index.js

/**
 * Redirects naked(root domain) requests to www or its reverse.
 *
 * @author GONZO <oss@dp.farm>
 */

const subdomainParser = (function () {
  const { parseDomain } = require('parse-domain')
  const parsedDomain = {}

  return {
    get: function (hostname) {
      // Cache, Touch
      if (parsedDomain[hostname] === undefined) {
        try {
          const ps = parseDomain(hostname)
          parsedDomain[hostname] = [ps.subDomains.join('.'), ps.domain + '.' + ps.topLevelDomains.join('.')]
        } catch (e) {
          parsedDomain[hostname] = [null, null]
        }
      }
      return parsedDomain[hostname]
    }
  }
}())

module.exports = function (reverse, subDomain, status) {
  let options = {}

  if (arguments.length === 1 && typeof arguments[0] === 'object') {
    options = arguments[0]
  } else {
    options = {
      reverse: reverse,
      subDomain: subDomain,
      status: status
    }
  }

  if (options.except) {
    if (typeof options.except === 'string') {
      options.except = [options.except]
    }

    // Assertion
    if (typeof options.except.length !== 'number') {
      throw new Error('Except option must be set with an array or string.')
    }

    let UrlPattern

    try {
      UrlPattern = require('url-pattern')
    } catch (e) {
      console.error(e)
      throw new Error('The third party module `url-pattern` is required.')
    }

    for (let i = 0; i < options.except.length; i++) {
      options.except[i] = new UrlPattern(options.except[i])
    }
  }

  return function (req, res, next) {
    const domain = subdomainParser.get(req.hostname)
    options.subDomain = options.subDomain || 'www'

    if (options.except) {
      for (let i = 0; i < options.except.length; i++) {
        if (options.except[i].match(req.url)) {
          return next()
        }
      }
    }

    if (typeof (options.reverse) === 'string' && options.subDomain === undefined) {
      options.subDomain = options.reverse
      options.reverse = false
    }
    if (options.status === undefined) {
      options.status = 302
    }

    if (typeof (options.protocol) === 'string') {
      options.protocol = options.protocol // eslint-disable-line
    } else if (typeof (options.https) === 'boolean' && options.https) {
      options.protocol = 'https'
    } else {
      options.protocol = req.protocol
    }

    let redirectTo = null

    if (domain[0] === '' && !options.reverse) {
      redirectTo = `${options.protocol}://${options.subDomain}.${domain[1]}${req.url}`
    } else if (domain[0] === options.subDomain && options.reverse) {
      redirectTo = `${options.protocol}://${domain[1]}${req.url}`
    } else if (options.protocol !== req.protocol) {
      redirectTo = `${options.protocol}://${req.hostname}${req.url}`
    }

    if (redirectTo !== null) {
      res.redirect(options.status, redirectTo)
      return
    }

    return next()
  }
}