refactor(street-level): slim Mapillary tile proxy — memory cache only, no server holds

Drop the disk tile cache (.gev-cache/mapillary/tiles, background sweep,
size cap, legacy retrim), the server-side 401/403/429 holds, the upstream
concurrency semaphore and per-waiter abort bookkeeping. The client already
pauses on 429 and stops on a rejected key.

Keep: server-side token, {configured}-only status, strict coverage path
validation (z11-14), image-layer trimming, same-site gate and per-IP limit,
HTTPS redirect pinning to the tile origin, the streamed size cap, the error
mapping the client reads, a 24 h byte-budget LRU memory cache, in-flight
coalescing via the shared coalesceProxyRequest, and browser Cache-Control.

Routes and constants fold into mapillary.js and mapillary/tiles.js.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

server/providers/mapillary.js

@@ -1,19 +1,105 @@
-import { installMapillaryRoutes } from './mapillary/routes.js';
+import { sameSiteGated } from './common/same-site.js';
+import { makeRateLimiter, clientKey } from './common/rate-limit.js';
+import {
+  fetchTile,
+  mapillaryToken,
+  parseTilePath,
+  TileUpstreamError,
+} from './mapillary/tiles.js';
 
 /**
- * Vite plugin: cached Mapillary coverage tiles (token added server-side) and a
- * status route that says whether a token is configured.
+ * Tile requests per client IP per minute, cache hits included: 24 new 25-tile
+ * views a minute, more than a person flying the camera reaches.
  */
-function mapillaryProxy() {
-  return {
-    name: 'mapillary-proxy',
-    configureServer(server) {
-      installMapillaryRoutes(server.middlewares);
-    },
-    configurePreviewServer(server) {
-      installMapillaryRoutes(server.middlewares);
-    },
-  };
+export const TILE_ROUTE_MAX_PER_MIN = 600;
+/** The longest upstream Retry-After passed on, in seconds. */
+const MAX_RETRY_AFTER_SEC = 600;
+
+function sendJson(res, status, payload) {
+  res.statusCode = status;
+  res.setHeader('Content-Type', 'application/json; charset=utf-8');
+  res.setHeader('Cache-Control', 'no-store');
+  res.end(JSON.stringify(payload));
 }
 
-export { mapillaryProxy };
+/** GET /api/mapillary/status — whether a token is configured, never its value. */
+function handleStatus(req, res) {
+  if (req.method !== 'GET')
+    return sendJson(res, 405, { error: 'Method not allowed' });
+  sendJson(res, 200, { configured: Boolean(mapillaryToken()) });
+}
+
+/** GET /api/mapillary/tiles/coverage/{z}/{x}/{y} — trimmed protobuf tile. */
+async function handleTile(req, res, allow) {
+  if (req.method !== 'GET')
+    return sendJson(res, 405, { error: 'Method not allowed' });
+  if (!allow(clientKey(req))) {
+    res.setHeader('Retry-After', '5');
+    return sendJson(res, 429, {
+      error: 'Too many tile requests',
+      retryAfter: 5,
+    });
+  }
+  const address = parseTilePath((req.url || '').split('?')[0]);
+  if (!address)
+    return sendJson(res, 400, {
+      error: 'Tile path must be /coverage/{z}/{x}/{y} with z 11–14',
+    });
+  if (!mapillaryToken())
+    return sendJson(res, 503, { error: 'no_key', keyRequired: true });
+  try {
+    const { bytes, source } = await fetchTile(address);
+    res.statusCode = bytes.length ? 200 : 204;
+    res.setHeader('Content-Type', 'application/x-protobuf');
+    res.setHeader('Cache-Control', 'public, max-age=3600');
+    res.setHeader('X-Gev-Cache', source);
+    res.end(bytes.length ? bytes : undefined);
+  } catch (error) {
+    const status = error instanceof TileUpstreamError ? error.status : 0;
+    // A rejected token is a key problem the panel can name, not a fault.
+    if (status === 401 || status === 403)
+      return sendJson(res, 403, {
+        error: 'Mapillary rejected the access token',
+        keyRejected: true,
+      });
+    if (status === 429) {
+      const sent = Number(error.retryAfter);
+      const retryAfter =
+        Number.isInteger(sent) && sent > 0
+          ? Math.min(sent, MAX_RETRY_AFTER_SEC)
+          : 60;
+      res.setHeader('Retry-After', String(retryAfter));
+      return sendJson(res, 429, {
+        error: 'Mapillary is rate-limiting tile requests',
+        retryAfter,
+      });
+    }
+    // An upstream 400 must not read as a malformed request to this proxy.
+    sendJson(res, 502, { error: error?.message || 'Tile fetch failed' });
+  }
+}
+
+/**
+ * Vite plugin: Mapillary coverage tiles with the token added server-side, and
+ * a status route. Both refuse cross-site requests so another page cannot
+ * spend the token.
+ */
+export function mapillaryProxy() {
+  const install = (middlewares) => {
+    const allow = makeRateLimiter({
+      windowMs: 60_000,
+      max: TILE_ROUTE_MAX_PER_MIN,
+      globalMax: TILE_ROUTE_MAX_PER_MIN * 4,
+    });
+    middlewares.use('/api/mapillary/status', sameSiteGated(handleStatus));
+    middlewares.use(
+      '/api/mapillary/tiles',
+      sameSiteGated((req, res) => handleTile(req, res, allow)),
+    );
+  };
+  return {
+    name: 'mapillary-proxy',
+    configureServer: (server) => install(server.middlewares),
+    configurePreviewServer: (server) => install(server.middlewares),
+  };
+}