// Licensed to the Software Freedom Conservancy (SFC) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The SFC licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

'use strict'

const os = require('os')

function getLoInterface() {
  let name
  if (process.platform === 'darwin') {
    name = 'lo0'
  } else if (process.platform === 'linux') {
    name = 'lo'
  }
  return name ? os.networkInterfaces()[name] : null
}

/**
 * Queries the system network interfaces for an IP address.
 * @param {boolean} loopback Whether to find a loopback address.
 * @param {string} family The IP family (IPv4 or IPv6). Defaults to IPv4.
 * @return {(string|undefined)} The located IP address or undefined.
 */
function getIPAddress(loopback, family) {
  let interfaces
  if (loopback) {
    const lo = getLoInterface()
    interfaces = lo ? [lo] : null
  }
  interfaces = interfaces || os.networkInterfaces()
  for (let key in interfaces) {
    if (!Object.prototype.hasOwnProperty.call(interfaces, key)) {
      continue
    }

    for (let ipAddress of interfaces[key]) {
      if ((ipAddress.family === family || `IPv${ipAddress.family}` === family) && ipAddress.internal === loopback) {
        return ipAddress.address
      }
    }
  }
  return undefined
}

// PUBLIC API

/**
 * Retrieves the external IP address for this host.
 * @param {string=} family The IP family to retrieve. Defaults to "IPv4".
 * @return {(string|undefined)} The IP address or undefined if not available.
 */
function getAddress(family = 'IPv4') {
  return getIPAddress(false, family)
}

/**
 * Retrieves a loopback address for this machine.
 * @param {string=} family The IP family to retrieve. Defaults to "IPv4".
 * @return {(string|undefined)} The IP address or undefined if not available.
 */
function getLoopbackAddress(family = 'IPv4') {
  return getIPAddress(true, family)
}

/**
 * Splits a hostport string, e.g. "www.example.com:80", into its component
 * parts.
 *
 * @param {string} hostport The string to split.
 * @return {{host: string, port: ?number}} A host and port. If no port is
 *     present in the argument `hostport`, port is null.
 */
function splitHostAndPort(hostport) {
  let lastIndex = hostport.lastIndexOf(':')
  if (lastIndex < 0) {
    return { host: hostport, port: null }
  }

  let firstIndex = hostport.indexOf(':')
  if (firstIndex != lastIndex && !hostport.includes('[')) {
    // Multiple colons but no brackets, so assume the string is an IPv6 address
    // with no port (e.g. "1234:5678:9:0:1234:5678:9:0").
    return { host: hostport, port: null }
  }

  let host = hostport.slice(0, lastIndex)
  if (host.startsWith('[') && host.endsWith(']')) {
    host = host.slice(1, -1)
  }

  let port = parseInt(hostport.slice(lastIndex + 1), 10)
  return { host, port }
}

// PUBLIC API
module.exports = {
  splitHostAndPort,
  getLoopbackAddress,
  getAddress,
}
