/**
 * Derive the live WebSocket path from `NEXT_PUBLIC_LIVE_WS_PUBLIC_URL`.
 *
 * Only `ws://` or `wss://` URLs are accepted (mirrors the scheme guard in
 * `getLivePublicUrl()`). The pathname is extracted and used as the WS upgrade
 * path; if the URL has no pathname (or is `/`), falls back to `/live-ws`.
 *
 * Used by:
 * - `src/app/api/v1/ws/route.ts` — handshake response `path` field
 * - `src/hooks/useLiveDashboard.ts` — build-time path constant + runtime discovery
 *
 * No env var is introduced — this reads the existing `NEXT_PUBLIC_LIVE_WS_PUBLIC_URL`.
 */
export function deriveLiveWsPath(publicUrl?: string): string {
  if (!publicUrl) return "/live-ws";
  if (!publicUrl.startsWith("ws://") && !publicUrl.startsWith("wss://")) return "/live-ws";
  try {
    const parsed = new URL(publicUrl);
    const pathname = parsed.pathname;
    return pathname && pathname !== "/" ? pathname : "/live-ws";
  } catch {
    return "/live-ws";
  }
}

/** Convenience: read the env var at call time and derive the path. */
export function getLiveWsPath(): string {
  return deriveLiveWsPath(process.env.NEXT_PUBLIC_LIVE_WS_PUBLIC_URL);
}