@haelp/teto/src/engine/utils/rng/index.ts

A typescript-based controllable TETR.IO client.

export class RNG {
  private static readonly MODULUS: number = 2147483647;
  private static readonly MULTIPLIER: number = 16807;
  private static readonly MAX_FLOAT: number = 2147483646;

  private value: number;

  index = 0;

  constructor(seed: number) {
    this.value = seed % RNG.MODULUS;

    if (this.value <= 0) {
      this.value += RNG.MAX_FLOAT;
    }

    this.next = this.next.bind(this);
    this.nextFloat = this.nextFloat.bind(this);
    this.shuffleArray = this.shuffleArray.bind(this);
    this.updateFromIndex = this.updateFromIndex.bind(this);
    this.clone = this.clone.bind(this);
  }

  next(): number {
    this.index++;
    return (this.value = (RNG.MULTIPLIER * this.value) % RNG.MODULUS);
  }

  nextFloat(): number {
    return (this.next() - 1) / RNG.MAX_FLOAT;
  }

  shuffleArray<T extends any[]>(array: T): T {
    if (array.length === 0) {
      return array;
    }

    for (let i = array.length - 1; i !== 0; i--) {
      const r = Math.floor(this.nextFloat() * (i + 1));
      [array[i], array[r]] = [array[r], array[i]];
    }

    return array;
  }

  get seed() {
    return this.value;
  }

  set seed(value: number) {
    this.value = value % RNG.MODULUS;

    if (this.value <= 0) {
      this.value += RNG.MAX_FLOAT;
    }
  }

  updateFromIndex(index: number) {
    while (this.index < index) {
      this.next();
    }
  }

  clone() {
    return new RNG(this.value);
  }
}