Render guild invites in HTML

Closes #649

DiscordChatExporter.Core/Markdown/FormattingNode.cs

@@ -2,4 +2,7 @@
 
 namespace DiscordChatExporter.Core.Markdown;
 
-internal record FormattingNode(FormattingKind Kind, IReadOnlyList<MarkdownNode> Children) : MarkdownNode;
+internal record FormattingNode(
+    FormattingKind Kind,
+    IReadOnlyList<MarkdownNode> Children
+) : MarkdownNode, IContainerNode;

DiscordChatExporter.Core/Markdown/IContainerNode.cs

@@ -0,0 +1,8 @@
+using System.Collections.Generic;
+
+namespace DiscordChatExporter.Core.Markdown;
+
+internal interface IContainerNode
+{
+    IReadOnlyList<MarkdownNode> Children { get; }
+}

DiscordChatExporter.Core/Markdown/LinkNode.cs

@@ -2,9 +2,10 @@
 
 namespace DiscordChatExporter.Core.Markdown;
 
+// Named links can contain child nodes (e.g. [**bold URL**](https://test.com))
 internal record LinkNode(
     string Url,
-    IReadOnlyList<MarkdownNode> Children) : MarkdownNode
+    IReadOnlyList<MarkdownNode> Children) : MarkdownNode, IContainerNode
 {
     public LinkNode(string url)
         : this(url, new[] { new TextNode(url) })

DiscordChatExporter.Core/Markdown/Parsing/MarkdownParser.cs

@@ -385,12 +385,32 @@ internal static partial class MarkdownParser
     private static IReadOnlyList<MarkdownNode> Parse(StringSegment segment) =>
         Parse(segment, AggregateNodeMatcher);
 
+    public static IReadOnlyList<MarkdownNode> Parse(string markdown) =>
+        Parse(new StringSegment(markdown));
+
     private static IReadOnlyList<MarkdownNode> ParseMinimal(StringSegment segment) =>
         Parse(segment, MinimalAggregateNodeMatcher);
 
-    public static IReadOnlyList<MarkdownNode> Parse(string input) =>
-        Parse(new StringSegment(input));
+    public static IReadOnlyList<MarkdownNode> ParseMinimal(string markdown) =>
+        ParseMinimal(new StringSegment(markdown));
 
-    public static IReadOnlyList<MarkdownNode> ParseMinimal(string input) =>
-        ParseMinimal(new StringSegment(input));
+    private static void ExtractLinks(IEnumerable<MarkdownNode> nodes, ICollection<LinkNode> links)
+    {
+        foreach (var node in nodes)
+        {
+            if (node is LinkNode linkNode)
+                links.Add(linkNode);
+
+            if (node is IContainerNode containerNode)
+                ExtractLinks(containerNode.Children, links);
+        }
+    }
+
+    public static IReadOnlyList<LinkNode> ExtractLinks(string markdown)
+    {
+        var links = new List<LinkNode>();
+        ExtractLinks(Parse(markdown), links);
+
+        return links;
+    }
 }