OpenFrontIO/src/core/PseudoRandom.ts

export class PseudoRandom {
  private m: number = 0x80000000; // 2**31
  private a: number = 1103515245;
  private c: number = 12345;
  private state: number;

  constructor(seed: number) {
    this.state = seed % this.m;
  }

  /**
   * Generates the next pseudorandom number.
   * @returns A number between 0 (inclusive) and 1 (exclusive).
   */
  next(): number {
    this.state = (this.a * this.state + this.c) % this.m;
    return this.state / this.m;
  }

  /**
   * Generates a random integer between min (inclusive) and max (exclusive).
   */
  nextInt(min: number, max: number): number {
    return Math.floor(this.next() * (max - min) + min);
  }

  /**
   * Generates a random float between min (inclusive) and max (exclusive).
   */
  nextFloat(min: number, max: number): number {
    return this.next() * (max - min) + min;
  }

  nextID(): string {
    return this.nextInt(0, Math.pow(36, 8)) // 36^8 possibilities
      .toString(36) // Convert to base36 (0-9 and a-z)
      .padStart(8, "0"); // Ensure 8 chars by padding with zeros
  }

  randElement<T>(arr: T[]): T {
    if (arr.length == 0) {
      throw new Error("array must not be empty");
    }
    return arr[this.nextInt(0, arr.length)];
  }

  chance(odds: number): boolean {
    return this.nextInt(0, odds) == 0;
  }

  shuffleArray(array: any[]) {
    for (let i = array.length - 1; i >= 0; i--) {
      const j = Math.floor(this.nextInt(0, i + 1));
      [array[i], array[j]] = [array[j], array[i]];
    }

    return array;
  }
}