RoleEnumJsonAdapter.kt

enum class Role(override val value: Int) : IEnumValue {
    Admin(1),
    Moderator(2)
}

object GenericEnumFactory {
    inline fun <reified T> fromValueOrNull(rawValue: Int?): T? where T : Enum<T>, T : IEnumValue {
        return enumValues<T>().firstOrNull { it.value == rawValue }
    }
}

class RoleEnumJsonAdapter : JsonAdapter<Role>() {
    @FromJson
    override fun fromJson(reader: JsonReader): Role? {
        return if (reader.peek() != JsonReader.Token.NULL) {
            GenericEnumFactory.fromValueOrNull(reader.nextInt())
        } else {
            reader.nextNull()
        }
    }

    @ToJson
    override fun toJson(writer: JsonWriter, value: Role?) {
        writer.value(value?.value)
    }
}