Provides delegates for implementing regular and lazy not nullable properties which should be disposed in some moment to free memory

DisposablePropertyManager.kt

/**
 * Created with Android Studio
 * User: electrolobzik [email protected]
 * Date: 07/04/2017
 * Time: 18:55
 *
 * Provides delegates for implementing regular and lazy not nullable properties which should be disposed in some moment to free memory
 */
class DisposablePropertyManager {

    private val propertyDelegates: ArrayList<Disposable> = ArrayList()

    fun <T : Any> disposableLazy(initializer: () -> T): ReadOnlyProperty<Any?, T> {
        return SynchronizedLazyDisposableImpl(initializer).apply { propertyDelegates.add(this) }
    }

    fun <T : Any> disposable(): ReadWriteProperty<Any?, T> {
        return RegularDisposableImpl<T>().apply { propertyDelegates.add(this) }
    }

    fun dispose() {
        for (delegate in propertyDelegates) {
            delegate.dispose()
        }
    }

    fun restore() {
        for (delegate in propertyDelegates) {
            delegate.restore()
        }
    }
}

private interface Disposable {
    fun dispose()
    fun restore()
}

private class RegularDisposableImpl<T: Any> : ReadWriteProperty<Any?, T>, Disposable {

    private var value: T? = null
    private var disposed: Boolean = false

    override fun getValue(thisRef: Any?, property: KProperty<*>): T {
        if (disposed) {
            throw IllegalStateException("Property ${property.name} has been disposed and should be restored before get.")
        }

        return value ?: throw IllegalStateException("Property ${property.name} should be initialized before get.")
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        this.value = value
    }

    override fun dispose() {
        disposed = true
        value = null
    }

    override fun restore() {
        disposed = false
    }
}

private class SynchronizedLazyDisposableImpl<out T>(initializer: () -> T, lock: Any? = null) : ReadOnlyProperty<Any?, T>, Disposable {

    @Volatile private var value: Any? = UNINITIALIZED_VALUE
    private var disposed: Boolean = false
    private var initializer: (() -> T) = initializer
    private val lock = lock ?: this

    override fun getValue(thisRef: Any?, property: KProperty<*>): T {
        if (disposed) {
            throw IllegalStateException("Property ${property.name} has been disposed and should be restored before get.")
        }

        val _v1 = value
        if (_v1 !== UNINITIALIZED_VALUE) {
            @Suppress("UNCHECKED_CAST")
            return _v1 as T
        }

        return synchronized(lock) {
            val _v2 = value
            if (_v2 !== UNINITIALIZED_VALUE) {
                @Suppress("UNCHECKED_CAST") (_v2 as T)
            }
            else {
                val typedValue = initializer()
                value = typedValue
                typedValue
            }
        }
    }

    override fun dispose() {
        disposed = true
        value = UNINITIALIZED_VALUE
    }

    override fun restore() {
        disposed = false
    }
}

private object UNINITIALIZED_VALUE