source: trip-planner-front/node_modules/http-proxy-middleware/lib/config-factory.js@ eed0bf8

var _ = require('lodash')
var url = require('url')
var ERRORS = require('./errors')
var logger = require('./logger').getInstance()

module.exports = {
  createConfig: createConfig
}

function createConfig(context, opts) {
  // structure of config object to be returned
  var config = {
    context: undefined,
    options: {}
  }

  // app.use('/api', proxy({target:'http://localhost:9000'}));
  if (isContextless(context, opts)) {
    config.context = '/'
    config.options = _.assign(config.options, context)

    // app.use('/api', proxy('http://localhost:9000'));
    // app.use(proxy('http://localhost:9000/api'));
  } else if (isStringShortHand(context)) {
    var oUrl = url.parse(context)
    var target = [oUrl.protocol, '//', oUrl.host].join('')

    config.context = oUrl.pathname || '/'
    config.options = _.assign(config.options, { target: target }, opts)

    if (oUrl.protocol === 'ws:' || oUrl.protocol === 'wss:') {
      config.options.ws = true
    }
    // app.use('/api', proxy({target:'http://localhost:9000'}));
  } else {
    config.context = context
    config.options = _.assign(config.options, opts)
  }

  configureLogger(config.options)

  if (!config.options.target) {
    throw new Error(ERRORS.ERR_CONFIG_FACTORY_TARGET_MISSING)
  }

  // Legacy option.proxyHost
  config.options = mapLegacyProxyHostOption(config.options)

  // Legacy option.proxyTable > option.router
  config.options = mapLegacyProxyTableOption(config.options)

  return config
}

/**
 * Checks if a String only target/config is provided.
 * This can be just the host or with the optional path.
 *
 * @example
 *      app.use('/api', proxy('http://localhost:9000'));
        app.use(proxy('http://localhost:9000/api'));
 *
 * @param  {String}  context [description]
 * @return {Boolean}         [description]
 */
function isStringShortHand(context) {
  if (_.isString(context)) {
    return !!url.parse(context).host
  }
}

/**
 * Checks if a Object only config is provided, without a context.
 * In this case the all paths will be proxied.
 *
 * @example
 *     app.use('/api', proxy({target:'http://localhost:9000'}));
 *
 * @param  {Object}  context [description]
 * @param  {*}       opts    [description]
 * @return {Boolean}         [description]
 */
function isContextless(context, opts) {
  return _.isPlainObject(context) && _.isEmpty(opts)
}

function mapLegacyProxyHostOption(options) {
  // set options.headers.host when option.proxyHost is provided
  if (options.proxyHost) {
    logger.warn('*************************************')
    logger.warn('[HPM] Deprecated "option.proxyHost"')
    logger.warn(
      '      Use "option.changeOrigin" or "option.headers.host" instead'
    )
    logger.warn('      "option.proxyHost" will be removed in future release.')
    logger.warn('*************************************')

    options.headers = options.headers || {}
    options.headers.host = options.proxyHost
  }

  return options
}

// Warn deprecated proxyTable api usage
function mapLegacyProxyTableOption(options) {
  if (options.proxyTable) {
    logger.warn('*************************************')
    logger.warn('[HPM] Deprecated "option.proxyTable"')
    logger.warn('      Use "option.router" instead')
    logger.warn('      "option.proxyTable" will be removed in future release.')
    logger.warn('*************************************')

    options.router = _.clone(options.proxyTable)
    _.omit(options, 'proxyTable')
  }

  return options
}

function configureLogger(options) {
  if (options.logLevel) {
    logger.setLevel(options.logLevel)
  }

  if (options.logProvider) {
    logger.setProvider(options.logProvider)
  }
}