import crypto from 'node:crypto';

// UUIDv7 (RFC 9562): 48-bit ms timestamp, version 7, variant 10, 74 random bits
export function uuidv7(): string {
  const now = Date.now();
  const random = crypto.randomBytes(10);

  const bytes = Buffer.alloc(16);
  bytes[0] = (now / 2 ** 40) & 0xff;
  bytes[1] = (now / 2 ** 32) & 0xff;
  bytes[2] = (now / 2 ** 24) & 0xff;
  bytes[3] = (now / 2 ** 16) & 0xff;
  bytes[4] = (now / 2 ** 8) & 0xff;
  bytes[5] = now & 0xff;

  bytes[6] = 0x70 | (random[0]! & 0x0f);
  bytes[7] = random[1]!;

  bytes[8] = 0x80 | (random[2]! & 0x3f);
  bytes[9] = random[3]!;
  bytes[10] = random[4]!;
  bytes[11] = random[5]!;
  bytes[12] = random[6]!;
  bytes[13] = random[7]!;
  bytes[14] = random[8]!;
  bytes[15] = random[9]!;

  const hex = bytes.toString('hex');
  return (
    hex.slice(0, 8) + '-' +
    hex.slice(8, 12) + '-' +
    hex.slice(12, 16) + '-' +
    hex.slice(16, 20) + '-' +
    hex.slice(20, 32)
  );
}

export function generateNonce(): string {
  const bytes = crypto.randomBytes(16);
  return base64urlEncode(bytes);
}

export function base64urlEncode(data: Buffer | Uint8Array): string {
  const buf = Buffer.isBuffer(data) ? data : Buffer.from(data);
  return buf.toString('base64url');
}

export function base64urlDecode(input: string): Buffer {
  return Buffer.from(input, 'base64url');
}