feat: add manual PI WEB update checks

src/server/piWebReleaseLookupCache.ts

@@ -0,0 +1,57 @@
+const DEFAULT_PI_WEB_RELEASE_LOOKUP_CACHE_TTL_MS = 6 * 60 * 60 * 1000;
+
+export interface PiWebReleaseLookup {
+  checkedAtMs: number;
+  latestVersion?: string;
+  error?: string;
+}
+
+export interface PiWebReleaseLookupCacheOptions {
+  ttlMs?: number;
+  now?: () => number;
+}
+
+export interface PiWebReleaseLookupOptions {
+  force?: boolean;
+}
+
+export interface PiWebReleaseLookupCache {
+  get(currentVersion: string, options?: PiWebReleaseLookupOptions): Promise<PiWebReleaseLookup>;
+}
+
+export function createPiWebReleaseLookupCache(
+  load: (currentVersion: string) => Promise<string>,
+  options: PiWebReleaseLookupCacheOptions = {},
+): PiWebReleaseLookupCache {
+  const ttlMs = options.ttlMs ?? DEFAULT_PI_WEB_RELEASE_LOOKUP_CACHE_TTL_MS;
+  const now = options.now ?? Date.now;
+  let cached: PiWebReleaseLookup | undefined;
+  let pending: { promise: Promise<PiWebReleaseLookup>; force: boolean; sequence: number } | undefined;
+  let loadSequence = 0;
+
+  return {
+    get(currentVersion: string, lookupOptions: PiWebReleaseLookupOptions = {}): Promise<PiWebReleaseLookup> {
+      const force = lookupOptions.force === true;
+      if (pending?.force === true) return pending.promise;
+
+      const checkedAtMs = now();
+      if (!force && cached !== undefined && checkedAtMs - cached.checkedAtMs < ttlMs) return Promise.resolve(cached);
+      if (!force && pending !== undefined) return pending.promise;
+
+      const sequence = ++loadSequence;
+      const promise = Promise.resolve()
+        .then(() => load(currentVersion))
+        .then((latestVersion): PiWebReleaseLookup => ({ checkedAtMs, latestVersion }))
+        .catch((error: unknown): PiWebReleaseLookup => ({ checkedAtMs, error: error instanceof Error ? error.message : String(error) }))
+        .then((lookup) => {
+          if (sequence === loadSequence) cached = lookup;
+          return lookup;
+        })
+        .finally(() => {
+          if (pending?.sequence === sequence) pending = undefined;
+        });
+      pending = { promise, force, sequence };
+      return promise;
+    },
+  };
+}