using System;
using System.IO;
using System.Net;

namespace Y.Utils.NetworkUtils
{
    /// <summary>
    /// FTP 帮助类
    /// </summary>
    public class FtpHelper
    {
        private string ftpHostIP { get; set; }
        private string username { get; set; }
        private string password { get; set; }
        private string ftpURI { get { return $@"ftp://{ftpHostIP}/"; } }
        public FtpHelper(string ftpHostIP, string username, string password)
        {
            this.ftpHostIP = ftpHostIP;
            this.username = username;
            this.password = password;
        }
        private FtpWebRequest GetRequest(string URI)
        {
            //根据服务器信息FtpWebRequest创建类的对象
            FtpWebRequest result = (FtpWebRequest)WebRequest.Create(URI);
            result.Credentials = new NetworkCredential(username, password);
            result.KeepAlive = false;
            result.UsePassive = false;
            result.UseBinary = true;
            return result;
        }
        public bool DownloadFile(string ftpFilePath, string saveDir)
        {
            string filename = ftpFilePath.Substring(ftpFilePath.LastIndexOf("\\") + 1);
            string tmpname = Guid.NewGuid().ToString();
            string uri = Path.Combine(ftpURI, ftpFilePath);
            if (!Directory.Exists(saveDir)) Directory.CreateDirectory(saveDir);
            FtpWebRequest ftp = GetRequest(uri);
            ftp.Method = WebRequestMethods.Ftp.DownloadFile;
            using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
            {
                using (Stream responseStream = response.GetResponseStream())
                {
                    using (FileStream fs = new FileStream(Path.Combine(saveDir, filename), FileMode.CreateNew))
                    {
                        byte[] buffer = new byte[2048];
                        int read = 0;
                        do
                        {
                            read = responseStream.Read(buffer, 0, buffer.Length);
                            fs.Write(buffer, 0, read);
                        } while (!(read == 0));
                        fs.Flush();
                    }
                }
            }
            return false;
        }
    }
}