using System;
using System.Globalization;
using System.IO;
using System.Web;

namespace VHelms.Web.Filemanager
{
    public class HttpDownload : IHttpHandler
    {
        public void ProcessRequest(HttpContext context)
        {
            try
            {
                if (!string.IsNullOrEmpty(context.Request["File"]))
                {
                    string fileName = context.Request["File"];
                    DownloadFile(fileName, context);
                }
                else
                {
                    throw new ArgumentException("The File-ID is not available anymore. Please reload the page and try again.");
                }
            }
            catch (Exception ex)
            {
                context.Response.ContentType = "text/plain";
                context.Response.Write(string.Format("Error:\r\n{0}", ex));
            }
        }

        public bool IsReusable
        {
            get { return true; }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="filepath"></param>
        /// <param name="context"></param>
        private static void DownloadFile(string filepath, HttpContext context)
        {
            HttpResponse response = context.Response;
            // Buffer to read 10K bytes in chunk:
            var buffer = new Byte[10000];
            // Identify the file name.
            string filename = Path.GetFileName(filepath);
            string appPath = context.Request.PhysicalApplicationPath;
            string completeFilePath = appPath + filename;
            FileStream fileStream = null;
            try
            {
                // Open the file.
                fileStream = new FileStream(completeFilePath, FileMode.Open, FileAccess.Read, FileShare.Read);

                // Total bytes to read:
                long dataToRead = fileStream.Length;
                response.ContentType = "application/octet-stream";
                response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
                response.AddHeader("Content-Length", fileStream.Length.ToString());

                // Read the bytes.
                while (dataToRead > 0)
                {
                    // Verify that the client is connected.
                    if (response.IsClientConnected)
                    {
                        // Read the data in buffer.
                        int length = fileStream.Read(buffer, 0, 10000);

                        // Write the data to the current output stream.
                        response.OutputStream.Write(buffer, 0, length);

                        // Flush the data to the HTML output.
                        response.Flush();

                        buffer = new Byte[10000];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        //prevent infinite loop if user disconnects
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                // Trap the error, if any.
                response.ContentType = "text/plain";
                response.Write(string.Format("Error:\r\n{0}", ex));
                //Response.Write("Error : " + ex.Message);
            }
            finally
            {
                if (fileStream != null)
                {
                    //Close the file.
                    fileStream.Close();
                }

                // delete tmp file, if the file is stored in the temp directory
                if (filepath.StartsWith(Path.GetTempPath()))
                {
                    // delete temp file
                    var tempFile = new FileInfo(filepath);
                    tempFile.Delete();
                }
            }
        }
    }
}