using System;
using System.IO;
using System.Threading.Tasks;

namespace SearchObjFiles
{
    class Program
    {
        static async Task Main(string[] args)
        {
            try
            {
                // Ask the user to enter the directory to search
                Console.WriteLine("请输入要搜索的目录：");
                string dir = Console.ReadLine();

                // Validate the directory input
                if (string.IsNullOrEmpty(dir))
                {
                    throw new ArgumentException("目录不能为空。");
                }
                if (!Directory.Exists(dir))
                {
                    throw new DirectoryNotFoundException("目录不存在。");
                }

                // Ask the user to enter the file extension to search for
                Console.WriteLine("请输入要搜索的文件扩展名：");
                string ext = Console.ReadLine();

                // Validate the file extension input
                if (string.IsNullOrEmpty(ext))
                {
                    throw new ArgumentException("文件扩展名不能为空。");
                }
                
                 // Ask the user to enter the output file name
                 Console.WriteLine("请输入输出文件的名称：");
                 string output = Console.ReadLine();
 
                 // Validate the output file name input
                 if (string.IsNullOrEmpty(output))
                 {
                     throw new ArgumentException("输出文件名称不能为空。");
                 }

                 // Ask the user to enter whether to search subdirectories or not
                 Console.WriteLine("是否要搜索子目录？(y/n)");
                 string option = Console.ReadLine();

                 // Validate and parse the option input
                 SearchOption searchOption;
                 switch (option.ToLower())
                 {
                     case "y":
                         searchOption = SearchOption.AllDirectories;
                         break;
                     case "n":
                         searchOption = SearchOption.TopDirectoryOnly;
                         break;
                     default:
                         throw new ArgumentException("无效的选项，请输入y或n。");
                         
                  }

                  // Get all files with the specified extension in the directory and subdirectories
                  string[] files = Directory.GetFiles(dir, "*" + ext, searchOption);

                  // Write the file names and paths to the output file asynchronously 
                  using (StreamWriter sw = new StreamWriter(output))
                  {
                      foreach (string file in files)
                      {
                          await sw.WriteLineAsync(file);
                      }
                  }

                  // Display a success message
                  Console.WriteLine("检索完成，共找到{0}个文件，已写入{1}。", files.Length, output);
              }
              catch (Exception ex)
              {
                  // Display an error message
                  Console.WriteLine("发生错误：{0}", ex.Message);
              }
          }
      }
  }