1 files changed, 44 insertions, 0 deletions
diff --git a/src/marlin.web/TagHelpers/ActiveLinkTagHelper.cs b/src/marlin.web/TagHelpers/ActiveLinkTagHelper.cs
new file mode 100644
index 0000000..759b701
--- /dev/null
+++ b/src/marlin.web/TagHelpers/ActiveLinkTagHelper.cs
@@ -0,0 +1,44 @@
+namespace marlin.web.TagHelpers;
+
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+
+[HtmlTargetElement("a", Attributes = "active-when")]
+public class ActiveLinkTagHelper : TagHelper
+{
+    [HtmlAttributeName("asp-controller")]
+    public string Controller { get; set; }
+
+    [HtmlAttributeName("asp-action")]
+    public string Action { get; set; }
+    
+    [HtmlAttributeName("active-when")]
+    public ActiveLinkWhen ActiveWhen { get; set; }
+
+    [ViewContext]
+    [HtmlAttributeNotBound]
+    public ViewContext ViewContext { get; set; }
+
+    public override void Process(TagHelperContext context, TagHelperOutput output)
+    {
+        var currentController = ViewContext.RouteData.Values["controller"]?.ToString();
+        var currentAction = ViewContext.RouteData.Values["action"]?.ToString();
+
+        if (!string.Equals(currentController, Controller, StringComparison.OrdinalIgnoreCase))
+            return;
+
+        if (!string.Equals(currentAction, Action, StringComparison.OrdinalIgnoreCase)
+            && this.ActiveWhen == ActiveLinkWhen.ControllerAndAction)
+            return;
+
+        var existingClasses = output.Attributes["class"]?.Value?.ToString() ?? "";
+        output.Attributes.SetAttribute("class", $"{existingClasses} active".Trim());
+    }
+}
+
+public enum ActiveLinkWhen
+{
+    Controller,
+    ControllerAndAction
+}
+\ No newline at end of file