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|
package dencoding
import (
"encoding/json"
"fmt"
"io"
"reflect"
"strings"
)
// JSONDecoder wraps a standard json encoder to implement custom ordering logic.
type JSONDecoder struct {
decoder *json.Decoder
}
// NewJSONDecoder returns a new dencoding JSONDecoder.
func NewJSONDecoder(r io.Reader, options ...JSONDecoderOption) *JSONDecoder {
jsonDecoder := json.NewDecoder(r)
jsonDecoder.UseNumber()
decoder := &JSONDecoder{
decoder: jsonDecoder,
}
for _, o := range options {
o.ApplyDecoder(decoder)
}
return decoder
}
// Decode decodes the next item found in the decoder and writes it to v.
func (decoder *JSONDecoder) Decode(v any) error {
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Pointer || rv.IsNil() {
return fmt.Errorf("invalid decode target: %s", reflect.TypeOf(v))
}
rve := rv.Elem()
t, err := decoder.decoder.Token()
if err != nil {
return err
}
switch t {
case jsonOpenObject:
object, err := decoder.decodeObject()
if err != nil {
return fmt.Errorf("could not decode object: %w", err)
}
rve.Set(reflect.ValueOf(object))
case jsonOpenArray:
arr, err := decoder.decodeArray()
if err != nil {
return fmt.Errorf("could not decode array: %w", err)
}
rve.Set(reflect.ValueOf(arr))
default:
value, err := decoder.decodeValue(t)
if err != nil {
return err
}
rve.Set(reflect.ValueOf(value))
}
return nil
}
func (decoder *JSONDecoder) decodeObject() (*Map, error) {
res := NewMap()
var key any = nil
for {
t, err := decoder.decoder.Token()
if err != nil {
// We don't expect an EOF here since we're in the middle of processing an object.
return res, err
}
switch t {
case jsonOpenArray:
if key == nil {
return res, fmt.Errorf("unexpected token: %v", t)
}
value, err := decoder.decodeArray()
if err != nil {
return res, err
}
res.Set(key.(string), value)
key = nil
case jsonCloseArray:
return res, fmt.Errorf("unexpected token: %v", t)
case jsonCloseObject:
return res, nil
case jsonOpenObject:
if key == nil {
return res, fmt.Errorf("unexpected token: %v", t)
}
value, err := decoder.decodeObject()
if err != nil {
return res, err
}
res.Set(key.(string), value)
key = nil
default:
if key == nil {
key = t
} else {
value, err := decoder.decodeValue(t)
if err != nil {
return nil, err
}
res.Set(key.(string), value)
key = nil
}
}
}
}
func (decoder *JSONDecoder) decodeValue(t json.Token) (any, error) {
switch tv := t.(type) {
case json.Number:
strNum := tv.String()
if strings.Contains(strNum, ".") {
floatNum, err := tv.Float64()
if err == nil {
return floatNum, nil
}
return nil, err
}
intNum, err := tv.Int64()
if err == nil {
return intNum, nil
}
return nil, err
}
return t, nil
}
func (decoder *JSONDecoder) decodeArray() ([]any, error) {
res := make([]any, 0)
for {
t, err := decoder.decoder.Token()
if err != nil {
// We don't expect an EOF here since we're in the middle of processing an object.
return res, err
}
switch t {
case jsonOpenArray:
value, err := decoder.decodeArray()
if err != nil {
return res, err
}
res = append(res, value)
case jsonCloseArray:
return res, nil
case jsonCloseObject:
return res, fmt.Errorf("unexpected token: %t", t)
case jsonOpenObject:
value, err := decoder.decodeObject()
if err != nil {
return res, err
}
res = append(res, value)
default:
value, err := decoder.decodeValue(t)
if err != nil {
return nil, err
}
res = append(res, value)
}
}
}
|
