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package main
// example for https://blog.kowalczyk.info/article/cxn3/advanced-markdown-processing-in-go.html
import (
"fmt"
"io"
"github.com/gomarkdown/markdown"
"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"
)
var (
htmlFormatter *html.Formatter
highlightStyle *chroma.Style
)
func init() {
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))
}
}
// based on https://github.com/alecthomas/chroma/blob/master/quick/quick.go
func 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 htmlFormatter.Format(w, highlightStyle, it)
}
// an actual rendering of Paragraph is more complicated
func renderCode(w io.Writer, codeBlock *ast.CodeBlock, entering bool) {
defaultLang := ""
lang := string(codeBlock.Info)
htmlHighlight(w, string(codeBlock.Literal), lang, defaultLang)
}
func myRenderHook(w io.Writer, node ast.Node, entering bool) (ast.WalkStatus, bool) {
if code, ok := node.(*ast.CodeBlock); ok {
renderCode(w, code, entering)
return ast.GoToNext, true
}
return ast.GoToNext, false
}
func newCustomizedRender() *mdhtml.Renderer {
opts := mdhtml.RendererOptions{
Flags: mdhtml.CommonFlags,
RenderNodeHook: myRenderHook,
}
return mdhtml.NewRenderer(opts)
}
var mds = "code block:\n```go\nvar n = 384\n```"
func codeHighlight() {
md := []byte(mds)
renderer := newCustomizedRender()
html := markdown.ToHTML(md, nil, renderer)
fmt.Printf("--- Markdown:\n%s\n\n--- HTML:\n%s\n", md, html)
}
func main() {
codeHighlight()
}
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