async function uploadFileInChunks(file, uploadUrl, chunkSize = 1024 * 1024) {
  const fileSize = file.size;
  let start = 0;
  let chunkIndex = 0;
  
  while (start < fileSize) {
    const end = Math.min(start + chunkSize, fileSize);
    const chunk = file.slice(start, end);
    
    const formData = new FormData();
    formData.append('file', chunk);
    formData.append('chunkIndex', chunkIndex);
    formData.append('totalChunks', Math.ceil(fileSize / chunkSize));
    formData.append('originalFilename', file.name);
    
    try {
      await fetch(uploadUrl, {
        method: 'POST',
        body: formData,
        headers: {
          'X-Chunk-Index': chunkIndex,
          'X-Total-Chunks': Math.ceil(fileSize / chunkSize),
          'X-File-Name': encodeURIComponent(file.name)
        }
      });
      
      start = end;
      chunkIndex++;
    } catch (error) {
      console.error('上传失败:', error);
      throw error;
    }
  }
  
  // 通知服务器所有分块已上传
  await fetch(`${uploadUrl}/complete`, {
    method: 'POST',
    body: JSON.stringify({
      filename: file.name,
      totalChunks: Math.ceil(fileSize / chunkSize)
    }),
    headers: {
      'Content-Type': 'application/json'
    }
  });
}

const express = require('express');
const fs = require('fs');
const path = require('path');
const multer = require('multer');
const app = express();

// 临时存储分块
const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    const tempDir = path.join(__dirname, 'temp');
    if (!fs.existsSync(tempDir)) {
      fs.mkdirSync(tempDir, { recursive: true });
    }
    cb(null, tempDir);
  },
  filename: (req, file, cb) => {
    const filename = req.headers['x-file-name'] || file.originalname;
    const chunkIndex = req.headers['x-chunk-index'];
    cb(null, `${filename}.part${chunkIndex}`);
  }
});

const upload = multer({ storage });

app.post('/upload', upload.single('file'), (req, res) => {
  res.status(200).json({ message: '分块上传成功' });
});

app.post('/upload/complete', express.json(), (req, res) => {
  const { filename, totalChunks } = req.body;
  const tempDir = path.join(__dirname, 'temp');
  const outputPath = path.join(__dirname, 'uploads', filename);
  
  // 确保上传目录存在
  if (!fs.existsSync(path.dirname(outputPath))) {
    fs.mkdirSync(path.dirname(outputPath), { recursive: true });
  }
  
  // 合并所有分块
  const writeStream = fs.createWriteStream(outputPath);
  
  for (let i = 0; i < totalChunks; i++) {
    const chunkPath = path.join(tempDir, `${filename}.part${i}`);
    const chunkData = fs.readFileSync(chunkPath);
    writeStream.write(chunkData);
    fs.unlinkSync(chunkPath); // 删除临时分块
  }
  
  writeStream.end();
  res.status(200).json({ message: '文件合并完成' });
});

app.listen(3000, () => console.log('服务器运行在3000端口'));