// app.js - Modern, idiot-proof, client-only (Overpass + Leaflet)
// Features: Dark mode toggle (persist), caching (5 min), top-5 list, multiple Overpass endpoints fallback
// --- UI elements
const findBtn = document.getElementById('findBtn');
const resetBtn = document.getElementById('resetBtn');
const statusEl = document.getElementById('status');
const outputEl = document.getElementById('output');
const themeSwitch = document.getElementById('themeSwitch');
// --- Map state
let map, userMarker, shopMarker;
// --- Overpass endpoints fallback (CORS-friendly mirrors)
const OVERPASS_ENDPOINTS = [
'https://overpass-api.de/api/interpreter',
'https://overpass.kumi.systems/api/interpreter',
'https://lz4.overpass-api.de/api/interpreter'
];
// --- small helpers
function setStatus(txt) { statusEl.textContent = txt; }
function showHTML(html) { outputEl.innerHTML = html; outputEl.style.display = 'block'; }
function clearOutput() { outputEl.innerHTML = ''; outputEl.style.display = 'none'; }
function roundCoord(x){ return Math.round(x*10000)/10000; } // for cache key
// --- caching: simple localStorage cache (keyed by rounded coords)
// stores { ts: timestamp_ms, payload: {...} }
const CACHE_TTL = 1000 * 60 * 5; // 5 minutes
function getCacheKey(lat, lon, radius=3000){ return `osm_nearest_${roundCoord(lat)}_${roundCoord(lon)}_${radius}`;}
function readCache(key){
try {
const s = localStorage.getItem(key);
if(!s) return null;
const obj = JSON.parse(s);
if(Date.now() - obj.ts > CACHE_TTL) { localStorage.removeItem(key); return null; }
return obj.payload;
} catch(e){ return null; }
}
function writeCache(key, payload){
try { localStorage.setItem(key, JSON.stringify({ ts: Date.now(), payload })); } catch(e){}
}
// --- haversine distance (meters)
function haversine(lat1, lon1, lat2, lon2){
const R = 6371e3;
const toRad = d => d * Math.PI / 180;
const φ1 = toRad(lat1), φ2 = toRad(lat2);
const Δφ = toRad(lat2 - lat1), Δλ = toRad(lon2 - lon1);
const a = Math.sin(Δφ/2)**2 + Math.cos(φ1)*Math.cos(φ2)*Math.sin(Δλ/2)**2;
return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
}
// --- build Overpass QL
function buildQuery(lat, lon, radius=3000, maxResults=30){
return `
[out:json][timeout:25];
(
node["shop"~"supermarket|grocery|convenience"](around:${radius},${lat},${lon});
way["shop"~"supermarket|grocery|convenience"](around:${radius},${lat},${lon});
relation["shop"~"supermarket|grocery|convenience"](around:${radius},${lat},${lon});
);
out center ${maxResults};
`;
}
// --- try endpoints sequentially
async function queryOverpass(query){
let lastError = null;
for(const ep of OVERPASS_ENDPOINTS){
try {
console.log('Trying Overpass endpoint:', ep);
const resp = await fetch(ep, {
method: 'POST',
headers: { 'Content-Type': 'text/plain' },
body: query,
mode: 'cors'
});
if(!resp.ok){
const t = await resp.text().catch(()=>null);
lastError = { endpoint: ep, status: resp.status, text: t };
console.warn('Overpass returned non-OK', lastError);
continue;
}
const data = await resp.json();
return { data, endpoint: ep };
} catch(err){
lastError = { endpoint: ep, message: err.message || String(err) };
console.warn('Overpass fetch error', lastError);
continue;
}
}
const e = new Error('All Overpass endpoints failed');
e.details = lastError;
throw e;
}
// --- map helpers
function initMap(lat=20, lon=0, zoom=2){
if(!map){
map = L.map('map', { zoomControl:true, attributionControl: true }).setView([lat, lon], zoom);
L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', { maxZoom: 19 }).addTo(map);
} else {
map.setView([lat, lon], zoom);
}
}
function setMarkers(userLat, userLon, shopLat, shopLon, shopName){
if(userMarker) userMarker.remove(); if(shopMarker) shopMarker.remove();
userMarker = L.marker([userLat, userLon]).addTo(map).bindPopup('You are here').openPopup();
shopMarker = L.marker([shopLat, shopLon]).addTo(map).bindPopup(shopName || 'Supermarket');
const bounds = L.latLngBounds([[userLat, userLon],[shopLat, shopLon]]);
map.fitBounds(bounds.pad(0.2));
}
// --- main search flow
async function findNearest(){
clearOutput();
setStatus('Requesting your location — please allow location access.');
if(!navigator.geolocation){
setStatus('Geolocation not supported by your browser.');
return;
}
navigator.geolocation.getCurrentPosition(async pos=>{
const lat = pos.coords.latitude;
const lon = pos.coords.longitude;
const radius = 3000;
setStatus(`Location acquired: ${lat.toFixed(5)}, ${lon.toFixed(5)} — searching within ${radius} m...`);
initMap(lat, lon, 15);
const cacheKey = getCacheKey(lat, lon, radius);
const cached = readCache(cacheKey);
if(cached){
setStatus(`Using cached result (${Math.round((cached.sourceAge||0)/1000)}s ago).`);
renderResults(cached.payload, lat, lon);
return;
}
const q = buildQuery(lat, lon, radius, 40);
try {
const { data, endpoint } = await queryOverpass(q);
if(!data || !Array.isArray(data.elements) || data.elements.length === 0){
setStatus('No supermarkets found within radius. Try increasing radius or moving closer to shops.');
showHTML(`No supermarkets found within ${radius} m.
Endpoint: ${endpoint || 'none'}
`);
return;
}
// build candidate list with usable coords + distance
const candidates = [];
for(const el of data.elements){
let elLat = null, elLon = null;
if(el.type === 'node'){ elLat = el.lat; elLon = el.lon; }
else if(el.type === 'way' || el.type === 'relation'){
if(el.center && typeof el.center.lat === 'number'){ elLat = el.center.lat; elLon = el.center.lon; }
else continue;
} else continue;
const dist = Math.round(haversine(lat, lon, elLat, elLon));
candidates.push({ el, lat: elLat, lon: elLon, dist });
}
if(candidates.length === 0){
setStatus('No usable coordinates in results.');
showHTML(`Overpass returned results, but none had usable coordinates.
`);
return;
}
candidates.sort((a,b)=>a.dist - b.dist);
// prepare a compact payload to cache & render
const payload = {
endpoint,
results: candidates.slice(0,10).map(c => ({
id: c.el.id,
type: c.el.type,
name: c.el.tags?.name || c.el.tags?.operator || 'Unnamed',
lat: c.lat,
lon: c.lon,
dist: c.dist
}))
};
// cache it
writeCache(cacheKey, { payload, sourceAge:0 });
// store sourceAge in payload for immediate display clarity
payload.sourceAge = 0;
renderResults(payload, lat, lon);
setStatus(`Found ${payload.results.length} nearby supermarkets (endpoint: ${endpoint}).`);
} catch(err){
console.error('Search failed', err);
const msg = err?.message || 'Search failed';
setStatus('Search failed — see details below.');
showHTML(`${msg}
Possible reason: Overpass endpoint unreachable or rate-limited. Try again later or use a different network.
`);
}
}, err=>{
if(err.code === 1) setStatus('Location access denied. Allow location permissions for this site.');
else if(err.code === 2) setStatus('Position unavailable.');
else if(err.code === 3) setStatus('Timeout while getting location.');
else setStatus('Unknown geolocation error.');
}, { enableHighAccuracy:true, maximumAge:0, timeout:20000 });
}
// --- render results to UI
function renderResults(payload, originLat, originLon){
if(!payload || !Array.isArray(payload.results)) { showHTML('No results to display.
'); return; }
const nearest = payload.results[0];
let html = `${escapeHtml(nearest.name)}
`;
html += `
${(nearest.dist/1000).toFixed(2)} km · ${nearest.dist} m away
`;
const mapsLink = `https://www.openstreetmap.org/${nearest.type}/${nearest.id}`;
const directionsLink = `https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=${originLat},${originLon};${nearest.lat},${nearest.lon}`;
html += `
`;
html += `
Endpoint: ${escapeHtml(payload.endpoint || 'unknown')}
`;
// top list
html += `
`;
html += `
Other nearby supermarkets (top ${Math.min(5,payload.results.length)}):
`;
const top = payload.results.slice(0,5);
for(const r of top){
const rlink = `https://www.openstreetmap.org/${r.type}/${r.id}`;
html += `- ${escapeHtml(r.name)} — ${(r.dist/1000).toFixed(2)} km
`;
}
html += `