The json(/gson) deserializer for mix-structure response

ResponseWrapper.kt

import android.os.Parcelable
import com.google.gson.JsonDeserializationContext
import com.google.gson.JsonDeserializer
import com.google.gson.JsonElement
import java.lang.reflect.ParameterizedType
import java.lang.reflect.Type

sealed class ResponseWrapper<out T> {
    class Anomaly(val value: com.xxx.model.wrapper.Anomaly) : ResponseWrapper<Nothing>()
    class Single<T : Parcelable>(val value: T) : ResponseWrapper<T>()
    class List<T : ArrayList<out Parcelable>>(val value: T) : ResponseWrapper<T>()
    object ParseError : ResponseWrapper<Nothing>()
}

class ResponseJsonDeserializer : JsonDeserializer<ResponseWrapper<*>> {
    override fun deserialize(
        json: JsonElement,
        typeOfT: Type,
        context: JsonDeserializationContext
    ): ResponseWrapper<*> {
        val obj = json.asJsonObject
        val rltType = (typeOfT as ParameterizedType).actualTypeArguments[0]

        if (obj.isJsonObject) {
            val anomaly = obj.get("anomaly")
            if (anomaly != null) {
                // Return anomaly
                return ResponseWrapper.Anomaly(context.deserialize(obj, Anomaly::class.java))
            }
            // Return single object
            return ResponseWrapper.Single(context.deserialize(obj, rltType))

        } else if (obj.isJsonArray) {
            // Return a list
            return ResponseWrapper.List(context.deserialize(obj, rltType))
        }

        // Parse failed
        return ResponseWrapper.ParseError
    }
}