Show Interrail reservation fees as an opt-in setting

docs/user-flows.md

@@ -239,7 +239,12 @@ the destination is reachable, with its calendar open.
   with driving alone and flying, from ADEME factors over the straight-line distance
   (`src/util/eco.ts`).
 - **Settings** — theme, MAX Jeune/Senior, comfortable/compact, and Low-end mode (map off +
-  reduced motion + compact) with a one-time nudge on weak devices; language.
+  reduced motion + compact) with a one-time nudge on weak devices; language. "Interrail
+  reservation fees" (off by default) adds each trip's pass-holder reservation fee, 2nd class,
+  to the Interrail exact-trip list (connections add up their trains), a "Cheapest
+  reservation" sort and a note linking Interrail's fee page. The fees come from
+  `src/data/fees.ts`, the same table train-api publishes; a train with no published fee
+  (SNCF coaches) shows none and sorts last.
 - **Mobile** — the form is a sheet that collapses to a search bar (a long route wraps it to
   two lines); results are a bottom-sheet drawer with peek / half / full detents measured
   below that bar, so the full sheet never covers it. Back navigation preserves form state

src/app.ts

@@ -27,6 +27,7 @@ import { findHiddenTrains } from "./core/hidden";
 import { addDays, dayIndex, formatDuration, minutesToHHMM } from "./util/time";
 import { haversineKm } from "./util/geo";
 import { tripCo2 } from "./util/eco";
+import { journeyFee, type Fee } from "./data/fees";
 import { el, clear, isTouch } from "./ui/dom";
 import { buildShell, applyTheme, applyDensity, applyReduceMotion, applyMap, closeHeaderMenu } from "./ui/shell";
 import { showPostcard } from "./ui/toast";
@@ -53,6 +54,7 @@ import {
   MAX_SENIOR_URL,
   INTERRAIL_FRANCE_URL,
   INTERRAIL_PASS_URL,
+  INTERRAIL_FEES_URL,
   ADEME_CO2_URL,
   GITHUB_URL,
   GITHUB_ISSUES_URL,
@@ -929,6 +931,8 @@ function cityInfoUrl(id: string): string {
 function ctx(): RenderCtx {
   return {
     label: (id) => deps.registry.label(id),
+    // Interrail reservation fees: an opt-in setting, and only for the Interrail pass.
+    fee: settings.fees && !deps.profile.seatKnown ? journeyFee : undefined,
     formatDate,
     formatWeekday,
     // Deep-link to SNCF Connect with the trip pre-filled (clean station names, the
@@ -1730,6 +1734,7 @@ const SORT_LABEL = {
   name: "sort_name",
   arrival: "sort_arrival",
   departure: "sort_departure",
+  cheapest: "sort_cheapest",
 } as const;
 
 /** Build the sort-picker option list for a mode from its applicable keys. */
@@ -1751,6 +1756,7 @@ interface SortAccessors<T> {
   durationMin?: (x: T) => number;
   arriveMin?: (x: T) => number; // absolute arrival minutes (earliest first)
   departMin?: (x: T) => number; // departure minutes (earliest first)
+  fee?: (x: T) => Fee | undefined; // Interrail reservation fees (cheapest first, unknown last)
 }
 
 /**
@@ -1784,6 +1790,14 @@ function applySort<T>(items: T[], acc: SortAccessors<T>): T[] {
     case "name":
       arr.sort((a, b) => acc.name(a).localeCompare(acc.name(b)));
       break;
+    case "cheapest":
+      if (acc.fee) {
+        const fee = acc.fee;
+        const lo = (x: T): number => fee(x)?.min ?? Infinity;
+        const hi = (x: T): number => fee(x)?.max ?? Infinity;
+        arr.sort((a, b) => lo(a) - lo(b) || hi(a) - hi(b));
+      }
+      break;
   }
   return arr;
 }
@@ -2690,6 +2704,18 @@ function appendNearbyAlternatives(
  * journey list booked on click, hidden-city trains and radius alternatives. Round /
  * day trips take the separate {@link runTripSearch} 2-leg accordion instead.
  */
+/** Under an exact trip's list when fees are on: they are indicative, with their source. */
+function feeNoteEl(): HTMLElement {
+  return el("p", { class: "muted small fee-note" }, [
+    el("span", { text: `${t("fee_note")} ` }),
+    el("a", {
+      href: INTERRAIL_FEES_URL,
+      text: t("fee_link"),
+      attrs: { target: "_blank", rel: "noopener noreferrer" },
+    }),
+  ]);
+}
+
 function runOdSearch(c: RenderCtx): void {
   const { trains, registry } = deps;
   if (!query.origin || !query.destination) {
@@ -2761,6 +2787,7 @@ function runOdSearch(c: RenderCtx): void {
       durationMin: (j) => j.totalDurationMin,
       arriveMin: (j) => (flex > 0 ? dayIndex(j.date) * 1440 : 0) + journeyArriveAbs(j),
       departMin: (j) => (flex > 0 ? dayIndex(j.date) * 1440 : 0) + j.departMin,
+      fee: c.fee,
     },
   );
 
@@ -2786,11 +2813,12 @@ function runOdSearch(c: RenderCtx): void {
     refs.results.append(
       render.listToolbarEl(
         t("badge_trains", { n: journeys.length }),
-        query.sort ?? "rec",
-        sortOptions(["rec", "arrival", "departure", "fastest"]),
+        query.sort === "cheapest" && !c.fee ? "rec" : query.sort ?? "rec",
+        sortOptions(c.fee ? ["rec", "arrival", "departure", "fastest", "cheapest"] : ["rec", "arrival", "departure", "fastest"]),
         onSort,
       ),
     );
+    if (c.fee) refs.results.append(feeNoteEl());
     for (const j of journeys)
       refs.results.append(
         render.journeyEl(j, c, { bookOnClick: true, dateLabel: flex > 0 ? formatDate(j.date) : undefined }),
@@ -3530,6 +3558,7 @@ function openSettings(): void {
     reduceMotion: settings.reduceMotion,
     map: settings.map,
     compact: settings.density === "compact",
+    fees: settings.fees,
     onReduceMotion: (v) => {
       settings = { ...settings, reduceMotion: v };
       store.saveSettings(settings);
@@ -3549,6 +3578,11 @@ function openSettings(): void {
       store.saveSettings(settings);
       applyDensity(density);
     },
+    onFees: (v) => {
+      settings = { ...settings, fees: v };
+      store.saveSettings(settings);
+      refreshInPlace();
+    },
     // Master "Low-end mode": flip all three savers together. ON = the light experience
     // (no motion, no map, compact); OFF = the full experience (motion, map, comfortable).
     onLowEnd: (v) => {

src/config.ts

@@ -82,6 +82,9 @@ export const MAX_SENIOR_URL = "https://www.sncf-connect.com/catalogue/descriptio
 export const INTERRAIL_FRANCE_URL = "https://www.interrail.com/en/plan-your-trip/reservations/reservations-france";
 /** Interrail Global Pass conditions: who can buy it, and the country-of-residence rule. */
 export const INTERRAIL_PASS_URL = "https://www.interrail.com/en/interrail-passes/global-pass";
+/** Interrail's pass-holder reservation fees, the source of src/data/fees.ts. */
+export const INTERRAIL_FEES_URL =
+  "https://www.interrail.com/en/book-reservations/reservation-fees/domestic-train-reservation-fees";
 /** ADEME's CO₂ comparator, the source of the per-km factors in src/util/eco.ts. */
 export const ADEME_CO2_URL = "https://impactco2.fr/outils/transport";
 

src/data/fees.ts

@@ -0,0 +1,93 @@
+import type { Journey } from "../types";
+
+/**
+ * What an Interrail pass holder pays to reserve a seat on SNCF trains, in euros, 2nd
+ * class. The same table train-api publishes as v1/sncf/interrail/fees.json (see its
+ * src/operators/interrail-fees.ts), hand-entered from Interrail's fee pages and checked
+ * on 2026-10-12. Indicative: the app says so and links the source.
+ *
+ * A stop abroad sets the international fee for that country; otherwise the train's axe
+ * sets the domestic one.
+ */
+
+/** A pass-holder reservation in euros; `min === max` for a fixed fee. */
+export interface Fee {
+  min: number;
+  max: number;
+}
+
+type Country = "BE" | "CH" | "DE" | "ES" | "IT" | "LU";
+
+/** Whole words of SNCF stop names abroad, by country (accents and case ignored). */
+const FOREIGN_STOPS: Record<Country, string[]> = {
+  BE: ["bruxelles", "brussel", "liege", "anvers", "antwerpen"],
+  CH: ["geneve", "lausanne", "zurich", "basel", "bale", "bern", "vallorbe", "neuchatel"],
+  DE: [
+    "mannheim", "saarbrucken", "saarbruecken", "kaiserslautern", "frankfurt", "karlsruhe",
+    "stuttgart", "augsburg", "munchen", "baden baden", "ulm", "freiburg", "koln", "dortmund",
+  ],
+  ES: ["barcelona", "girona", "figueres", "madrid"],
+  IT: ["torino", "milano", "oulx", "oux"],
+  LU: ["luxembourg"],
+};
+
+const BY_COUNTRY: Record<Exclude<Country, "ES">, Fee> = {
+  BE: { min: 20, max: 35 }, // TGV to Brussels
+  CH: { min: 25, max: 25 }, // TGV Lyria
+  DE: { min: 19, max: 19 }, // ICE & TGV France–Germany
+  IT: { min: 31, max: 31 }, // TGV France–Italy
+  LU: { min: 10, max: 20 }, // TGV to Luxembourg
+};
+const SPAIN_FROM_PARIS: Fee = { min: 35, max: 35 };
+const SPAIN_OTHER: Fee = { min: 25, max: 25 };
+
+const BY_AXE: Record<string, Fee> = {
+  "SUD EST": { min: 10, max: 20 }, // TGV INOUI
+  EST: { min: 10, max: 20 },
+  ATLANTIQUE: { min: 10, max: 20 },
+  NORD: { min: 10, max: 20 },
+  INTERNATIONAL: { min: 10, max: 20 }, // a stretch inside France
+  "IC SRO": { min: 10, max: 20 }, // Intercités, reservation compulsory
+  "IC ARO": { min: 10, max: 20 },
+  "IC NUIT": { min: 10, max: 25 }, // seat €10, couchette €19–25
+};
+
+function fold(s: string): string {
+  return ` ${s.normalize("NFD").replace(/[̀-ͯ]/g, "").toLowerCase().replace(/[^a-z0-9]+/g, " ")} `;
+}
+
+function foreignCountry(stop: string): Country | undefined {
+  const f = fold(stop);
+  for (const [country, names] of Object.entries(FOREIGN_STOPS) as [Country, string[]][]) {
+    if (names.some((n) => f.includes(` ${n} `))) return country;
+  }
+  return undefined;
+}
+
+/** The fee for one SNCF train between two stops, or undefined when no fee page covers it. */
+export function interrailFee(axe: string | undefined, origin: string, destination: string): Fee | undefined {
+  const abroad = foreignCountry(origin) ?? foreignCountry(destination);
+  if (abroad === "ES") return [origin, destination].some((s) => fold(s).includes(" paris ")) ? SPAIN_FROM_PARIS : SPAIN_OTHER;
+  if (abroad) return BY_COUNTRY[abroad];
+  return axe ? BY_AXE[axe] : undefined;
+}
+
+/** The fees of every train in a journey added up, or undefined when one train has none. */
+export function journeyFee(j: Journey): Fee | undefined {
+  let min = 0;
+  let max = 0;
+  for (const leg of j.legs) {
+    const fee = interrailFee(leg.axe, leg.origin, leg.destination);
+    if (!fee) return undefined;
+    min += fee.min;
+    max += fee.max;
+  }
+  return { min, max };
+}
+
+/** "€19" or "€10–20", in the reader's locale. */
+export function formatFee(fee: Fee, lang: string): string {
+  const eur = (v: number): string =>
+    new Intl.NumberFormat(lang, { style: "currency", currency: "EUR", maximumFractionDigits: 0 }).format(v);
+  return fee.min === fee.max ? eur(fee.min) : `${eur(fee.min)}–${eur(fee.max)}`;
+}

src/i18n/ar.ts

@@ -108,6 +108,8 @@ export const ar: Dict = {
   set_show_map_hint: "أوقفها لتطبيق أخفّ وأسرع على الهواتف الضعيفة.",
   set_compact: "نتائج مضغوطة",
   set_compact_hint: "مزيد من القطارات في الشاشة.",
+  set_fees: "رسوم حجز إنتررييل",
+  set_fees_hint: "يعرض تكلفة الحجز الإلزامي لكل قطار، في الدرجة الثانية.",
   set_lowend: "جهاز ضعيف",
   set_lowend_hint: "تقليل الحركة وإخفاء الخريطة وضغط القائمة بضغطة واحدة.",
   lowend_prompt_title: "تسريع التطبيق؟",
@@ -250,6 +252,7 @@ export const ar: Dict = {
   sort_fastest: "الأسرع",
   sort_arrival: "الوصول الأبكر",
   sort_departure: "المغادرة الأبكر",
+  sort_cheapest: "أرخص حجز",
   sort_name: "أ–ي",
 
   mode_oneway: "ذهاب فقط",
@@ -302,6 +305,9 @@ export const ar: Dict = {
   how_eco: "البيئة: رحلة بقطار TGV تُصدر نحو 50 مرة أقل من ثاني أكسيد الكربون مقارنة بالسيارة لشخص واحد، و100 مرة أقل من الطائرة (أرقام ADEME).",
   eco_trip: "بالقطار، تُصدر هذه الرحلة نحو {train} كغ من مكافئ CO₂، مقابل {car} كغ بالسيارة لشخص واحد و{plane} كغ بالطائرة (ADEME، {km} كم في خط مستقيم).",
   eco_link: "أرقام CO₂ من ADEME",
+  fee_chip: "الحجز {fee}",
+  fee_note: "رسوم حجز إنتررييل تقريبية، الدرجة الثانية.",
+  fee_link: "رسوم إنتررييل",
   tagline_ir: "قطارات SNCF بتذكرة Interrail.",
   how_note_ir: "تعرض هذه الأداة القطارات التي تسير (البيانات المفتوحة لـ SNCF)؛ ولا تعرف إن بقي مقعد لحاملي التذكرة. تحقق على SNCF Connect.",
   multi_incomplete_ir: "بعض المقاطع لا يوجد فيها قطار — هذا المسار غير مكتمل.",

src/i18n/de.ts

@@ -108,6 +108,8 @@ export const de: Dict = {
   set_show_map_hint: "Aus für eine leichtere, schnellere App auf schwachen Handys.",
   set_compact: "Kompakte Ergebnisse",
   set_compact_hint: "Mehr Züge pro Bildschirm.",
+  set_fees: "Interrail-Reservierungsgebühren",
+  set_fees_hint: "Zeigt, was die Pflichtreservierung jedes Zuges in der 2. Klasse kostet.",
   set_lowend: "Schwaches Gerät",
   set_lowend_hint: "Bewegung reduzieren, Karte ausblenden und Liste kompakt — mit einem Tipp.",
   lowend_prompt_title: "App beschleunigen?",
@@ -251,6 +253,7 @@ export const de: Dict = {
   sort_fastest: "Schnellste",
   sort_arrival: "Früheste Ankunft",
   sort_departure: "Früheste Abfahrt",
+  sort_cheapest: "Günstigste Reservierung",
   sort_name: "A–Z",
 
   mode_oneway: "Einfache Fahrt",
@@ -303,6 +306,9 @@ export const de: Dict = {
   how_eco: "Ökologie: Eine TGV-Fahrt verursacht etwa 50-mal weniger CO₂ als allein mit dem Auto und 100-mal weniger als mit dem Flugzeug (ADEME-Zahlen).",
   eco_trip: "Mit dem Zug verursacht diese Fahrt etwa {train} kg CO₂e, gegenüber {car} kg allein im Auto und {plane} kg im Flugzeug (ADEME, {km} km Luftlinie).",
   eco_link: "CO₂-Zahlen der ADEME",
+  fee_chip: "Reservierung {fee}",
+  fee_note: "Richtwerte für Interrail-Reservierungsgebühren, 2. Klasse.",
+  fee_link: "Interrail-Gebühren",
   tagline_ir: "SNCF-Züge mit einem Interrail-Pass.",
   how_note_ir: "Dieses Tool zeigt fahrende Züge (offene SNCF-Daten); es sieht nicht, ob noch ein Pass-Platz frei ist. Prüfe auf SNCF Connect.",
   multi_incomplete_ir: "Für einige Abschnitte gibt es keinen Zug — diese Reise ist unvollständig.",

src/i18n/en.ts

@@ -112,6 +112,8 @@ export const en: Dict = {
   set_show_map_hint: "Turn off for a lighter, faster app on low-end phones.",
   set_compact: "Compact results",
   set_compact_hint: "More trains per screen.",
+  set_fees: "Interrail reservation fees",
+  set_fees_hint: "Shows what each train's compulsory reservation costs, 2nd class.",
   set_lowend: "Low-end device",
   set_lowend_hint: "Reduce motion, hide the map and compact the list, in one tap.",
   lowend_prompt_title: "Speed up the app?",
@@ -263,6 +265,7 @@ export const en: Dict = {
   sort_fastest: "Fastest",
   sort_arrival: "Earliest arrival",
   sort_departure: "Earliest departure",
+  sort_cheapest: "Cheapest reservation",
   sort_name: "A–Z",
 
   mode_oneway: "One-way",
@@ -315,6 +318,9 @@ export const en: Dict = {
   how_eco: "Ecology: a TGV trip emits about 50 times less CO₂ than driving alone and 100 times less than flying (ADEME figures).",
   eco_trip: "By train, this trip emits about {train} kg CO₂e, against {car} kg driving alone and {plane} kg flying (ADEME, {km} km as the crow flies).",
   eco_link: "ADEME CO₂ figures",
+  fee_chip: "Reservation {fee}",
+  fee_note: "Indicative Interrail reservation fees, 2nd class.",
+  fee_link: "Interrail fees",
   tagline_ir: "SNCF trains on an Interrail pass.",
   how_note_ir: "This tool shows trains that run (SNCF open data); it can't see whether a pass-holder seat is left. Check SNCF Connect.",
   multi_incomplete_ir: "Some legs have no train — this itinerary is incomplete.",

src/i18n/es.ts

@@ -108,6 +108,8 @@ export const es: Dict = {
   set_show_map_hint: "Desactívalo para una app más ligera y rápida en móviles básicos.",
   set_compact: "Resultados compactos",
   set_compact_hint: "Más trenes por pantalla.",
+  set_fees: "Suplementos de reserva Interrail",
+  set_fees_hint: "Muestra el precio de la reserva obligatoria de cada tren, en 2.ª clase.",
   set_lowend: "Dispositivo básico",
   set_lowend_hint: "Reduce animaciones, oculta el mapa y compacta la lista, de una vez.",
   lowend_prompt_title: "¿Acelerar la app?",
@@ -251,6 +253,7 @@ export const es: Dict = {
   sort_fastest: "Más rápido",
   sort_arrival: "Llegada más temprana",
   sort_departure: "Salida más temprana",
+  sort_cheapest: "Reserva más barata",
   sort_name: "A–Z",
 
   mode_oneway: "Solo ida",
@@ -303,6 +306,9 @@ export const es: Dict = {
   how_eco: "Ecología: un viaje en TGV emite unas 50 veces menos CO₂ que en coche solo y 100 veces menos que en avión (cifras de ADEME).",
   eco_trip: "En tren, este viaje emite unos {train} kg de CO₂e, frente a {car} kg en coche solo y {plane} kg en avión (ADEME, {km} km en línea recta).",
   eco_link: "Cifras de CO₂ de ADEME",
+  fee_chip: "Reserva {fee}",
+  fee_note: "Suplementos de reserva Interrail orientativos, en 2.ª clase.",
+  fee_link: "Tarifas Interrail",
   tagline_ir: "Trenes SNCF con un pase Interrail.",
   how_note_ir: "Esta herramienta muestra los trenes que circulan (datos abiertos de SNCF); no sabe si queda plaza de pase. Verifica en SNCF Connect.",
   multi_incomplete_ir: "Algunos trayectos no tienen tren — este itinerario está incompleto.",

src/i18n/fr.ts

@@ -110,6 +110,8 @@ export const fr = {
   set_show_map_hint: "Désactivez-la pour une appli plus légère et rapide sur mobile bas de gamme.",
   set_compact: "Résultats compacts",
   set_compact_hint: "Plus de trains par écran.",
+  set_fees: "Frais de réservation Interrail",
+  set_fees_hint: "Affiche le prix de la réservation obligatoire de chaque train, en 2de classe.",
   set_lowend: "Appareil bas de gamme",
   set_lowend_hint: "Réduit les animations, masque la carte et compacte la liste, en un geste.",
   lowend_prompt_title: "Accélérer l'appli ?",
@@ -261,6 +263,7 @@ export const fr = {
   sort_fastest: "Plus rapide",
   sort_arrival: "Arrivée la plus tôt",
   sort_departure: "Départ le plus tôt",
+  sort_cheapest: "Réservation la moins chère",
   sort_name: "A–Z",
 
   mode_oneway: "Aller simple",
@@ -319,6 +322,9 @@ export const fr = {
   how_eco: "Écologie : en TGV, un trajet émet environ 50 fois moins de CO₂ qu'en voiture seul et 100 fois moins qu'en avion (chiffres ADEME).",
   eco_trip: "En train, ce trajet émet environ {train} kg de CO₂e, contre {car} kg en voiture seul et {plane} kg en avion (ADEME, {km} km à vol d'oiseau).",
   eco_link: "Calculs CO₂ de l'ADEME",
+  fee_chip: "Résa {fee}",
+  fee_note: "Frais de réservation Interrail indicatifs, en 2de classe.",
+  fee_link: "Tarifs Interrail",
   tagline_ir: "Trains SNCF avec un pass Interrail.",
   how_note_ir: "Cet outil affiche les trains qui circulent (open data SNCF) ; il ne sait pas s'il reste une place pass. Vérifiez sur SNCF Connect.",
   multi_incomplete_ir: "Certains trajets n'ont aucun train — cet itinéraire est incomplet.",