basic single run caching

index.ts

@@ -1,6 +1,84 @@
 import "dotenv/config";
 
+const AUTH_KEY = Bun.env.TBA_AUTH_KEY;
+if (!AUTH_KEY) {
+  process.exit();
+}
+
+const authHeaders = new Headers({
+  "X-TBA-Auth-Key": AUTH_KEY,
+});
+
 const BASE_URL = "https://www.thebluealliance.com/api/v3";
 
-console.log("Hello via Bun!");
+interface CacheEntry {
+  etag: string;
+  data: string;
+  staleTime: number;
+}
+
+const tbaCache: { [name: string]: CacheEntry } = {};
+
+interface TBAResponse {
+  data: string;
+  status: number;
+}
+
+function updateCache(
+  endpoint: string,
+  etag: string | null,
+  data: string,
+  maxAge: number,
+) {
+  if (etag) {
+    tbaCache[endpoint] = { etag, data, staleTime: Date.now() + maxAge };
+  }
+}
+
+function fetchCache(endpoint: string) {
+  return tbaCache[endpoint];
+}
+
+async function getTBAEndpoint(endpoint: string): Promise<TBAResponse> {
+  const time = Date.now();
+  console.log(tbaCache[endpoint]);
+  if (tbaCache[endpoint] && tbaCache[endpoint].staleTime > time) {
+    console.log("Cache hit... " + endpoint);
+    return { data: fetchCache(endpoint).data, status: 200 };
+  }
+
+  console.log("Fetching... " + endpoint);
+  const headers = new Headers(authHeaders);
+  const response = await fetch(BASE_URL + endpoint, { headers });
+
+  let data;
+  if (response.status === 200) {
+    data = await response.text();
+    const maxAge = parseInt(
+      response.headers
+        .get("cache-control")
+        ?.split(",")
+        .filter((d) => d.includes("max-age"))[0]
+        .trim()
+        .split("=")[1] as string,
+    );
+    updateCache(endpoint, response.headers.get("ETag"), data, maxAge);
+  } else if (response.status === 304) {
+    // Safety: a 304 response indicates out cache is valid based on ETag
+    data = fetchCache(endpoint).data as string;
+
+    console.log("Unchanged... " + endpoint);
+  } else {
+    data = "";
+  }
+
+  return {
+    data,
+    status: response.status,
+  };
+}
+
+const response = await getTBAEndpoint("/team/frc4043/events/simple");
+
+console.log(response);