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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/parser"
"bytes"
"net/url"
)
// mds shows the two extensions provided in this example. The tricky
// part about the wiki link example is that we need to defer to the
// original code in the library if the opening square bracket we're
// looking at is not a wiki link.
var mds = `This is a [[wiki link]].
#markdown #example`
// wikiLink returns an inline parser function. This indirection is
// required because we want to call the previous definition in case
// this is not a wikiLink.
func wikiLink(p *parser.Parser, fn func(p *parser.Parser, data []byte, offset int) (int, ast.Node)) func(p *parser.Parser, data []byte, offset int) (int, ast.Node) {
return func (p *parser.Parser, original []byte, offset int) (int, ast.Node) {
data := original[offset:]
n := len(data)
// minimum: [[X]]
if n < 5 || data[1] != '[' {
return fn(p, original, offset)
}
i := 2
for i+1 < n && data[i] != ']' && data[i+1] != ']' {
i++
}
text := data[2:i+1]
link := &ast.Link{
Destination: []byte(url.PathEscape(string(text))),
}
ast.AppendChild(link, &ast.Text{Leaf: ast.Leaf{Literal: text}})
return i+3, link
}
}
// hashtag links every hashtag to a search for that tag. How this
// search is then handled is of course a different problem. For your
// own code, you probably need to use a different destination URL.
func hashtag(p *parser.Parser, data []byte, offset int) (int, ast.Node) {
data = data[offset:]
i := 0
n := len(data)
for i < n && !parser.IsSpace(data[i]) {
i++
}
if i == 0 {
return 0, nil
}
link := &ast.Link{
Destination: append([]byte("/search?q=%23"), data[1:i]...),
}
text := bytes.ReplaceAll(data[0:i], []byte("_"), []byte(" "))
ast.AppendChild(link, &ast.Text{Leaf: ast.Leaf{Literal: text}})
return i, link
}
func inlineExample() {
md := []byte(mds)
parser := parser.New()
prev := parser.RegisterInline('[', nil)
parser.RegisterInline('[', wikiLink(parser, prev))
parser.RegisterInline('#', hashtag)
html := markdown.ToHTML(md, parser, nil)
fmt.Printf("--- Markdown:\n%s\n\n--- HTML:\n%s\n", md, html)
}
func main() {
inlineExample()
}
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