Allow link nodes to have markdown children instead of just text

Closes #640

DiscordChatExporter.Core/Exporting/Writers/MarkdownVisitors/HtmlMarkdownVisitor.cs

@@ -30,22 +30,22 @@ namespace DiscordChatExporter.Core.Exporting.Writers.MarkdownVisitors
             return base.VisitText(text);
         }
 
-        protected override MarkdownNode VisitFormatted(FormattedNode formatted)
+        protected override MarkdownNode VisitFormatting(FormattingNode formatting)
         {
-            var (tagOpen, tagClose) = formatted.Formatting switch
+            var (tagOpen, tagClose) = formatting.Kind switch
             {
-                TextFormatting.Bold => ("<strong>", "</strong>"),
-                TextFormatting.Italic => ("<em>", "</em>"),
-                TextFormatting.Underline => ("<u>", "</u>"),
-                TextFormatting.Strikethrough => ("<s>", "</s>"),
-                TextFormatting.Spoiler => (
+                FormattingKind.Bold => ("<strong>", "</strong>"),
+                FormattingKind.Italic => ("<em>", "</em>"),
+                FormattingKind.Underline => ("<u>", "</u>"),
+                FormattingKind.Strikethrough => ("<s>", "</s>"),
+                FormattingKind.Spoiler => (
                     "<span class=\"spoiler-text spoiler-text--hidden\" onclick=\"showSpoiler(event, this)\">", "</span>"),
-                TextFormatting.Quote => ("<div class=\"quote\">", "</div>"),
-                _ => throw new ArgumentOutOfRangeException(nameof(formatted.Formatting))
+                FormattingKind.Quote => ("<div class=\"quote\">", "</div>"),
+                _ => throw new ArgumentOutOfRangeException(nameof(formatting.Kind))
             };
 
             _buffer.Append(tagOpen);
-            var result = base.VisitFormatted(formatted);
+            var result = base.VisitFormatting(formatting);
             _buffer.Append(tagClose);
 
             return result;
@@ -77,25 +77,22 @@ namespace DiscordChatExporter.Core.Exporting.Writers.MarkdownVisitors
 
         protected override MarkdownNode VisitLink(LinkNode link)
         {
-            // Extract message ID if the link points to a Discord message
-            var linkedMessageId = Regex.Match(link.Url, "^https?://(?:discord|discordapp).com/channels/.*?/(\\d+)/?$").Groups[1].Value;
+            // Try to extract message ID if the link refers to a Discord message
+            var linkedMessageId = Regex.Match(
+                link.Url,
+                "^https?://(?:discord|discordapp).com/channels/.*?/(\\d+)/?$"
+            ).Groups[1].Value;
 
-            if (!string.IsNullOrWhiteSpace(linkedMessageId))
-            {
-                _buffer
-                    .Append($"<a href=\"{Uri.EscapeUriString(link.Url)}\" onclick=\"scrollToMessage(event, '{linkedMessageId}')\">")
-                    .Append(HtmlEncode(link.Title))
-                    .Append("</a>");
-            }
-            else
-            {
-                _buffer
-                    .Append($"<a href=\"{Uri.EscapeUriString(link.Url)}\">")
-                    .Append(HtmlEncode(link.Title))
-                    .Append("</a>");
-            }
+            _buffer.Append(
+                !string.IsNullOrWhiteSpace(linkedMessageId)
+                    ? $"<a href=\"{Uri.EscapeUriString(link.Url)}\" onclick=\"scrollToMessage(event, '{linkedMessageId}')\">"
+                    : $"<a href=\"{Uri.EscapeUriString(link.Url)}\">"
+            );
 
-            return base.VisitLink(link);
+            var result = base.VisitLink(link);
+            _buffer.Append("</a>");
+
+            return result;
         }
 
         protected override MarkdownNode VisitEmoji(EmojiNode emoji)

DiscordChatExporter.Core/Markdown/FormattedNode.cs

@@ -1,21 +0,0 @@
-using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
-
-namespace DiscordChatExporter.Core.Markdown
-{
-    internal class FormattedNode : MarkdownNode
-    {
-        public TextFormatting Formatting { get; }
-
-        public IReadOnlyList<MarkdownNode> Children { get; }
-
-        public FormattedNode(TextFormatting formatting, IReadOnlyList<MarkdownNode> children)
-        {
-            Formatting = formatting;
-            Children = children;
-        }
-
-        [ExcludeFromCodeCoverage]
-        public override string ToString() => $"<{Formatting}> (+{Children.Count})";
-    }
-}

DiscordChatExporter.Core/Markdown/FormattingKind.cs

@@ -1,6 +1,6 @@
 namespace DiscordChatExporter.Core.Markdown
 {
-    internal enum TextFormatting
+    internal enum FormattingKind
     {
         Bold,
         Italic,

DiscordChatExporter.Core/Markdown/FormattingNode.cs

@@ -0,0 +1,29 @@
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+
+namespace DiscordChatExporter.Core.Markdown
+{
+    internal class FormattingNode : MarkdownNode
+    {
+        public FormattingKind Kind { get; }
+
+        public IReadOnlyList<MarkdownNode> Children { get; }
+
+        public FormattingNode(FormattingKind kind, IReadOnlyList<MarkdownNode> children)
+        {
+            Kind = kind;
+            Children = children;
+        }
+
+        [ExcludeFromCodeCoverage]
+        public override string ToString()
+        {
+            var childrenFormatted = Children.Count == 1
+                ? Children.Single().ToString()
+                : "+" + Children.Count;
+
+            return $"<{Kind}> ({childrenFormatted})";
+        }
+    }
+}

DiscordChatExporter.Core/Markdown/LinkNode.cs

@@ -1,4 +1,6 @@
-using System.Diagnostics.CodeAnalysis;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 
 namespace DiscordChatExporter.Core.Markdown
 {
@@ -6,20 +8,27 @@ namespace DiscordChatExporter.Core.Markdown
     {
         public string Url { get; }
 
-        public string Title { get; }
+        public IReadOnlyList<MarkdownNode> Children { get; }
 
-        public LinkNode(string url, string title)
+        public LinkNode(string url, IReadOnlyList<MarkdownNode> children)
         {
             Url = url;
-            Title = title;
+            Children = children;
         }
 
         public LinkNode(string url)
-            : this(url, url)
+            : this(url, new[] {new TextNode(url)})
         {
         }
 
         [ExcludeFromCodeCoverage]
-        public override string ToString() => $"<Link> {Title}";
+        public override string ToString()
+        {
+            var childrenFormatted = Children.Count == 1
+                ? Children.Single().ToString()
+                : "+" + Children.Count;
+
+            return $"<Link> ({childrenFormatted})";
+        }
     }
 }

DiscordChatExporter.Core/Markdown/Parsing/MarkdownParser.cs

@@ -7,7 +7,10 @@ using DiscordChatExporter.Core.Utils;
 
 namespace DiscordChatExporter.Core.Markdown.Parsing
 {
-    // The following parsing logic is meant to replicate Discord's markdown grammar as close as possible
+    // Discord does NOT use a recursive-descent parser for markdown which becomes evident in some
+    // scenarios, like when multiple formatting nodes are nested together.
+    // To replicate Discord's behavior, we're employing a special parser that uses a set of regular
+    // expressions that are executed sequentially in a first-match-first-serve manner.
     internal static partial class MarkdownParser
     {
         private const RegexOptions DefaultRegexOptions =
@@ -18,64 +21,64 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
         /* Formatting */
 
         // Capture any character until the earliest double asterisk not followed by an asterisk
-        private static readonly IMatcher<MarkdownNode> BoldFormattedNodeMatcher = new RegexMatcher<MarkdownNode>(
+        private static readonly IMatcher<MarkdownNode> BoldFormattingNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("\\*\\*(.+?)\\*\\*(?!\\*)", DefaultRegexOptions | RegexOptions.Singleline),
-            (p, m) => new FormattedNode(TextFormatting.Bold, Parse(p.Slice(m.Groups[1])))
+            (p, m) => new FormattingNode(FormattingKind.Bold, Parse(p.Slice(m.Groups[1])))
         );
 
         // Capture any character until the earliest single asterisk not preceded or followed by an asterisk
         // Opening asterisk must not be followed by whitespace
         // Closing asterisk must not be preceded by whitespace
-        private static readonly IMatcher<MarkdownNode> ItalicFormattedNodeMatcher = new RegexMatcher<MarkdownNode>(
+        private static readonly IMatcher<MarkdownNode> ItalicFormattingNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("\\*(?!\\s)(.+?)(?<!\\s|\\*)\\*(?!\\*)", DefaultRegexOptions | RegexOptions.Singleline),
-            (p, m) => new FormattedNode(TextFormatting.Italic, Parse(p.Slice(m.Groups[1])))
+            (p, m) => new FormattingNode(FormattingKind.Italic, Parse(p.Slice(m.Groups[1])))
         );
 
         // Capture any character until the earliest triple asterisk not followed by an asterisk
-        private static readonly IMatcher<MarkdownNode> ItalicBoldFormattedNodeMatcher = new RegexMatcher<MarkdownNode>(
+        private static readonly IMatcher<MarkdownNode> ItalicBoldFormattingNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("\\*(\\*\\*.+?\\*\\*)\\*(?!\\*)", DefaultRegexOptions | RegexOptions.Singleline),
-            (p, m) => new FormattedNode(TextFormatting.Italic, Parse(p.Slice(m.Groups[1]), BoldFormattedNodeMatcher))
+            (p, m) => new FormattingNode(FormattingKind.Italic, Parse(p.Slice(m.Groups[1]), BoldFormattingNodeMatcher))
         );
 
         // Capture any character except underscore until an underscore
         // Closing underscore must not be followed by a word character
-        private static readonly IMatcher<MarkdownNode> ItalicAltFormattedNodeMatcher = new RegexMatcher<MarkdownNode>(
+        private static readonly IMatcher<MarkdownNode> ItalicAltFormattingNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("_([^_]+)_(?!\\w)", DefaultRegexOptions | RegexOptions.Singleline),
-            (p, m) => new FormattedNode(TextFormatting.Italic, Parse(p.Slice(m.Groups[1])))
+            (p, m) => new FormattingNode(FormattingKind.Italic, Parse(p.Slice(m.Groups[1])))
         );
 
         // Capture any character until the earliest double underscore not followed by an underscore
-        private static readonly IMatcher<MarkdownNode> UnderlineFormattedNodeMatcher = new RegexMatcher<MarkdownNode>(
+        private static readonly IMatcher<MarkdownNode> UnderlineFormattingNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("__(.+?)__(?!_)", DefaultRegexOptions | RegexOptions.Singleline),
-            (p, m) => new FormattedNode(TextFormatting.Underline, Parse(p.Slice(m.Groups[1])))
+            (p, m) => new FormattingNode(FormattingKind.Underline, Parse(p.Slice(m.Groups[1])))
         );
 
         // Capture any character until the earliest triple underscore not followed by an underscore
-        private static readonly IMatcher<MarkdownNode> ItalicUnderlineFormattedNodeMatcher =
+        private static readonly IMatcher<MarkdownNode> ItalicUnderlineFormattingNodeMatcher =
             new RegexMatcher<MarkdownNode>(
                 new Regex("_(__.+?__)_(?!_)", DefaultRegexOptions | RegexOptions.Singleline),
-                (p, m) => new FormattedNode(TextFormatting.Italic,
-                    Parse(p.Slice(m.Groups[1]), UnderlineFormattedNodeMatcher))
+                (p, m) => new FormattingNode(FormattingKind.Italic,
+                    Parse(p.Slice(m.Groups[1]), UnderlineFormattingNodeMatcher))
             );
 
         // Capture any character until the earliest double tilde
-        private static readonly IMatcher<MarkdownNode> StrikethroughFormattedNodeMatcher =
+        private static readonly IMatcher<MarkdownNode> StrikethroughFormattingNodeMatcher =
             new RegexMatcher<MarkdownNode>(
                 new Regex("~~(.+?)~~", DefaultRegexOptions | RegexOptions.Singleline),
-                (p, m) => new FormattedNode(TextFormatting.Strikethrough, Parse(p.Slice(m.Groups[1])))
+                (p, m) => new FormattingNode(FormattingKind.Strikethrough, Parse(p.Slice(m.Groups[1])))
             );
 
         // Capture any character until the earliest double pipe
-        private static readonly IMatcher<MarkdownNode> SpoilerFormattedNodeMatcher = new RegexMatcher<MarkdownNode>(
+        private static readonly IMatcher<MarkdownNode> SpoilerFormattingNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("\\|\\|(.+?)\\|\\|", DefaultRegexOptions | RegexOptions.Singleline),
-            (p, m) => new FormattedNode(TextFormatting.Spoiler, Parse(p.Slice(m.Groups[1])))
+            (p, m) => new FormattingNode(FormattingKind.Spoiler, Parse(p.Slice(m.Groups[1])))
         );
 
         // Capture any character until the end of the line
         // Opening 'greater than' character must be followed by whitespace
         private static readonly IMatcher<MarkdownNode> SingleLineQuoteNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("^>\\s(.+\n?)", DefaultRegexOptions),
-            (p, m) => new FormattedNode(TextFormatting.Quote, Parse(p.Slice(m.Groups[1])))
+            (p, m) => new FormattingNode(FormattingKind.Quote, Parse(p.Slice(m.Groups[1])))
         );
 
         // Repeatedly capture any character until the end of the line
@@ -86,7 +89,7 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
                 (_, m) =>
                 {
                     var content = string.Concat(m.Groups[1].Captures.Select(c => c.Value));
-                    return new FormattedNode(TextFormatting.Quote, Parse(content));
+                    return new FormattingNode(FormattingKind.Quote, Parse(content));
                 }
             );
 
@@ -94,7 +97,7 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
         // Opening 'greater than' characters must be followed by whitespace
         private static readonly IMatcher<MarkdownNode> MultiLineQuoteNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("^>>>\\s(.+)", DefaultRegexOptions | RegexOptions.Singleline),
-            (p, m) => new FormattedNode(TextFormatting.Quote, Parse(p.Slice(m.Groups[1])))
+            (p, m) => new FormattingNode(FormattingKind.Quote, Parse(p.Slice(m.Groups[1])))
         );
 
         /* Code blocks */
@@ -147,7 +150,7 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
             (_, m) => new MentionNode(m.Groups[1].Value, MentionKind.Role)
         );
 
-        /* Emojis */
+        /* Emoji */
 
         // Capture any country flag emoji (two regional indicator surrogate pairs)
         // ... or "miscellaneous symbol" character
@@ -165,7 +168,7 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
             (_, m) =>
             {
                 var name = EmojiIndex.TryGetName(m.Groups[1].Value);
-                return name is not null
+                return !string.IsNullOrWhiteSpace(name)
                     ? new EmojiNode(name)
                     : null;
             }
@@ -182,10 +185,11 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
         // Capture [title](link)
         private static readonly IMatcher<MarkdownNode> TitledLinkNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("\\[(.+?)\\]\\((.+?)\\)", DefaultRegexOptions),
-            (_, m) => new LinkNode(m.Groups[2].Value, m.Groups[1].Value)
+            (p, m) => new LinkNode(m.Groups[2].Value, Parse(p.Slice(m.Groups[1])))
         );
 
-        // Capture any non-whitespace character after http:// or https:// until the last punctuation character or whitespace
+        // Capture any non-whitespace character after http:// or https://
+        // until the last punctuation character or whitespace
         private static readonly IMatcher<MarkdownNode> AutoLinkNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("(https?://\\S*[^\\.,:;\"\'\\s])", DefaultRegexOptions),
             (_, m) => new LinkNode(m.Groups[1].Value)
@@ -199,14 +203,14 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
 
         /* Text */
 
-        // Capture the shrug emoticon
+        // Capture the shrug kaomoji
         // This escapes it from matching for formatting
         private static readonly IMatcher<MarkdownNode> ShrugTextNodeMatcher = new StringMatcher<MarkdownNode>(
             @"¯\_(ツ)_/¯",
             p => new TextNode(p.ToString())
         );
 
-        // Capture some specific emojis that don't get rendered
+        // Capture some specific emoji that don't get rendered
         // This escapes it from matching for emoji
         private static readonly IMatcher<MarkdownNode> IgnoredEmojiTextNodeMatcher = new RegexMatcher<MarkdownNode>(
             new Regex("(\\u26A7|\\u2640|\\u2642|\\u2695|\\u267E|\\u00A9|\\u00AE|\\u2122)", DefaultRegexOptions),
@@ -257,14 +261,14 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
             EscapedCharacterTextNodeMatcher,
 
             // Formatting
-            ItalicBoldFormattedNodeMatcher,
-            ItalicUnderlineFormattedNodeMatcher,
-            BoldFormattedNodeMatcher,
-            ItalicFormattedNodeMatcher,
-            UnderlineFormattedNodeMatcher,
-            ItalicAltFormattedNodeMatcher,
-            StrikethroughFormattedNodeMatcher,
-            SpoilerFormattedNodeMatcher,
+            ItalicBoldFormattingNodeMatcher,
+            ItalicUnderlineFormattingNodeMatcher,
+            BoldFormattingNodeMatcher,
+            ItalicFormattingNodeMatcher,
+            UnderlineFormattingNodeMatcher,
+            ItalicAltFormattingNodeMatcher,
+            StrikethroughFormattingNodeMatcher,
+            SpoilerFormattingNodeMatcher,
             MultiLineQuoteNodeMatcher,
             RepeatedSingleLineQuoteNodeMatcher,
             SingleLineQuoteNodeMatcher,

DiscordChatExporter.Core/Markdown/Parsing/MarkdownVisitor.cs

@@ -8,10 +8,10 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
         protected virtual MarkdownNode VisitText(TextNode text) =>
             text;
 
-        protected virtual MarkdownNode VisitFormatted(FormattedNode formatted)
+        protected virtual MarkdownNode VisitFormatting(FormattingNode formatting)
         {
-            Visit(formatted.Children);
-            return formatted;
+            Visit(formatting.Children);
+            return formatting;
         }
 
         protected virtual MarkdownNode VisitInlineCodeBlock(InlineCodeBlockNode inlineCodeBlock) =>
@@ -20,8 +20,11 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
         protected virtual MarkdownNode VisitMultiLineCodeBlock(MultiLineCodeBlockNode multiLineCodeBlock) =>
             multiLineCodeBlock;
 
-        protected virtual MarkdownNode VisitLink(LinkNode link) =>
-            link;
+        protected virtual MarkdownNode VisitLink(LinkNode link)
+        {
+            Visit(link.Children);
+            return link;
+        }
 
         protected virtual MarkdownNode VisitEmoji(EmojiNode emoji) =>
             emoji;
@@ -35,7 +38,7 @@ namespace DiscordChatExporter.Core.Markdown.Parsing
         public MarkdownNode Visit(MarkdownNode node) => node switch
         {
             TextNode text => VisitText(text),
-            FormattedNode formatted => VisitFormatted(formatted),
+            FormattingNode formatting => VisitFormatting(formatting),
             InlineCodeBlockNode inlineCodeBlock => VisitInlineCodeBlock(inlineCodeBlock),
             MultiLineCodeBlockNode multiLineCodeBlock => VisitMultiLineCodeBlock(multiLineCodeBlock),
             LinkNode link => VisitLink(link),