lgtm 2

frontend/src/lib/active-filter-scroll.ts

@@ -0,0 +1,12 @@
+export function findActiveFilterElement(root: ParentNode | null, filterName: string) {
+  if (!root) return null;
+
+  const cards = root.querySelectorAll<HTMLElement>('[data-filter-name]');
+  for (let i = cards.length - 1; i >= 0; i -= 1) {
+    if (cards[i].dataset.filterName === filterName) {
+      return cards[i];
+    }
+  }
+
+  return null;
+}

frontend/src/lib/api.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, it } from 'vitest';
 
 import type { FeatureMeta } from '../types';
-import { apiUrl, assertOk, buildFilterString, isAbortError } from './api';
+import { apiUrl, assertOk, buildFilterString, isAbortError, paramsWithLanguage } from './api';
 import { createSchoolFilterKey } from './school-filter';
 import { createSpecificCrimeFilterKey } from './crime-filter';
 import { createElectionVoteShareFilterKey } from './election-filter';
@@ -38,6 +38,11 @@ describe('api utilities', () => {
     expect(isAbortError(regular)).toBe(false);
   });
 
+  it('adds supported language parameters without overriding explicit languages', () => {
+    expect(paramsWithLanguage('lat=51.5&lon=-0.1', 'fr-FR')).toBe('lat=51.5&lon=-0.1&lang=fr');
+    expect(paramsWithLanguage('lat=51.5&lang=de', 'fr')).toBe('lat=51.5&lang=de');
+  });
+
   it('serializes numeric, absolute, and enum filters for backend routes', () => {
     const features: FeatureMeta[] = [
       { name: 'Last known price', type: 'numeric', min: 0, max: 1_000_000 },

frontend/src/lib/api.ts

@@ -7,6 +7,8 @@ import { getElectionVoteShareFeatureName } from './election-filter';
 import { getEthnicityFeatureName } from './ethnicity-filter';
 import { getPoiDistanceFeatureName } from './poi-distance-filter';
 
+const SCREENSHOT_LANGUAGES = new Set(['en', 'fr', 'de', 'zh', 'hi', 'hu']);
+
 export function logNonAbortError(label: string, error: unknown): void {
   if (error instanceof Error && error.name === 'AbortError') {
     return;
@@ -42,6 +44,36 @@ export function apiUrl(endpoint: string, params?: URLSearchParams): string {
   return query ? `${path}?${query}` : path;
 }
 
+function toSupportedLanguage(value: string | undefined): string | null {
+  if (!value) return null;
+  const lower = value.toLowerCase();
+  if (SCREENSHOT_LANGUAGES.has(lower)) return lower;
+
+  const prefix = lower.split('-')[0];
+  if (SCREENSHOT_LANGUAGES.has(prefix)) return prefix;
+
+  return null;
+}
+
+function browserLanguage(): string | null {
+  if (typeof navigator === 'undefined') return null;
+  const languages = navigator.languages?.length ? navigator.languages : [navigator.language];
+  for (const language of languages) {
+    const supported = toSupportedLanguage(language);
+    if (supported) return supported;
+  }
+  return null;
+}
+
+export function paramsWithLanguage(params: string, language?: string): string {
+  const qs = new URLSearchParams(params.replace(/^\?/, ''));
+  if (!qs.has('lang')) {
+    const supported = toSupportedLanguage(language) ?? browserLanguage();
+    if (supported) qs.set('lang', supported);
+  }
+  return qs.toString();
+}
+
 export async function fetchWithRetry<T>(
   url: string,
   onSuccess: (data: T) => void,
@@ -65,17 +97,19 @@ export async function fetchWithRetry<T>(
 }
 
 /** Fire-and-forget request to pre-warm the screenshot cache for OG images. */
-export function prewarmScreenshot(params: string): void {
-  fetch(apiUrl('screenshot', new URLSearchParams(`og=1&${params}`)), authHeaders()).catch(() => {}); // best-effort, don't care if it fails
+export function prewarmScreenshot(params: string, language?: string): void {
+  const qs = new URLSearchParams(paramsWithLanguage(params, language));
+  qs.set('og', '1');
+  fetch(apiUrl('screenshot', qs), authHeaders()).catch(() => {}); // best-effort, don't care if it fails
 }
 
-export async function shortenUrl(params: string): Promise<string> {
+export async function shortenUrl(params: string, language?: string): Promise<string> {
   const res = await fetch(
     apiUrl('shorten'),
     authHeaders({
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ params }),
+      body: JSON.stringify({ params: paramsWithLanguage(params, language) }),
     })
   );
   if (!res.ok) throw new Error(`HTTP ${res.status}`);

frontend/src/lib/external-search.test.ts

@@ -76,7 +76,7 @@ describe('external property search URLs', () => {
     expect(new URL(urls!.zoopla).searchParams.get('radius')).toBe('0.25');
   });
 
-  it('uses Rightmove this-area-only radius when an exact postcode identifier is provided', () => {
+  it('uses Rightmove quarter-mile radius when an exact postcode identifier is provided', () => {
     const urls = buildPropertySearchUrls({
       location: {
         lat: 51.501,
@@ -93,7 +93,28 @@ describe('external property search URLs', () => {
 
     expect(rightmove.searchParams.get('searchLocation')).toBe('SW1A 1AA');
     expect(rightmove.searchParams.get('locationIdentifier')).toBe('POSTCODE^837246');
+    expect(rightmove.searchParams.get('radius')).toBe('0.25');
+  });
+
+  it('uses Rightmove outcode-only radius when an outcode identifier is provided', () => {
+    const urls = buildPropertySearchUrls({
+      location: {
+        lat: 51.501,
+        lon: -0.141,
+        resolution: 8,
+        postcode: 'SW1A 1AA',
+        isPostcode: false,
+      },
+      rightmoveLocationId: 'OUTCODE^2506',
+      filters: {},
+    });
+
+    const rightmove = new URL(urls!.rightmove!);
+
+    expect(rightmove.searchParams.get('locationIdentifier')).toBe('OUTCODE^2506');
     expect(rightmove.searchParams.get('radius')).toBe('0.0');
+    expect(new URL(urls!.onthemarket).searchParams.get('radius')).toBe('0.5');
+    expect(new URL(urls!.zoopla).searchParams.get('radius')).toBe('0.5');
   });
 
   it('builds a same-origin Rightmove redirect for exact postcode clicks', () => {

frontend/src/lib/external-search.ts

@@ -36,7 +36,10 @@ export const H3_RADIUS_MILES: Record<number, number> = {
   12: 1,
 };
 
+export const POSTCODE_RADIUS_MILES = 0.25;
+
 const RIGHTMOVE_RADII = [0.25, 0.5, 1, 3, 5, 10, 15, 20, 30, 40];
+const RIGHTMOVE_OUTCODE_RADIUS_MILES = '0.0';
 const OTM_RADII = [0.25, 0.5, 1, 3, 5, 10, 15, 20, 30, 40];
 const ZOOPLA_RADII = [0.25, 0.5, 1, 3, 5, 10, 15, 20, 25, 30];
 
@@ -111,7 +114,7 @@ export function buildPropertySearchUrls({
   const { postcode, resolution, isPostcode } = location;
   if (!postcode) return null;
 
-  const radiusMiles = isPostcode ? 0 : (H3_RADIUS_MILES[resolution] ?? 1);
+  const radiusMiles = isPostcode ? POSTCODE_RADIUS_MILES : (H3_RADIUS_MILES[resolution] ?? 1);
 
   const priceFilter = filters['Estimated current price'] ?? filters['Last known price'];
   const minPrice =
@@ -150,8 +153,8 @@ export function buildPropertySearchUrls({
     rmParams.set('locationIdentifier', rightmoveLocationId);
     rmParams.set(
       'radius',
-      isPostcode && rightmoveLocationId.startsWith('POSTCODE^')
-        ? '0.0'
+      rightmoveLocationId.startsWith('OUTCODE^')
+        ? RIGHTMOVE_OUTCODE_RADIUS_MILES
         : String(nearestRadius(radiusMiles, RIGHTMOVE_RADII))
     );
     if (minPrice !== undefined)

frontend/src/lib/poi-distance-filter.test.ts

@@ -5,15 +5,17 @@ import {
   POI_COUNT_2KM_FILTER_NAME,
   POI_DISTANCE_FILTER_NAME,
   TRANSPORT_DISTANCE_FILTER_NAME,
+  clampPoiFilterRange,
   getPoiFilterFeatureOptions,
   getPoiFilterName,
 } from './poi-distance-filter';
 
-const numeric = (name: string): FeatureMeta => ({
+const numeric = (name: string, overrides: Partial<FeatureMeta> = {}): FeatureMeta => ({
   name,
   type: 'numeric',
   min: 0,
   max: 5,
+  ...overrides,
 });
 
 describe('poi-distance-filter', () => {
@@ -57,4 +59,13 @@ describe('poi-distance-filter', () => {
     );
     expect(getPoiFilterName('Number of amenities (Bus stop) within 2km')).toBeNull();
   });
+
+  it('clamps fixed amenity distance scales to the 0-5km slider bounds', () => {
+    const feature = numeric('Distance to nearest amenity (Cafe) (km)', {
+      absolute: true,
+      histogram: { min: 0.2, max: 12, p1: 0.3, p99: 9, counts: [1, 2, 3] },
+    });
+
+    expect(clampPoiFilterRange([-1, 8], feature)).toEqual([0, 5]);
+  });
 });

frontend/src/lib/poi-distance-filter.ts

@@ -136,6 +136,10 @@ export function isPoiDistanceFeatureName(name: string): boolean {
   return isDynamicPoiDistanceFeatureName(name);
 }
 
+export function usesFixedPoiDistanceScale(feature?: FeatureMeta): boolean {
+  return Boolean(feature?.absolute && isPoiDistanceFeatureName(feature.name));
+}
+
 export function isPoiFilterFeatureName(name: string): boolean {
   return getPoiMetric(name) != null;
 }
@@ -263,6 +267,7 @@ export function getPoiFilterMeta(features: FeatureMeta[], filterName: PoiFilterN
     detail: config.detail,
     source: sourceFeature?.source ?? 'osm-pois',
     suffix: config.suffix,
+    absolute: sourceFeature?.absolute,
   };
 }
 
@@ -295,8 +300,12 @@ export function clampPoiFilterRange(
   value: [number, number],
   feature?: FeatureMeta
 ): [number, number] {
-  const min = feature?.histogram?.min ?? feature?.min ?? 0;
-  const max = feature?.histogram?.max ?? feature?.max ?? Math.max(1, value[1]);
+  const min = usesFixedPoiDistanceScale(feature)
+    ? (feature?.min ?? 0)
+    : (feature?.histogram?.min ?? feature?.min ?? 0);
+  const max = usesFixedPoiDistanceScale(feature)
+    ? (feature?.max ?? 5)
+    : (feature?.histogram?.max ?? feature?.max ?? Math.max(1, value[1]));
   return [Math.max(min, Math.min(value[0], max)), Math.max(min, Math.min(value[1], max))];
 }
 

frontend/src/lib/url-state.ts

@@ -47,6 +47,7 @@ import {
   isPoiDistanceFilterName,
   type PoiFilterName,
 } from './poi-distance-filter';
+import { dedupeTravelTimeEntries } from './travel-params';
 
 const POI_NONE_PARAM = '__none';
 
@@ -280,7 +281,7 @@ export function parseUrlState(): UrlState {
       entries.push({ mode, slug, label, timeRange, useBest });
     }
     if (entries.length > 0) {
-      result.travelTime = { entries };
+      result.travelTime = { entries: dedupeTravelTimeEntries(entries) };
     }
   }
 
@@ -379,7 +380,7 @@ export function stateToParams(
 
   // Travel time: repeated `tt` params
   if (travelTimeEntries) {
-    for (const entry of travelTimeEntries) {
+    for (const entry of dedupeTravelTimeEntries(travelTimeEntries)) {
       if (!entry.slug) continue;
       let val = `${entry.mode}:${entry.slug}:${encodeURIComponent(entry.label)}`;
       if (entry.useBest) val += ':b';