Rename MarkDown -> Markdown to resolve differences for non-Windows machines (#3758)

src/modules/previewpane/MarkdownPreviewHandler/HTMLParsingExtension.cs

@@ -0,0 +1,103 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.IO;
+using Markdig;
+using Markdig.Extensions.Figures;
+using Markdig.Extensions.Tables;
+using Markdig.Renderers;
+using Markdig.Renderers.Html;
+using Markdig.Syntax;
+using Markdig.Syntax.Inlines;
+
+namespace MarkdownPreviewHandler
+{
+    /// <summary>
+    /// Callback if extension blocks external images.
+    /// </summary>
+    public delegate void ImagesBlockedCallBack();
+
+    /// <summary>
+    /// Markdig Extension to process html nodes in markdown AST.
+    /// </summary>
+    public class HTMLParsingExtension : IMarkdownExtension
+    {
+        /// <summary>
+        /// Callback if extension blocks external images.
+        /// </summary>
+        private readonly ImagesBlockedCallBack imagesBlockedCallBack;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="HTMLParsingExtension"/> class.
+        /// </summary>
+        /// <param name="imagesBlockedCallBack">Callback function if image is blocked by extension.</param>
+        /// <param name="baseUrl">Absolute path of markdown file.</param>
+        public HTMLParsingExtension(ImagesBlockedCallBack imagesBlockedCallBack, string baseUrl = "")
+        {
+            this.imagesBlockedCallBack = imagesBlockedCallBack;
+            this.BaseUrl = baseUrl;
+        }
+
+        /// <summary>
+        /// Gets or sets path to directory containing markdown file.
+        /// </summary>
+        public string BaseUrl { get; set; }
+
+        /// <inheritdoc/>
+        public void Setup(MarkdownPipelineBuilder pipeline)
+        {
+            // Make sure we don't have a delegate twice
+            pipeline.DocumentProcessed -= this.PipelineOnDocumentProcessed;
+            pipeline.DocumentProcessed += this.PipelineOnDocumentProcessed;
+        }
+
+        /// <inheritdoc/>
+        public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer)
+        {
+        }
+
+        /// <summary>
+        /// Process nodes in markdown AST.
+        /// </summary>
+        /// <param name="document">Markdown Document.</param>
+        public void PipelineOnDocumentProcessed(MarkdownDocument document)
+        {
+            foreach (var node in document.Descendants())
+            {
+                if (node is Block)
+                {
+                    if (node is Table)
+                    {
+                        node.GetAttributes().AddClass("table table-striped table-bordered");
+                    }
+                    else if (node is QuoteBlock)
+                    {
+                        node.GetAttributes().AddClass("blockquote");
+                    }
+                    else if (node is Figure)
+                    {
+                        node.GetAttributes().AddClass("figure");
+                    }
+                    else if (node is FigureCaption)
+                    {
+                        node.GetAttributes().AddClass("figure-caption");
+                    }
+                }
+                else if (node is Inline)
+                {
+                    if (node is LinkInline link)
+                    {
+                        if (link.IsImage)
+                        {
+                            link.Url = "#";
+                            link.GetAttributes().AddClass("img-fluid");
+                            this.imagesBlockedCallBack();
+                        }
+                    }
+                }
+            }
+        }
+    }
+}