feat: Implement rate limiting functionality

Author: ericc-ch

src/lib/rate-limit.ts

@@ -0,0 +1,30 @@
+import consola from "consola"
+
+import type { State } from "./state"
+
+import { HTTPError } from "./http-error"
+
+export function checkRateLimit(state: State) {
+  if (state.rateLimitSeconds === undefined) return
+
+  const now = Date.now()
+
+  if (!state.lastRequestTimestamp) {
+    state.lastRequestTimestamp = now
+    return
+  }
+
+  const elapsedSeconds = (now - state.lastRequestTimestamp) / 1000
+
+  if (elapsedSeconds > state.rateLimitSeconds) {
+    state.lastRequestTimestamp = now
+    return
+  }
+
+  const waitTimeSeconds = Math.round(state.rateLimitSeconds - elapsedSeconds)
+  consola.warn(
+    `Rate limit exceeded. Need to wait ${waitTimeSeconds} more seconds.`,
+  )
+
+  throw new HTTPError("Rate limit exceeded", Response.json({ status: 429 }))
+}