Fix Remote Doc/Image Caching in Sample App

Create Remote_DOCS compiler directive to make it easier to debug, now Debug mode only uses local packages assets, and can add compiler directive to test remote doc scenarios and caching while in Debug mode still.
Fixes issue where images wouldn't be pulled from packaged assets in offline mode.

Author: michael-hawker

Microsoft.Toolkit.Uwp.SampleApp/Microsoft.Toolkit.Uwp.SampleApp.csproj

@@ -37,7 +37,7 @@
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x86'">
     <OutputPath>bin\x86\Release\</OutputPath>
-    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP;REMOTE_DOCS</DefineConstants>
     <Optimize>true</Optimize>
     <NoWarn>;2008</NoWarn>
     <DebugType>pdbonly</DebugType>
@@ -63,7 +63,7 @@
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|ARM'">
     <OutputPath>bin\ARM\Release\</OutputPath>
-    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP;REMOTE_DOCS</DefineConstants>
     <Optimize>true</Optimize>
     <NoWarn>;2008</NoWarn>
     <DebugType>pdbonly</DebugType>
@@ -89,7 +89,7 @@
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
     <OutputPath>bin\x64\Release\</OutputPath>
-    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP;REMOTE_DOCS</DefineConstants>
     <Optimize>true</Optimize>
     <NoWarn>;2008</NoWarn>
     <DebugType>pdbonly</DebugType>
@@ -1484,7 +1484,7 @@
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|ARM64'">
     <OutputPath>bin\ARM64\Release\</OutputPath>
-    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP;REMOTE_DOCS</DefineConstants>
     <Optimize>true</Optimize>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <NoWarn>;2008</NoWarn>

Microsoft.Toolkit.Uwp.SampleApp/Models/Sample.cs

@@ -115,7 +115,7 @@ public string CodeUrl
 
             set
             {
-#if DEBUG
+#if !REMOTE_DOCS
                 _codeUrl = value;
 #else
                 var regex = new Regex("^https://github.com/windows-toolkit/WindowsCommunityToolkit/(tree|blob)/(?<branch>.+?)/(?<path>.*)");
@@ -221,12 +221,13 @@ public async Task<string> GetDocumentationAsync()
             if (docMatch.Success)
             {
                 filepath = docMatch.Groups["file"].Value;
-                filename = Path.GetFileName(RemoteDocumentationPath);
+                filename = Path.GetFileName(filepath);
+
                 RemoteDocumentationPath = Path.GetDirectoryName(filepath);
-                LocalDocumentationFilePath = $"ms-appx:///docs/{RemoteDocumentationPath}/";
+                LocalDocumentationFilePath = $"ms-appx:///docs/{filepath}/";
             }
 
-#if !DEBUG // use the docs repo in release mode
+#if REMOTE_DOCS // use the docs repo in release mode
             string modifiedDocumentationUrl = $"{_docsOnlineRoot}live/docs/{filepath}";
 
             // Read from Cache if available.
@@ -285,6 +286,11 @@ public async Task<string> GetDocumentationAsync()
             return _cachedDocumentation;
         }
 
+        public Uri GetOnlineResourcePath(string relativePath)
+        {
+            return new Uri($"{_docsOnlineRoot}live/docs/{RemoteDocumentationPath}/{relativePath}");
+        }
+
         /// <summary>
         /// Gets the image data from a Uri, with Caching.
         /// </summary>
@@ -301,45 +307,61 @@ async Task<Stream> CopyStream(HttpContent source)
             }
 
             IRandomAccessStream imageStream = null;
-            var localPath = $"{uri.Host}/{uri.LocalPath}";
+            var localPath = $"{uri.Host}/{uri.LocalPath}".Replace("//", "/");
+
+            if (localPath.StartsWith(_docsOnlineRoot.Substring(8)))
+            {
+                // If we're looking for docs we should look in our local area first.
+                localPath = localPath.Substring(_docsOnlineRoot.Length - 3); // want to chop "live/" but missing https:// as well.
+            }
 
-            // Cache only in Release
-#if !DEBUG
+            // Try cache only in Release (using remote docs)
+#if REMOTE_DOCS
             try
             {
                 imageStream = await StreamHelper.GetLocalCacheFileStreamAsync(localPath, Windows.Storage.FileAccessMode.Read);
             }
             catch
             {
             }
-#endif
 
             if (imageStream == null)
             {
                 try
                 {
+                    // Our docs don't reference any external images, this should only be for getting latest image from repo.
                     using (var response = await client.GetAsync(uri))
                     {
                         if (response.IsSuccessStatusCode)
                         {
                             var imageCopy = await CopyStream(response.Content);
                             imageStream = imageCopy.AsRandomAccessStream();
 
-                            // Cache only in Release
-#if !DEBUG
                             // Takes a second copy of the image stream, so that is can save the image data to cache.
                             using (var saveStream = await CopyStream(response.Content))
                             {
                                 await SaveImageToCache(localPath, saveStream);
                             }
-#endif
                         }
                     }
                 }
                 catch
                 {
                 }
             }
+#endif
+
+            // If we don't have internet, then try to see if we have a packaged copy
+            if (imageStream == null)
+            {
+                try
+                {
+                    imageStream = await StreamHelper.GetPackagedFileStreamAsync(localPath);
+                }
+                catch
+                {
+                }
+            }
 
             return imageStream;
         }

Microsoft.Toolkit.Uwp.SampleApp/Pages/SampleController.xaml.cs

@@ -453,15 +453,21 @@ private async void DocumentationTextBlock_ImageResolving(object sender, ImageRes
             // Determine if the link is not absolute, meaning it is relative.
             if (!Uri.TryCreate(e.Url, UriKind.Absolute, out Uri url))
             {
-                url = new Uri(CurrentSample.LocalDocumentationFilePath + e.Url);
-            }
+                var imageStream = await CurrentSample.GetImageStream(CurrentSample.GetOnlineResourcePath(e.Url));
 
-            if (url.Scheme == "ms-appx")
+                if (imageStream != null)
+                {
+                    image = new BitmapImage();
+                    await image.SetSourceAsync(imageStream);
+                }
+            }
+            else if (url.Scheme == "ms-appx")
             {
                 image = new BitmapImage(url);
             }
             else
             {
+                // Cache a remote image from the internet.
                 var imageStream = await CurrentSample.GetImageStream(url);
 
                 if (imageStream != null)