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WebDownloader.cs
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WebDownloader.cs
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//--------------------------------------------------------------------------
// <summary>
//
// </summary>
// <copyright file="WebDownloader.cs" company="Chuck Hill">
// Copyright (c) 2020 Chuck Hill.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public License
// as published by the Free Software Foundation; either version 2.1
// of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// The GNU Lesser General Public License can be viewed at
// http://www.opensource.org/licenses/lgpl-license.php. If
// you unfamiliar with this license or have questions about
// it, here is an http://www.gnu.org/licenses/gpl-faq.html.
//
// All code and executables are provided "as is" with no warranty
// either express or implied. The author accepts no liability for
// any damage or loss of business that this product may cause.
// </copyright>
// <repository>https://github.com/ChuckHill2/DownloadiingTest</repository>
// <author>Chuck Hill</author>
//--------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Win32;
namespace DownloadingTest
{
/// <summary>
/// Data downloader. This is not thread-safe. Use once and dispose.
/// Exception: NotSupportedException:WebClient does not support concurrent I/O operations.
/// </summary>
public class WebDownloader : IDisposable
{
//private const string UserAgent = @"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:96.0) Gecko/20100101 Firefox/96.0";
private const string UserAgent = @"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.88 Safari/537.36";
private MyWebClient Client;
/// <summary>
/// Enable logging by assigning a logging writer function. This may be a performance hit. Setting it back to null effectively disables logging.
/// </summary>
public Action<Severity, string> LogWriter { get; set; }
private void LogWrite(Severity severity, string fmt, params object[] args)
{
if (LogWriter == null) return;
if (args != null && args.Length > 0)
fmt = string.Format(fmt, args);
LogWriter(severity, fmt);
}
public WebDownloader()
{
Client = new MyWebClient();
}
public void Dispose()
{
if (Client == null) return;
Client.Dispose();
Client = null;
}
public async Task<bool> DownloadAsync(Job job)
{
bool success = false;
for (int retry = 0; retry <= 0; retry++) //maybe retry for redirects.
{
success = false;
SetJobException(job, null);
try
{
await DownloadThrow(job);
return true;
}
catch (Exception ex)
{
SetJobException(job, ex);
IncrementJobFailureCount(job);
#region Handle Disk-full error
const int ERROR_HANDLE_DISK_FULL = 0x27;
const int ERROR_DISK_FULL = 0x70;
int hResult = ex.HResult & 0xFFFF;
if (hResult == ERROR_HANDLE_DISK_FULL || hResult == ERROR_DISK_FULL) //There is not enough space on the disk.
{
LogWrite(Severity.Error, "<<<<<<< Disk Full >>>>>>>\r\n{0}", ex);
throw ex; //very bad
}
#endregion Handle Disk-full error
if (job.Filename != null) FileEx.Delete(job.Filename);
HttpStatusCode httpStatus = 0;
WebExceptionStatus webStatus = WebExceptionStatus.Success;
if (ex is WebException)
{
WebException we = (WebException)ex;
HttpWebResponse response = we.Response as System.Net.HttpWebResponse;
httpStatus = response?.StatusCode ?? 0;
webStatus = we.Status;
}
if (webStatus == WebExceptionStatus.TrustFailure)
{
if (job.FailureCount <= 1)
{
var newurl = job.Url;
if (newurl.StartsWith("https://")) newurl = newurl.Replace("https://", "http://");
else if (newurl.StartsWith("http://")) newurl = newurl.Replace("http://", "https://");
LogWrite(Severity.Warning, "{0}{1}: Retry {2} ==> {3}", JobNumberMsg(job), webStatus, newurl, job.Url);
SetJobUrl(job, newurl);
retry--;
continue;
}
}
//Occurs when the web server is flooded with our requests due to multi-threading.
if (webStatus == WebExceptionStatus.RequestCanceled
|| webStatus == WebExceptionStatus.Timeout
|| webStatus == WebExceptionStatus.UnknownError)
{
if (job.FailureCount <= 1)
{
LogWrite(Severity.Warning, "{0}{1}: Retry {2}", JobNumberMsg(job), DownloadStatus(webStatus, httpStatus), Url2FilenameMsg(job));
Thread.Sleep(2000);
retry--;
continue;
}
}
#if DEBUG
LogWrite(Severity.Error, "{0}{1} {2}\r\n{3}", JobNumberMsg(job), DownloadStatus(webStatus, httpStatus), ex, Url2FilenameMsg(job));
#else
LogWrite(Severity.Error, "{0}{1}{2}:{3} : {4}", JobNumberMsg(job), DownloadStatus(webStatus, httpStatus), ex.GetType().Name, ex.Message, Url2FilenameMsg(job));
#endif
}
}
return success;
}
private async Task DownloadThrow(Job job)
{
Stream stream = null;
Client.Headers[HttpRequestHeader.UserAgent] = UserAgent;
if (!string.IsNullOrEmpty(job.Referer)) Client.Headers[HttpRequestHeader.Referer] = job.Referer;
if (!string.IsNullOrEmpty(job.Cookie)) Client.Headers[HttpRequestHeader.Cookie] = job.Cookie;
Client.Headers[HttpRequestHeader.AcceptLanguage] = "en-US,en;q=0.5"; //always set language to english so our web scraper only has to deal with only a single language.
job.Filename = FileEx.GetUniqueFilename(job.Filename); //creates empty file as placeholder
if (job.Filename != null)
await Client.DownloadFileTaskAsync(job.Url, job.Filename); //This will throw an exception if the url cannot be downloaded.
else
stream = await Client.OpenReadTaskAsync(job.Url);
SetJobUrl(job, Client.ResponseUrl??job.Url); //update url to what the Web server thinks it is.
string cookie = Client.ResponseHeaders[HttpResponseHeader.SetCookie];
if (!string.IsNullOrEmpty(cookie)) job.Cookie = cookie;
SetJobLastModified(job,
!DateTime.TryParse(Client.ResponseHeaders[HttpResponseHeader.LastModified] ?? string.Empty, out var lastModified) ?
!DateTime.TryParse(Client.ResponseHeaders[HttpResponseHeader.Date] ?? string.Empty, out lastModified) ?
DateTime.Now : lastModified : lastModified);
SetJobMimeType(job, GetMimeType(Client, out var charset));
int contentLength = int.TryParse(Client.ResponseHeaders[HttpResponseHeader.ContentLength], out var __contentLength) ? __contentLength : 0;
if (job.Filename == null)
{
if (charset == null) //string field cannot have binary data
{
if (contentLength==0 || contentLength > 1024 * 1024) //Any larger and we may run out of memory!
job.Body = $"{job.MimeType ?? "UNKNOWN"} binary data in excess of 1Mb is not stored in this object. Try again with a provided file destination.";
else
{
var ms = new MemoryStream(contentLength);
await stream.CopyToAsync(ms);
ms.Position = 0;
job.Body = System.Convert.ToBase64String(ms.ToArray(), Base64FormattingOptions.InsertLineBreaks);
stream.Dispose();
ms.Dispose();
//use: var bytes = Convert.FromBase64String(job.Body); to decode.
}
}
else
{
using (StreamReader reader = new StreamReader(stream, Encoding.GetEncoding(charset)))
{
job.Body = await reader.ReadToEndAsync();
}
}
}
else
{
if (!FileEx.Exists(job.Filename)) throw new FileNotFoundException(""); //should never occur due to GetUniqueFilename()
if (FileEx.Length(job.Filename) < 8) { FileEx.Delete(job.Filename); throw new FileNotFoundException("No Data."); }
//Adjust extension to reflect true filetype, BUT make sure that new filename does not exist.
var oldExt = Path.GetExtension(job.Filename);
var newExt = FileEx.GetDefaultExtension(job.MimeType, oldExt);
if (!oldExt.Equals(newExt, StringComparison.OrdinalIgnoreCase))
{
var newfilename = Path.ChangeExtension(job.Filename, newExt);
newfilename = FileEx.GetUniqueFilename(newfilename); //creates empty file as placeholder
FileEx.Delete(newfilename); //delete the placeholder. Move will throw exception if it already exists
FileEx.Move(job.Filename, newfilename);
job.Filename = newfilename; //return new filename to caller.
}
FileEx.SetFileDateTime(job.Filename, job.LastModified);
}
}
private static string GetMimeType(WebClient client, out string charset)
{
charset = null;
var contentType = client.ResponseHeaders[HttpResponseHeader.ContentType]; //"text/html; charset=UTF-8"
if (string.IsNullOrEmpty(contentType)) return null;
var items = contentType.Split(new char[] { ';', ' ', '=' }, StringSplitOptions.RemoveEmptyEntries);
if (items.Length > 2 && items[1].Equals("charset", StringComparison.OrdinalIgnoreCase)) charset = items[2];
return items[0];
}
#region Private Job Setters
// Only *We* are allowed to set these Job values.
//private static readonly MethodInfo jobRetry = typeof(Job).GetProperty("FailureCount").GetSetMethod(true);
private static void IncrementJobFailureCount(Job job) => job.FailureCount++; // jobRetry.Invoke(job, new object[] { job.FailureCount + 1 });
//private static readonly MethodInfo jobUrl = typeof(Job).GetProperty("Url").GetSetMethod(true);
private static void SetJobUrl(Job job, string url) => job.Url = url; // jobUrl.Invoke(job, new object[] { url });
//private static readonly MethodInfo jobMimeType = typeof(Job).GetProperty("MimeType").GetSetMethod(true);
private static void SetJobMimeType(Job job, string mimetype) => job.MimeType = mimetype; // jobMimeType.Invoke(job, new object[] { mimetype });
//private static readonly MethodInfo jobLastModified = typeof(Job).GetProperty("LastModified").GetSetMethod(true);
private static void SetJobLastModified(Job job, DateTime lastModified) => job.LastModified = lastModified; // jobLastModified.Invoke(job, new object[] { lastModified });
//private static readonly MethodInfo jobException = typeof(Job).GetProperty("Exception").GetSetMethod(true);
private static void SetJobException(Job job, Exception exception) => job.Exception = exception; // jobException.Invoke(job, new object[] { exception });
#endregion
#region Log.Write message formatted fragments
private string JobNumberMsg(Job job)
{
if (LogWriter == null) return string.Empty;
return job.JobNumber < 0 ? "" : job.JobNumber.ToString("0000 "); // "0012 " or ""
}
private string Url2FilenameMsg(Job job)
{
if (LogWriter == null) return string.Empty;
return job.Url + (job.Filename == null ? "" : " ==> " + Truncate(job.Filename)); // " ==> ...ster\mydir\myfile.htm" or ""
}
private string Truncate(string s)
{
if (LogWriter == null) return string.Empty;
const int maxLen = 35; //does not include ellipsis prefix.
if (string.IsNullOrEmpty(s)) return s;
if (s.Length <= maxLen) return s;
return "\x2026" + s.Substring(s.Length - maxLen, maxLen);
}
private string DownloadStatus(WebExceptionStatus webStatus, HttpStatusCode httpStatus)
{
if (LogWriter == null) return string.Empty;
var sb = new StringBuilder();
if (webStatus != 0) sb.Append(webStatus);
if (httpStatus != 0)
{
if (sb.Length > 0) sb.Append("/");
var desc = (int)httpStatus == 308 ? "PermenentRedirect" : httpStatus.ToString();
sb.Append($"{desc}({(int)httpStatus})");
}
return sb.ToString();
}
#endregion
private class MyWebClient : WebClient
{
public WebRequest Request { get; private set; }
public WebResponse Response { get; private set; }
public string ResponseUrl => this.Response?.ResponseUri?.AbsoluteUri;
public CookieContainer CookieManager { get; } = new CookieContainer();
protected override WebResponse GetWebResponse(WebRequest request, IAsyncResult result)
{
Request = request;
Response = base.GetWebResponse(request, result);
return Response;
}
protected override WebResponse GetWebResponse(WebRequest request) //used internally
{
Request = request;
Response = base.GetWebResponse(request);
return Response;
}
protected override WebRequest GetWebRequest(Uri address) //used internally
{
Request = base.GetWebRequest(address);
HttpWebRequest request = Request as HttpWebRequest; //there are others: e.g. FtpWebRequest (ftp://) and FileWebRequest (file://).
if (request != null) //for http and https only
{
//request.SupportsCookieContainer = true; not settable but always true
if (request.CookieContainer == null) request.CookieContainer = CookieManager;
request.AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip; //Allow this API to decompress http output.
request.AllowAutoRedirect = true; //always true
}
return Request;
}
}
}
}