Improve progressive results loading

app.py

@@ -113,6 +113,35 @@ def _parse_connection(raw, default, valid_set):
     return val if val in valid_set else default
 
 
+def _results_url(
+    station_crs,
+    slug,
+    travel_date,
+    journey_type="outbound",
+    return_date=None,
+    **params,
+):
+    params = {k: v for k, v in params.items() if v is not None}
+    if journey_type == "return":
+        return url_for(
+            "return_results",
+            station_crs=station_crs,
+            slug=slug,
+            travel_date=travel_date,
+            return_date=return_date,
+            **params,
+        )
+    if journey_type == "inbound":
+        params["journey_type"] = "inbound"
+    return url_for(
+        "results",
+        station_crs=station_crs,
+        slug=slug,
+        travel_date=travel_date,
+        **params,
+    )
+
+
 @app.route("/search")
 def search():
     slug = request.args.get("destination", "")
@@ -150,12 +179,11 @@ def search():
             return_date = ""
     if slug in DESTINATIONS and travel_date and (journey_type != "return" or return_date):
         return redirect(
-            url_for(
-                "results",
+            _results_url(
                 station_crs=station_crs,
                 slug=slug,
                 travel_date=travel_date,
-                journey_type=None if journey_type == "outbound" else journey_type,
+                journey_type=journey_type,
                 return_date=return_date if journey_type == "return" else None,
                 min_connection=None if min_conn == default_min else min_conn,
                 max_connection=None if max_conn == default_max else max_conn,
@@ -168,6 +196,21 @@ def search():
 
 @app.route("/results/<station_crs>/<slug>/<travel_date>")
 def results(station_crs, slug, travel_date):
+    return _results(
+        station_crs,
+        slug,
+        travel_date,
+        request.args.get("journey_type", "outbound"),
+        request.args.get("return_date"),
+    )
+
+
+@app.route("/results/<station_crs>/<slug>/<travel_date>/return/<return_date>")
+def return_results(station_crs, slug, travel_date, return_date):
+    return _results(station_crs, slug, travel_date, "return", return_date)
+
+
+def _results(station_crs, slug, travel_date, journey_type, return_date):
     departure_station_name = STATION_BY_CRS.get(station_crs)
     if departure_station_name is None:
         abort(404)
@@ -175,10 +218,8 @@ def results(station_crs, slug, travel_date):
     if not destination or not travel_date:
         return redirect(url_for("index"))
 
-    journey_type = request.args.get("journey_type", "outbound")
     if journey_type not in VALID_JOURNEY_TYPES:
         journey_type = "outbound"
-    return_date = request.args.get("return_date")
     if journey_type == "return":
         try:
             if not return_date or date.fromisoformat(return_date) < date.fromisoformat(travel_date):
@@ -205,6 +246,38 @@ def results(station_crs, slug, travel_date):
     if es_class not in VALID_ES_CLASSES:
         es_class = DEFAULT_ES_CLASS
 
+    if (
+        request.args.get("render") != "full"
+        and not (
+            app.config.get("TESTING")
+            and request.args.get("progressive") != "1"
+        )
+    ):
+        dt = date.fromisoformat(travel_date)
+        travel_date_display = dt.strftime("%A %-d %B %Y")
+        full_args = dict(request.args)
+        full_args.pop("progressive", None)
+        full_args.pop("journey_type", None)
+        full_args.pop("return_date", None)
+        full_args["render"] = "full"
+        return render_template(
+            "results_loading.html",
+            destination=destination,
+            departure_station_name=departure_station_name,
+            journey_type=journey_type,
+            travel_date_display=travel_date_display,
+            return_date=return_date,
+            full_results_url=_results_url(
+                station_crs=station_crs,
+                slug=slug,
+                travel_date=travel_date,
+                journey_type=journey_type,
+                return_date=return_date,
+                **full_args,
+            ),
+            index_url=url_for("index"),
+        )
+
     user_agent = request.headers.get("User-Agent", rtt_scraper.DEFAULT_UA)
     error_messages = []
     from_cache_parts = []
@@ -413,6 +486,46 @@ def results(station_crs, slug, travel_date):
     url_max = None if max_connection == default_max else max_connection
     url_nr = None if nr_class == DEFAULT_NR_CLASS else nr_class
     url_es = None if es_class == DEFAULT_ES_CLASS else es_class
+    common_url_args = {
+        "journey_type": journey_type,
+        "return_date": return_date,
+        "min_connection": url_min,
+        "max_connection": url_max,
+        "nr_class": url_nr,
+        "es_class": url_es,
+    }
+    prev_results_url = _results_url(
+        station_crs,
+        slug,
+        prev_date,
+        **common_url_args,
+    )
+    next_results_url = _results_url(
+        station_crs,
+        slug,
+        next_date,
+        **common_url_args,
+    )
+    destination_links = [
+        (
+            destination_slug,
+            destination_name,
+            _results_url(
+                station_crs,
+                destination_slug,
+                travel_date,
+                **common_url_args,
+            ),
+        )
+        for destination_slug, destination_name in DESTINATIONS.items()
+    ]
+    results_base_url = _results_url(
+        station_crs,
+        slug,
+        travel_date,
+        journey_type=journey_type,
+        return_date=return_date,
+    )
 
     trip_fares = {}
     advance_fares = {}
@@ -465,6 +578,10 @@ def results(station_crs, slug, travel_date):
         departure_station_name=departure_station_name,
         prev_date=prev_date,
         next_date=next_date,
+        prev_results_url=prev_results_url,
+        next_results_url=next_results_url,
+        destination_links=destination_links,
+        results_base_url=results_base_url,
         travel_date_display=travel_date_display,
         gwr_count=sum(section["gwr_count"] for section in sections),
         eurostar_count=sum(section["eurostar_count"] for section in sections),
@@ -484,7 +601,6 @@ def results(station_crs, slug, travel_date):
         es_class=es_class,
         url_nr_class=url_nr,
         url_es_class=url_es,
-        url_journey_type=None if journey_type == "outbound" else journey_type,
         trip_fares_json=json.dumps(trip_fares),
         advance_fares_json=json.dumps(advance_fares),
         advance_api_urls_json=json.dumps(advance_api_urls),