Add first implementation of Node, El, Attr, Text

1 files changed, 100 insertions, 0 deletions

diff --git a/gomponents.go b/gomponents.go
new file mode 100644
index 0000000..bd7e09c
--- /dev/null
+++ b/gomponents.go
@@ -0,0 +1,100 @@
+package gomponents
+
+import (
+	"fmt"
+	"html/template"
+	"strings"
+)
+
+// Node is a DOM node that can Render itself to a string representation.
+type Node interface {
+	Render() string
+}
+
+// NodeFunc is render function that is also a Node.
+type NodeFunc func() string
+
+func (n NodeFunc) Render() string {
+	return n()
+}
+
+// El creates an element DOM Node with a name and child Nodes.
+// Use this if no convenience creator exists.
+func El(name string, children ...Node) NodeFunc {
+	return func() string {
+		var b, attrString, childrenString strings.Builder
+
+		b.WriteString("<")
+		b.WriteString(name)
+
+		if len(children) == 0 {
+			b.WriteString("/>")
+			return b.String()
+		}
+
+		for _, c := range children {
+			s := c.Render()
+			if _, ok := c.(attr); ok {
+				attrString.WriteString(s)
+				continue
+			}
+			childrenString.WriteString(c.Render())
+		}
+
+		b.WriteString(attrString.String())
+
+		if childrenString.Len() == 0 {
+			b.WriteString("/>")
+			return b.String()
+		}
+
+		b.WriteString(">")
+		b.WriteString(childrenString.String())
+		b.WriteString("</")
+		b.WriteString(name)
+		b.WriteString(">")
+		return b.String()
+	}
+}
+
+// Attr creates an attr DOM Node.
+// If one parameter is passed, it's a name-only attribute (like "required").
+// If two parameters are passed, it's a name-value attribute (like `class="header"`).
+// More parameter counts make Attr panic.
+// Use this if no convenience creator exists.
+func Attr(name string, value ...string) Node {
+	switch len(value) {
+	case 0:
+		return attr{name: name}
+	case 1:
+		return attr{name: name, value: &value[0]}
+	default:
+		panic("attribute must be just name or name and value pair")
+	}
+}
+
+type attr struct {
+	name  string
+	value *string
+}
+
+func (a attr) Render() string {
+	if a.value == nil {
+		return fmt.Sprintf(" %v", a.name)
+	}
+	return fmt.Sprintf(` %v="%v"`, a.name, *a.value)
+}
+
+// Text creates a text DOM Node that Renders the escaped string t.
+func Text(t string) NodeFunc {
+	return func() string {
+		return template.HTMLEscaper(t)
+	}
+}
+
+// Raw creates a raw Node that just Renders the unescaped string t.
+func Raw(t string) NodeFunc {
+	return func() string {
+		return t
+	}
+}