feat(web): Add Cloudflare Workers geolocation fallback

Add a minimal cfgeo Cloudflare Worker that returns coarse location
from Cloudflare's edge geolocation data. Use it as a fast default
location on load, preferring browser geolocation or an explicit
search/URL selection whenever those are available.

cfgeo/.gitignore

@@ -0,0 +1,2 @@
+.wrangler/
+node_modules/

cfgeo/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "cfgeo",
+  "private": true,
+  "scripts": {
+    "dev": "wrangler dev",
+    "deploy": "wrangler deploy"
+  },
+  "devDependencies": {
+    "wrangler": "^3.90.0"
+  }
+}

cfgeo/src/index.js

@@ -0,0 +1,23 @@
+export default {
+    async fetch(request) {
+        const cf = request.cf || {};
+
+        const body = {
+            latitude: cf.latitude ? Number(cf.latitude) : null,
+            longitude: cf.longitude ? Number(cf.longitude) : null,
+            city: cf.city ?? null,
+            region: cf.region ?? null,
+            country: cf.country ?? null,
+            timezone: cf.timezone ?? null,
+            postalCode: cf.postalCode ?? null,
+        };
+
+        return new Response(JSON.stringify(body), {
+            headers: {
+                'content-type': 'application/json',
+                'access-control-allow-origin': '*',
+                'cache-control': 'no-store',
+            },
+        });
+    },
+};

cfgeo/wrangler.toml

@@ -0,0 +1,3 @@
+name = "cfgeo"
+main = "src/index.js"
+compatibility_date = "2024-01-01"

templates/static/main.js

@@ -1,3 +1,6 @@
+const CFGEO_ENDPOINT = "https://cfgeo.abdusco.workers.dev/";
+const CFGEO_TIMEOUT_MS = 2000;
+
 const app = () => ({
     futureTimes: [],
     selectedLocation: Alpine.$persist(null),
@@ -34,12 +37,29 @@ const app = () => ({
         }, 500);
 
         if (!urlCoords) {
-            try {
-                const coords = await getUserLocation();
-                await this.selectNearestLocation(coords.latitude, coords.longitude, {updateURL: true});
-            } catch (_error) {
-                // Ignore geolocation errors and rely on manual search.
+            await this.resolveDefaultLocation();
         }
+    },
+
+    async resolveDefaultLocation() {
+        let browserResolved = false;
+        const geoPromise = getUserLocation()
+            .then((coords) => {
+                browserResolved = true;
+                return coords;
+            })
+            .catch(() => null);
+
+        if (!this.selectedLocation) {
+            const cfCoords = await withTimeout(getCFGeoLocation(), CFGEO_TIMEOUT_MS);
+            if (cfCoords && !browserResolved) {
+                await this.selectNearestLocation(cfCoords.latitude, cfCoords.longitude, {updateURL: false});
+            }
+        }
+
+        const geoCoords = await geoPromise;
+        if (geoCoords) {
+            await this.selectNearestLocation(geoCoords.latitude, geoCoords.longitude, {updateURL: true});
         }
     },
 
@@ -396,6 +416,26 @@ function getUserLocation() {
     });
 }
 
+async function getCFGeoLocation() {
+    if (!CFGEO_ENDPOINT) {
+        return null;
+    }
+
+    const data = await fetchJSON(CFGEO_ENDPOINT);
+    if (typeof data.latitude !== "number" || typeof data.longitude !== "number") {
+        return null;
+    }
+
+    return {latitude: data.latitude, longitude: data.longitude};
+}
+
+function withTimeout(promise, ms) {
+    return Promise.race([
+        promise,
+        new Promise((resolve) => setTimeout(() => resolve(null), ms))
+    ]).catch(() => null);
+}
+
 function normalizeLanguageTag(tag) {
     return String(tag).toLowerCase().split("-")[0];
 }