feat: add protected public web lyrics workflow

web/app.js

@@ -2,6 +2,9 @@ const form = document.querySelector('#search-form');
 const keyword = document.querySelector('#keyword');
 const notice = document.querySelector('#notice');
 const results = document.querySelector('#results');
+const modeNote = document.querySelector('#mode-note');
+const localDownloads = document.querySelector('#local-downloads');
+const lyricCache = new Map();
 
 function text(value) { return document.createTextNode(value ?? ''); }
 function safeName(value) { return (value || 'unknown').replace(/[\\/:*?"<>|\u0000-\u001f]/g, '_').trim().slice(0, 180) || 'unknown'; }
@@ -15,6 +18,21 @@ async function api(path, payload) {
   return data;
 }
 
+async function loadInfo() {
+  try {
+    const response = await fetch('/api/info');
+    const info = await response.json();
+    if (info.mode === 'local') {
+      modeNote.textContent = '本机模式：查询从这台电脑直接发出，不经过 lrc.flechazo.xin。';
+    } else {
+      modeNote.textContent = '网页模式：查询由本站后端转发，但不会写入数据库或日志正文。下载文件在浏览器中生成。';
+      localDownloads.hidden = false;
+    }
+  } catch {
+    modeNote.textContent = '无法确认运行模式，请刷新页面重试。';
+  }
+}
+
 function download(name, body, type = 'text/plain;charset=utf-8') {
   const url = URL.createObjectURL(new Blob([body], {type}));
   const anchor = document.createElement('a');
@@ -27,7 +45,8 @@ async function fetchAndSave(song, kind, button) {
   button.disabled = true;
   notice.className = 'notice'; notice.textContent = `正在读取《${song.name}》…`;
   try {
-    const data = await api('/api/lyrics', {mid: song.mid});
+    if (!lyricCache.has(song.mid)) lyricCache.set(song.mid, api('/api/lyrics', {mid: song.mid}));
+    const data = await lyricCache.get(song.mid).catch(error => { lyricCache.delete(song.mid); throw error; });
     const base = safeName(`${song.name} - ${song.singer}`);
     if (kind === 'lrc') download(`${base}.lrc`, data.lyric);
     if (kind === 'txt') download(`${base}.txt`, plainText(data.lyric));
@@ -35,7 +54,7 @@ async function fetchAndSave(song, kind, button) {
       if (!data.trans) throw new Error('这首歌没有翻译歌词');
       download(`${base}.trans.lrc`, data.trans);
     }
-    notice.textContent = '文件已在浏览器中生成，内容未上传。';
+    notice.textContent = '文件已在浏览器中生成。';
   } catch (error) {
     notice.className = 'notice error'; notice.textContent = error.message;
   } finally { button.disabled = false; }
@@ -61,10 +80,12 @@ function renderSongs(songs) {
 
 form.addEventListener('submit', async event => {
   event.preventDefault(); const submit = form.querySelector('button'); submit.disabled = true;
-  notice.className = 'notice'; notice.textContent = '正在从这台电脑搜索…'; results.replaceChildren();
+  notice.className = 'notice'; notice.textContent = '正在搜索…'; results.replaceChildren(); lyricCache.clear();
   try {
     const data = await api('/api/search', {keyword: keyword.value.trim(), limit: 15});
     renderSongs(data.songs || []); notice.textContent = data.songs?.length ? `找到 ${data.songs.length} 条结果。` : '没有找到相关歌曲。';
   } catch (error) { notice.className = 'notice error'; notice.textContent = error.message; }
   finally { submit.disabled = false; }
 });
+
+loadInfo();