ru.hnau.jutils.producer.CachingProducer.kt Maven / Gradle / Ivy

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JUtils

There is a newer version: 2.1.1

package ru.hnau.jutils.producer

import ru.hnau.jutils.TimeValue
import ru.hnau.jutils.handle
import ru.hnau.jutils.helpers.*


abstract class CachingProducer(
        private val valueLifetime: TimeValue? = null
) : Producer() {

    private var isObserving = false

    private var cachedValue: Outdatable? = null

    protected abstract fun getNewValue(): T

    protected fun update(newValue: T?) {
        synchronized(this) {
            cachedValue = newValue?.toOutdatable(valueLifetime)
            newValue?.let(this::call)
        }
    }

    protected fun clear() =
            update(null)

    protected fun invalidate() = synchronized(this) {
        val newValue = if (isObserving) getNewValue() else null
        update(newValue)
    }

    override fun onAttached(listener: (T) -> Unit) {
        super.onAttached(listener)
        synchronized(this) {
            cachedValue?.value?.let {
                listener.invoke(it)
                return@synchronized
            }
            invalidate()
        }
    }

    override fun onIsObservingChanged(isObserving: Boolean) {
        super.onIsObservingChanged(isObserving)
        this.isObserving = isObserving
    }

}