1 files changed, 21 insertions, 2 deletions
diff --git a/mardown/ast_header.go b/mardown/ast_header.go
index c7bc85d..7c997d5 100644
--- a/mardown/ast_header.go
+++ b/mardown/ast_header.go
@@ -1,12 +1,31 @@
 package mardown
 
+import (
+	"errors"
+	"fmt"
+	"html/template"
+)
+
+var ErrInvalidHeader = errors.New("invalid header")
+
 type astHeader struct {
 	level   uint
 	content []block
 }
 
-func (a *astHeader) Eval() error {
-	return nil
+func (a *astHeader) Eval() (template.HTML, error) {
+	if a.level > 6 {
+		return "", ErrInvalidHeader
+	}
+	var content template.HTML
+	for _, b := range a.content {
+		c, err := b.Eval()
+		if err != nil {
+			return "", err
+		}
+		content += c
+	}
+	return template.HTML(fmt.Sprintf("<h%d>%s<h%d>", a.level, content, a.level)), nil
 }
 
 func header(lxs lexers) (block, error) {