refactor: split downloader into modules

lib/catalog.js

@@ -0,0 +1,47 @@
+const { API } = require('./config');
+const { fetchJSON } = require('./network');
+
+async function searchSongs(keyword, limit = 10) {
+  const res = await fetchJSON(`${API.search}?keyword=${encodeURIComponent(keyword)}&limit=${limit}`);
+  if (res.code !== 200) {
+    console.log('❌ 搜索无结果');
+    return [];
+  }
+  const songs = Array.isArray(res.data) ? res.data : (res.data?.songs || []);
+  if (!songs.length) console.log('❌ 搜索无结果');
+  return songs;
+}
+
+async function interactiveSearch(rl, ask) {
+  const keyword = await ask('🔍 搜索关键词: ');
+  if (!keyword.trim()) return null;
+  const results = await searchSongs(keyword.trim(), 10);
+  if (!results.length) return null;
+
+  console.log('\n  #  歌曲名                  歌手                专辑');
+  console.log('  ' + '─'.repeat(70));
+  results.forEach((song, index) => {
+    const num = String(index + 1).padStart(2);
+    const name = song.name.slice(0, 20).padEnd(22);
+    const artist = song.artists.slice(0, 16).padEnd(18);
+    console.log(`  ${num} ${name} ${artist} ${song.album}`);
+  });
+
+  const pick = await ask('\n选择序号 (多个用逗号分隔, 0=取消): ');
+  if (!pick.trim() || pick.trim() === '0') return null;
+  return pick.split(/[,，\s]+/)
+    .map(value => parseInt(value, 10))
+    .filter(value => value >= 1 && value <= results.length)
+    .map(value => results[value - 1]);
+}
+
+async function fetchPlaylist(playlistId) {
+  const res = await fetchJSON(`${API.playlist}?id=${playlistId}`);
+  if (!res.data?.tracks?.length) {
+    console.log('❌ 歌单获取失败或为空');
+    return null;
+  }
+  return res.data;
+}
+
+module.exports = { searchSongs, interactiveSearch, fetchPlaylist };