Added If for conditional adding of content

Author: resc

src/Cubist.Helium.Tests/HeTests.cs

@@ -54,4 +54,41 @@ public void CanRenderImportMap()
         _output.WriteLine(html);
         Assert.Equal(@"<script type=""importmap"">{""import"":{""name"":""./path/to/module""}}</script>", html);
     }
+
+
+
+
+    [Fact]
+    public void CanRenderConditionalFalse()
+    {
+        var hasClass = false;
+        var div = Div(If(hasClass, Class("class")));
+
+        var html = div.ToString();
+        _output.WriteLine(html);
+        Assert.Equal("<div></div>", html);
+
+    }
+
+    [Fact]
+    public void CanRenderConditionalTrue()
+    {
+        var hasClass = true;
+        var div = Div(If(hasClass, Class("class")));
+
+        var html = div.ToString();
+        _output.WriteLine(html);
+        Assert.Equal("<div class=\"class\"></div>", html);
+    }
+
+    [Fact]
+    public void CanRenderConditionalTrueFunctionContent()
+    {
+        var hasClass = true;
+        var div = Div(If(hasClass,()=> Class("class")));
+
+        var html = div.ToString();
+        _output.WriteLine(html);
+        Assert.Equal("<div class=\"class\"></div>", html);
+    }
 }

src/Cubist.Helium/Conditional.cs

@@ -0,0 +1,23 @@
+using System.Collections;
+
+namespace Cubist.Helium;
+
+/// <summary> Adds content or not, based on a condition </summary>
+public class Conditional : IEnumerable
+{
+    private readonly Func<bool> _condition;
+    private readonly Func<object> _content;
+
+    /// <summary> Creates a new <see cref="Conditional"/> instance </summary> 
+    public Conditional(Func<bool> condition, Func<object> content)
+    {
+        _condition = condition;
+        _content = content;
+    }
+    /// <inheritdoc cref="IEnumerable.GetEnumerator"/>>
+    public IEnumerator GetEnumerator()
+    {
+        if (_condition())
+            yield return _content();
+    }
+}

src/Cubist.Helium/He.Factory.cs

@@ -227,6 +227,22 @@ public static (string, object?) Class(params string[] classes)
     /// <inheritdoc cref="Tags.I"/>
     public static He I(params object[] content) => new(Tags.I) { content };
 
+    /// <inheritdoc cref="Conditional"/>
+    public static object If(bool condition, params object[] content)
+        => If(() => condition, content);
+
+    /// <inheritdoc cref="Conditional"/>
+    public static object If(Func<bool> condition, params object[] content)
+        => new Conditional(condition, () => content);
+
+    /// <inheritdoc cref="Conditional"/>
+    public static object If<T>(bool condition, Func<T> content) where T : notnull
+        => If(() => condition, content);
+
+    /// <inheritdoc cref="Conditional"/>
+    public static object If<T>(Func<bool> condition, Func<T> content) where T : notnull
+        => new Conditional(condition, () => content());
+
     /// <inheritdoc cref="Tags.Iframe"/>
     public static He Iframe(string title, string src) => new(Tags.Iframe)
     {