package markdown

import (
	"bytes"
	"sync"

	"github.com/yuin/goldmark"
	emoji "github.com/yuin/goldmark-emoji"
	highlighting "github.com/yuin/goldmark-highlighting/v2"
	"github.com/yuin/goldmark/extension"
	"github.com/yuin/goldmark/parser"
	"github.com/yuin/goldmark/renderer/html"
)

var (
	renderers   = make(map[string]goldmark.Markdown)
	renderersMu sync.RWMutex
)

func getRenderer(codeTheme string) goldmark.Markdown {
	if codeTheme == "" {
		codeTheme = "github"
	}

	renderersMu.RLock()
	if md, ok := renderers[codeTheme]; ok {
		renderersMu.RUnlock()
		return md
	}
	renderersMu.RUnlock()

	renderersMu.Lock()
	defer renderersMu.Unlock()

	if md, ok := renderers[codeTheme]; ok {
		return md
	}

	md := goldmark.New(
		goldmark.WithExtensions(
			extension.GFM,
			extension.Typographer,
			emoji.Emoji,
			highlighting.NewHighlighting(
				highlighting.WithStyle(codeTheme),
			),
		),
		goldmark.WithParserOptions(
			parser.WithAutoHeadingID(),
		),
		goldmark.WithRendererOptions(
			html.WithHardWraps(),
			html.WithXHTML(),
			html.WithUnsafe(),
		),
	)
	renderers[codeTheme] = md
	return md
}

func Render(source string) (string, error) {
	return RenderWithTheme(source, "github")
}

func RenderWithTheme(source, codeTheme string) (string, error) {
	md := getRenderer(codeTheme)
	var buf bytes.Buffer
	if err := md.Convert([]byte(source), &buf); err != nil {
		return "", err
	}
	return buf.String(), nil
}