields (dep_time, fares_list) for each unique departure time seen.
+    first_class=True switches the request to first class fares.
     """
-    result: dict[str, dict] = {}
-
+    seen: set[str] = set()
     with httpx.Client(headers=_headers(), timeout=30) as client:
         conversation_token = None
         later = False
-
         for _ in range(_MAX_PAGES):
             body = _request_body(station_crs, travel_date, conversation_token, later)
+            if first_class:
+                body["firstclass"] = True
+                body["standardclass"] = False
             resp = client.post(_API_URL, json=body)
             resp.raise_for_status()
             data = resp.json().get("data", {})
-
             conversation_token = data.get("conversationToken")
-
             for journey in data.get("outwardOpenPureReturnFare", []):
                 dep_iso = journey.get("departureTime", "")
                 dep_time = dep_iso[11:16]  # "HH:MM" from "2026-04-10T09:08:00"
-                if not dep_time or dep_time in result:
+                if not dep_time or dep_time in seen:
                     continue
-
-                cheapest = None
-                for fare in journey.get("journeyFareDetails", []):
-                    code = fare.get("ticketTypeCode")
-                    if code not in _WANTED_CODES:
-                        continue
-                    if not fare.get("isStandardClass"):
-                        continue
-                    price_pence = fare.get("fare", 0)
-                    if cheapest is None or price_pence < cheapest["price_pence"]:
-                        cheapest = {
-                            "ticket": fare.get("ticketType", ""),
-                            "price": price_pence / 100,
-                            "price_pence": price_pence,
-                            "code": code,
-                        }
-
-                if cheapest:
-                    result[dep_time] = {
-                        "ticket": cheapest["ticket"],
-                        "price": cheapest["price"],
-                        "code": cheapest["code"],
-                    }
-
+                seen.add(dep_time)
+                yield dep_time, journey.get("journeyFareDetails", [])
             if not data.get("showLaterOutward", False):
                 break
             later = True
 
+
+def fetch(station_crs: str, travel_date: str) -> dict[str, dict]:
+    """
+    Fetch GWR walk-on single fares from station_crs to London Paddington on travel_date.
+
+    Returns {departure_time: {'ticket': name, 'price': float, 'code': code}}
+    where price is in £ and only the cheapest available standard-class walk-on
+    ticket per departure (with restrictions already applied by GWR) is kept.
+    """
+    result: dict[str, dict] = {}
+    for dep_time, fares in _run_pages(station_crs, travel_date):
+        cheapest = None
+        for fare in fares:
+            code = fare.get("ticketTypeCode")
+            if code not in _WALKON_CODES:
+                continue
+            if not fare.get("isStandardClass"):
+                continue
+            price_pence = fare.get("fare", 0)
+            if cheapest is None or price_pence < cheapest["price_pence"]:
+                cheapest = {
+                    "ticket": fare.get("ticketType", ""),
+                    "price": price_pence / 100,
+                    "price_pence": price_pence,
+                    "code": code,
+                }
+        if cheapest:
+            result[dep_time] = {
+                "ticket": cheapest["ticket"],
+                "price": cheapest["price"],
+                "code": cheapest["code"],
+            }
     return result
+
+
+def fetch_advance(station_crs: str, travel_date: str) -> dict[str, dict]:
+    """
+    Fetch advance fares: cheapest standard advance and first-class advance per departure.
+
+    Makes two sets of paginated API calls (standard class, then first class).
+    Returns {departure_time: {'advance_std': dict or None, 'advance_1st': dict or None}}
+    where each sub-dict has keys 'ticket', 'price', 'code'.
+    """
+    std_advance: dict[str, dict] = {}
+    for dep_time, fares in _run_pages(station_crs, travel_date, first_class=False):
+        cheapest = None
+        for fare in fares:
+            code = fare.get("ticketTypeCode")
+            if code in _WALKON_CODES:
+                continue  # skip walk-on fares
+            if not fare.get("isStandardClass"):
+                continue
+            price_pence = fare.get("fare", 0)
+            if cheapest is None or price_pence < cheapest["price_pence"]:
+                cheapest = {
+                    "ticket": fare.get("ticketType", ""),
+                    "price": price_pence / 100,
+                    "price_pence": price_pence,
+                    "code": code,
+                }
+        if cheapest:
+            std_advance[dep_time] = {
+                "ticket": cheapest["ticket"],
+                "price": cheapest["price"],
+                "code": cheapest["code"],
+            }
+
+    first_advance: dict[str, dict] = {}
+    for dep_time, fares in _run_pages(station_crs, travel_date, first_class=True):
+        cheapest = None
+        for fare in fares:
+            price_pence = fare.get("fare", 0)
+            if cheapest is None or price_pence < cheapest["price_pence"]:
+                cheapest = {
+                    "ticket": fare.get("ticketType", ""),
+                    "price": price_pence / 100,
+                    "price_pence": price_pence,
+                    "code": fare.get("ticketTypeCode"),
+                }
+        if cheapest:
+            first_advance[dep_time] = {
+                "ticket": cheapest["ticket"],
+                "price": cheapest["price"],
+                "code": cheapest["code"],
+            }
+
+    all_times = set(std_advance) | set(first_advance)
+    return {
+        t: {
+            "advance_std": std_advance.get(t),
+            "advance_1st": first_advance.get(t),
+        }
+        for t in all_times
+    }