package markdown

import (
	"bytes"
	"html/template"

	"github.com/microcosm-cc/bluemonday"
	"github.com/yuin/goldmark"
	highlighting "github.com/yuin/goldmark-highlighting/v2"
	"github.com/yuin/goldmark/extension"
	"github.com/yuin/goldmark/renderer/html"
)

var (
	md     goldmark.Markdown
	policy *bluemonday.Policy
)

func init() {
	md = goldmark.New(
		goldmark.WithExtensions(
			extension.GFM,
			highlighting.NewHighlighting(
				highlighting.WithStyle("github"),
			),
		),
		goldmark.WithRendererOptions(
			html.WithHardWraps(),
		),
	)

	policy = bluemonday.UGCPolicy()
	policy.AllowAttrs("class").OnElements("code", "pre", "span", "div")
	policy.AllowAttrs("style").OnElements("span", "pre", "code")
}

// RenderMarkdown converts markdown text to sanitized HTML.
func RenderMarkdown(input string) template.HTML {
	var buf bytes.Buffer
	if err := md.Convert([]byte(input), &buf); err != nil {
		return template.HTML(template.HTMLEscapeString(input))
	}
	sanitized := policy.SanitizeBytes(buf.Bytes())
	return template.HTML(sanitized)
}