feat: add YouTube API helper functions

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/lib/api.js

@@ -0,0 +1,70 @@
+export class ApiError extends Error {
+  constructor(kind, message, status = null) {
+    super(message);
+    this.name = 'ApiError';
+    this.kind = kind;
+    this.status = status;
+  }
+}
+
+export function chunk(items, size) {
+  const batches = [];
+  for (let i = 0; i < items.length; i += size) batches.push(items.slice(i, i + size));
+  return batches;
+}
+
+export function parseIsoDuration(iso) {
+  const match = /^P(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?$/.exec(iso ?? '');
+  if (!match) return null;
+  const [, days = 0, hours = 0, minutes = 0, seconds = 0] = match;
+  return Number(days) * 86400 + Number(hours) * 3600 + Number(minutes) * 60 + Number(seconds);
+}
+
+const THUMBNAIL_ORDER = ['maxres', 'standard', 'high', 'medium', 'default'];
+
+export function pickThumbnail(thumbnails) {
+  for (const size of THUMBNAIL_ORDER) {
+    const url = thumbnails?.[size]?.url;
+    if (url) return url;
+  }
+  return null;
+}
+
+const QUOTA_REASONS = new Set(['quotaExceeded', 'dailyLimitExceeded']);
+const KEY_REASONS = new Set([
+  'keyInvalid',
+  'API_KEY_INVALID',
+  'accessNotConfigured',
+  'ipRefererBlocked',
+  'API_KEY_HTTP_REFERRER_BLOCKED',
+  'API_KEY_SERVICE_BLOCKED',
+  'SERVICE_DISABLED',
+]);
+
+export function errorReasons(body) {
+  const error = body?.error;
+  return [...(error?.errors ?? []), ...(error?.details ?? [])].map((entry) => entry.reason).filter(Boolean);
+}
+
+export function classifyError(status, body) {
+  const reasons = errorReasons(body);
+  if (reasons.some((reason) => QUOTA_REASONS.has(reason))) return 'quota';
+  if (reasons.some((reason) => KEY_REASONS.has(reason))) return 'invalid-key';
+  if (status >= 500 || status === 429) return 'server';
+  return 'other';
+}
+
+// The Data API quota resets at midnight Pacific Time.
+export function nextQuotaReset(now = new Date()) {
+  const parts = new Intl.DateTimeFormat('en-US', {
+    timeZone: 'America/Los_Angeles',
+    hourCycle: 'h23',
+    hour: 'numeric',
+    minute: 'numeric',
+    second: 'numeric',
+  }).formatToParts(now);
+  const part = (type) => Number(parts.find((p) => p.type === type).value);
+  const sinceMidnightMs =
+    ((part('hour') * 60 + part('minute')) * 60 + part('second')) * 1000 + now.getMilliseconds();
+  return now.getTime() - sinceMidnightMs + 24 * 60 * 60 * 1000;
+}