import { createCipheriv, createDecipheriv, createHash, randomBytes } from "crypto";
import { totpVerify } from "../totp";

/* An operator's second factor, stored under the console's own key.
 *
 * lib/totp.ts encrypts a coordinator's TOTP secret with a key derived from SESSION_SECRET, and
 * that is the right blast radius there: rotating the product's secret invalidates customer
 * sessions and customer second factors together. It is the wrong blast radius here. An
 * operator's secret is kept under a key derived from OPS_SESSION_SECRET, so rotating either
 * secret touches only its own side. The cipher, the format and the verification arithmetic are
 * the product's own — nothing new is invented, only the key underneath it. */

function key(): Buffer {
  const s = process.env.OPS_SESSION_SECRET;
  if (!s) throw new Error("OPS_SESSION_SECRET is required to store an operator's TOTP secret");
  return createHash("sha256").update(`ops-totp:${s}`).digest();
}

export function encryptOpsSecret(plain: string): string {
  const iv = randomBytes(12);
  const c = createCipheriv("aes-256-gcm", key(), iv);
  const enc = Buffer.concat([c.update(plain, "utf8"), c.final()]);
  return `v1.${iv.toString("base64url")}.${c.getAuthTag().toString("base64url")}.${enc.toString("base64url")}`;
}

export function decryptOpsSecret(stored: string): string | null {
  try {
    const [v, iv, tag, enc] = stored.split(".");
    if (v !== "v1") return null;
    const d = createDecipheriv("aes-256-gcm", key(), Buffer.from(iv, "base64url"));
    d.setAuthTag(Buffer.from(tag, "base64url"));
    return Buffer.concat([d.update(Buffer.from(enc, "base64url")), d.final()]).toString("utf8");
  } catch {
    return null;
  }
}

/** True only when the operator has a second factor enrolled AND the code matches it. */
export function verifyOperatorCode(op: { totpSecret: string; totpEnabledAt: Date | null }, code: string): boolean {
  if (!op.totpEnabledAt) return false;
  const secret = decryptOpsSecret(op.totpSecret);
  if (!secret) return false;
  return totpVerify(secret, String(code || "").replace(/\s+/g, ""));
}