2 files changed, 63 insertions, 6 deletions

diff --git a/dom/css_class.go b/dom/css_class.go
new file mode 100644
index 0000000..633869e
--- /dev/null
+++ b/dom/css_class.go
@@ -0,0 +1,43 @@
+package dom
+
+type ClassList map[string]struct{}
+
+func (cl ClassList) set(e Element) Element {
+	if len(cl) == 0 {
+		return e
+	}
+	classes := ""
+	for k := range cl {
+		classes += k + " "
+	}
+	classes = classes[:len(cl)-1]
+	return e.SetAttribute("class", classes)
+}
+
+func (cl ClassList) Has(v string) bool {
+	_, ok := cl[v]
+	return ok
+}
+
+func (cl ClassList) Add(v string) ClassList {
+	cl[v] = struct{}{}
+	return cl
+}
+
+func (cl ClassList) Remove(v string) ClassList {
+	delete(cl, v)
+	return cl
+}
+
+func (cl ClassList) Toggle(v string) ClassList {
+	if cl.Has(v) {
+		cl.Remove(v)
+	} else {
+		cl.Add(v)
+	}
+	return cl
+}
+
+func NewClassList() ClassList {
+	return ClassList(make(map[string]struct{}))
+}
diff --git a/dom/html.go b/dom/html.go
index f43526c..360a33b 100644
--- a/dom/html.go
+++ b/dom/html.go
@@ -22,6 +22,7 @@ type Element interface {
 	HasAttribute(string) bool
 	SetAttribute(string, string) Element
 	RemoveAttribute(string) Element
+	ClassList() ClassList
 }
 
 type LiteralElement struct {
@@ -44,6 +45,10 @@ func (e LiteralElement) RemoveAttribute(string) Element {
 	return e
 }
 
+func (e LiteralElement) ClassList() ClassList {
+	return nil
+}
+
 func NewLiteralElement(s string) LiteralElement {
 	return LiteralElement{s}
 }
@@ -51,9 +56,11 @@ func NewLiteralElement(s string) LiteralElement {
 type VoidElement struct {
 	Tag        string
 	attributes map[string]string
+	cl         ClassList
 }
 
 func (e VoidElement) Render() template.HTML {
+	e = e.cl.set(e).(VoidElement)
 	return render(e.Tag, e.attributes, true)
 }
 
@@ -72,8 +79,12 @@ func (e VoidElement) RemoveAttribute(k string) Element {
 	return e
 }
 
+func (e VoidElement) ClassList() ClassList {
+	return e.cl
+}
+
 func NewVoidElement(tag string) VoidElement {
-	return VoidElement{tag, make(map[string]string)}
+	return VoidElement{tag, make(map[string]string), NewClassList()}
 }
 
 func NewImg(src, alt string) Element {
@@ -82,19 +93,22 @@ func NewImg(src, alt string) Element {
 
 type ContentElement struct {
 	VoidElement
-	Content Element
+	Contents []Element
 }
 
 func (e ContentElement) Render() template.HTML {
+	e = e.cl.set(e).(ContentElement)
 	base := render(e.Tag, e.attributes, false)
-	base += e.Content.Render()
+	for _, el := range e.Contents {
+		base += el.Render()
+	}
 	return base + template.HTML(fmt.Sprintf(`</%s>`, e.VoidElement.Tag))
 }
 
-func NewContentElement(tag string, content Element) ContentElement {
-	return ContentElement{NewVoidElement(tag), content}
+func NewContentElement(tag string, contents []Element) ContentElement {
+	return ContentElement{NewVoidElement(tag), contents}
 }
 
 func NewParagraph(content string) Element {
-	return NewContentElement("p", NewLiteralElement(content))
+	return NewContentElement("p", []Element{NewLiteralElement(content)})
 }