using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;

namespace Falit.Run
{
    /// <summary>
    /// Web下载文件(单线程下载,速度慢)
    /// </summary>
    public static class WebFileDown
    {
        /// 下载文件方法
        /// 文件保存路径和文件名
        /// 返回服务器文件名
        public static bool DeownloadFile(string sourceFile, string desFile, int dataIndex,
                    System.Windows.Forms.ProgressBar prog, System.Windows.Forms.Label label1, System.Windows.Forms.DataGridView dataGridView)
        {
            float percent = 0;
            long sPosition = 0;
            FileStream FStream = null;
            Stream myStream = null;
            string fileName = sourceFile.Substring(sourceFile.LastIndexOf(@"/") + 1);
            try
            {
                if (File.Exists(desFile))
                {
                    FStream = File.OpenWrite(desFile);
                    sPosition = FStream.Length;
                    long serverFileLength = GetHttpLength(sourceFile);
                    if (sPosition == serverFileLength)
                    {
                        dataGridView.Rows[dataIndex].DefaultCellStyle.ForeColor = Color.Red;
                        dataGridView.Rows[dataIndex].Cells["进度"].Value = "100%";
                        return true;
                    }
                    FStream.Seek(sPosition, SeekOrigin.Current);
                }
                else
                {
                    //文件不保存创建一个文件
                    FStream = new FileStream(desFile, FileMode.Create);
                    sPosition = 0;
                }
                HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(sourceFile);
                System.Net.HttpWebResponse myrp = (System.Net.HttpWebResponse)myRequest.GetResponse();
                if (sPosition > 0)
                {
                    myRequest.AddRange(sPosition);             
                }
                long totalBytes = myrp.ContentLength;
                myStream = myRequest.GetResponse().GetResponseStream();
                byte[] btContent = new byte[512];
                int intSize = 0;
                long totalDownloadedByte = 0;
                intSize = myStream.Read(btContent, 0, 512);
                while (intSize > 0)
                {
                    FStream.Write(btContent, 0, intSize);
                    intSize = myStream.Read(btContent, 0, 512);
                    totalDownloadedByte = intSize + totalDownloadedByte;
                    dataGridView.Rows[dataIndex].Cells["进度"].Value = (float)totalDownloadedByte / (float)totalBytes * 100 + "%";
                    percent = (float)totalDownloadedByte / (float)totalBytes * 100;
                    label1.Text = percent.ToString("0.00") + "%";
                    //System.Windows.Forms.Application.DoEvents();
                }
                return true;
            }
            catch (Exception ex)
            {
                return true;
            }
            finally
            {
                if (myStream != null)
                {
                    myStream.Close();
                    myStream.Dispose();
                }
                if (FStream != null)
                {
                    FStream.Close();
                    FStream.Dispose();
                }
            }
        }

        static long GetHttpLength(string url)
        {
            long length = 0;
            try
            {
                var req = (HttpWebRequest)WebRequest.CreateDefault(new Uri(url));
                req.Method = "HEAD";
                req.Timeout = 5000;
                var res = (HttpWebResponse)req.GetResponse();
                if (res.StatusCode == HttpStatusCode.OK)
                {
                    length = res.ContentLength;
                }
                res.Close();
                return length;
            }
            catch (WebException wex)
            {
                throw wex;
            }
        }
    }
}