/**
 * Camera stream resolution, on its own with no imports - the same reason as
 * `dispatch/job_status.ts`: `../db` opens a connection at import time, and
 * the distinct failure messages here are worth testing without one.
 *
 * This used to hand back the gateway's own LAN address for the browser to
 * play from. It cannot: go2rtc sends no CORS headers and checks its API
 * password before CORS, so a browser's unauthenticated preflight gets a 401 -
 * measured against 1.9.14 - and a gateway is behind a workshop NAT anyway.
 * So there is no URL to give out. What a viewer needs is a camera name to ask
 * for and a gateway that is connected to relay the SDP exchange.
 */

export const NO_CAMERA_MESSAGE = "this printer reports no camera that can be streamed";
export const NO_GATEWAY_MESSAGE =
  "this farm's gateway is not connected, so its camera cannot be negotiated";

export type StreamResolution =
  | { ok: true; stream: { cameraId: string } }
  | { ok: false; reason: "no_camera" | "gateway_offline"; message: string };

/**
 * A camera name, or an error naming what is missing. The printer is checked
 * first: if it can never stream, saying the gateway is offline would send
 * someone off to fix the wrong thing - and a P1/A1 can never stream, so this
 * is the common case rather than the unlucky one.
 */
export function resolveStream(
  cameraStream: string | null | undefined,
  gatewayOnline: boolean,
): StreamResolution {
  if (!cameraStream) return { ok: false, reason: "no_camera", message: NO_CAMERA_MESSAGE };
  if (!gatewayOnline) {
    return { ok: false, reason: "gateway_offline", message: NO_GATEWAY_MESSAGE };
  }
  return { ok: true, stream: { cameraId: cameraStream } };
}