1 files changed, 75 insertions, 0 deletions
diff --git a/html/highlight.go b/html/highlight.go
new file mode 100644
index 0000000..72b8d79
--- /dev/null
+++ b/html/highlight.go
@@ -0,0 +1,75 @@
+package html
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/gomarkdown/markdown/ast"
+	mdhtml "github.com/gomarkdown/markdown/html"
+
+	"github.com/alecthomas/chroma"
+	"github.com/alecthomas/chroma/formatters/html"
+	"github.com/alecthomas/chroma/lexers"
+	"github.com/alecthomas/chroma/styles"
+)
+
+type Highlighter struct {
+	htmlFormatter  *html.Formatter
+	highlightStyle *chroma.Style
+}
+
+func (h Highlighter) htmlHighlight(w io.Writer, source, lang, defaultLang string) error {
+
+	if lang == "" {
+		lang = defaultLang
+	}
+	l := lexers.Get(lang)
+	if l == nil {
+		l = lexers.Analyse(source)
+	}
+	if l == nil {
+		l = lexers.Fallback
+	}
+	l = chroma.Coalesce(l)
+
+	it, err := l.Tokenise(nil, source)
+	if err != nil {
+		return err
+	}
+	return h.htmlFormatter.Format(w, h.highlightStyle, it)
+}
+
+func (h Highlighter) renderCode(w io.Writer, codeBlock *ast.CodeBlock, entering bool) {
+	defaultLang := ""
+	lang := string(codeBlock.Info)
+	h.htmlHighlight(w, string(codeBlock.Literal), lang, defaultLang)
+}
+
+func (h Highlighter) myRenderHook(w io.Writer, node ast.Node, entering bool) (ast.WalkStatus, bool) {
+	if code, ok := node.(*ast.CodeBlock); ok {
+		h.renderCode(w, code, entering)
+		return ast.GoToNext, true
+	}
+	return ast.GoToNext, false
+}
+
+func newRenderer() *mdhtml.Renderer {
+	htmlFormatter := html.New(html.WithClasses(true), html.TabWidth(2))
+	if htmlFormatter == nil {
+		panic("couldn't create html formatter")
+	}
+	styleName := "monokailight"
+	highlightStyle := styles.Get(styleName)
+	if highlightStyle == nil {
+		panic(fmt.Sprintf("didn't find style '%s'", styleName))
+	}
+	h := Highlighter{
+		htmlFormatter:  htmlFormatter,
+		highlightStyle: highlightStyle,
+	}
+	opts := mdhtml.RendererOptions{
+		Flags:          mdhtml.CommonFlags,
+		RenderNodeHook: h.myRenderHook,
+	}
+	return mdhtml.NewRenderer(opts)
+}