als-send-file/lib/send-file.js

file serving with advanced options for caching, headers, and error handling, compatible with Express middleware.

const { createReadStream } = require('fs');
const rangeParser = require('range-parser');
const {basename} = require('path')

/**
 * Sends a file to the client with support for ranges and error handling.
 * @param {http.IncomingMessage} req - The request object.
 * @param {http.ServerResponse} res - The response object.
 * @param {string} filePath - The path to the file.
 * @param {Object} stats - The file stats object.
 * @param {Function} httpErrorHandler - Function to handle HTTP errors.
*/

async function sendFile(req, res, filePath, stats, httpErrorHandler) {
   const options = {}
   if (req.headers.range) {
      const ranges = rangeParser(stats.size, req.headers.range); // Parse Range header
      if (ranges === -1 || ranges.type !== 'bytes' || ranges.length > 1) {
         return httpErrorHandler(res,416, 'Range is not valid')
      }
      const { start, end } = ranges[0];
      res.statusCode = 206;
      res.setHeader('Content-Range', `bytes ${start}-${end}/${stats.size}`);
      res.setHeader('Content-Length', (end - start + 1).toString());
      options.start = start;
      options.end = end;
   }

   const fileStream = createReadStream(filePath, options);
   return new Promise((resolve, reject) => {
      let closed = false
      const close = (err) => {
         fileStream.destroy();
         if (res.finished || closed) return resolve()
         closed = true
         if(err) httpErrorHandler(res,500,err)
         else res.end()
         resolve()
      }
      fileStream.on('error', () => close(`file ${basename(filePath)} error`));
      fileStream.on('end', close);
      res.on('close', close);
      fileStream.pipe(res); // Passing data from a stream to a response
   })
}

module.exports = sendFile