initial commit

.agents/skills/expo-cicd-workflows/scripts/fetch.js

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+#!/usr/bin/env node
+
+import { createHash } from "node:crypto";
+import { readFile, writeFile, mkdir } from "node:fs/promises";
+import { resolve } from "node:path";
+import process from "node:process";
+
+const CACHE_DIRECTORY = resolve(import.meta.dirname, ".cache");
+const DEFAULT_TTL_SECONDS = 15 * 60; // 15 minutes
+
+export async function fetchCached(url) {
+  await mkdir(CACHE_DIRECTORY, { recursive: true });
+
+  const cacheFile = resolve(CACHE_DIRECTORY, hashUrl(url) + ".json");
+  const cached = await loadCacheEntry(cacheFile);
+  if (cached && cached.expires > Math.floor(Date.now() / 1000)) {
+    return cached.data;
+  }
+
+  // Make request, with conditional If-None-Match if we have an ETag.
+  // Cache-Control: max-age=0 overrides Node's default 'no-cache' to allow 304 responses.
+  const response = await fetch(url, {
+    headers: {
+      "Cache-Control": "max-age=0",
+      ...(cached?.etag && { "If-None-Match": cached.etag }),
+    },
+  });
+
+  if (response.status === 304 && cached) {
+    // Refresh expiration and return cached data
+    const entry = { ...cached, expires: getExpires(response.headers) };
+    await saveCacheEntry(cacheFile, entry);
+    return cached.data;
+  }
+
+  if (!response.ok) {
+    throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+  }
+
+  const etag = response.headers.get("etag");
+  const data = await response.text();
+  const expires = getExpires(response.headers);
+
+  await saveCacheEntry(cacheFile, { url, etag, expires, data });
+
+  return data;
+}
+
+function hashUrl(url) {
+  return createHash("sha256").update(url).digest("hex").slice(0, 16);
+}
+
+async function loadCacheEntry(cacheFile) {
+  try {
+    return JSON.parse(await readFile(cacheFile, "utf-8"));
+  } catch {
+    return null;
+  }
+}
+
+async function saveCacheEntry(cacheFile, entry) {
+  await writeFile(cacheFile, JSON.stringify(entry, null, 2));
+}
+
+function getExpires(headers) {
+  const now = Math.floor(Date.now() / 1000);
+
+  // Prefer Cache-Control: max-age
+  const maxAgeSeconds = parseMaxAge(headers.get("cache-control"));
+  if (maxAgeSeconds != null) {
+    return now + maxAgeSeconds;
+  }
+
+  // Fall back to Expires header
+  const expires = headers.get("expires");
+  if (expires) {
+    const expiresTime = Date.parse(expires);
+    if (!Number.isNaN(expiresTime)) {
+      return Math.floor(expiresTime / 1000);
+    }
+  }
+
+  // Default TTL
+  return now + DEFAULT_TTL_SECONDS;
+}
+
+function parseMaxAge(cacheControl) {
+  if (!cacheControl) {
+    return null;
+  }
+  const match = cacheControl.match(/max-age=(\d+)/i);
+  return match ? parseInt(match[1], 10) : null;
+}
+
+if (import.meta.main) {
+  const url = process.argv[2];
+
+  if (!url || url === "--help" || url === "-h") {
+    console.log(`Usage: fetch <url>
+
+Fetches a URL with HTTP caching (ETags + Cache-Control/Expires).
+Default TTL: ${DEFAULT_TTL_SECONDS / 60} minutes.
+Cache is stored in: ${CACHE_DIRECTORY}/`);
+    process.exit(url ? 0 : 1);
+  }
+
+  const data = await fetchCached(url);
+  console.log(data);
+}