// https://stackoverflow.com/a/424445 thanks my dude

export type State = number;

const M = 0x80000000;
const A = 1103515245;
const C = 12345;

export class Rand {
  state: number;

  constructor(state?: State) {
    this.state = typeof state == 'number' && !isNaN(state) ?
      state : Math.floor(Math.random() * (M - 1));
  }

  #next(): number { return this.state = (A * this.state + C) % M; }

  #float(x?: number, y?: number): number {
    const [lo, hi] =
      x === undefined ? [0, 1] :
      y === undefined ? [0, x] :
      [Math.min(x, y), Math.max(x, y)];

    return lo + this.#next() / (M - 1) * (hi - lo);
  }

  int(): number; // whole int32 range
  int(x: number): number; // [0, x)
  int(x: number, y: number): number; // [x, y)
  int(x?: number, y?: number): number {
    return x === undefined ? this.#next() : Math.floor(this.#float(x, y));
  }

  float(): number; // [0, 1)
  float(x: number): number; // [0, x)
  float(x: number, y: number): number; // [x, y)
  float(x?: number, y?: number): number { return this.#float(x, y); }

  choice<A>(array: A[]): A {
    return array[this.int(0, array.length)]!;
  }

  boolean(): boolean { return this.float() > 0.5; }
}