HORIZON PROJECT

/*!

 * uid-safe

 * Copyright(c) 2014 Jonathan Ong

 * Copyright(c) 2015-2017 Douglas Christopher Wilson

 * MIT Licensed

 */

'use strict'

/**

 * Module dependencies.

 * @private

 */

var randomBytes = require('random-bytes')

/**

 * Module variables.

 * @private

 */

var EQUAL_END_REGEXP = /=+$/

var PLUS_GLOBAL_REGEXP = /\+/g

var SLASH_GLOBAL_REGEXP = /\//g

/**

 * Module exports.

 * @public

 */

module.exports = uid

module.exports.sync = uidSync

/**

 * Create a unique ID.

 *

 * @param {number} length

 * @param {function} [callback]

 * @return {Promise}

 * @public

 */

function uid (length, callback) {

  // validate callback is a function, if provided

  if (callback !== undefined && typeof callback !== 'function') {

    throw new TypeError('argument callback must be a function')

  }

  // require the callback without promises

  if (!callback && !global.Promise) {

    throw new TypeError('argument callback is required')

  }

  if (callback) {

    // classic callback style

    return generateUid(length, callback)

  }

  return new Promise(function executor (resolve, reject) {

    generateUid(length, function onUid (err, str) {

      if (err) return reject(err)

      resolve(str)

    })

  })

}

/**

 * Create a unique ID sync.

 *

 * @param {number} length

 * @return {string}

 * @public

 */

function uidSync (length) {

  return toString(randomBytes.sync(length))

}

/**

 * Generate a unique ID string.

 *

 * @param {number} length

 * @param {function} callback

 * @private

 */

function generateUid (length, callback) {

  randomBytes(length, function (err, buf) {

    if (err) return callback(err)

    callback(null, toString(buf))

  })

}

/**

 * Change a Buffer into a string.

 *

 * @param {Buffer} buf

 * @return {string}

 * @private

 */

function toString (buf) {

  return buf.toString('base64')

    .replace(EQUAL_END_REGEXP, '')

    .replace(PLUS_GLOBAL_REGEXP, '-')

    .replace(SLASH_GLOBAL_REGEXP, '_')

}