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|
package walk
import (
"bufio"
"math"
"strings"
"strconv"
)
type JSONInStructure int
const (
JSONInRoot JSONInStructure = iota
JSONInMap
JSONInArray
JSONInValueEnd
)
type JSONIn struct {
path []Atom
reader *bufio.Reader
structure []JSONInStructure
}
func NewJSONIn(reader *bufio.Reader) JSONIn {
return JSONIn {
path: make([]Atom, 0, 256),
reader: reader,
structure: []JSONInStructure{JSONInRoot},
}
}
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 == '.'
}
func (in *JSONIn) popPath() {
if len(in.path) == 0 {
panic("Tried to pop from empty path")
}
finalAtom := in.path[len(in.path) - 1]
if finalAtom.Typ != AtomStringTerminal {
in.path = in.path[:len(in.path) - 1]
return
}
i := len(in.path) - 2
for {
if i < 0 {
panic("Missing string begin in path")
}
if in.path[i].Typ == AtomStringTerminal {
break
}
i--
}
in.path = in.path[:i]
}
func (in *JSONIn) nextNonWsRune() (rune, error) {
for {
r, _, err := in.reader.ReadRune()
if err != nil {
return 0, err
}
if !isWhitespace(r) {
return r, nil
}
}
}
func (in *JSONIn) requireString(criteria string) {
for _, r := range criteria {
in.require(r)
}
}
func (in *JSONIn) require(criterion rune) {
r, _, err := in.reader.ReadRune()
if err != nil {
panic("Error while reading required rune: " + err.Error())
}
if r != criterion {
panic("Required rune not read")
}
}
func (in *JSONIn) readString(out []Atom) []Atom {
// TODO: improve
out = append(out, NewAtomStringTerminal())
for {
r, _, err := in.reader.ReadRune()
if err != nil {
panic("Missing closing terminal in string input: " + err.Error())
}
if r == '"' {
break
}
if r == '\\' {
r, _, err = in.reader.ReadRune()
if err != nil {
panic("Missing rune after \\")
}
if len(out) == cap(out) {
newOut := make([]Atom, len(out), cap(out) * 2)
copy(newOut, out)
out = newOut
}
out = append(out, NewAtomStringRune(r))
continue
}
if len(out) == cap(out) {
newOut := make([]Atom, len(out), cap(out) * 2)
copy(newOut, out)
out = newOut
}
out = append(out, NewAtomStringRune(r))
}
out = append(out, NewAtomStringTerminal())
return out
}
func (in *JSONIn) Read() (WalkItem, error) {
restart:
// TODO: Escaping
// TODO: Don't allow trailing commas
// TODO: Proper float parsing with e and stuff
r, err := in.nextNonWsRune()
if err != nil {
return WalkItem {}, err
}
state := in.structure[len(in.structure) - 1]
switch state {
case JSONInMap:
in.popPath()
if r == '}' {
in.structure[len(in.structure) - 1] = JSONInValueEnd
return WalkItem {
Value: []Atom{NewAtomTerminal(MapEnd)},
Path: in.path,
}, nil
}
if r != '"' {
panic("Expected key, found something else")
}
in.path = in.readString(in.path)
r, err = in.nextNonWsRune()
if err != nil {
panic("Expected : got: " + err.Error())
}
if r != ':' {
panic("Expected : after key")
}
r, err = in.nextNonWsRune()
if err != nil {
panic("Missing map value after key: " + err.Error())
}
case JSONInArray:
if r == ']' {
in.structure[len(in.structure) - 1] = JSONInValueEnd
in.popPath()
return WalkItem {
Value: []Atom{NewAtomTerminal(ArrayEnd)},
Path: in.path,
}, nil
}
prevIndex := in.path[len(in.path) - 1]
if prevIndex.Typ == AtomNull {
prevIndex.Typ = AtomNumber
prevIndex.data = math.Float64bits(0)
} else if prevIndex.Typ == AtomNumber {
prevIndex.data = math.Float64bits(math.Float64frombits(prevIndex.data) + 1)
} else {
panic("Invalid index in array input")
}
in.path[len(in.path) - 1] = prevIndex
case JSONInRoot:
case JSONInValueEnd:
in.structure = in.structure[:len(in.structure) - 1]
underState := in.structure[len(in.structure) - 1]
if underState == JSONInRoot {
panic("More input after root JSON object ends")
} else if underState == JSONInMap && r == '}' {
in.structure[len(in.structure) - 1] = JSONInValueEnd
in.popPath()
return WalkItem {
Value: []Atom{NewAtomTerminal(MapEnd)},
Path: in.path,
}, nil
} else if underState == JSONInArray && r == ']' {
in.structure[len(in.structure) - 1] = JSONInValueEnd
in.popPath()
return WalkItem {
Value: []Atom{NewAtomTerminal(ArrayEnd)},
Path: in.path,
}, nil
}
if r != ',' {
panic("Expected , after JSON value, found: \"" + string(r) + "\"")
}
goto restart
default:
panic("Invalid JSONIn state")
}
switch r {
case 'n':
in.requireString("ull")
in.structure = append(in.structure, JSONInValueEnd)
return WalkItem {
Value: []Atom{NewAtomNull()},
Path: in.path,
}, nil
case 'f':
in.requireString("alse")
in.structure = append(in.structure, JSONInValueEnd)
return WalkItem {
Value: []Atom{NewAtomBool(false)},
Path: in.path,
}, nil
case 't':
in.requireString("rue")
in.structure = append(in.structure, JSONInValueEnd)
return WalkItem {
Value: []Atom{NewAtomBool(true)},
Path: in.path,
}, nil
case '"':
value := make([]Atom, 0, 64)
value = in.readString(value)
in.structure = append(in.structure, JSONInValueEnd)
return WalkItem {
Value: value,
Path: in.path,
}, nil
case '{':
in.structure = append(in.structure, JSONInMap)
in.path = append(in.path, NewAtomNull())
return WalkItem {
Value: []Atom{NewAtomTerminal(MapBegin)},
Path: in.path[:len(in.path) - 1],
}, nil
case '[':
in.structure = append(in.structure, JSONInArray)
in.path = append(in.path, NewAtomNull())
return WalkItem {
Value: []Atom{NewAtomTerminal(ArrayBegin)},
Path: in.path[:len(in.path) - 1],
}, nil
}
if isNumberRune(r) {
var builder strings.Builder
builder.WriteRune(r)
for {
r, _, err = in.reader.ReadRune()
if err != nil || !isNumberRune(r) {
break
}
builder.WriteRune(r)
}
in.reader.UnreadRune()
number, parseError := strconv.ParseFloat(builder.String(), 64)
if parseError != nil {
panic("Invalid number")
}
in.structure = append(in.structure, JSONInValueEnd)
return WalkItem {
Value: []Atom{NewAtomNumber(number)},
Path: in.path,
}, nil
}
panic("Invalid JSON value")
}
func (in *JSONIn) AssertDone() {
if len(in.structure) != 2 || in.structure[0] != JSONInRoot || in.structure[1] != JSONInValueEnd {
panic("Input ended on incomplete JSON root")
}
}
|
