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

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

const { stat } = require('fs/promises')
const { basename } = require('path')
const mime = require('mime-types');
const generateETag = require('./etag')
const sendFile = require('./send-file')
const cachControl = require('./cache-control')
const optionsSchema = require('./options-schema')
/**
 * Handles file requests and sends the file to the client.
 * @param {http.IncomingMessage} req - The request object.
 * @param {http.ServerResponse} res - The response object.
 * @param {string} filePath - The path to the file.
 * @param {Object} options - Options for handling the file.
 * @param {Function} httpErrorHandler - Function to handle HTTP errors.
*/

async function fileHandler(req, res, filePath, options, httpErrorHandler) {
   let stats
   const name = basename(filePath)
   try { stats = await stat(filePath) }
   catch (error) { return httpErrorHandler(res, 404, `File ${name} not found`) }

   const { download, charset, etag, maxAge, noCache, noStore, public } = optionsSchema.validate(options)
   if (etag && generateETag(req, res, stats)) return
   cachControl(res, { maxAge, noCache, noStore, public })
   res.setHeader('Content-Disposition', `${download ? 'attachment' : 'inline'}; filename="${name}"`)

   const contentType = mime.lookup(name) || 'text/plain';
   res.setHeader('Content-Type', `${contentType}${charset ? `; charset=${charset}` : ''}`);
   return sendFile(req, res, filePath, stats, httpErrorHandler)
}

module.exports = fileHandler