如何从multipart/formData请求在Firestore数据库中保存文件？

<form action="/upload" method="POST" enctype="multipart/form-data">
  <input type="file" name="file">
  <input type="submit" value="Upload">
</form>

const express = require('express');
const multer = require('multer');
const COS = require('cos-nodejs-sdk-v5');
const admin = require('firebase-admin');

const app = express();
const upload = multer();

// 初始化腾讯云COS SDK
const cos = new COS({
  SecretId: 'your-secret-id',
  SecretKey: 'your-secret-key',
});

// 初始化Firebase Admin SDK
admin.initializeApp({
  credential: admin.credential.applicationDefault(),
});

// 处理文件上传请求
app.post('/upload', upload.single('file'), async (req, res) => {
  try {
    const file = req.file;

    // 将文件上传到腾讯云COS
    const cosResult = await cos.putObject({
      Bucket: 'your-bucket',
      Region: 'your-region',
      Key: file.originalname,
      Body: file.buffer,
    }).promise();

    const fileUrl = cosResult.Location;

    // 将文件URL保存到Firestore
    const firestore = admin.firestore();
    const docRef = firestore.collection('files').doc();
    await docRef.set({
      url: fileUrl,
    });

    res.send('File uploaded successfully.');
  } catch (error) {
    console.error(error);
    res.status(500).send('Error uploading file.');
  }
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});