111 lines
2.6 KiB
Go
111 lines
2.6 KiB
Go
package md
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import (
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"bytes"
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"strings"
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"github.com/yuin/goldmark"
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"github.com/yuin/goldmark/ast"
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"github.com/yuin/goldmark/renderer"
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"github.com/yuin/goldmark/renderer/html"
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"github.com/yuin/goldmark/util"
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)
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type UrlTransformer = func(string) (string, error)
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type urlTransformerExtension struct {
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transformer UrlTransformer
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}
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func (e *urlTransformerExtension) Extend(m goldmark.Markdown) {
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m.Renderer().AddOptions(renderer.WithNodeRenderers(
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util.Prioritized(&urlRenderer{e.transformer}, 500),
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))
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}
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type urlRenderer struct {
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transformer UrlTransformer
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}
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func (r *urlRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
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reg.Register(ast.KindImage, r.renderImage)
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reg.Register(ast.KindLink, r.renderLink)
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}
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func (r *urlRenderer) renderImage(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
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if !entering {
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return ast.WalkContinue, nil
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}
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n := node.(*ast.Image)
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url, err := r.resolveUrl(string(n.Destination))
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if err != nil {
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return ast.WalkStop, err
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}
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_, _ = w.WriteString(`<img src="`)
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_, _ = w.WriteString(url)
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_, _ = w.WriteString(`" alt="`)
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_, _ = w.Write(nodeToHTMLText(n, source))
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_ = w.WriteByte('"')
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if n.Title != nil {
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_, _ = w.WriteString(` title="`)
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_, _ = w.Write(n.Title)
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_ = w.WriteByte('"')
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}
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if n.Attributes() != nil {
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html.RenderAttributes(w, n, html.ImageAttributeFilter)
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}
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_, _ = w.WriteString(">")
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return ast.WalkSkipChildren, nil
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}
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func (r *urlRenderer) renderLink(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
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if !entering {
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return ast.WalkContinue, nil
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}
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n := node.(*ast.Link)
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url, err := r.resolveUrl(string(n.Destination))
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if err != nil {
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return ast.WalkStop, err
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}
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_, _ = w.WriteString(`<a href="`)
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_, _ = w.WriteString(url)
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_, _ = w.WriteString(`"`)
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if n.Attributes() != nil {
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html.RenderAttributes(w, n, html.ImageAttributeFilter)
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}
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_, _ = w.WriteString(`>`)
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if n.Title != nil {
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_, _ = w.Write(n.Title)
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}
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_, _ = w.WriteString("</a>")
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return ast.WalkSkipChildren, nil
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}
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func (r *urlRenderer) resolveUrl(url string) (string, error) {
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if !strings.HasPrefix(url, "http://") && !strings.HasPrefix(url, "https://") {
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return r.transformer(url)
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}
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return url, nil
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}
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func nodeToHTMLText(n ast.Node, source []byte) []byte {
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var buf bytes.Buffer
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for c := n.FirstChild(); c != nil; c = c.NextSibling() {
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if s, ok := c.(*ast.String); ok && s.IsCode() {
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buf.Write(s.Text(source))
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} else if !c.HasChildren() {
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buf.Write(util.EscapeHTML(c.Text(source)))
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} else {
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buf.Write(nodeToHTMLText(c, source))
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}
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}
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return buf.Bytes()
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}
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