Warn when a driver's transponder collides with a different driver

Registering or editing a driver with a transponder already assigned
to a different driver (e.g. a wrong-class typo) previously saved
silently - the only symptom was that driver's laps never registering
during their heat, with no indication why. Now a confirm dialog names
the conflicting driver and their class before saving; the same
person's own multiple class entries sharing one physical transponder
are correctly never flagged.

Also confirms two things the user asked to verify: the race clock
already counts down for all timed session types (only open practice
counts up unbounded), and a driver not entered in a heat already has
their laps fully discarded rather than recorded - both were already
correct, no changes needed there.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app.js

@@ -866,6 +866,7 @@ const TRANSLATIONS = {
     "drivers.brand_placeholder": "Team / märke (valfritt)",
     "drivers.brand_filter_placeholder": "Sök namn / transponder / märke / klubb / land",
     "drivers.transponder_placeholder": "Personlig transponder (valfritt)",
+    "drivers.transponder_conflict_confirm": "Transpondern {tp} används redan av {name} ({class}). Spara ändå?",
     "drivers.speech_name": "Uttalsnamn",
     "drivers.speech_name_placeholder": "Uttal för uppläsning (valfritt)",
     "drivers.speech_name_hint": "Skriv namnet som webbläsarrösten ska uttala det. Lämna tomt för vanligt förarnamn.",
@@ -2381,6 +2382,7 @@ const TRANSLATIONS = {
     "drivers.brand_placeholder": "Team / brand (optional)",
     "drivers.brand_filter_placeholder": "Search name / transponder / brand / club / country",
     "drivers.transponder_placeholder": "Personal transponder (optional)",
+    "drivers.transponder_conflict_confirm": "Transponder {tp} is already used by {name} ({class}). Save anyway?",
     "drivers.speech_name": "Spoken name",
     "drivers.speech_name_placeholder": "Pronunciation for announcements (optional)",
     "drivers.speech_name_hint": "Enter the name as the browser voice should pronounce it. Leave blank to use the regular driver name.",

src/core_views.js

@@ -1,4 +1,4 @@
-import { getDriverProfileGroups, getDriverProfileId } from "./driver_profile_logic.js";
+import { getDriverProfileGroups, getDriverProfileId, findTransponderConflict } from "./driver_profile_logic.js";
 
 function getScheduleDriftSummary(state) {
   const scheduledSessions = state.sessions
@@ -515,13 +515,18 @@ export function renderDriversView(deps) {
         ? uid("profile")
         : sameNameProfile?.id || uid("profile");
     const linkedProfile = profileGroups.find((profile) => profile.id === profileId);
+    const cleanedTransponder = String(form.get("transponder") || "").trim();
+    const transponderConflict = findTransponderConflict(state.drivers, { transponder: cleanedTransponder, profileId });
+    if (transponderConflict && !window.confirm(t("drivers.transponder_conflict_confirm", { tp: cleanedTransponder, name: transponderConflict.name, class: getClassName(transponderConflict.classId) }))) {
+      return;
+    }
     state.drivers.push(
       normalizeDriver({
         id: driverId,
         name: driverName,
         classId: String(form.get("classId")),
         brand: String(form.get("brand") || "").trim(),
-        transponder: String(form.get("transponder") || "").trim(),
+        transponder: cleanedTransponder,
         speechName: String(form.get("speechName") || "").trim(),
         passSound: String(form.get("passSound") || "").trim(),
         profileId,
@@ -634,6 +639,10 @@ export function renderDriversView(deps) {
       setFormError("driverEditError", t("validation.invalid_selection"));
       return;
     }
+    const transponderConflict = findTransponderConflict(state.drivers, { transponder: cleanedTp, profileId: cleanedProfileId, excludeDriverId: editingDriver.id });
+    if (transponderConflict && !window.confirm(t("drivers.transponder_conflict_confirm", { tp: cleanedTp, name: transponderConflict.name, class: getClassName(transponderConflict.classId) }))) {
+      return;
+    }
     setFormError("driverEditError", "");
     state.drivers = state.drivers.map((item) => {
       if (item.id === editingDriver.id) {

src/driver_profile_logic.js

@@ -44,3 +44,19 @@ export function getDriverProfileReferences(state, reference) {
   profile.driverIds.forEach((driverId) => references.add(driverId));
   return references;
 }
+
+// A transponder is one physical chip, so the same value legitimately repeats across a
+// single person's own multi-class driver entries (same profile) - that is not a
+// conflict. It only means something went wrong when it also shows up on a driver
+// belonging to a DIFFERENT profile, since two different people can't share one chip:
+// most often a typo at registration that quietly grabbed someone else's transponder.
+export function findTransponderConflict(drivers, { transponder, profileId, excludeDriverId } = {}) {
+  const value = String(transponder || "").trim();
+  if (!value) return null;
+  const list = Array.isArray(drivers) ? drivers : [];
+  return list.find((driver) => (
+    String(driver.id || "") !== String(excludeDriverId || "")
+    && String(driver.transponder || "").trim() === value
+    && getDriverProfileId(driver) !== String(profileId || "")
+  )) || null;
+}