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// Copyright 2020 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package markdown
import (
"bytes"
"errors"
"unicode"
"unicode/utf8"
"gopkg.in/yaml.v3"
)
func isYAMLSeparator(line []byte) bool {
idx := 0
for ; idx < len(line); idx++ {
if line[idx] >= utf8.RuneSelf {
r, sz := utf8.DecodeRune(line[idx:])
if !unicode.IsSpace(r) {
return false
}
idx += sz
continue
}
if line[idx] != ' ' {
break
}
}
dashCount := 0
for ; idx < len(line); idx++ {
if line[idx] != '-' {
break
}
dashCount++
}
if dashCount < 3 {
return false
}
for ; idx < len(line); idx++ {
if line[idx] >= utf8.RuneSelf {
r, sz := utf8.DecodeRune(line[idx:])
if !unicode.IsSpace(r) {
return false
}
idx += sz
continue
}
if line[idx] != ' ' {
return false
}
}
return true
}
// ExtractMetadata consumes a markdown file, parses YAML frontmatter,
// and returns the frontmatter metadata separated from the markdown content
func ExtractMetadata(contents string, out any) (string, error) {
body, err := ExtractMetadataBytes([]byte(contents), out)
return string(body), err
}
// ExtractMetadata consumes a markdown file, parses YAML frontmatter,
// and returns the frontmatter metadata separated from the markdown content
func ExtractMetadataBytes(contents []byte, out any) ([]byte, error) {
var front, body []byte
start, end := 0, len(contents)
idx := bytes.IndexByte(contents[start:], '\n')
if idx >= 0 {
end = start + idx
}
line := contents[start:end]
if !isYAMLSeparator(line) {
return contents, errors.New("frontmatter must start with a separator line")
}
frontMatterStart := end + 1
for start = frontMatterStart; start < len(contents); start = end + 1 {
end = len(contents)
idx := bytes.IndexByte(contents[start:], '\n')
if idx >= 0 {
end = start + idx
}
line := contents[start:end]
if isYAMLSeparator(line) {
front = contents[frontMatterStart:start]
if end+1 < len(contents) {
body = contents[end+1:]
}
break
}
}
if len(front) == 0 {
return contents, errors.New("could not determine metadata")
}
if err := yaml.Unmarshal(front, out); err != nil {
return contents, err
}
return body, nil
}
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