Fix issue #231 Download gifv / pnj with their real file extension

- Tumblr serves gifs as gif or webm and png as png or jpg for performance and bandwidth reasons. They use the "virtual" file extensions gifv and pnj in their urls, in recent days also only the png extension, although a jpg could be returned.
- So instead of saving the downloaded files with these "virtual" extensions we save them with the real extensions now.

src/TumblThree/TumblThree.Applications/Crawler/AbstractTumblrCrawler.cs

@@ -586,11 +586,14 @@ private string BuildFileNameCore(string url, string blogName, DateTime date, int
                 %x  "_{number}" ({number}: 2..n)
                 %y  " ({number})" ({number}: 2..n)
              */
-            string filename = Blog.FilenameTemplate;
-
             url = url.IndexOf('?') > 0 ? url.Substring(0, url.IndexOf('?')) : url;
 
-            filename += Path.GetExtension(FileName(url));
+            string extension = Path.GetExtension(FileName(url));
+            if (extension.ToLower() == ".gifv")
+                extension = ".gif";
+            else if (extension.ToLower() == ".pnj")
+                extension += ".png";
+            string filename = Blog.FilenameTemplate + extension;
             if (ContainsCI(filename, "%f")) filename = ReplaceCI(filename, "%f", Path.GetFileNameWithoutExtension(FileName(url)));
             if (ContainsCI(filename, "%d")) filename = ReplaceCI(filename, "%d", date.ToString("yyyyMMdd"));
             if (ContainsCI(filename, "%e")) filename = ReplaceCI(filename, "%e", date.ToString("yyyyMMddHHmmss"));

src/TumblThree/TumblThree.Applications/Downloader/AbstractDownloader.cs

@@ -289,7 +289,8 @@ protected virtual async Task<bool> DownloadBinaryPostAsync(TumblrPost downloadIt
                 string fileName = FileName(downloadItem);
                 UpdateProgressQueueInformation(Resources.ProgressSkipFile, fileName);
             }
-            else if (!shellService.Settings.LoadAllDatabases && blog.CheckDirectoryForFiles && blog.CheckIfBlogShouldCheckDirectory(FileName(downloadItem), FileNameNew(downloadItem)))
+            else if (!shellService.Settings.LoadAllDatabases && blog.CheckDirectoryForFiles && (blog.CheckIfBlogShouldCheckDirectory(FileNameUrl(downloadItem), FileNameNew(downloadItem))
+                || blog.CheckIfBlogShouldCheckDirectory(FileName(downloadItem), FileNameNew(downloadItem))))
             {
                 string fileName = AddFileToDb(downloadItem);
                 UpdateProgressQueueInformation(Resources.ProgressSkipFile, fileName);
@@ -346,7 +347,7 @@ protected string AddFileToDb(TumblrPost downloadItem)
         {
             if (AppendTemplate == null)
             {
-                files.AddFileToDb(FileName(downloadItem), downloadItem.Filename);
+                files.AddFileToDb(FileNameUrl(downloadItem), downloadItem.Filename);
                 return downloadItem.Filename;
             }
             return files.AddFileToDb(FileName(downloadItem), downloadItem.Filename, AppendTemplate);
@@ -359,7 +360,7 @@ public bool CheckIfFileExistsInDB(string filenameUrl)
 
         protected bool CheckIfFileExistsInDB(TumblrPost downloadItem)
         {
-            string filename = FileName(downloadItem);
+            string filename = FileNameUrl(downloadItem);
             if (shellService.Settings.LoadAllDatabases)
             {
                 return managerService.CheckIfFileExistsInDB(filename, shellService.Settings.LoadArchive);
@@ -410,11 +411,21 @@ protected static string Url(TumblrPost downloadItem)
             return downloadItem.Url;
         }
 
-        protected virtual string FileName(TumblrPost downloadItem)
+        protected virtual string FileNameUrl(TumblrPost downloadItem)
         {
             return downloadItem.Url.Split('/').Last();
         }
 
+        protected virtual string FileName(TumblrPost downloadItem)
+        {
+            string filename = downloadItem.Url.Split('/').Last();
+            if (Path.GetExtension(filename).ToLower() == ".gifv")
+                filename = Path.GetFileNameWithoutExtension(filename) + ".gif";
+            if (Path.GetExtension(filename).ToLower() == ".pnj")
+                filename += ".png";
+            return filename;
+        }
+
         protected static string FileNameNew(TumblrPost downloadItem)
         {
             return downloadItem.Filename;

src/TumblThree/TumblThree.Applications/Downloader/FileDownloader.cs

@@ -42,14 +42,23 @@ public async Task<bool> DownloadFileWithResumeAsync(string url, string destinati
             {
                 var fileInfo = new FileInfo(destinationPath);
                 totalBytesReceived = fileInfo.Length;
-                if (totalBytesReceived >= await CheckDownloadSizeAsync(url).TimeoutAfter(settings.TimeOut)) return true;
+                var result = await CheckDownloadSizeAsync(url, destinationPath).TimeoutAfter(settings.TimeOut);
+                if (totalBytesReceived >= result.contentLength) return true;
+                if (destinationPath != result.destinationPath)
+                {
+                    File.Delete(destinationPath);
+                    destinationPath = result.destinationPath;
+                    fileInfo = new FileInfo(destinationPath);
+                    totalBytesReceived = fileInfo.Length;
+                }
             }
 
             if (ct.IsCancellationRequested) return false;
 
             var fileMode = totalBytesReceived > 0 ? FileMode.Append : FileMode.Create;
 
-            using (var fileStream = new FileStream(destinationPath, fileMode, FileAccess.Write, FileShare.Read, bufferSize, true))
+            var fileStream = new FileStream(destinationPath, fileMode, FileAccess.Write, FileShare.Read, bufferSize, true);
+            try
             {
                 while (true)
                 {
@@ -69,6 +78,15 @@ public async Task<bool> DownloadFileWithResumeAsync(string url, string destinati
                         bool isChunked = false;
                         using (var response = await request.GetResponseAsync().TimeoutAfter(settings.TimeOut))
                         {
+                            if (url.Contains("tumblr.com") && (url.Contains(".png") || url.Contains(".pnj"))
+                                && Path.GetExtension(destinationPath).ToLower() == ".png" && (response.Headers["Content-Type"]?.Contains("jpeg") ?? false))
+                            {
+                                fileStream.Dispose();
+                                File.Delete(destinationPath);
+                                destinationPath = Path.Combine(Path.GetDirectoryName(destinationPath), Path.GetFileNameWithoutExtension(destinationPath) + ".jpg");
+                                fileStream = new FileStream(destinationPath, FileMode.Create, FileAccess.Write, FileShare.Read, bufferSize, true);
+                            }
+
                             isChunked = response.Headers.ToString().Contains("chunked");
                             totalBytesToReceive = totalBytesReceived + (response.ContentLength == -1 ? 0 : response.ContentLength);
 
@@ -124,9 +142,13 @@ public async Task<bool> DownloadFileWithResumeAsync(string url, string destinati
 
                 return true;
             }
+            finally
+            {
+                fileStream?.Dispose();
+            }
         }
 
-        private async Task<long> CheckDownloadSizeAsync(string url)
+        private async Task<(long contentLength, string destinationPath)> CheckDownloadSizeAsync(string url, string destinationPath)
         {
             var requestRegistration = new CancellationTokenRegistration();
             try
@@ -136,7 +158,12 @@ private async Task<long> CheckDownloadSizeAsync(string url)
 
                 using (var response = await request.GetResponseAsync())
                 {
-                    return response.ContentLength;
+                    if (url.Contains("tumblr.com") && (url.Contains(".png") || url.Contains(".pnj"))
+                        && Path.GetExtension(destinationPath).ToLower() == ".png" && (response.Headers["Content-Type"]?.Contains("jpeg") ?? false))
+                    {
+                        destinationPath = Path.Combine(Path.GetDirectoryName(destinationPath), Path.GetFileNameWithoutExtension(destinationPath) + ".jpg");
+                    }
+                    return (response.ContentLength, destinationPath);
                 }
             }
             finally