octo-deno/lib/random/random.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

var random = {
  twister: null,

  /**
   * Must be called before any other methods can be called to initialize MersenneTwister.
   * @param {number|null|undefined} seed Value to initialize MersenneTwister.
   */
  init: function (seed) {
    if (seed === null || seed === undefined) {
      seed = new Date().getTime();
    }
    this.twister = new MersenneTwister();
    this.twister.seed(seed);
  },
  number: function (limit) {
    // Returns an integer in [0, limit). Uniform distribution.
    if (limit === 0) {
      return limit;
    }
    if (limit === null || limit === undefined) {
      limit = 0xffffffff;
    }
    let x = (0x100000000 / limit) >>> 0,
      y = (x * limit) >>> 0, r;
    do {
      r = this.twister.int32();
    } while (y && r >= y);
    return (r / x) >>> 0;
  },
  float: function () {
    // Returns a float in [0, 1). Uniform distribution.
    return this.twister.real2();
  },
  range: function (start, limit) {
    // Returns an integer in [start, limit]. Uniform distribution.
    if (isNaN(start) || isNaN(limit)) {
      logger.traceback();
      throw new TypeError("random.range() received a non number type: '" + start + "', '" + limit + "')");
    }
    return this.number(limit - start + 1) + start;
  },
  ludOneTo: function (limit) {
    // Returns a float in [1, limit]. The logarithm has uniform distribution.
    return Math.exp(this.float() * Math.log(limit));
  },
  item: function (list) {
    if (!(list instanceof Array || (list !== undefined && typeof list !== "string" && list.hasOwnProperty("length")))) {
      logger.traceback();
      throw new TypeError("this.item() received a non array type: '" + list + "'");
    }
    return list[this.number(list.length)];
  },
  key: function (obj) {
    let list = [];
    for (let i in obj) {
      list.push(i);
    }
    return this.item(list);
  },
  bool: function () {
    return this.item([true, false]);
  },
  pick: function (obj) {
    if (typeof obj === "function") {
      return obj();
    }
    if (obj instanceof Array) {
      return this.pick(this.item(obj));
    }
    return obj;
  },
  chance: function (limit) {
    if (limit === null || limit === undefined) {
      limit = 2;
    }
    if (isNaN(limit)) {
      logger.traceback();
      throw new TypeError("random.chance() received a non number type: '" + limit + "'");
    }
    return this.number(limit) === 1;
  },
  choose: function (list, flat) {
    if (!(list instanceof Array)) {
      logger.traceback();
      throw new TypeError("random.choose() received a non-array type: '" + list + "'");
    }
    let total = 0;
    for (let i = 0; i < list.length; i++) {
      total += list[i][0];
    }
    let n = this.number(total);
    for (let i = 0; i < list.length; i++) {
      if (n < list[i][0]) {
        if (flat === true) {
          return list[i][1];
        } else {
          return this.pick([list[i][1]]);
        }
      }
      n = n - list[i][0];
    }
    if (flat === true) {
      return list[0][1];
    }
    return this.pick([list[0][1]]);
  },
  weighted: function (wa) {
    // More memory-hungry but hopefully faster than random.choose$flat
    let a = [];
    for (let i = 0; i < wa.length; ++i) {
      for (let j = 0; j < wa[i].w; ++j) {
        a.push(wa[i].v);
      }
    }
    return a;
  },
  use: function (obj) {
    return this.bool() ? obj : "";
  },
  shuffle: function (arr) {
    let i = arr.length;
    while (i--) {
      let p = this.number(i + 1);
      let t = arr[i];
      arr[i] = arr[p];
      arr[p] = t;
    }
  },
  shuffled: function (arr) {
    let newArray = arr.slice();
    this.shuffle(newArray);
    return newArray;
  },
  subset: function (list, limit) {
    if (!(list instanceof Array)) {
      logger.traceback();
      throw new TypeError("random.some() received a non-array type: '" + list + "'");
    }
    if (typeof limit !== 'number') {
      limit = this.number(list.length + 1);
    }
    let result = [];
    for (let i = 0; i < limit; i++) {
      result.push(this.pick(list));
    }
    return result;
  },
  pop: function (arr) {
    // Removes and returns a random item from an array
    let i, obj;

    i = this.number(arr.length);
    obj = arr[i];
    arr.splice(i, 1);

    return obj;
  }
};