web-core/posts/render.go

package posts

import (
	"github.com/microcosm-cc/bluemonday"
	"github.com/writeas/saturday"
	"regexp"
)

var (
	blockReg    = regexp.MustCompile("<(ul|ol|blockquote)>\n")
	endBlockReg = regexp.MustCompile("</([a-z]+)>\n</(ul|ol|blockquote)>")
)

func ApplyMarkdown(data []byte) string {
	mdExtensions := 0 |
		blackfriday.EXTENSION_TABLES |
		blackfriday.EXTENSION_FENCED_CODE |
		blackfriday.EXTENSION_AUTOLINK |
		blackfriday.EXTENSION_STRIKETHROUGH |
		blackfriday.EXTENSION_SPACE_HEADERS |
		blackfriday.EXTENSION_HEADER_IDS
	htmlFlags := 0 |
		blackfriday.HTML_USE_SMARTYPANTS |
		blackfriday.HTML_SMARTYPANTS_DASHES

	// Generate Markdown
	md := blackfriday.Markdown([]byte(data), blackfriday.HtmlRenderer(htmlFlags, "", ""), mdExtensions)
	// Strip out bad HTML
	policy := bluemonday.UGCPolicy()
	policy.AllowAttrs("class", "id").Globally()
	outHTML := string(policy.SanitizeBytes(md))
	// Strip newlines on certain block elements that render with them
	outHTML = blockReg.ReplaceAllString(outHTML, "<$1>")
	outHTML = endBlockReg.ReplaceAllString(outHTML, "</$1></$2>")

	return outHTML
}