BurpPreferenceDelegates.kt

private object UninitializedValue

open class NullablePreferenceDelegate<T : @Serializable Any?>(
    protected val montoya: MontoyaApi,
    protected var key: String? = null,
    protected val customSerializer: KSerializer<in T>? = null,
    protected val default: () -> T?
) : ReadWriteProperty<Any?, T?> {
    protected val preferences: Preferences = montoya.persistence().preferences()
    private val json = Json { ignoreUnknownKeys = true }
    private var _value: Any? = UninitializedValue
    private var serializer: KSerializer<in T>? = null

    init {
        montoya.extension().registerUnloadingHandler { saveValue(_value as T) }
    }

    override operator fun getValue(thisRef: Any?, property: KProperty<*>): T? {
        if (key == null) {
            key = property.name
        }
        if (serializer == null) {
            serializer = customSerializer ?: serializer(property.returnType)
        }

        if (_value == UninitializedValue) {
            _value = loadValue()
        }

        return _value as T?
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) {
        if (key == null) {
            key = property.name
        }
        if (serializer == null) {
            serializer = customSerializer ?: serializer(property.returnType)
        }

        this._value = value
        if (value != null) saveValue(value)
    }

    protected open fun loadValue(): T? {
        val value = preferences.getString(key!!)
        val toReturn = if (value == null) {
            default()
        } else {
            json.decodeFromString(serializer!!, value) as T
        }
//        println("Loading value ${this.key}: ${toReturn}")
        return toReturn
    }

    internal fun saveValue(value: T) {
//        println("Saving value ${this.key}: ${json.encodeToString(serializer!!, value)}")
        preferences.setString(this.key, json.encodeToString(serializer!!, value))
    }
}

open class PreferenceDelegate<T : @Serializable Any>(
    montoya: MontoyaApi,
    key: String? = null,
    customSerializer: KSerializer<in T>? = null,
    default: () -> T
) : NullablePreferenceDelegate<T>(montoya, key, customSerializer, default) {
    override operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
        return super.getValue(thisRef, property)!!
    }
}