import { TOTP, URI } from "otpauth";

export type TOTPAlgorithm = "SHA1" | "SHA256" | "SHA512";

export interface TOTPParams {
  secret: string;
  algorithm?: TOTPAlgorithm;
  digits?: number;
  period?: number;
}

export function generateTOTP(
  base32Secret: string,
  algorithm: TOTPAlgorithm = "SHA1",
  digits: number = 6,
  period: number = 30
): { code: string; remaining: number } {
  // PCH-01-019: honour the entry's stored algorithm/digits/period; absent
  // params (undefined) fall through to the RFC defaults (SHA-1 / 6 / 30 s).
  const totp = new TOTP({ secret: base32Secret, digits, period, algorithm });
  const code = totp.generate();
  const remaining = period - (Math.floor(Date.now() / 1000) % period);
  return { code, remaining };
}

export function parseOtpauthURI(uri: string): TOTPParams | null {
  try {
    const parsed = URI.parse(uri);
    if (parsed instanceof TOTP) {
      return {
        secret: parsed.secret.base32,
        algorithm: parsed.algorithm as TOTPAlgorithm,
        digits: parsed.digits,
        period: parsed.period,
      };
    }
    return null;
  } catch {
    return null;
  }
}