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package main
// example for https://blog.kowalczyk.info/article/cxn3/advanced-markdown-processing-in-go.html
import (
"fmt"
"github.com/gomarkdown/markdown"
"github.com/gomarkdown/markdown/ast"
"github.com/gomarkdown/markdown/html"
"github.com/gomarkdown/markdown/parser"
"bytes"
"io"
"strings"
)
type Gallery struct {
ast.Leaf
ImageURLS []string
}
var gallery = []byte(":gallery\n")
func parseGallery(data []byte) (ast.Node, []byte, int) {
if !bytes.HasPrefix(data, gallery) {
return nil, nil, 0
}
fmt.Printf("Found a gallery!\n\n")
i := len(gallery)
// find empty line
// TODO: should also consider end of document
end := bytes.Index(data[i:], []byte("\n\n"))
if end < 0 {
return nil, data, 0
}
end = end + i
lines := string(data[i:end])
parts := strings.Split(lines, "\n")
res := &Gallery{
ImageURLS: parts,
}
return res, nil, end
}
func parserHook(data []byte) (ast.Node, []byte, int) {
if node, d, n := parseGallery(data); node != nil {
return node, d, n
}
return nil, nil, 0
}
func newMarkdownParser() *parser.Parser {
extensions := parser.CommonExtensions
p := parser.NewWithExtensions(extensions)
p.Opts.ParserHook = parserHook
return p
}
func galleryRenderHook(w io.Writer, node ast.Node, entering bool) (ast.WalkStatus, bool) {
if _, ok := node.(*Gallery); ok {
if entering {
// note: just for illustration purposes
// actual implemenation of gallery in HTML / JavaScript is long
io.WriteString(w, "\n<gallery></gallery>\n\n")
}
return ast.GoToNext, true
}
return ast.GoToNext, false
}
func newGalleryRender() *html.Renderer {
opts := html.RendererOptions{
Flags: html.CommonFlags,
RenderNodeHook: galleryRenderHook,
}
return html.NewRenderer(opts)
}
var mds = `document
:gallery
/img/image-1.png
/img/image-2.png
Rest of the document.`
func parserHookExample() {
md := []byte(mds)
p := newMarkdownParser()
doc := p.Parse([]byte(md))
renderer := newGalleryRender()
html := markdown.Render(doc, renderer)
fmt.Printf("--- Markdown:\n%s\n\n--- HTML:\n%s\n", md, html)
}
func main() {
parserHookExample()
}
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