export const DEV_RELOAD_EXISTING_ARG = '--metoyou-dev-reload-existing';

export type SecondInstanceAction = 'reload-existing' | 'focus';

export interface SecondInstanceInput {
  argv: string[];
  devSingleInstanceExitCode: number | null;
}

/**
 * A dev launch always carries `--metoyou-dev-reload-existing`, so the running
 * instance reloads in place. It must never answer by relaunching itself: the
 * successor inherits the same argument and asks for the single-instance lock
 * while the dying parent still holds it, so the refused successor fires
 * `second-instance` again and the pair respawns forever.
 */
export function resolveSecondInstanceAction(input: SecondInstanceInput): SecondInstanceAction {
  const isDevelopmentLaunch = input.devSingleInstanceExitCode != null;

  return isDevelopmentLaunch && input.argv.includes(DEV_RELOAD_EXISTING_ARG)
    ? 'reload-existing'
    : 'focus';
}