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package json_array
import (
"main/walk"
"encoding/json"
"errors"
"bufio"
)
type state int
const (
stateStart state = iota
stateValueStart
stateEnd
stateDead
)
func atomiseValue(value interface{}) []walk.Atom {
switch v := value.(type) {
case nil:
return []walk.Atom{walk.NewAtomNull()}
case bool:
return []walk.Atom{walk.NewAtomBool(v)}
case float64:
return []walk.Atom{walk.NewAtomNumber(v)}
case string:
atoms := []walk.Atom{walk.NewAtomStringTerminal()}
for _, r := range v {
atoms = append(atoms, walk.NewAtomStringRune(r))
}
atoms = append(atoms, walk.NewAtomStringTerminal())
return atoms
case []interface{}:
atoms := []walk.Atom{walk.NewAtomTerminal(walk.ArrayBegin)}
for _, element := range v {
atoms = append(atoms, atomiseValue(element)...)
}
atoms = append(atoms, walk.NewAtomTerminal(walk.ArrayEnd))
return atoms
case map[string]interface{}:
atoms := []walk.Atom{walk.NewAtomTerminal(walk.MapBegin)}
for key, element := range v {
atoms = append(atoms, atomiseValue(key)...)
atoms = append(atoms, atomiseValue(element)...)
}
atoms = append(atoms, walk.NewAtomTerminal(walk.MapEnd))
return atoms
default:
panic("Invalid JSON value type")
}
}
func NewJSONArrayReader(reader *bufio.Reader) *JSONArrayReader {
return &JSONArrayReader {
decoder: json.NewDecoder(reader),
state: stateStart,
index: 0,
}
}
type JSONArrayReader struct {
decoder *json.Decoder
state state
index int
}
func (in *JSONArrayReader) Read() (walk.WalkItem, error) {
restart:
switch in.state {
case stateStart:
arrayStart, err := in.decoder.Token()
if err != nil {
panic("Error reading start of JSON array")
}
delim, isDelim := arrayStart.(json.Delim)
if !isDelim || delim != '[' {
panic("JSON input is not an array!")
}
in.state = stateValueStart
goto restart
case stateValueStart:
if !in.decoder.More() {
in.state = stateEnd
goto restart
}
var m interface{}
err := in.decoder.Decode(&m)
if err != nil {
panic("Error decoding array value")
}
in.index += 1
return walk.WalkItem {
Path: []walk.Atom{walk.NewAtomNumber(float64(in.index - 1))},
Value: atomiseValue(m),
}, nil
case stateEnd:
arrayEnd, err := in.decoder.Token()
if err != nil {
panic("Error reading end of JSON array")
}
delim, isDelim := arrayEnd.(json.Delim)
if !isDelim || delim != ']' {
panic("JSON array wasn't ended")
}
in.state = stateDead
return walk.WalkItem{}, errors.New("eof")
case stateDead:
return walk.WalkItem{}, errors.New("eof")
default:
panic("Unreachable!!!")
}
}
func (in *JSONArrayReader) AssertDone() {
if in.state != stateDead || in.decoder.More() {
panic("More JSON after array value")
}
}
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