1 | 'use strict';
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2 |
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3 | var randomFromSeed = require('./random/random-from-seed');
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4 |
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5 | var ORIGINAL = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-';
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6 | var alphabet;
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7 | var previousSeed;
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8 |
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9 | var shuffled;
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10 |
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11 | function reset() {
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12 | shuffled = false;
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13 | }
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14 |
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15 | function setCharacters(_alphabet_) {
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16 | if (!_alphabet_) {
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17 | if (alphabet !== ORIGINAL) {
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18 | alphabet = ORIGINAL;
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19 | reset();
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20 | }
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21 | return;
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22 | }
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23 |
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24 | if (_alphabet_ === alphabet) {
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25 | return;
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26 | }
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27 |
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28 | if (_alphabet_.length !== ORIGINAL.length) {
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29 | throw new Error('Custom alphabet for shortid must be ' + ORIGINAL.length + ' unique characters. You submitted ' + _alphabet_.length + ' characters: ' + _alphabet_);
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30 | }
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31 |
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32 | var unique = _alphabet_.split('').filter(function(item, ind, arr){
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33 | return ind !== arr.lastIndexOf(item);
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34 | });
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35 |
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36 | if (unique.length) {
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37 | throw new Error('Custom alphabet for shortid must be ' + ORIGINAL.length + ' unique characters. These characters were not unique: ' + unique.join(', '));
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38 | }
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39 |
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40 | alphabet = _alphabet_;
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41 | reset();
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42 | }
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43 |
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44 | function characters(_alphabet_) {
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45 | setCharacters(_alphabet_);
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46 | return alphabet;
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47 | }
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48 |
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49 | function setSeed(seed) {
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50 | randomFromSeed.seed(seed);
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51 | if (previousSeed !== seed) {
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52 | reset();
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53 | previousSeed = seed;
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54 | }
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55 | }
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56 |
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57 | function shuffle() {
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58 | if (!alphabet) {
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59 | setCharacters(ORIGINAL);
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60 | }
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61 |
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62 | var sourceArray = alphabet.split('');
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63 | var targetArray = [];
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64 | var r = randomFromSeed.nextValue();
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65 | var characterIndex;
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66 |
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67 | while (sourceArray.length > 0) {
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68 | r = randomFromSeed.nextValue();
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69 | characterIndex = Math.floor(r * sourceArray.length);
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70 | targetArray.push(sourceArray.splice(characterIndex, 1)[0]);
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71 | }
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72 | return targetArray.join('');
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73 | }
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74 |
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75 | function getShuffled() {
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76 | if (shuffled) {
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77 | return shuffled;
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78 | }
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79 | shuffled = shuffle();
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80 | return shuffled;
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81 | }
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82 |
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83 |
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84 |
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85 |
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86 |
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87 |
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88 | function lookup(index) {
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89 | var alphabetShuffled = getShuffled();
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90 | return alphabetShuffled[index];
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91 | }
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92 |
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93 | module.exports = {
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94 | characters: characters,
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95 | seed: setSeed,
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96 | lookup: lookup,
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97 | shuffled: getShuffled
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98 | };
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