// An authentication proxy is a reverse proxy

// that sends a logged-in Solid user's details to a backend

module.exports = addAuthProxyHandlers

const { createProxyMiddleware } = require('http-proxy-middleware')

const debug = require('../debug')

const allow = require('./allow')

const PROXY_SETTINGS = {

logLevel: 'silent',

changeOrigin: true

}

const REQUIRED_PERMISSIONS = {

get: ['Read'],

options: ['Read'],

use: ['Read', 'Write']

}

// Registers Auth Proxy handlers for each target

function addAuthProxyHandlers (app, targets) {

for (const sourcePath in targets) {

addAuthProxyHandler(app, sourcePath, targets[sourcePath])

}

}

// Registers an Auth Proxy handler for the given target

function addAuthProxyHandler (app, sourcePath, target) {

debug.settings(`Add auth proxy from ${sourcePath} to ${target}`)

// Proxy to the target, removing the source path

// (e.g., /my/proxy/path resolves to http://my.proxy/path)

const sourcePathLength = sourcePath.length

const settings = Object.assign({

target,

onProxyReq: addAuthHeaders,

onProxyReqWs: addAuthHeaders,

pathRewrite: path => path.substr(sourcePathLength)

}, PROXY_SETTINGS)

// Activate the proxy

const proxy = createProxyMiddleware(settings)

for (const action in REQUIRED_PERMISSIONS) {

const permissions = REQUIRED_PERMISSIONS[action]

app[action](`${sourcePath}*`, setOriginalUrl, ...permissions.map(allow), proxy)

}

}

// Adds a headers with authentication information

function addAuthHeaders (proxyReq, req) {

const { session = {}, headers = {} } = req

if (session.userId) {

proxyReq.setHeader('User', session.userId)

}

if (headers.host) {

proxyReq.setHeader('Forwarded', `host=${headers.host}`)

}

}

// Sets the original URL on the request (for the ACL handler)

function setOriginalUrl (req, res, next) {

res.locals.path = req.originalUrl

next()

}