import { Injectable } from '@nestjs/common';

@Injectable()
export class ClockIDGenService {
  private _counter = 0n;
  private timestampBits = 42;
  private timestampMask = BigInt(
    Math.floor(Math.pow(2, this.timestampBits)) - 1,
  );
  private counterBits = 10;
  private counterMask = BigInt(Math.floor(Math.pow(2, this.counterBits)) - 1);

  idGenerator(prefix?: string): string {
    const timestamp = BigInt(Date.now()) & this.timestampMask;
    const counter = BigInt(this._counter++) & this.counterMask;
    let now = timestamp << BigInt(this.counterBits);
    now = now | counter;
    const id = now.toString(36).toUpperCase();
    return prefix ? prefix + id : id;
  }
}