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-rw-r--r--modules/markup/markdown/meta.go103
1 files changed, 103 insertions, 0 deletions
diff --git a/modules/markup/markdown/meta.go b/modules/markup/markdown/meta.go
new file mode 100644
index 0000000..e76b253
--- /dev/null
+++ b/modules/markup/markdown/meta.go
@@ -0,0 +1,103 @@
+// 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
+}