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|
package json
import (
"bufio"
"main/walk"
"strings"
"strconv"
"errors"
)
func isWhitespace(r rune) bool {
for _, ws := range " \t\r\n" {
if r == ws {
return true
}
}
return false
}
func isNumberRune(r rune) bool {
return '0' <= r && r <= '9' || r == '.'
}
type JSONReaderStructure int
const (
JSONReaderStructureArray JSONReaderStructure = iota
JSONReaderStructureMap
)
type JSONReaderState int
const (
JSONReaderStateValue JSONReaderState = iota
JSONReaderStateValueEnd
)
func NewJSONReader(reader *bufio.Reader) *JSONReader {
return &JSONReader {
path: nil,
structure: nil,
state: JSONReaderStateValue,
reader: reader,
}
}
type JSONReader struct {
path []walk.PathSegment
structure []JSONReaderStructure
state JSONReaderState
reader *bufio.Reader
prevStart bool
}
func (reader *JSONReader) Read() (walk.WalkItem, error) {
switch reader.state {
case JSONReaderStateValue:
if len(reader.structure) == 0 {
// Before the start of a root JSON value
return reader.readValue()
}
switch reader.structure[len(reader.structure) - 1] {
case JSONReaderStructureArray:
// Before a value inside an array
r, err := reader.nextNonWsRune()
if err != nil {
panic("Missing rest of array")
}
if r == ']' {
// End of an array
reader.structure = reader.structure[:len(reader.structure) - 1]
reader.path = reader.path[:len(reader.path) - 1]
reader.state = JSONReaderStateValueEnd
item := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.ArrayValue([]walk.ArrayElement{})),
Start: false,
PrevStart: reader.prevStart,
End: true,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return item, nil
}
// Element in array
reader.reader.UnreadRune()
prevIndex := reader.path[len(reader.path) - 1].(int)
reader.path[len(reader.path) - 1] = prevIndex + 1
return reader.readValue()
case JSONReaderStructureMap:
// Before a value inside a map
r, err := reader.nextNonWsRune()
if err != nil {
panic("Reached EOF inside JSON map")
}
if r == '}' {
// End of a map
reader.structure = reader.structure[:len(reader.structure) - 1]
reader.path = reader.path[:len(reader.path) - 1]
reader.state = JSONReaderStateValueEnd
item := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.MapValue([]walk.MapElement{})),
Start: false,
PrevStart: reader.prevStart,
End: true,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return item, nil
}
// Element in map
if r != '"' {
panic("Expected key in map, found something else")
}
key := reader.readString()
reader.path[len(reader.path) - 1] = key
r, err = reader.nextNonWsRune()
if err != nil {
panic("Reached EOF after map key")
}
if r != ':' {
panic("Expected : after map key, found something else")
}
return reader.readValue()
default:
panic("Invalid JSONReaderStructure")
}
case JSONReaderStateValueEnd:
if len(reader.structure) == 0 {
_, err := reader.nextNonWsRune()
if err == nil {
panic("input continues after JSON value")
}
return walk.WalkItem{}, errors.New("eof")
}
switch reader.structure[len(reader.structure) - 1] {
case JSONReaderStructureArray:
r, err := reader.nextNonWsRune()
if err != nil {
panic("Missing end of array")
}
if r == ']' {
reader.path = reader.path[:len(reader.path) - 1]
reader.structure = reader.structure[:len(reader.structure) - 1]
reader.state = JSONReaderStateValueEnd
item := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.ArrayValue([]walk.ArrayElement{})),
Start: false,
PrevStart: reader.prevStart,
End: true,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return item, nil
}
if r != ',' {
panic("Missing , after array value")
}
reader.state = JSONReaderStateValue
return reader.Read()
case JSONReaderStructureMap:
r, err := reader.nextNonWsRune()
if err != nil {
panic("Missing end of map")
}
if r == '}' {
reader.path = reader.path[:len(reader.path) - 1]
reader.structure = reader.structure[:len(reader.structure) - 1]
reader.state = JSONReaderStateValueEnd
item := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.MapValue([]walk.MapElement{})),
Start: false,
PrevStart: reader.prevStart,
End: true,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return item, nil
}
if r != ',' {
panic("Missing , after map value")
}
reader.state = JSONReaderStateValue
return reader.Read()
default:
panic("Invalid JSONReaderStructure")
}
default:
panic("Invalid JSONReaderState")
}
}
func (reader *JSONReader) readValue() (walk.WalkItem, error) {
r, err := reader.nextNonWsRune()
if err != nil {
panic("Missing value in JSON")
}
switch r {
case 'n':
reader.requireString("ull")
reader.state = JSONReaderStateValueEnd
value := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.NullValue{}),
Start: false,
PrevStart: reader.prevStart,
End: false,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return value, nil
case 'f':
reader.requireString("alse")
reader.state = JSONReaderStateValueEnd
value := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.BoolValue(false)),
Start: false,
PrevStart: reader.prevStart,
End: false,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return value, nil
case 't':
reader.requireString("rue")
reader.state = JSONReaderStateValueEnd
value := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.BoolValue(true)),
Start: false,
PrevStart: reader.prevStart,
End: false,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return value, nil
case '"':
v := reader.readString()
reader.state = JSONReaderStateValueEnd
value := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.StringValue(v)),
Start: false,
PrevStart: reader.prevStart,
End: false,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return value, nil
case '{':
reader.state = JSONReaderStateValue
reader.structure = append(reader.structure, JSONReaderStructureMap)
value := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.MapValue([]walk.MapElement{})),
Start: true,
PrevStart: reader.prevStart,
End: false,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = true
reader.path = append(reader.path, walk.StringValue(""))
return value, nil
case '[':
reader.state = JSONReaderStateValue
reader.structure = append(reader.structure, JSONReaderStructureArray)
value := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.ArrayValue([]walk.ArrayElement{})),
Start: true,
PrevStart: reader.prevStart,
End: false,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = true
reader.path = append(reader.path, -1)
return value, nil
}
if isNumberRune(r) {
var builder strings.Builder
builder.WriteRune(r)
for {
r, _, err = reader.reader.ReadRune()
if err != nil {
break
}
if !isNumberRune(r) {
reader.reader.UnreadRune()
break
}
builder.WriteRune(r)
}
number, parseError := strconv.ParseFloat(builder.String(), 64)
if parseError != nil {
panic("Invalid number")
}
reader.state = JSONReaderStateValueEnd
value := walk.WalkItem {
Value: reader.buildWalkItemValue(walk.NumberValue(number)),
Start: false,
PrevStart: reader.prevStart,
End: false,
NextEnd: reader.isNextEnd(),
}
reader.prevStart = false
return value, nil
}
panic("Invalid JSON value starting with: " + string(r))
}
func (reader *JSONReader) buildWalkItemValue(value walk.Value) walk.Value {
for i := len(reader.path) - 1; i >= 0; i -= 1 {
switch segment := reader.path[i].(type) {
case int:
value = walk.ArrayValue {
walk.ArrayElement {
Index: segment,
Value: value,
},
}
case string:
value = walk.MapValue {
walk.MapElement {
Key: segment,
Value: value,
},
}
default:
panic("Invalid segment type")
}
}
return value
}
func (reader *JSONReader) readString() string {
var builder strings.Builder
for {
r, _, err := reader.reader.ReadRune()
if err != nil {
panic("Missing rest of string")
}
if r == '"' {
break
}
if r == '\\' {
r, _, err = reader.reader.ReadRune()
if err != nil {
panic("Missing rune after \\")
}
builder.WriteRune(r)
continue
}
builder.WriteRune(r)
}
return builder.String()
}
func (reader *JSONReader) isNextEnd() bool {
r, err := reader.peekNonWsRune()
if err != nil {
return false
}
return r == ']' || r == '}'
}
func (reader *JSONReader) peekNonWsRune() (rune, error) {
r, err := reader.nextNonWsRune()
if err != nil {
return 0, err
}
reader.reader.UnreadRune()
return r, nil
}
func (reader *JSONReader) nextNonWsRune() (rune, error) {
for {
r, _, err := reader.reader.ReadRune()
if err != nil {
return 0, err
}
if !isWhitespace(r) {
return r, nil
}
}
}
func (reader *JSONReader) requireString(criteria string) {
for _, r := range criteria {
reader.require(r)
}
}
func (reader *JSONReader) require(criterion rune) {
r, _, err := reader.reader.ReadRune()
if err != nil {
panic("Error while reading required rune: " + err.Error())
}
if r != criterion {
panic("Required rune not read")
}
}
func (reader *JSONReader) AssertDone() {
// TODO
}
|
