feat(themes): custom theme loading with file-stamp cache

HellionChat/Themes/ThemeRegistry.cs

@@ -7,9 +7,11 @@ public sealed class ThemeRegistry
     public const string DefaultSlug = HellionArctic.Slug;
 
     private readonly Dictionary<string, Theme> _builtIns;
+    private readonly Dictionary<string, (Theme Theme, DateTime Stamp)> _customCache = new(StringComparer.OrdinalIgnoreCase);
+    private readonly string? _customThemesDir;
     private Theme _active;
 
-    public ThemeRegistry()
+    public ThemeRegistry(string? customThemesDir = null)
     {
         _builtIns = new Dictionary<string, Theme>(StringComparer.OrdinalIgnoreCase)
         {
@@ -20,23 +22,75 @@ public sealed class ThemeRegistry
             { MintGrove.Slug,     MintGrove.Build() },
         };
         _active = _builtIns[DefaultSlug];
+        _customThemesDir = customThemesDir;
     }
 
     public Theme Active => _active;
 
-    // Active-Lookup: liefert das angeforderte Theme oder fällt auf Hellion Arctic
-    // zurück, wenn der Slug unbekannt ist.
     public Theme Get(string slug)
     {
-        return _builtIns.TryGetValue(slug, out var theme)
-            ? theme
-            : _builtIns[DefaultSlug];
+        if (_builtIns.TryGetValue(slug, out var b)) return b;
+
+        var custom = LoadCustomBySlug(slug);
+        if (custom != null) return custom;
+
+        return _builtIns[DefaultSlug];
     }
 
     public IEnumerable<Theme> AllBuiltIns() => _builtIns.Values;
 
-    public void Switch(string slug)
+    public IEnumerable<Theme> AllCustom() => RefreshCustomCache();
+
+    public void Switch(string slug) => _active = Get(slug);
+
+    // Custom-Themes werden lazy aus dem Verzeichnis geladen, Cache mit
+    // LastWriteTime-Token. Eine geänderte JSON wird beim nächsten Lookup
+    // neu eingelesen.
+    private Theme? LoadCustomBySlug(string slug)
     {
-        _active = Get(slug);
+        if (_customThemesDir is null) return null;
+        if (!Directory.Exists(_customThemesDir)) return null;
+
+        foreach (var theme in RefreshCustomCache())
+            if (string.Equals(theme.Slug, slug, StringComparison.OrdinalIgnoreCase))
+                return theme;
+        return null;
+    }
+
+    private IEnumerable<Theme> RefreshCustomCache()
+    {
+        if (_customThemesDir is null || !Directory.Exists(_customThemesDir))
+            yield break;
+
+        var seenSlugs = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+        foreach (var path in Directory.EnumerateFiles(_customThemesDir, "*.json"))
+        {
+            Theme? theme = null;
+            var stamp = File.GetLastWriteTimeUtc(path);
+            var key = path;
+            if (_customCache.TryGetValue(key, out var cached) && cached.Stamp == stamp)
+            {
+                theme = cached.Theme;
+            }
+            else
+            {
+                try
+                {
+                    theme = ThemeJsonLoader.LoadFromFile(path);
+                    _customCache[key] = (theme, stamp);
+                }
+                catch (Exception ex)
+                {
+                    // Logging passiert in Plugin.cs durch den Aufrufer; hier still
+                    // ignorieren, damit ein einzelnes kaputtes JSON nicht alle
+                    // Custom-Themes blockt.
+                    _ = ex;
+                    continue;
+                }
+            }
+
+            if (theme is not null && seenSlugs.Add(theme.Slug))
+                yield return theme;
+        }
     }
 }