octo-deno/lib/random/random.ts

/* 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/. */

import MersenneTwister from "./mersennetwister.ts";

export default class random {
  static twister: MersenneTwister;

  /**
   * Must be called before any other methods can be called to initialize MersenneTwister
   * @param {?number} seed - Value to initialize MersenneTwister
   */
  static init(seed = null) {
    if (seed === null) {
      seed = new Date().getTime();
    }
    random.twister = new MersenneTwister();
    random.twister.seed(seed);
  }

  /**
   * Returns an integer in [0, limit) (uniform distribution)
   * @param {number} limit
   */
  static number(limit = 0xffffffff) {
    if (!random.twister) {
      throw new Error("random.init must be called first.");
    }

    let x = (0x100000000 / limit) >>> 0;
    let y = (x * limit) >>> 0;
    let r;
    do {
      r = random.twister.int32();
    } while (y && r >= y); // eslint-disable-line no-unmodified-loop-condition
    return (r / x) >>> 0;
  }

  /**
   * Returns a float in [0, 1) (uniform distribution)
   */
  static float() {
    if (!random.twister) {
      throw new Error("random.init must be called first.");
    }

    return random.twister.real2();
  }

  /**
   * Returns an integer in [start, limit) (uniform distribution)
   * @param {number} start
   * @param {number} limit
   */
  static range(start, limit) {
    if (!random.twister) {
      throw new Error("random.init must be called first.");
    }

    if (isNaN(start) || isNaN(limit)) {
      throw new TypeError(
        `random.range() received non-number type: (${start}, ${limit})`
      );
    }

    return random.number(limit - start + 1) + start;
  }

  /**
   * Returns a float in [1, limit). The logarithm has uniform distribution.
   * @param {number} limit
   */
  static ludOneTo(limit) {
    return Math.exp(random.float() * Math.log(limit));
  }

  /**
   * Returns a random index from a list
   * @param {Array} list
   * @returns {*}
   */
  static item<T>(list: T[]): T {
    if (!Array.isArray(list)) {
      throw new TypeError(`random.item() received invalid object: (${list})`);
    }

    return list[random.number(list.length)];
  }

  /**
   * Returns a random key of a provided object
   * @param {Object} obj
   */
  static key(obj) {
    return random.item(Object.keys(obj));
  }

  /**
   * Return a random Boolean value
   */
  static bool() {
    return random.item([true, false]);
  }

  /**
   * Recursively iterate over array until non-array item identified
   * If item is a function, evaluate it with no args
   * @param {*} obj
   * @returns {*}
   */
  static pick(obj) {
    if (typeof obj === "function") {
      return obj();
    } else if (Array.isArray(obj)) {
      return random.pick(random.item(obj));
    }

    return obj;
  }

  /**
   * Returns a boolean result based on limit
   * @param limit
   * @returns {boolean}
   */
  static chance(limit = 2) {
    if (isNaN(limit)) {
      throw new TypeError(
        `random.chance() received non-number type: (${limit})`
      );
    }

    return random.number(limit) === 1;
  }

  /**
   * Return an item from an array of arrays where the first index in each sub-array denotes the weight
   * @param {Array} list - Array of arrays
   * @param {Boolean} flat - Indicates whether we should iterate over the arrays recursively
   * @returns {*}
   */
  static choose(list, flat = false) {
    if (!Array.isArray(list)) {
      throw new TypeError(`random.choose() received non-array type: (${list})`);
    }

    const expanded = [];
    list.forEach(([weight, value]) => {
      while (weight--) {
        expanded.push(value);
      }
    });

    if (flat) {
      return random.item(expanded);
    }

    return random.pick(expanded);
  }

  /**
   * Return a flattened list of weighted values
   * [{w: 1, v: 'foo'}, {w: 1, v: 'bar'}]
   * @param {Array} list
   * @param {Array}
   */
  static weighted(list) {
    const expanded = [];
    list.forEach(item => {
      while (item.w--) {
        expanded.push(item.v);
      }
    });

    return expanded;
  }

  static use(obj) {
    return random.bool() ? obj : "";
  }

  /**
   * Returns arr shuffled
   * @param arr
   */
  static shuffle(arr) {
    let i = arr.length;
    while (i--) {
      let p = random.number(i + 1);
      let t = arr[i];
      arr[i] = arr[p];
      arr[p] = t;
    }
  }

  /**
   * Returns a shuffled copy of arr
   * @param arr
   * @returns {*}
   */
  static shuffled(arr) {
    let newArray = arr.slice();
    random.shuffle(newArray);
    return newArray;
  }

  /**
   * Select an array containing a subset of 'list'
   * @param list
   * @param limit
   * @returns {Array}
   */
  static subset(list, limit?) {
    if (!Array.isArray(list)) {
      throw new TypeError(`random.subset() received non-array type: (${list})`);
    }

    if (typeof limit !== "number") {
      limit = random.number(list.length + 1);
    }

    // Deepclone list
    const temp = JSON.parse(JSON.stringify(list));
    const result = [];
    while (limit--) {
      result.push(random.pop(temp));
    }

    return result;
  }

  /**
   * Removes and returns a random item from an array.
   * @param {*} arr
   */
  static pop(arr) {
    let i, obj;

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

    return obj;
  }

  static hex(len) {
    return random.number(Math.pow(2, len * 4)).toString(16);
  }
}