Add parser.RegisterInline example

examples/inline.go

@@ -0,0 +1,83 @@
+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()
+}