/**
 * New-deploy detection for the SPA.
 *
 * The server stamps every response with `X-App-Version`. `apiFetch` feeds that
 * header here via `reportServerVersion`. When it differs from the version baked
 * into THIS bundle at build time (`BUILD_VERSION`), a deploy has happened — we
 * latch it and notify subscribers (the refresh banner). We never force a
 * reload; the user picks the moment (they may be mid-form).
 */

// Injected by Vite `define` at build time; falls back to "dev" in tests / when
// running unbuilt. `typeof` guard avoids a ReferenceError when undefined.
declare const __APP_VERSION__: string;
export const BUILD_VERSION: string =
  typeof __APP_VERSION__ !== "undefined" ? __APP_VERSION__ : "dev";

let newVersion: string | null = null;
const listeners = new Set<() => void>();

/**
 * Compare a server-reported version against this bundle's build version. Latches
 * the first genuine mismatch and notifies subscribers exactly once.
 */
export function reportServerVersion(
  serverVersion: string | null | undefined,
): void {
  if (newVersion) return; // already latched — banner is up
  if (!serverVersion || serverVersion === BUILD_VERSION) return;
  newVersion = serverVersion;
  for (const l of listeners) l();
}

export function subscribeNewVersion(listener: () => void): () => void {
  listeners.add(listener);
  return () => {
    listeners.delete(listener);
  };
}

export function getNewVersion(): string | null {
  return newVersion;
}

/** Test-only: reset the module singleton between cases. */
export function __resetVersionStateForTest(): void {
  newVersion = null;
  listeners.clear();
}