veloze/src/middleware/send.js

A modern and fast express-like webserver for the web

import { createHash } from 'node:crypto'
import { send as resSend, redirect as resRedirect } from '../response/index.js'
import { RES_ETAG } from '../constants.js'

/**
 * @typedef {import('../types.js').HandlerCb} HandlerCb
 * @typedef {import('../types.js').Response} Response
 * @typedef { import('../types.js').Request } Request
 */

/**
 * connect middleware which adds `res.send` to the response.
 * @param {Request} req
 * @param {Response} res
 * @param {Function} next
 */
export function send(req, res, next) {
  res.send = resSend.bind(null, res)
  res.redirect = resRedirect.bind(null, res)
  next()
}

/**
 * `res.send` with ETag header generation.
 * @param {object} [options]
 * @param {string} [options.algorithm='sha1']
 * @returns {HandlerCb}
 */
export function sendEtag(options) {
  const { algorithm = 'sha1' } = options || {}

  const hash = (chunk = '') =>
    '"' + createHash(algorithm).update(chunk).digest('base64') + '"'

  const calcEtag = (req, res, chunk) => {
    if (res.statusCode !== 200) {
      return
    }

    const etag = hash(chunk)
    res.setHeader('etag', etag)

    if (req.headers['if-none-match'] === etag) {
      res.statusCode = 304
    }
  }

  return function sendEtagMw(req, res, next) {
    res.send = resSend.bind(null, res)
    res.redirect = resRedirect.bind(null, res)
    if (['GET', 'HEAD'].includes(req.method || '')) {
      res[RES_ETAG] = calcEtag.bind(null, req, res)
    }
    next()
  }
}