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json.go
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json.go
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package parser
import (
"encoding/json"
"fmt"
"io"
"strconv"
"github.com/ChrisTrenkamp/xsel/node"
)
type JsonElement struct {
local string
}
func (j JsonElement) Space() string {
return ""
}
func (j JsonElement) Local() string {
return j.local
}
type JsonCharData struct {
value string
}
func (j JsonCharData) CharDataValue() string {
return j.value
}
type stateType int
const (
arrayState stateType = iota
objectState
rootState
)
type jsonState struct {
stateType stateType
onField bool
emitEndElement bool
}
type jsonParser struct {
jsonReader *json.Decoder
stateStack []jsonState
}
func (j *jsonParser) pushState(s stateType) {
j.stateStack = append(j.stateStack, jsonState{stateType: s})
}
func (j *jsonParser) currentState() stateType {
if len(j.stateStack) == 0 {
return rootState
}
return j.stateStack[len(j.stateStack)-1].stateType
}
func (j *jsonParser) popState() {
j.stateStack = j.stateStack[:len(j.stateStack)-1]
}
func (j *jsonParser) setOnField(b bool) {
if len(j.stateStack) > 0 {
j.stateStack[len(j.stateStack)-1].onField = b
}
}
func (j *jsonParser) isOnField() bool {
if len(j.stateStack) == 0 {
return false
}
return j.stateStack[len(j.stateStack)-1].onField
}
func (j *jsonParser) setEmitEndElement(b bool) {
if len(j.stateStack) > 0 {
j.stateStack[len(j.stateStack)-1].emitEndElement = b
}
}
func (j *jsonParser) isOnEmitEndElement() bool {
if len(j.stateStack) == 0 {
return false
}
return j.stateStack[len(j.stateStack)-1].emitEndElement
}
func jsonTokenValue(tok json.Token) string {
switch t := tok.(type) {
case bool:
return fmt.Sprintf("%t", t)
case float64:
str := strconv.FormatFloat(t, 'g', -1, 64)
return str
case json.Number:
return string(t)
case string:
return t
}
return "null"
}
func (j *jsonParser) Pull() (node.Node, bool, error) {
if j.isOnEmitEndElement() {
j.setEmitEndElement(false)
return nil, true, nil
}
tok, err := j.jsonReader.Token()
if err != nil {
return nil, false, err
}
switch t := tok.(type) {
case json.Delim:
switch t.String() {
case "{":
if j.currentState() == objectState {
j.setOnField(true)
}
j.pushState(objectState)
j.setOnField(true)
return JsonElement{local: "#obj"}, false, nil
case "}":
j.popState()
if j.isOnField() {
j.setEmitEndElement(true)
}
return nil, true, nil
case "[":
if j.currentState() == objectState {
j.setOnField(true)
}
j.pushState(arrayState)
return JsonElement{local: "#arr"}, false, nil
case "]":
j.popState()
if j.isOnField() {
j.setEmitEndElement(true)
}
return nil, true, nil
}
}
val := jsonTokenValue(tok)
switch j.currentState() {
case rootState:
return JsonCharData{value: val}, false, nil
case objectState:
if j.isOnField() {
j.setOnField(false)
return JsonElement{local: val}, false, nil
} else {
j.setOnField(true)
j.setEmitEndElement(true)
}
}
return JsonCharData{value: val}, false, nil
}
// Create a Parser that reads the given JSON document.
func ReadJson(in io.Reader) Parser {
jsonReader := json.NewDecoder(in)
return &jsonParser{
jsonReader: jsonReader,
stateStack: make([]jsonState, 0),
}
}