/**
 * Shared constants + mint helper for the Fitbit OAuth state nonce ledger.
 * Mirrors `src/lib/whoop/oauth-state.ts`. (v1.20.0 — the PKCE `code_verifier`
 * lives on the `FitbitOAuthState` row; the connect route mints it via the
 * client's `generatePkcePair`.)
 *
 * The nonce is random + opaque; a short-lived `FitbitOAuthState` row carries
 * the `(nonce → userId)` mapping so the user id never leaks into request logs
 * or network captures via the OAuth `state` param. The connect route, the
 * callback route, and the cleanup cron all read these constants so the
 * contract has one source of truth and the unit tests can pin it without
 * importing either route file.
 */
import { randomBytes } from "node:crypto";

/**
 * Cookie name carrying the in-flight state nonce. httpOnly + Secure +
 * sameSite:lax at the connect route (mirrors the WHOOP cookie shape).
 */
export const FITBIT_OAUTH_STATE_COOKIE = "fitbit_state" as const;

/**
 * 10-minute TTL on the state row. Matches the cookie `maxAge`. Long enough to
 * cover a user approving the Fitbit consent prompt; short enough that an
 * abandoned handshake doesn't strand a row for hours.
 */
export const FITBIT_OAUTH_STATE_TTL_MS = 10 * 60 * 1000;

/**
 * Mint a fresh state nonce. 16 random bytes → 22 base64url chars without
 * padding — 128 bits of entropy, aligned with the OAuth 2.0 §10.10
 * "at least 128 bits" recommendation.
 */
export function mintFitbitOAuthStateNonce(): string {
  return randomBytes(16).toString("base64url");
}