andromeda-viewer/server/httpProxy.js

'use strict'

const express = require('express')
const httpProxy = require('http-proxy')

const router = express.Router()

module.exports = router

const proxy = httpProxy.createProxyServer({})

proxy.on('proxyReq', (proxyReq, _req, _res, _options) => {
  // Remove the internal session id
  proxyReq.removeHeader('x-andromeda-session-id')
})

proxy.on('error', (err, _req, res) => {
  res.statusCode = 500
  res.setHeader('content-type', 'application/json')
  res.write(JSON.stringify({
    errors: [{
      status: err.status || err.statusCode || 500,
      title: err.title || err.name,
      detail: err.detail || err.message
    }]
  }))
  res.end()
})

router.all('/:protocol/:hostname/:path(*$)', validateSession, (req, res) => {
  const { protocol, hostname, path } = req.params

  if (!protocol || !hostname) {
    res.sendStatus(404)
    return
  }

  const target = new URL(`${protocol}://${hostname}/${path || ''}`)
  proxy.web(req, res, {
    target: target.href,
    secure: false, // Self signed certificate of SL.
    xfwd: true,
    changeOrigin: true,
    followRedirects: true
  })
})

// Error handler
// This transforms the different error styles into application/vnd.api+json errors.
router.use((err, _req, res, next) => {
  if (!err) {
    next()
    return
  }
  res.type('application/vnd.api+json')

  const getStatus = anError => Number(anError.status || anError.statusCode) || 500
  const format = anError => ({
    status: getStatus(anError),
    title: anError.title || anError.name,
    detail: anError.reason || anError.detail || anError.message
  })

  if (Array.isArray(err)) {
    res.status(getStatus(err[0]))
    res.json({
      errors: err.map(format)
    })
  } else {
    res.status(getStatus(err))
    res.json({
      errors: [format(err)]
    })
  }
})

/**
 * Validate if the request is made by a logged in user.
 * @param {express.Request} req        Express Request Object.
 * @param {express.Response} _res      Express Response Object.
 * @param {express.NextFunction} next  Call next middleware.
 */
function validateSession (req, _res, next) {
  try {
    const sessionId = req.headers['x-andromeda-session-id']
    const checkSession = req.app.get('checkSession')
    checkSession(sessionId)
    next()
  } catch (err) {
    next(err)
  }
}