import { randomBytes } from 'node:crypto';

/**
 * Generate UUID v7 (time-ordered, sortable).
 * Simplified implementation: timestamp (48 bit) + random (74 bit).
 */
export function uuid7(): string {
  const timestamp = Date.now();
  const random = randomBytes(10);

  const high = (timestamp / 0x100000000) >>> 0;
  const low = timestamp >>> 0;

  const b = new Uint8Array(16);
  b[0] = (high >> 24) & 0xff;
  b[1] = (high >> 16) & 0xff;
  b[2] = (high >> 8) & 0xff;
  b[3] = high & 0xff;
  b[4] = (low >> 24) & 0xff;
  b[5] = (low >> 16) & 0xff;
  b[6] = ((low >> 8) & 0x3f) | 0x70;
  b[7] = low & 0xff;
  b[8] = 0x80 | (random[0] & 0x3f);
  b[9] = random[1];
  b[10] = random[2];
  b[11] = random[3];
  b[12] = random[4];
  b[13] = random[5];
  b[14] = random[6];
  b[15] = random[7];

  const hex = Array.from(b)
    .map((x) => x.toString(16).padStart(2, '0'))
    .join('');

  return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
}