go-html/node.go

package html

import "strings"

// Node is anything renderable.
type Node interface {
	Render(ctx *Context) string
}

// voidElements is the set of HTML elements that must not have a closing tag.
var voidElements = map[string]bool{
	"area":   true,
	"base":   true,
	"br":     true,
	"col":    true,
	"embed":  true,
	"hr":     true,
	"img":    true,
	"input":  true,
	"link":   true,
	"meta":   true,
	"source": true,
	"track":  true,
	"wbr":    true,
}

// escapeAttr escapes a string for use in an HTML attribute value.
func escapeAttr(s string) string {
	s = strings.ReplaceAll(s, "&", "&")
	s = strings.ReplaceAll(s, "\"", """)
	s = strings.ReplaceAll(s, "'", "'")
	s = strings.ReplaceAll(s, "<", "&lt;")
	s = strings.ReplaceAll(s, ">", "&gt;")
	return s
}

// --- rawNode ---

type rawNode struct {
	content string
}

// Raw creates a node that renders without escaping (escape hatch for trusted content).
func Raw(content string) Node {
	return &rawNode{content: content}
}

func (n *rawNode) Render(_ *Context) string {
	return n.content
}

// --- elNode ---

type elNode struct {
	tag      string
	children []Node
	attrs    map[string]string
}

// El creates an HTML element node with children.
func El(tag string, children ...Node) Node {
	return &elNode{
		tag:      tag,
		children: children,
		attrs:    make(map[string]string),
	}
}

func (n *elNode) Render(ctx *Context) string {
	var b strings.Builder

	b.WriteByte('<')
	b.WriteString(n.tag)

	for key, val := range n.attrs {
		b.WriteByte(' ')
		b.WriteString(key)
		b.WriteString(`="`)
		b.WriteString(escapeAttr(val))
		b.WriteByte('"')
	}

	b.WriteByte('>')

	if voidElements[n.tag] {
		return b.String()
	}

	for _, child := range n.children {
		b.WriteString(child.Render(ctx))
	}

	b.WriteString("</")
	b.WriteString(n.tag)
	b.WriteByte('>')

	return b.String()
}