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// Copyright 2019 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package mdstripper
import (
"bytes"
"io"
"github.com/russross/blackfriday/v2"
)
// MarkdownStripper extends blackfriday.Renderer
type MarkdownStripper struct {
links []string
coallesce bool
empty bool
}
const (
blackfridayExtensions = 0 |
blackfriday.NoIntraEmphasis |
blackfriday.Tables |
blackfriday.FencedCode |
blackfriday.Strikethrough |
blackfriday.NoEmptyLineBeforeBlock |
blackfriday.DefinitionLists |
blackfriday.Footnotes |
blackfriday.HeadingIDs |
blackfriday.AutoHeadingIDs |
// Not included in modules/markup/markdown/markdown.go;
// required here to process inline links
blackfriday.Autolink
)
// StripMarkdown parses markdown content by removing all markup and code blocks
// in order to extract links and other references
func StripMarkdown(rawBytes []byte) (string, []string) {
buf, links := StripMarkdownBytes(rawBytes)
return string(buf), links
}
// StripMarkdownBytes parses markdown content by removing all markup and code blocks
// in order to extract links and other references
func StripMarkdownBytes(rawBytes []byte) ([]byte, []string) {
stripper := &MarkdownStripper{
links: make([]string, 0, 10),
empty: true,
}
parser := blackfriday.New(blackfriday.WithRenderer(stripper), blackfriday.WithExtensions(blackfridayExtensions))
ast := parser.Parse(rawBytes)
var buf bytes.Buffer
stripper.RenderHeader(&buf, ast)
ast.Walk(func(node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
return stripper.RenderNode(&buf, node, entering)
})
stripper.RenderFooter(&buf, ast)
return buf.Bytes(), stripper.GetLinks()
}
// RenderNode is the main rendering method. It will be called once for
// every leaf node and twice for every non-leaf node (first with
// entering=true, then with entering=false). The method should write its
// rendition of the node to the supplied writer w.
func (r *MarkdownStripper) RenderNode(w io.Writer, node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
if !entering {
return blackfriday.GoToNext
}
switch node.Type {
case blackfriday.Text:
r.processString(w, node.Literal, node.Parent == nil)
return blackfriday.GoToNext
case blackfriday.Link:
r.processLink(w, node.LinkData.Destination)
r.coallesce = false
return blackfriday.SkipChildren
}
r.coallesce = false
return blackfriday.GoToNext
}
// RenderHeader is a method that allows the renderer to produce some
// content preceding the main body of the output document.
func (r *MarkdownStripper) RenderHeader(w io.Writer, ast *blackfriday.Node) {
}
// RenderFooter is a symmetric counterpart of RenderHeader.
func (r *MarkdownStripper) RenderFooter(w io.Writer, ast *blackfriday.Node) {
}
func (r *MarkdownStripper) doubleSpace(w io.Writer) {
if !r.empty {
_, _ = w.Write([]byte{'\n'})
}
}
func (r *MarkdownStripper) processString(w io.Writer, text []byte, coallesce bool) {
// Always break-up words
if !coallesce || !r.coallesce {
r.doubleSpace(w)
}
_, _ = w.Write(text)
r.coallesce = coallesce
r.empty = false
}
func (r *MarkdownStripper) processLink(w io.Writer, link []byte) {
// Links are processed out of band
r.links = append(r.links, string(link))
r.coallesce = false
}
// GetLinks returns the list of link data collected while parsing
func (r *MarkdownStripper) GetLinks() []string {
return r.links
}
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