Improved raw size handling

- Allows to specify which hosts to check for a _raw image version. The
failback now iterates through all sizes of the original found host until
a valid size was found that can be downloaded.
- The tumblr hosts can be set in the settings.json in the  TumblrHosts
variable. The first entry is check first, if there was no _raw image
found, the next entry is checked, until the list is exhausted. Then the
_1280 size of the original host is tried, the _500, _400 until the
request was successfully.

src/TumblThree/SharedAssemblyInfo.cs

@@ -12,5 +12,5 @@
 
 [assembly: ComVisible(false)]
 [assembly: NeutralResourcesLanguage("en-US", UltimateResourceFallbackLocation.MainAssembly)]
-[assembly: AssemblyVersion("1.0.6.8")]
-[assembly: AssemblyFileVersion("1.0.6.8")]
+[assembly: AssemblyVersion("1.0.6.9")]
+[assembly: AssemblyFileVersion("1.0.6.9")]

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

@@ -394,8 +394,10 @@ private async Task DownloadPhotoAsync(IProgress<DataModels.DownloadProgress> pro
             TumblrPost downloadItem, CancellationToken ct)
         {
             string blogDownloadLocation = blog.DownloadLocation();
-            string fileName = FileName(downloadItem);
             string url = Url(downloadItem);
+            var fileDownloader = new FileDownloader();
+            url = await fileDownloader.TestImageRawUrl(url, shellService.Settings);
+            string fileName = url.Split('/').Last();
             string fileLocation = FileLocation(blogDownloadLocation, fileName);
             string fileLocationUrlList = FileLocationLocalized(blogDownloadLocation, Resources.FileNamePhotos);
             DateTime postDate = PostDate(downloadItem);

src/TumblThree/TumblThree.Applications/FileDownloader.cs

@@ -166,25 +166,65 @@ public async Task<bool> DownloadFileWithResumeAsync(string url, string destinati
                         }
                         else
                         {
-                            // TODO: Ugly hack: Many "_raw" requests seem to fail with '403 -- access denied' whereas usually
-                            // the file just contained a lower resolution if it didn't had the specified size.
-                            // We just replace the "_raw" with "_1280" and try again since "_1280" images are around for longer.
-                            // Else, we finally give up.
-                            if (url.Contains("_raw"))
-                            {
-                                url = url.Replace("_raw", "_1280");
-                            }
-                            else
-                            {
-                                throw;
-                            }
+                            throw;
                         }
                     }
                 }
                 return true;
             }
         }
 
+        public async Task<string> TestImageRawUrl(string url, AppSettings settings)
+        {
+            if (settings.ImageSize == "raw")
+            {
+                return await TestRawUrl(url, settings);
+            }
+            return url;
+        }
+
+        public async Task<string> TestRawUrl(string url, AppSettings settings)
+        {
+            if (!url.Contains("_raw"))
+                return url;
+            string path = new Uri(url).LocalPath.TrimStart('/');
+
+            foreach (string host in settings.TumblrHosts)
+            {
+                string rawUrl = "https://" + host + "/" + path;
+                if (await UrlExists(rawUrl, settings))
+                    return rawUrl;
+            }
+
+            foreach (string size in settings.ImageSizes)
+            {
+                string rawUrl = url.Replace(settings.ImageSize, size);
+                if (await UrlExists(rawUrl, settings))
+                    return rawUrl;
+            }
+
+            return url;
+        }
+
+        private async Task<bool> UrlExists(string url, AppSettings settings)
+        {
+            HttpWebRequest request = CreateWebReqeust(url, settings);
+            request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
+            request.Method = "HEAD";
+
+            try
+            {
+                using (var response = (HttpWebResponse)await request.GetResponseAsync())
+                {
+                    return response.StatusCode == HttpStatusCode.OK;
+                }
+            }
+            catch
+            {
+                return false;
+            }
+        }
+
         public static async Task<bool> SaveStreamToDisk(Stream input, string destinationFileName, CancellationToken ct)
         {
             using (var stream = new FileStream(destinationFileName, FileMode.OpenOrCreate, FileAccess.Write))

src/TumblThree/TumblThree.Applications/Properties/AppSettings.cs

@@ -27,6 +27,12 @@ public sealed class AppSettings : IExtensibleDataObject
                 "1080", "480"
             };
 
+        private static readonly string[] tumblrHosts =
+            new string[]
+            {
+                        "media.tumblr.com", "68.media.tumblr.com", "66.media.tumblr.com"
+            };
+
         public AppSettings()
         {
             Initialize();
@@ -230,6 +236,11 @@ public ObservableCollection<string> BlogTypes
             get { return new ObservableCollection<string>(blogTypes); }
         }
 
+        public ObservableCollection<string> TumblrHosts
+        {
+            get { return new ObservableCollection<string>(tumblrHosts); }
+        }
+
         ExtensionDataObject IExtensibleDataObject.ExtensionData { get; set; }
 
         private void Initialize()