feat: fetch videos and channels from the YouTube Data API

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

src/lib/api.js

@@ -68,3 +68,106 @@ export function nextQuotaReset(now = new Date()) {
     ((part('hour') * 60 + part('minute')) * 60 + part('second')) * 1000 + now.getMilliseconds();
   return now.getTime() - sinceMidnightMs + 24 * 60 * 60 * 1000;
 }
+
+const API_BASE = 'https://www.googleapis.com/youtube/v3';
+const BATCH_SIZE = 50;
+const RETRIES = 3;
+const BASE_DELAY_MS = 500;
+
+const defaultSleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
+
+async function requestOnce(path, params, { apiKey, fetchImpl = fetch }) {
+  const url = `${API_BASE}/${path}?${new URLSearchParams({ ...params, key: apiKey })}`;
+  let response;
+  try {
+    response = await fetchImpl(url);
+  } catch (err) {
+    throw new ApiError('network', err.message);
+  }
+  if (response.ok) {
+    try {
+      return await response.json();
+    } catch {
+      throw new ApiError('server', 'Invalid JSON in API response', response.status);
+    }
+  }
+  let body = null;
+  try {
+    body = await response.json();
+  } catch {
+    // error responses are not always JSON
+  }
+  throw new ApiError(classifyError(response.status, body), body?.error?.message ?? `HTTP ${response.status}`, response.status);
+}
+
+async function request(path, params, opts) {
+  const sleep = opts.sleep ?? defaultSleep;
+  for (let attempt = 0; ; attempt += 1) {
+    try {
+      return await requestOnce(path, params, opts);
+    } catch (err) {
+      const retryable = err instanceof ApiError && (err.kind === 'network' || err.kind === 'server');
+      if (!retryable || attempt >= RETRIES) throw err;
+      await sleep(BASE_DELAY_MS * 2 ** attempt);
+    }
+  }
+}
+
+export function normalizeVideo(item) {
+  const { snippet = {}, statistics = {}, contentDetails = {} } = item;
+  return {
+    videoId: item.id,
+    title: snippet.title ?? '',
+    thumbnailUrl: pickThumbnail(snippet.thumbnails),
+    channelId: snippet.channelId,
+    channelTitle: snippet.channelTitle ?? '',
+    views: Number(statistics.viewCount ?? 0),
+    publishedAt: snippet.publishedAt ?? null,
+    durationSec: parseIsoDuration(contentDetails.duration),
+  };
+}
+
+export function normalizeChannel(item) {
+  const customUrl = item.snippet?.customUrl;
+  const stats = item.statistics ?? {};
+  return {
+    channelId: item.id,
+    title: item.snippet?.title ?? '',
+    url: customUrl?.startsWith('@')
+      ? `https://www.youtube.com/${customUrl}`
+      : `https://www.youtube.com/channel/${item.id}`,
+    subscribers: stats.hiddenSubscriberCount || stats.subscriberCount === undefined ? null : Number(stats.subscriberCount),
+  };
+}
+
+export async function fetchVideos(ids, opts) {
+  const videos = [];
+  const found = new Set();
+  for (const batch of chunk(ids, BATCH_SIZE)) {
+    const data = await request(
+      'videos',
+      { part: 'snippet,statistics,contentDetails', id: batch.join(',') },
+      opts,
+    );
+    for (const item of data.items ?? []) {
+      videos.push(normalizeVideo(item));
+      found.add(item.id);
+    }
+  }
+  return { videos, missingIds: ids.filter((id) => !found.has(id)) };
+}
+
+// maxResults is sent here only: videos.list rejects it together with `id`,
+// while channels.list would otherwise default to 5 results.
+export async function fetchChannels(ids, opts) {
+  const channels = [];
+  for (const batch of chunk(ids, BATCH_SIZE)) {
+    const data = await request(
+      'channels',
+      { part: 'statistics,snippet', id: batch.join(','), maxResults: String(BATCH_SIZE) },
+      opts,
+    );
+    for (const item of data.items ?? []) channels.push(normalizeChannel(item));
+  }
+  return channels;
+}