1'use strict';
  2
  3var alphabet = require('./alphabet');
  4var encode = require('./encode');
  5var decode = require('./decode');
  6var isValid = require('./is-valid');
  7
  8// Ignore all milliseconds before a certain time to reduce the size of the date entropy without sacrificing uniqueness.
  9// This number should be updated every year or so to keep the generated id short.
 10// To regenerate `new Date() - 0` and bump the version. Always bump the version!
 11var REDUCE_TIME = 1426452414093;
 12
 13// don't change unless we change the algos or REDUCE_TIME
 14// must be an integer and less than 16
 15var version = 5;
 16
 17// if you are using cluster or multiple servers use this to make each instance
 18// has a unique value for worker
 19// Note: I don't know if this is automatically set when using third
 20// party cluster solutions such as pm2.
 21var clusterWorkerId = require('./util/cluster-worker-id') || 0;
 22
 23// Counter is used when shortid is called multiple times in one second.
 24var counter;
 25
 26// Remember the last time shortid was called in case counter is needed.
 27var previousSeconds;
 28
 29/**
 30 * Generate unique id
 31 * Returns string id
 32 */
 33function generate() {
 34
 35    var str = '';
 36
 37    var seconds = Math.floor((Date.now() - REDUCE_TIME) * 0.001);
 38
 39    if (seconds === previousSeconds) {
 40        counter++;
 41    } else {
 42        counter = 0;
 43        previousSeconds = seconds;
 44    }
 45
 46    str = str + encode(alphabet.lookup, version);
 47    str = str + encode(alphabet.lookup, clusterWorkerId);
 48    if (counter > 0) {
 49        str = str + encode(alphabet.lookup, counter);
 50    }
 51    str = str + encode(alphabet.lookup, seconds);
 52
 53    return str;
 54}
 55
 56
 57/**
 58 * Set the seed.
 59 * Highly recommended if you don't want people to try to figure out your id schema.
 60 * exposed as shortid.seed(int)
 61 * @param seed Integer value to seed the random alphabet.  ALWAYS USE THE SAME SEED or you might get overlaps.
 62 */
 63function seed(seedValue) {
 64    alphabet.seed(seedValue);
 65    return module.exports;
 66}
 67
 68/**
 69 * Set the cluster worker or machine id
 70 * exposed as shortid.worker(int)
 71 * @param workerId worker must be positive integer.  Number less than 16 is recommended.
 72 * returns shortid module so it can be chained.
 73 */
 74function worker(workerId) {
 75    clusterWorkerId = workerId;
 76    return module.exports;
 77}
 78
 79/**
 80 *
 81 * sets new characters to use in the alphabet
 82 * returns the shuffled alphabet
 83 */
 84function characters(newCharacters) {
 85    if (newCharacters !== undefined) {
 86        alphabet.characters(newCharacters);
 87    }
 88
 89    return alphabet.shuffled();
 90}
 91
 92
 93// Export all other functions as properties of the generate function
 94module.exports = generate;
 95module.exports.generate = generate;
 96module.exports.seed = seed;
 97module.exports.worker = worker;
 98module.exports.characters = characters;
 99module.exports.decode = decode;
100module.exports.isValid = isValid;