Summary Update.

RelayClient/Helpers/SyntaxHighlighter.cs

@@ -2,21 +2,50 @@ using System.Text.RegularExpressions;
 
 namespace RelayClient.Helpers;
 
+/// <summary>
+/// Discord-style syntax highlighting for ```lang...``` fenced code blocks. Builds a list of
+/// MAUI Spans (with colors from the VS Code Dark+ palette) that the caller drops into a
+/// FormattedString.
+///
+/// How it works:
+///   - The opening fence captures an optional language tag (e.g. ```cs, ```python).
+///   - Aliases resolves "cs" → "csharp", "js" → "javascript", etc.
+///   - Tokenizers[lang] is a compiled regex with named groups (comment/string/number/word/…).
+///   - For each match, SpanForMatch picks a colour based on which group matched + whether
+///     a "word" hit a language keyword set.
+///
+/// Adding a new language: register an alias (if needed), a Keywords set, and a tokenizer regex.
+/// </summary>
 public static class SyntaxHighlighter
 {
+    /// <summary>Fallback identifier color (light grey). Used for any token we don't recognise.</summary>
     private static readonly Color DefaultColor  = Color.FromArgb("#D4D4D4");
+    /// <summary>Language keywords (if, for, return, etc.) — VS Code's "control flow" blue.</summary>
     private static readonly Color KeywordColor  = Color.FromArgb("#569CD6");
+    /// <summary>String literals — orange/salmon.</summary>
     private static readonly Color StringColor   = Color.FromArgb("#CE9178");
+    /// <summary>Numeric literals — soft green.</summary>
     private static readonly Color NumberColor   = Color.FromArgb("#B5CEA8");
+    /// <summary>Comments — green, rendered italic.</summary>
     private static readonly Color CommentColor  = Color.FromArgb("#6A9955");
+    /// <summary>Type names (heuristic: uppercase-start words in C#/JS/TS) — teal.</summary>
     private static readonly Color TypeColor     = Color.FromArgb("#4EC9B0");
+    /// <summary>Function names — yellow. Currently unused (we don't disambiguate function calls).</summary>
     private static readonly Color FunctionColor = Color.FromArgb("#DCDCAA");
+    /// <summary>Operators — same as default. Reserved for future use.</summary>
     private static readonly Color OperatorColor = Color.FromArgb("#D4D4D4");
+    /// <summary>HTML tag names (&lt;div&gt;, &lt;/p&gt;) — blue.</summary>
     private static readonly Color TagColor      = Color.FromArgb("#569CD6");
+    /// <summary>HTML/CSS attribute names, YAML keys, bash variables — light blue.</summary>
     private static readonly Color AttrColor     = Color.FromArgb("#9CDCFE");
 
+    /// <summary>Monospace font registered in MauiProgram. Used for all code-block spans.</summary>
     private const string FontFamily = "AnonymousProRegular";
 
+    /// <summary>
+    /// Short language tags → canonical names. So users can write ```cs (instead of ```csharp),
+    /// ```py instead of ```python, etc. Case-insensitive.
+    /// </summary>
     private static readonly Dictionary<string, string> Aliases = new(StringComparer.OrdinalIgnoreCase)
     {
         ["cs"] = "csharp",
@@ -34,6 +63,11 @@ public static class SyntaxHighlighter
         ["yml"] = "yaml"
     };
 
+    /// <summary>
+    /// Per-language keyword sets. A token in a "word" match-group that hits one of these
+    /// gets rendered with KeywordColor. Case-sensitivity matches the language — Ordinal
+    /// for most languages, OrdinalIgnoreCase for SQL and CSS.
+    /// </summary>
     private static readonly Dictionary<string, HashSet<string>> Keywords = new(StringComparer.OrdinalIgnoreCase)
     {
         ["csharp"] = new(StringComparer.Ordinal)
@@ -97,6 +131,11 @@ public static class SyntaxHighlighter
         }
     };
 
+    /// <summary>
+    /// Per-language compiled token regex. Each pattern uses named groups (comment/string/
+    /// number/word/tag/attr/…) which SpanForMatch dispatches on. Initialised lazily in the
+    /// static constructor so the heavy regex compilation is paid once at startup.
+    /// </summary>
     private static readonly Dictionary<string, Regex> Tokenizers = new(StringComparer.Ordinal);
 
     static SyntaxHighlighter()
@@ -186,6 +225,11 @@ public static class SyntaxHighlighter
             opts | RegexOptions.Multiline);
     }
 
+    /// <summary>
+    /// Entry point. Walks every regex match in the code, emits plain spans for the gaps and
+    /// styled spans for the matches. If the language is unknown (or not specified), returns a
+    /// single default-colored span — code still renders in the monospace font, just no colors.
+    /// </summary>
     public static List<Span> Highlight(string code, string? language, double fontSize)
     {
         var lang = Resolve(language);
@@ -215,6 +259,11 @@ public static class SyntaxHighlighter
         return spans;
     }
 
+    /// <summary>
+    /// Maps a regex Match to a colored Span by inspecting which named group succeeded. Words
+    /// fall through to a keyword-set lookup; in C#/JS/TS, uppercase-start words that aren't
+    /// keywords are treated as type names (a cheap heuristic that works surprisingly well).
+    /// </summary>
     private static Span SpanForMatch(Match m, string lang, HashSet<string>? keywords, double fontSize)
     {
         if (m.Groups["comment"].Success)
@@ -285,6 +334,7 @@ public static class SyntaxHighlighter
         return MakeSpan(m.Value, DefaultColor, fontSize);
     }
 
+    /// <summary>Helper: build a Span with the monospace code font and the given colour + bold/italic flags.</summary>
     private static Span MakeSpan(string text, Color color, double fontSize, bool bold = false, bool italic = false)
     {
         var attrs = FontAttributes.None;
@@ -301,6 +351,7 @@ public static class SyntaxHighlighter
         };
     }
 
+    /// <summary>Normalises a user-supplied language tag through the Aliases table. Returns null for empty/whitespace input.</summary>
     private static string? Resolve(string? language)
     {
         if (string.IsNullOrWhiteSpace(language)) return null;