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package templates
import (
"encoding/json"
"fmt"
"strings"
"unicode"
"github.com/naoina/toml"
"gopkg.in/yaml.v2"
)
func extractFrontMatter(input string) (map[string]interface{}, string, error) {
// get the bounds of the first non-empty line
var firstLineStart, firstLineEnd int
lineEmpty := true
for i, b := range input {
if b == '\n' {
firstLineStart = firstLineEnd
if firstLineStart > 0 {
firstLineStart++ // skip newline character
}
firstLineEnd = i
if !lineEmpty {
break
}
continue
}
lineEmpty = lineEmpty && unicode.IsSpace(b)
}
firstLine := input[firstLineStart:firstLineEnd]
// see what kind of front matter there is, if any
var closingFence string
var fmParser func([]byte) (map[string]interface{}, error)
switch string(firstLine) {
case yamlFrontMatterFenceOpen:
fmParser = yamlFrontMatter
closingFence = yamlFrontMatterFenceClose
case tomlFrontMatterFenceOpen:
fmParser = tomlFrontMatter
closingFence = tomlFrontMatterFenceClose
case jsonFrontMatterFenceOpen:
fmParser = jsonFrontMatter
closingFence = jsonFrontMatterFenceClose
default:
// no recognized front matter; whole document is body
return nil, input, nil
}
// find end of front matter
fmEndFenceStart := strings.Index(input[firstLineEnd:], "\n"+closingFence)
if fmEndFenceStart < 0 {
return nil, "", fmt.Errorf("unterminated front matter")
}
fmEndFenceStart += firstLineEnd + 1 // add 1 to account for newline
// extract and parse front matter
frontMatter := input[firstLineEnd:fmEndFenceStart]
fm, err := fmParser([]byte(frontMatter))
if err != nil {
return nil, "", err
}
// the rest is the body
body := input[fmEndFenceStart+len(closingFence):]
return fm, body, nil
}
func yamlFrontMatter(input []byte) (map[string]interface{}, error) {
m := make(map[string]interface{})
err := yaml.Unmarshal(input, &m)
return m, err
}
func tomlFrontMatter(input []byte) (map[string]interface{}, error) {
m := make(map[string]interface{})
err := toml.Unmarshal(input, &m)
return m, err
}
func jsonFrontMatter(input []byte) (map[string]interface{}, error) {
input = append([]byte{'{'}, input...)
input = append(input, '}')
m := make(map[string]interface{})
err := json.Unmarshal(input, &m)
return m, err
}
type parsedMarkdownDoc struct {
Meta map[string]interface{} `json:"meta,omitempty"`
Body string `json:"body,omitempty"`
}
const (
yamlFrontMatterFenceOpen, yamlFrontMatterFenceClose = "---", "---"
tomlFrontMatterFenceOpen, tomlFrontMatterFenceClose = "+++", "+++"
jsonFrontMatterFenceOpen, jsonFrontMatterFenceClose = "{", "}"
)
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