forked from caddyserver/caddy
/
metadata.go
242 lines (208 loc) · 5.78 KB
/
metadata.go
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package markdown
import (
"bytes"
"encoding/json"
"fmt"
"time"
"github.com/BurntSushi/toml"
"gopkg.in/yaml.v2"
)
// Metadata stores a page's metadata
type Metadata struct {
// Page title
Title string
// Page template
Template string
// Publish date
Date time.Time
// Variables to be used with Template
Variables map[string]string
// Flags to be used with Template
Flags map[string]bool
}
// load loads parsed values in parsedMap into Metadata
func (m *Metadata) load(parsedMap map[string]interface{}) {
if title, ok := parsedMap["title"]; ok {
m.Title, _ = title.(string)
}
if template, ok := parsedMap["template"]; ok {
m.Template, _ = template.(string)
}
if date, ok := parsedMap["date"].(string); ok {
if t, err := time.Parse(timeLayout, date); err == nil {
m.Date = t
}
}
// store everything as a variable
for key, val := range parsedMap {
switch v := val.(type) {
case string:
m.Variables[key] = v
case bool:
m.Flags[key] = v
}
}
}
// MetadataParser is a an interface that must be satisfied by each parser
type MetadataParser interface {
// Opening identifier
Opening() []byte
// Closing identifier
Closing() []byte
// Parse the metadata.
// Returns the remaining page contents (Markdown)
// after extracting metadata
Parse([]byte) ([]byte, error)
// Parsed metadata.
// Should be called after a call to Parse returns no error
Metadata() Metadata
}
// JSONMetadataParser is the MetadataParser for JSON
type JSONMetadataParser struct {
metadata Metadata
}
// Parse the metadata
func (j *JSONMetadataParser) Parse(b []byte) ([]byte, error) {
b, markdown, err := extractMetadata(j, b)
if err != nil {
return markdown, err
}
m := make(map[string]interface{})
// Read the preceding JSON object
decoder := json.NewDecoder(bytes.NewReader(b))
if err := decoder.Decode(&m); err != nil {
return markdown, err
}
j.metadata.load(m)
return markdown, nil
}
// Metadata returns parsed metadata. It should be called
// only after a call to Parse returns without error.
func (j *JSONMetadataParser) Metadata() Metadata {
return j.metadata
}
// Opening returns the opening identifier JSON metadata
func (j *JSONMetadataParser) Opening() []byte {
return []byte("{")
}
// Closing returns the closing identifier JSON metadata
func (j *JSONMetadataParser) Closing() []byte {
return []byte("}")
}
// TOMLMetadataParser is the MetadataParser for TOML
type TOMLMetadataParser struct {
metadata Metadata
}
// Parse the metadata
func (t *TOMLMetadataParser) Parse(b []byte) ([]byte, error) {
b, markdown, err := extractMetadata(t, b)
if err != nil {
return markdown, err
}
m := make(map[string]interface{})
if err := toml.Unmarshal(b, &m); err != nil {
return markdown, err
}
t.metadata.load(m)
return markdown, nil
}
// Metadata returns parsed metadata. It should be called
// only after a call to Parse returns without error.
func (t *TOMLMetadataParser) Metadata() Metadata {
return t.metadata
}
// Opening returns the opening identifier TOML metadata
func (t *TOMLMetadataParser) Opening() []byte {
return []byte("+++")
}
// Closing returns the closing identifier TOML metadata
func (t *TOMLMetadataParser) Closing() []byte {
return []byte("+++")
}
// YAMLMetadataParser is the MetadataParser for YAML
type YAMLMetadataParser struct {
metadata Metadata
}
// Parse the metadata
func (y *YAMLMetadataParser) Parse(b []byte) ([]byte, error) {
b, markdown, err := extractMetadata(y, b)
if err != nil {
return markdown, err
}
m := make(map[string]interface{})
if err := yaml.Unmarshal(b, &m); err != nil {
return markdown, err
}
y.metadata.load(m)
return markdown, nil
}
// Metadata returns parsed metadata. It should be called
// only after a call to Parse returns without error.
func (y *YAMLMetadataParser) Metadata() Metadata {
return y.metadata
}
// Opening returns the opening identifier YAML metadata
func (y *YAMLMetadataParser) Opening() []byte {
return []byte("---")
}
// Closing returns the closing identifier YAML metadata
func (y *YAMLMetadataParser) Closing() []byte {
return []byte("---")
}
// extractMetadata separates metadata content from from markdown content in b.
// It returns the metadata, the remaining bytes (markdown), and an error, if any.
func extractMetadata(parser MetadataParser, b []byte) (metadata []byte, markdown []byte, err error) {
b = bytes.TrimSpace(b)
openingLine := parser.Opening()
closingLine := parser.Closing()
if !bytes.HasPrefix(b, openingLine) {
return nil, b, fmt.Errorf("first line missing expected metadata identifier")
}
metaStart := len(openingLine)
if _, ok := parser.(*JSONMetadataParser); ok {
metaStart = 0
}
metaEnd := bytes.Index(b[metaStart:], closingLine)
if metaEnd == -1 {
return nil, nil, fmt.Errorf("metadata not closed ('%s' not found)", parser.Closing())
}
metaEnd += metaStart
if _, ok := parser.(*JSONMetadataParser); ok {
metaEnd += len(closingLine)
}
metadata = b[metaStart:metaEnd]
markdown = b[metaEnd:]
if _, ok := parser.(*JSONMetadataParser); !ok {
markdown = b[metaEnd+len(closingLine):]
}
return metadata, markdown, nil
}
// findParser finds the parser using line that contains opening identifier
func findParser(b []byte) MetadataParser {
var line []byte
// Read first line
if _, err := fmt.Fscanln(bytes.NewReader(b), &line); err != nil {
return nil
}
line = bytes.TrimSpace(line)
for _, parser := range parsers() {
if bytes.Equal(parser.Opening(), line) {
return parser
}
}
return nil
}
func newMetadata() Metadata {
return Metadata{
Variables: make(map[string]string),
Flags: make(map[string]bool),
}
}
// parsers returns all available parsers
func parsers() []MetadataParser {
return []MetadataParser{
&JSONMetadataParser{metadata: newMetadata()},
&TOMLMetadataParser{metadata: newMetadata()},
&YAMLMetadataParser{metadata: newMetadata()},
}
}