using System;
using System.IO;
using Renci.SshNet;
using Renci.SshNet.Sftp;
using System.Collections.Generic;

namespace SFTPUtils
{
    public class SftpClientWithKey
    {
        private SftpClient _sftpClient;
        private readonly string _host;
        private readonly int _port;
        private readonly string _username;
        private readonly string _privateKeyPath;

        /// <summary>
        /// 初始化 SFTP 客户端
        /// </summary>
        /// <param name="host">SFTP 服务器地址</param>
        /// <param name="port">端口（默认22）</param>
        /// <param name="username">用户名</param>
        /// <param name="privateKeyPath">OpenSSH 格式私钥文件路径</param>
        public SftpClientWithKey(string host, int port, string username, string privateKeyPath)
        {
            _host = host;
            _port = port;
            _username = username;
            _privateKeyPath = privateKeyPath;
        }

        /// <summary>
        /// 连接到 SFTP 服务器
        /// </summary>
        public void Connect()
        {
            try
            {
                if (_sftpClient != null && _sftpClient.IsConnected)
                {
                    return;
                }

                var keyFiles = new[] { new PrivateKeyFile(_privateKeyPath) };
                var connectionInfo = new ConnectionInfo(_host, _port, _username,
                    new PrivateKeyAuthenticationMethod(_username, keyFiles));

                _sftpClient = new SftpClient(connectionInfo);
                _sftpClient.Connect();
            }
            catch (Exception ex)
            {
                throw new Exception($"SFTP 连接失败: {ex.Message}", ex);
            }
        }

        /// <summary>
        /// 断开连接
        /// </summary>
        public void Disconnect()
        {
            if (_sftpClient != null && _sftpClient.IsConnected)
            {
                _sftpClient.Disconnect();
            }
        }

        /// <summary>
        /// 上传文件到 SFTP 服务器
        /// </summary>
        /// <param name="localFilePath">本地文件路径</param>
        /// <param name="remoteDirectory">远程目录</param>
        /// <param name="remoteFileName">远程文件名（可选，如果为空则使用本地文件名）</param>
        /// <returns>上传成功返回 true</returns>
        public bool UploadFile(string localFilePath, string remoteDirectory, string remoteFileName = null)
        {
            if (!File.Exists(localFilePath))
            {
                throw new FileNotFoundException("本地文件不存在", localFilePath);
            }

            Connect();

            try
            {
                // 确保远程目录存在
                CreateRemoteDirectory(remoteDirectory);

                // 确定远程文件名
                string finalRemoteFileName = string.IsNullOrEmpty(remoteFileName)
                    ? Path.GetFileName(localFilePath)
                    : remoteFileName;

                string remoteFilePath = $"{remoteDirectory.TrimEnd('/')}/{finalRemoteFileName}";

                using (var fileStream = new FileStream(localFilePath, FileMode.Open))
                {
                    _sftpClient.UploadFile(fileStream, remoteFilePath);
                }

                return true;
            }
            catch (Exception ex)
            {
                throw new Exception($"文件上传失败: {ex.Message}", ex);
            }
        }

        /// <summary>
        /// 创建远程目录（如果不存在）
        /// </summary>
        /// <param name="remoteDirectory">远程目录路径</param>
        private void CreateRemoteDirectory(string remoteDirectory)
        {
            try
            {
                var directories = remoteDirectory.Split(new[] { '/' }, StringSplitOptions.RemoveEmptyEntries);
                string currentPath = string.Empty;

                foreach (var directory in directories)
                {
                    currentPath += "/" + directory;

                    if (!_sftpClient.Exists(currentPath))
                    {
                        _sftpClient.CreateDirectory(currentPath);
                    }
                }
            }
            catch (Exception ex)
            {
                throw new Exception($"创建远程目录失败: {ex.Message}", ex);
            }
        }

        /// <summary>
        /// 检查文件是否存在
        /// </summary>
        /// <param name="remoteFilePath">远程文件路径</param>
        /// <returns>存在返回 true</returns>
        public bool FileExists(string remoteFilePath)
        {
            Connect();
            return _sftpClient.Exists(remoteFilePath);
        }

        /// <summary>
        /// 列出远程目录中的文件
        /// </summary>
        /// <param name="remoteDirectory">远程目录</param>
        /// <returns>文件列表</returns>
        public IEnumerable<ISftpFile> ListFiles(string remoteDirectory)
        {
            Connect();
            return _sftpClient.ListDirectory(remoteDirectory);
        }

        /// <summary>
        /// 删除远程文件
        /// </summary>
        /// <param name="remoteFilePath">远程文件路径</param>
        /// <returns>删除成功返回 true</returns>
        public bool DeleteFile(string remoteFilePath)
        {
            Connect();

            if (_sftpClient.Exists(remoteFilePath))
            {
                _sftpClient.DeleteFile(remoteFilePath);
                return true;
            }
            return false;
        }

        /// <summary>
        /// 释放资源
        /// </summary>
        public void Dispose()
        {
            Disconnect();
            _sftpClient?.Dispose();
        }
    }
}