import 'dart:async';
import 'dart:convert';
import 'dart:io';

/// 外部命令执行失败（非零退出/超时/无法启动）。
class CommandException implements Exception {
  CommandException(this.message);

  final String message;

  @override
  String toString() => message;
}

/// 运行外部命令（lp/lpoptions/lpstat）并返回标准输出。
///
/// 一律用参数列表传参不经过 shell，杜绝命令注入；
/// 强制 LC_ALL=C 英文输出（macOS 会把 lpstat/lp 本地化，中文系统队列名与状态词粘连无法按空格解析）。
Future<String> runCommand(
  String executable,
  List<String> arguments, {
  int timeoutMs = 15000,
  bool tolerateExit = false,
}) async {
  final Process process;
  try {
    process = await Process.start(
      executable,
      arguments,
      environment: const {'LC_ALL': 'C', 'LANG': 'C'},
    );
  } on ProcessException catch (e) {
    throw CommandException('无法启动 $executable：${e.message}');
  }

  // stdout/stderr 立即挂上消费 Future，避免管道缓冲区写满导致死锁
  final stdoutFuture = process.stdout.transform(utf8.decoder).join();
  final stderrFuture = process.stderr.transform(utf8.decoder).join();

  final int exitCode;
  try {
    exitCode = await process.exitCode.timeout(Duration(milliseconds: timeoutMs));
  } on TimeoutException {
    process.kill();
    throw CommandException('$executable 执行超时');
  }

  final out = await stdoutFuture;
  if (exitCode != 0 && !tolerateExit) {
    final err = await stderrFuture;
    throw CommandException('$executable 返回 $exitCode：${err.trim()}');
  }
  return out;
}