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// package meta is a extension for the goldmark(http://github.com/yuin/goldmark).
//
// This extension parses YAML metadata blocks and store metadata to a
// parser.Context.
package meta
import (
"bytes"
"fmt"
"github.com/yuin/goldmark"
gast "github.com/yuin/goldmark/ast"
east "github.com/yuin/goldmark/extension/ast"
"github.com/yuin/goldmark/parser"
"github.com/yuin/goldmark/text"
"github.com/yuin/goldmark/util"
"gopkg.in/yaml.v2"
)
type data struct {
Map map[string]interface{}
Items yaml.MapSlice
Error error
Node gast.Node
}
var contextKey = parser.NewContextKey()
// Get returns a YAML metadata.
func Get(pc parser.Context) map[string]interface{} {
v := pc.Get(contextKey)
if v == nil {
return nil
}
d := v.(*data)
return d.Map
}
// TryGet tries to get a YAML metadata.
// If there are YAML parsing errors, then nil and error are returned
func TryGet(pc parser.Context) (map[string]interface{}, error) {
dtmp := pc.Get(contextKey)
if dtmp == nil {
return nil, nil
}
d := dtmp.(*data)
if d.Error != nil {
return nil, d.Error
}
return d.Map, nil
}
// GetItems returns a YAML metadata.
// GetItems preserves defined key order.
func GetItems(pc parser.Context) yaml.MapSlice {
v := pc.Get(contextKey)
if v == nil {
return nil
}
d := v.(*data)
return d.Items
}
// TryGetItems returns a YAML metadata.
// TryGetItems preserves defined key order.
// If there are YAML parsing errors, then nil and erro are returned.
func TryGetItems(pc parser.Context) (yaml.MapSlice, error) {
dtmp := pc.Get(contextKey)
if dtmp == nil {
return nil, nil
}
d := dtmp.(*data)
if d.Error != nil {
return nil, d.Error
}
return d.Items, nil
}
type metaParser struct {
}
var defaultMetaParser = &metaParser{}
// NewParser returns a BlockParser that can parse YAML metadata blocks.
func NewParser() parser.BlockParser {
return defaultMetaParser
}
func isSeparator(line []byte) bool {
line = util.TrimRightSpace(util.TrimLeftSpace(line))
for i := 0; i < len(line); i++ {
if line[i] != '-' {
return false
}
}
return true
}
func (b *metaParser) Trigger() []byte {
return []byte{'-'}
}
func (b *metaParser) Open(parent gast.Node, reader text.Reader, pc parser.Context) (gast.Node, parser.State) {
linenum, _ := reader.Position()
if linenum != 0 {
return nil, parser.NoChildren
}
line, _ := reader.PeekLine()
if isSeparator(line) {
return gast.NewTextBlock(), parser.NoChildren
}
return nil, parser.NoChildren
}
func (b *metaParser) Continue(node gast.Node, reader text.Reader, pc parser.Context) parser.State {
line, segment := reader.PeekLine()
if isSeparator(line) && !util.IsBlank(line) {
reader.Advance(segment.Len())
return parser.Close
}
node.Lines().Append(segment)
return parser.Continue | parser.NoChildren
}
func (b *metaParser) Close(node gast.Node, reader text.Reader, pc parser.Context) {
lines := node.Lines()
var buf bytes.Buffer
for i := 0; i < lines.Len(); i++ {
segment := lines.At(i)
buf.Write(segment.Value(reader.Source()))
}
d := &data{}
d.Node = node
meta := map[string]interface{}{}
if err := yaml.Unmarshal(buf.Bytes(), &meta); err != nil {
d.Error = err
} else {
d.Map = meta
}
metaMapSlice := yaml.MapSlice{}
if err := yaml.Unmarshal(buf.Bytes(), &metaMapSlice); err != nil {
d.Error = err
} else {
d.Items = metaMapSlice
}
pc.Set(contextKey, d)
if d.Error == nil {
node.Parent().RemoveChild(node.Parent(), node)
}
}
func (b *metaParser) CanInterruptParagraph() bool {
return false
}
func (b *metaParser) CanAcceptIndentedLine() bool {
return false
}
type astTransformer struct {
}
var defaultASTTransformer = &astTransformer{}
func (a *astTransformer) Transform(node *gast.Document, reader text.Reader, pc parser.Context) {
dtmp := pc.Get(contextKey)
if dtmp == nil {
return
}
d := dtmp.(*data)
if d.Error != nil {
msg := gast.NewString([]byte(fmt.Sprintf("<!-- %s -->", d.Error)))
msg.SetCode(true)
d.Node.AppendChild(d.Node, msg)
return
}
meta := GetItems(pc)
if meta == nil {
return
}
table := east.NewTable()
alignments := []east.Alignment{}
for range meta {
alignments = append(alignments, east.AlignNone)
}
row := east.NewTableRow(alignments)
for _, item := range meta {
cell := east.NewTableCell()
cell.AppendChild(cell, gast.NewString([]byte(fmt.Sprintf("%v", item.Key))))
row.AppendChild(row, cell)
}
table.AppendChild(table, east.NewTableHeader(row))
row = east.NewTableRow(alignments)
for _, item := range meta {
cell := east.NewTableCell()
cell.AppendChild(cell, gast.NewString([]byte(fmt.Sprintf("%v", item.Value))))
row.AppendChild(row, cell)
}
table.AppendChild(table, row)
node.InsertBefore(node, node.FirstChild(), table)
}
// Option is a functional option type for this extension.
type Option func(*meta)
// WithTable is a functional option that renders a YAML metadata as a table.
func WithTable() Option {
return func(m *meta) {
m.Table = true
}
}
type meta struct {
Table bool
}
// Meta is a extension for the goldmark.
var Meta = &meta{}
// New returns a new Meta extension.
func New(opts ...Option) goldmark.Extender {
e := &meta{}
for _, opt := range opts {
opt(e)
}
return e
}
func (e *meta) Extend(m goldmark.Markdown) {
m.Parser().AddOptions(
parser.WithBlockParsers(
util.Prioritized(NewParser(), 0),
),
)
if e.Table {
m.Parser().AddOptions(
parser.WithASTTransformers(
util.Prioritized(defaultASTTransformer, 0),
),
)
}
}
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