export interface JsonEnvelope<T> {
  ok: boolean;
  command: string;
  data?: T;
  error?: unknown;
}

function isEpipe(error: unknown): boolean {
  return typeof error === "object" && error !== null && "code" in error && (error as { code?: unknown }).code === "EPIPE";
}

process.stdout.on("error", (error) => {
  if (isEpipe(error)) process.exit(0);
  throw error;
});

process.stderr.on("error", (error) => {
  if (isEpipe(error)) process.exit(0);
  throw error;
});

export function emitJson<T>(command: string, data: T, ok = true): void {
  const envelope: JsonEnvelope<T> = { ok, command, data };
  safeStdoutWrite(`${JSON.stringify(envelope, null, 2)}\n`);
}

export function emitError(command: string, error: unknown): void {
  const payload = error instanceof Error
    ? { name: error.name, message: error.message, stack: error.stack ?? null }
    : { message: String(error) };
  const envelope: JsonEnvelope<never> = { ok: false, command, error: payload };
  safeStdoutWrite(`${JSON.stringify(envelope, null, 2)}\n`);
}

function safeStdoutWrite(text: string): void {
  try {
    process.stdout.write(text);
  } catch (error) {
    if (isEpipe(error)) process.exit(0);
    throw error;
  }
}