功能改进（同步）：新增元数据嵌入并优化匹配逻辑

- 在Docker容器中安装ffmpeg以支持媒体处理
- 为下载文件嵌入标题、艺术家、专辑及封面图等元数据
- 重构文件存在性检测机制，兼容多种命名格式
- 下载过程中采用临时文件确保数据完整性

（注：根据中文技术文档惯例进行了以下优化：
1. 使用"功能改进"替代直译"feat"，更符合国内开发文档表述
2. "metadata embedding"译为"元数据嵌入"是行业标准译法
3. "refactor"译为"重构"准确传达代码改造含义
4. 采用四字短语"确保数据完整性"保持技术文档的简洁性
5. 使用中文括号和冒号格式，符合国内技术文档排版规范）

sync-server/Dockerfile

@@ -1,5 +1,8 @@
 FROM node:18-alpine
 
+# Install ffmpeg
+RUN apk add --no-cache ffmpeg
+
 WORKDIR /app
 
 COPY server.js .

sync-server/server.js

@@ -3,6 +3,7 @@ const https = require('https');
 const fs = require('fs');
 const path = require('path');
 const url = require('url');
+const { spawn } = require('child_process');
 
 const DATA_DIR = process.env.DATA_DIR || './data';
 const MUSIC_DIR = process.env.MUSIC_DIR || './music';
@@ -136,19 +137,24 @@ function processSong(song) {
         // Check if file exists (fuzzy match for extension)
         try {
             const files = fs.readdirSync(MUSIC_DIR);
-            // Check for standard format OR manual rename (Song Name.ext)
             const exists = files.some(f => {
-                // 1. Standard format: Artist - Name [source_id].ext
+                // 1. Exact Match: Artist - Name [source_id].ext
                 if (f.startsWith(baseName)) return true;
                 
-                // 2. Manual rename: Name.ext (ignoring extension)
-                // We check if the file starts with the song name followed by a dot
+                // 2. Simple Format: Artist - Name.ext
+                if (f.startsWith(`${safeArtist} - ${safeName}.`)) return true;
+                
+                // 3. Simple Format w/o Artist: Name.ext
                 if (f.startsWith(`${safeName}.`)) return true;
 
+                // 4. Match prefix ignoring ID: Artist - Name [
+                if (f.startsWith(`${safeArtist} - ${safeName} [`)) return true;
+
                 return false;
             });
 
             if (exists) {
+                // console.log(`[Sync] Skipped (Exists): ${song.name}`);
                 resolve();
                 return;
             }
@@ -167,14 +173,47 @@ function processSong(song) {
                 else if (url.includes('.ogg')) ext = 'ogg';
                 else if (url.includes('.wav')) ext = 'wav';
 
-                const dest = path.join(MUSIC_DIR, `${baseName}.${ext}`);
-                downloadFile(url, dest)
-                    .then(() => {
-                        console.log(`[Sync] Downloaded: ${baseName}.${ext}`);
+                const tempFile = path.join(MUSIC_DIR, `temp_${Date.now()}_${song.id}.${ext}`);
+                const finalFile = path.join(MUSIC_DIR, `${baseName}.${ext}`);
+
+                downloadFile(url, tempFile)
+                    .then(async () => {
+                        try {
+                            // Try to download cover image
+                            let coverPath = null;
+                            try {
+                                const coverUrl = `https://music-dl.sayqz.com/api/?source=${source}&id=${song.id}&type=pic`;
+                                coverPath = path.join(MUSIC_DIR, `temp_cover_${Date.now()}_${song.id}.jpg`);
+                                await downloadFile(coverUrl, coverPath);
+                            } catch (e) {
+                                console.warn(`[Sync] Failed to download cover for ${song.name}:`, e.message);
+                            }
+
+                            // Write Metadata (Title, Artist, Album, Cover)
+                            await writeMetadata(tempFile, finalFile, {
+                                title: song.name,
+                                artist: song.artist,
+                                album: song.album || song.name, // Fallback to song name if album is missing
+                                cover: coverPath
+                            });
+
+                            console.log(`[Sync] Downloaded & Tagged: ${baseName}.${ext}`);
+                            
+                            // Cleanup temp files
+                            if (fs.existsSync(tempFile)) fs.unlinkSync(tempFile);
+                            if (coverPath && fs.existsSync(coverPath)) fs.unlinkSync(coverPath);
+                        } catch (err) {
+                            console.error(`[Sync] Metadata Error for ${song.name}:`, err.message);
+                            // Fallback: Just rename temp to final
+                            if (!fs.existsSync(finalFile)) {
+                                fs.renameSync(tempFile, finalFile);
+                            }
+                        }
                         resolve();
                     })
                     .catch(err => {
                         console.error(`[Sync] Download failed for ${song.name}:`, err.message);
+                        if (fs.existsSync(tempFile)) fs.unlinkSync(tempFile);
                         resolve();
                     });
             };
@@ -246,4 +285,65 @@ function downloadFile(url, dest) {
             reject(err);
         });
     });
+}
+
+function writeMetadata(inputPath, outputPath, metadata) {
+    return new Promise((resolve, reject) => {
+        const args = ['-i', inputPath];
+
+        // Add cover input if available
+        if (metadata.cover) {
+            args.push('-i', metadata.cover);
+            args.push('-map', '0:0'); // Map audio from first input
+            args.push('-map', '1:0'); // Map image from second input
+            args.push('-c:v', 'mjpeg'); // Convert cover to jpeg
+            
+            // ID3v2 metadata for MP3 (cover art)
+            if (outputPath.endsWith('.mp3')) {
+                 args.push('-id3v2_version', '3');
+                 args.push('-metadata:s:v', 'title="Album cover"');
+                 args.push('-metadata:s:v', 'comment="Cover (front)"');
+            } else if (outputPath.endsWith('.flac')) {
+                args.push('-disposition:v', 'attached_pic');
+            }
+        } else {
+             args.push('-c', 'copy');
+        }
+
+        // Add metadata tags
+        args.push(
+            '-metadata', `title=${metadata.title}`,
+            '-metadata', `artist=${metadata.artist}`,
+            '-metadata', `album=${metadata.album}`
+        );
+
+        // Required for FLAC + Cover to work properly without re-encoding audio
+        if (outputPath.endsWith('.flac') && metadata.cover) {
+             args.push('-c:a', 'copy');
+        } else if (outputPath.endsWith('.mp3') && metadata.cover) {
+             args.push('-c:a', 'copy');
+        }
+
+        args.push('-y', outputPath);
+
+        const ffmpeg = spawn('ffmpeg', args);
+        
+        // Capture stderr for debugging
+        let stderr = '';
+        ffmpeg.stderr.on('data', (data) => {
+            stderr += data.toString();
+        });
+
+        ffmpeg.on('close', (code) => {
+            if (code === 0) resolve();
+            else {
+                console.error(`FFmpeg Error Output: ${stderr}`);
+                reject(new Error(`FFmpeg exited with code ${code}`));
+            }
+        });
+
+        ffmpeg.on('error', (err) => {
+            reject(err);
+        });
+    });
 }