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transcode.go
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transcode.go
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// Package transcode is a library that will convert markup languages (currently
// JSON and YAML) from one form to another.
package transcode
import (
"bytes"
"encoding/json"
"fmt"
"io"
"github.com/tidwall/gjson"
yaml "gopkg.in/yaml.v3"
)
var (
newline = []byte{'\n'}
quotation = []byte{'"'}
comma = []byte{','}
leftBracket = []byte{'['}
rightBracket = []byte{']'}
leftCurly = []byte{'{'}
rightCurly = []byte{'}'}
colon = []byte{':'}
)
func New(w io.Writer) Transcoder {
return Transcoder{
w: w,
Indent: 4,
}
}
type Transcoder struct {
Indent int
w io.Writer
written bool
}
// JSONFromYAML transcodes YAML contained in yamlData
//
// Multiple documents are not supported.
func (t Transcoder) JSONFromYAML(yamlData io.Reader) error {
dec := yaml.NewDecoder(yamlData)
var n yaml.Node
if err := dec.Decode(&n); err != nil {
return err
}
yn := yamlnode{&n}
return yn.encode(t.w)
}
// YAMLFromJSON transcodes JSON contained in jsonData into YAML
//
// Transcoding multiple items are not supported. Each root record will be seperated
// by "---"
func (t Transcoder) YAMLFromJSON(jsonData io.Reader) error {
var o json.RawMessage
dec := json.NewDecoder(jsonData)
dec.UseNumber()
if err := dec.Decode(&o); err != nil {
return err
}
in := bytes.Repeat([]byte{' '}, t.Indent)
err := jsonnode(o).encode(t.w, gjson.ParseBytes(o), 0, in)
if err != nil {
return err
}
for dec.More() {
t.w.Write(newline)
t.w.Write([]byte("---"))
t.w.Write(newline)
if err := dec.Decode(&o); err != nil {
return err
}
err = jsonnode(o).encode(t.w, gjson.ParseBytes(o), 0, in)
if err != nil {
return err
}
}
return nil
}
func JSONFromYAML(yamlData []byte) ([]byte, error) {
var yn yaml.Node
err := yaml.Unmarshal(yamlData, &yn)
if err != nil {
return nil, err
}
y := yamlnode{&yn}
b := bytes.NewBuffer(nil)
b.Grow(len(yamlData))
if err = y.EncodeJSON(b); err != nil {
return nil, err
}
return b.Bytes(), nil
}
func YAMLFromJSON(jsonData []byte) ([]byte, error) {
// going to do this twice to improve formatting
return jsonnode(jsonData).MarshalYAML()
}
type yamlnode struct{ *yaml.Node }
func (y yamlnode) EncodeJSON(w io.Writer) error {
return y.encode(w)
}
func (y yamlnode) encode(w io.Writer) error {
switch y.Kind {
case yaml.DocumentNode:
return y.encodeDocument(w)
case yaml.ScalarNode:
return y.encodeScalar(w)
case yaml.SequenceNode:
return y.encodeSequence(w)
case yaml.MappingNode:
return y.encodeMapping(w)
case yaml.AliasNode:
return fmt.Errorf("aliases are not currently supported")
default:
return fmt.Errorf("unknown node kind: %d", y.Kind)
}
}
func (y yamlnode) encodeDocument(w io.Writer) error {
for _, v := range y.Content {
return yamlnode{v}.EncodeJSON(w)
}
return nil
}
func (y yamlnode) encodeMapping(w io.Writer) error {
if len(y.Content)%2 != 0 {
return fmt.Errorf("mapping node has odd number of children")
}
w.Write(leftCurly)
var err error
var k []byte
for i := 0; i < len(y.Content); i += 2 {
if i > 0 {
w.Write(comma)
}
k, err = yamlnode{y.Content[i]}.encodeKey()
if err != nil {
return err
}
w.Write(k)
w.Write(colon)
err := yamlnode{y.Content[i+1]}.encode(w)
if err != nil {
return err
}
}
w.Write(rightCurly)
return nil
}
func (y yamlnode) encodeKey() ([]byte, error) {
switch y.Kind {
case yaml.ScalarNode:
sd, err := json.Marshal(y.Value)
if err != nil {
return nil, err
}
return sd, nil
default:
return nil, fmt.Errorf("unknown node key kind: %d", y.Kind)
}
}
func (y yamlnode) encodeSequence(w io.Writer) error {
w.Write(leftBracket)
var err error
for i, v := range y.Content {
if i > 0 {
w.Write(comma)
}
err = yamlnode{v}.encode(w)
if err != nil {
return err
}
}
w.Write(rightBracket)
return nil
}
func (y yamlnode) encodeScalar(w io.Writer) error {
switch y.Tag {
case "!!str":
b, err := y.encodeString()
if err != nil {
return err
}
_, err = w.Write(b)
return err
case "!!int", "!!float":
b, err := y.encodeNumber()
if err != nil {
return err
}
_, err = w.Write(b)
return err
case "!!bool":
w.Write([]byte(y.Value))
return nil
case "!!null":
w.Write([]byte("null"))
return nil
}
return fmt.Errorf("unknown scalar tag: %q", y.Tag)
}
func (y yamlnode) encodeString() ([]byte, error) {
return json.Marshal(y.Value)
}
func (y yamlnode) encodeNumber() ([]byte, error) {
if isNumber([]byte(y.Value)) {
return json.Marshal(json.Number(y.Value))
}
return json.Marshal(y.Value)
}
type jsonnode json.RawMessage
// MarshalYAML implements yaml.BytesMarshaler
func (j jsonnode) MarshalYAML() ([]byte, error) {
b := bytes.NewBuffer(nil)
b.Grow(len(j) * 2)
err := j.EncodeYAML(b)
if err != nil {
return nil, err
}
return b.Bytes(), nil
}
func (j jsonnode) EncodeYAML(w io.Writer) error {
return j.encode(w, gjson.ParseBytes(j), 0, []byte(" "))
}
func (j jsonnode) encode(w io.Writer, r gjson.Result, indent int, indention []byte) error {
switch r.Type {
case gjson.Null:
w.Write([]byte("null"))
return nil
case gjson.False:
w.Write([]byte("false"))
return nil
case gjson.True:
w.Write([]byte("true"))
return nil
case gjson.Number:
w.Write([]byte(r.Raw))
case gjson.String:
return j.encodeString(w, []byte(r.String()), indent, indention)
}
if r.IsArray() {
return j.encodeArray(w, r, indent, indention)
}
if r.IsObject() {
return j.encodeObject(w, r, indent, indention)
}
return nil
}
func isBool(k []byte) bool {
return bytes.Equal(k, []byte("true")) || bytes.Equal(k, []byte("false"))
}
func isYesNo(k []byte) bool {
return bytes.Equal(k, []byte("yes")) || bytes.Equal(k, []byte("no"))
}
func writeYAMLKey(w io.Writer, k []byte) {
quote := isNumber(k) || isBool(k) || isYesNo(k)
if quote {
w.Write(quotation)
}
w.Write(k)
if quote {
w.Write(quotation)
}
}
func writeIndention(w io.Writer, s []byte, i int) {
for j := 0; j < i; j++ {
w.Write(s)
}
}
func (j jsonnode) encodeObject(w io.Writer, r gjson.Result, indent int, indention []byte) error {
var err error
i := 0
r.ForEach(func(key, value gjson.Result) bool {
if i > 0 || indent > 0 {
w.Write(newline)
writeIndention(w, indention, indent)
}
i += 1
writeYAMLKey(w, []byte(key.String()))
w.Write([]byte(": "))
err = j.encode(w, value, indent+1, indention)
if err != nil {
return false
}
return err == nil
})
return nil
}
func (j jsonnode) encodeArray(w io.Writer, r gjson.Result, indent int, indention []byte) error {
var err error
i := 0
r.ForEach(func(_, value gjson.Result) bool {
if i > 0 || indent > 0 {
w.Write([]byte("\n"))
writeIndention(w, indention, indent)
}
i += 1
w.Write([]byte("- "))
err = j.encode(w, value, indent+1, indention)
if err != nil {
return false
}
return err == nil
})
return nil
}
func (j jsonnode) encodeString(w io.Writer, d []byte, indent int, indention []byte) error {
switch {
case isNumber(d) || isBool(d) || isYesNo(d) || bytes.ContainsAny(d, ":#\t\n\a\b\\\t\n\f\r\v\\'"):
w.Write(quotation)
for _, r := range d {
switch r {
case '\a':
w.Write([]byte("\\a"))
case '\b':
w.Write([]byte("\\b"))
case '\\':
w.Write([]byte("\\\\"))
case '\t':
w.Write([]byte("\\t"))
case '\n':
w.Write([]byte("\\n"))
case '\f':
w.Write([]byte("\\f"))
case '\r':
w.Write([]byte("\\r"))
case '\v':
w.Write([]byte("\\v"))
case '\'':
w.Write([]byte("\\'"))
case '"':
w.Write([]byte("\\\""))
default:
w.Write([]byte{r})
}
}
w.Write(quotation)
return nil
default:
// w.Write([]byte(strings.ReplaceAll(string(d), "\n", `\n`)))
for _, r := range d {
switch r {
case '\a':
w.Write([]byte("\\a"))
case '\b':
w.Write([]byte("\\b"))
case '\\':
w.Write([]byte("\\\\"))
case '\t':
w.Write([]byte("\\t"))
case '\n':
w.Write([]byte("\\n"))
case '\f':
w.Write([]byte("\\f"))
case '\r':
w.Write([]byte("\\r"))
case '\v':
w.Write([]byte("\\v"))
case '\'':
w.Write([]byte("\\'"))
case '"':
w.Write([]byte("\\\""))
default:
w.Write([]byte{r})
}
}
return nil
}
}
// func (j jsonnode) encodeStringBlock(r gjson.Result, indent int) ([]byte, error) {
// panic("not impl")
// }
// IsValid reports whether s is a valid JSON number literal.
//
// Taken from encoding/json/scanner.go
func isNumber(data []byte) bool {
// This function implements the JSON numbers grammar.
// See https://tools.ietf.org/html/rfc7159#section-6
// and https://www.json.org/img/number.png
if len(data) == 0 {
return false
}
// Optional -
if data[0] == '-' {
data = data[1:]
if len(data) == 0 {
return false
}
}
// Digits
switch {
default:
return false
case data[0] == '0':
data = data[1:]
case '1' <= data[0] && data[0] <= '9':
data = data[1:]
for len(data) > 0 && '0' <= data[0] && data[0] <= '9' {
data = data[1:]
}
}
// . followed by 1 or more digits.
if len(data) >= 2 && data[0] == '.' && '0' <= data[1] && data[1] <= '9' {
data = data[2:]
for len(data) > 0 && '0' <= data[0] && data[0] <= '9' {
data = data[1:]
}
}
// e or E followed by an optional - or + and
// 1 or more digits.
if len(data) >= 2 && (data[0] == 'e' || data[0] == 'E') {
data = data[1:]
if data[0] == '+' || data[0] == '-' {
data = data[1:]
if len(data) == 0 {
return false
}
}
for len(data) > 0 && '0' <= data[0] && data[0] <= '9' {
data = data[1:]
}
}
// Make sure we are at the end.
return len(data) == 0
}