server sided external api calls (#697)

* server sided external api calls

* fix uploading gpx files

* rename api/v1/nominatim with api/v1/geocoding to prepare photon support

* remove NOMINATIM_MAX_RETRIES (side-kick from other PR)

* re-add nominatim url fallback

* docu, env var defaults and fallbacks, docker compose files

* refactor

* furhter refactorings and fixes

* PUBLIC_VALHALLA_ENABLED in docker compose files added

* fix env var names

---------

Co-authored-by: Flomp <Flomp@users.noreply.github.com>

web/src/lib/server/nominatim.ts

@@ -0,0 +1,63 @@
+import { version } from "$app/environment";
+import { resolveBaseUrl } from "$lib/server/url";
+import type { RequestEvent } from "@sveltejs/kit";
+
+const NOMINATIM_RATE_LIMIT_MS = 1000;
+const NOMINATIM_MAX_RETRIES = 2;
+let lastNominatimCall = 0;
+
+function getNominatimBaseUrl(): string {
+    return resolveBaseUrl("NOMINATIM_URL", "https://nominatim.openstreetmap.org");
+}
+
+function needsRateLimiting(baseUrl: string): boolean {
+    return baseUrl.includes("nominatim.openstreetmap.org");
+}
+
+const waitTimer = (ms: number) => new Promise<void>((resolve) => setTimeout(resolve, ms));
+
+async function nominatimRateLimiter(baseUrl: string) {
+    if (!needsRateLimiting(baseUrl)) {
+        return;
+    }
+
+    const elapsedTimeMs = Date.now() - lastNominatimCall;
+    const waitTime = NOMINATIM_RATE_LIMIT_MS - elapsedTimeMs;
+    if (waitTime > 0) {
+        await waitTimer(waitTime);
+    }
+
+    lastNominatimCall = Date.now();
+}
+
+export async function fetchNominatim(event: RequestEvent, path: string, params: URLSearchParams): Promise<Response> {
+    const baseUrl = getNominatimBaseUrl();
+    const base = new URL(baseUrl.endsWith("/") ? baseUrl : `${baseUrl}/`);
+    const cleanPath = path.replace(/^\/+/, "");
+    const url = new URL(cleanPath, base);
+    const query = params.toString();
+    if (query.length) {
+        url.search = query;
+    }
+
+    let attempt = 0;
+
+    while (true) {
+        await nominatimRateLimiter(baseUrl);
+
+        try {
+            return await event.fetch(url.toString(), {
+                method: "GET",
+                headers: {
+                    "User-Agent": `wanderer/${version}`,
+                },
+            });
+        } catch (error) {
+            if (attempt < NOMINATIM_MAX_RETRIES) {
+                attempt++;
+                continue;
+            }
+            throw new Error(`Nominatim fetch failed for ${url.toString()}`, { cause: error });
+        }
+    }
+}