snowflakify/dist/mjs/Fragments/RandomFragment.js

The most complete Snowflake ID generator in TypeScript

import { randomInt } from 'crypto';
import FragmentBase from '../FragmentBase.js';
/**
 * RandomFragment class for random IDs.
 * @public
 */
export default class RandomFragment extends FragmentBase {
  /**
   * @remarks
   * When using a custom random function, please ensure it returns a positive number
   * no greater than `2 ** bits - 1`.
   *
   * @param bits - The number of bits for the fragment.
   * @param fn - Optional custom random function.
   *
   * @throws `[RND_FUNCTION_RETURN_TYPE]` If custom function does not return number or bigint.
   */
  constructor(bits, fn) {
    super(bits);
    this.fn = fn;
    if (fn && !['number', 'bigint'].includes(typeof fn()))
      throw new TypeError(
        `[RND_FUNCTION_RETURN_TYPE]: RandomFragment custom function return is of type: ${typeof fn()}; Expected number or bigint.`,
      );
  }
  getValue() {
    if (this.fn) {
      const rndNum = BigInt(this.fn());
      if (rndNum >= BigInt(1 << this.bits))
        throw new TypeError(
          `[RND_FUNCTION_BAD_RETURN]: RandomFragment custom function returned a value bigger than 2 ** ${this.bits} - 1.`,
        );
      return rndNum;
    }
    if (this.bits <= 48) return BigInt(randomInt(1, 1 << 48)) - BigInt(1);
    // 48 bit parts due to randomInt range limitation
    // max param limit of Number.MAX_SAFE_INTEGER
    let rndNum = BigInt(1);
    for (let i = 1; i < this.bits / 48; i += 1) {
      rndNum *= BigInt(randomInt(1, 1 << 48));
    }
    rndNum *= BigInt(randomInt(1, 1 << this.bits % 48));
    return rndNum - BigInt(1);
  }
  destructure(snowflake) {
    const bits = BigInt(snowflake) & this.bitMask;
    return {
      identifier: this.identifier,
      value: bits >> this.bitShift,
    };
  }
}
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