using System;
using System.Diagnostics;
using System.IO;
using System.Text;

namespace DrillTools
{
    internal static class CommandTypeFileReader
    {
        private const int Gb2312CodePage = 936;

        private static readonly char[] ForbiddenPathChars =
        {
            '&', '|', '<', '>', '^', '%', '!', '(', ')', '@', '"', '\r', '\n'
        };

        public static string ReadAllText(string filePath)
        {
            return ReadAllText(filePath, CreateAnsiEncoding());
        }

        public static string ReadAllText(string filePath, Encoding encoding)
        {
            string normalizedPath = ValidateAndNormalizePath(filePath);

            using var process = new Process
            {
                StartInfo = CreateStartInfo(normalizedPath, encoding)
            };

            if (!process.Start())
                throw new InvalidOperationException("无法启动文件读取进程");

            var outputTask = process.StandardOutput.ReadToEndAsync();
            var errorTask = process.StandardError.ReadToEndAsync();
            process.WaitForExit();

            string output = outputTask.GetAwaiter().GetResult();
            string error = errorTask.GetAwaiter().GetResult();

            if (process.ExitCode != 0)
                throw new InvalidOperationException($"读取文件失败，退出代码：{process.ExitCode}，错误：{error.Trim()}");

            return output;
        }

        private static ProcessStartInfo CreateStartInfo(string filePath, Encoding encoding)
        {
            return new ProcessStartInfo
            {
                FileName = "cmd.exe",
                Arguments = $"/d /c type \"{filePath}\"",
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                UseShellExecute = false,
                CreateNoWindow = true,
                StandardOutputEncoding = encoding,
                StandardErrorEncoding = encoding
            };
        }

        private static string ValidateAndNormalizePath(string filePath)
        {
            if (string.IsNullOrWhiteSpace(filePath))
                throw new ArgumentException("文件路径不能为空", nameof(filePath));

            if (filePath.IndexOfAny(ForbiddenPathChars) >= 0)
                throw new ArgumentException("文件路径包含不允许的命令行特殊字符", nameof(filePath));

            string normalizedPath = Path.GetFullPath(filePath);
            if (normalizedPath.IndexOfAny(ForbiddenPathChars) >= 0)
                throw new ArgumentException("文件路径包含不允许的命令行特殊字符", nameof(filePath));

            if (!File.Exists(normalizedPath))
                throw new FileNotFoundException($"文件不存在：{normalizedPath}", normalizedPath);

            return normalizedPath;
        }

        private static Encoding CreateAnsiEncoding()
        {
            return Encoding.GetEncoding(Gb2312CodePage);
        }
    }
}