export class RandomNumberGenerator {
  public readonly seed: string;
  private a: number;
  private b: number;
  private c: number;
  private d: number;
  private generator: () => number;

  public constructor(seed: string) {
    this.seed = seed;
    [this.a, this.b, this.c, this.d] = this.cyrb128(seed);
    this.generator = this.sfc32(this.a, this.b, this.c, this.d);
  }

  public rand(): number {
    return this.generator();
  }

  private cyrb128(str: string) {
    let h1 = 1779033703,
      h2 = 3144134277,
      h3 = 1013904242,
      h4 = 2773480762;
    for (let i = 0; i < str.length; i++) {
      const k = str.charCodeAt(i);
      h1 = h2 ^ Math.imul(h1 ^ k, 597399067);
      h2 = h3 ^ Math.imul(h2 ^ k, 2869860233);
      h3 = h4 ^ Math.imul(h3 ^ k, 951274213);
      h4 = h1 ^ Math.imul(h4 ^ k, 2716044179);
    }
    h1 = Math.imul(h3 ^ (h1 >>> 18), 597399067);
    h2 = Math.imul(h4 ^ (h2 >>> 22), 2869860233);
    h3 = Math.imul(h1 ^ (h3 >>> 17), 951274213);
    h4 = Math.imul(h2 ^ (h4 >>> 19), 2716044179);
    (h1 ^= h2 ^ h3 ^ h4), (h2 ^= h1), (h3 ^= h1), (h4 ^= h1);
    return [h1 >>> 0, h2 >>> 0, h3 >>> 0, h4 >>> 0];
  }

  private sfc32(a: number, b: number, c: number, d: number) {
    return function () {
      a |= 0;
      b |= 0;
      c |= 0;
      d |= 0;
      let t = (((a + b) | 0) + d) | 0;
      d = (d + 1) | 0;
      a = b ^ (b >>> 9);
      b = (c + (c << 3)) | 0;
      c = (c << 21) | (c >>> 11);
      c = (c + t) | 0;
      return (t >>> 0) / 4294967296;
    };
  }
}