Migrate json wrapper and badjson to library

common/json/badjson/json.go

@@ -0,0 +1,54 @@
+package badjson
+
+import (
+	"bytes"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/json"
+)
+
+func Decode(content []byte) (any, error) {
+	decoder := json.NewDecoder(bytes.NewReader(content))
+	return decodeJSON(decoder)
+}
+
+func decodeJSON(decoder *json.Decoder) (any, error) {
+	rawToken, err := decoder.Token()
+	if err != nil {
+		return nil, err
+	}
+	switch token := rawToken.(type) {
+	case json.Delim:
+		switch token {
+		case '{':
+			var object JSONObject
+			err = object.decodeJSON(decoder)
+			if err != nil {
+				return nil, err
+			}
+			rawToken, err = decoder.Token()
+			if err != nil {
+				return nil, err
+			} else if rawToken != json.Delim('}') {
+				return nil, E.New("excepted object end, but got ", rawToken)
+			}
+			return &object, nil
+		case '[':
+			var array JSONArray
+			err = array.decodeJSON(decoder)
+			if err != nil {
+				return nil, err
+			}
+			rawToken, err = decoder.Token()
+			if err != nil {
+				return nil, err
+			} else if rawToken != json.Delim(']') {
+				return nil, E.New("excepted array end, but got ", rawToken)
+			}
+			return array, nil
+		default:
+			return nil, E.New("excepted object or array end: ", token)
+		}
+	}
+	return rawToken, nil
+}