Toy templating in Go

output

<div
><div
><img
 src="http://lolcats.com/lolcat.jpg" alt="logo"></img>
<h1
>hello</h1>
</div>
<p
>little bobby tables: &lt;script&gt;alert(&#39;xss!&#39;)&lt;/script&gt;</p>
<ul
><li
>1</li>
<li
>2</li>
<li
>3</li>
<li
>4</li>
<li
>5</li>
<li
>6</li>
<li
>7</li>
<li
>8</li>
<li
>9</li>
</ul>
<p
>footer</p>
<ul
><li
>very important</li>
</ul>
<p
>no items</p>
</div>

reactoy.go

package main

import (
	"bytes"
	"fmt"
	"html/template"
)

type element interface {
	flatten() string
}

type basicElement struct {
	tag      string
	children []element
}

func (e basicElement) flatten() string {
	s := fmt.Sprintf("<%s\n", e.tag)
	closed := false
	for _, c := range e.children {
		if attr, ok := c.(attr); ok && !closed {
			s += attr.flatten()
		} else if !closed {
			closed = true
			s += ">" + c.flatten()
		} else {
			s += c.flatten()
		}
	}
	if !closed {
		s += ">"
	}
	s += fmt.Sprintf("</%s>\n", e.tag)
	return s
}

type genericElement struct {
	flat func() string
}

func (n genericElement) flatten() string {
	return n.flat()
}

var t = template.Must(template.New("text").Parse("{{.}}"))

func text(s string) element {
	return genericElement{
		flat: func() string {
			b := bytes.Buffer{}
			t.Execute(&b, s)
			return b.String()
		},
	}
}

func genElement(tag string) func(children ...element) element {
	return func(children ...element) element {
		return basicElement{
			tag:      tag,
			children: children,
		}
	}
}

type attr struct {
	k string
	v string
}

func (a attr) flatten() string {
	return " " + a.k + "=\"" + text(a.v).flatten() + "\""
}

var div = genElement("div")
var h1 = genElement("h1")
var p = genElement("p")
var ul = genElement("ul")
var li = genElement("li")
var img = genElement("img")

func header(h string) element {
	return div(
		img(attr{k: "src", v: "http://lolcats.com/lolcat.jpg"}, attr{k: "alt", v: "logo"}),
		h1(text(h)),
	)
}

func content() element {
	return p(text("little bobby tables: <script>alert('xss!')</script>"))
}

func fancyList(items ...element) element {
	if len(items) == 0 {
		return p(text("no items"))
	} else {
		list := []element{}
		for _, i := range items {
			list = append(list, li(i))
		}
		return ul(list...)
	}
}

func page() element {
	list := []element{}
	for i := 1; i < 10; i++ {
		list = append(list, li(text(fmt.Sprintf("%d", i))))
	}

	return div(
		header("hello"),
		content(),
		ul(list...),
		p(text("footer")),
		fancyList(text("very important")),
		fancyList(),
	)
}

func main() {
	fmt.Println(page().flatten())
}