Cache API responses for custom value providers

actions-languageserver/src/utils/cache.ts

@@ -0,0 +1,47 @@
+// From https://github.com/cschleiden/github-actions-parser/blob/a81dec9b7462dbcff08fbad0792f5ad549d9de7d/src/lib/workflowschema/workflowSchema.ts
+interface CacheEntry<T> {
+  cachedAt: number;
+  content: T;
+}
+
+export class TTLCache {
+  private cache = new Map<string, CacheEntry<unknown>>();
+
+  constructor(private defaultTTLinMS: number = 10 * 60 * 1000) {}
+
+  /**
+   *
+   * @param key Key to cache value under
+   * @param ttlInMS How long is the content valid. If optional, default value will be used
+   * @param getter Function to retrieve content if not in cache
+   */
+  async get<T>(
+    key: string,
+    ttlInMS: number | undefined,
+    getter: () => Promise<T>
+  ): Promise<T> {
+    const hasEntry = this.cache.has(key);
+    const e = hasEntry && this.cache.get(key);
+    if (
+      hasEntry &&
+      e &&
+      e.cachedAt > Date.now() - (ttlInMS || this.defaultTTLinMS)
+    ) {
+      return e.content as T;
+    }
+
+    try {
+      const content = await getter();
+
+      this.cache.set(key, {
+        cachedAt: Date.now(),
+        content,
+      });
+
+      return content;
+    } catch (e) {
+      this.cache.delete(key);
+      throw e;
+    }
+  }
+}