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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
package org.mozilla.tv.firefox.utils
/**
* A [MutableSet] that, on mutation, calls the observer functions provided to [attachObserver].
*
* This implementation is not thread safe.
*
* In general, using Rx Observables will produce more reliable code. However, when it's necessary to
* reduce allocations, this Set implementation is a good alternative.
*
* We should consider replacing this with an a-c solution or a third-party implementation (a-c #2845).
*/
class ObservableMutableSet<T> private constructor(
private val wrappedSet: MutableSet<T>
) : MutableSet<T> by wrappedSet {
private val observers = mutableListOf<(ObservableMutableSet<T>) -> Unit>()
/**
* Attaches an observer function: this will be called when the set is mutated.
*/
fun attachObserver(observer: (ObservableMutableSet<T>) -> Unit) {
observers.add(observer)
}
/**
* Removes a previously attached observer function.
*/
fun detachObserver(observer: (ObservableMutableSet<T>) -> Unit) {
observers.remove(observer)
}
override fun add(element: T): Boolean = wrappedSet.add(element).alsoNotifyObservers()
override fun addAll(elements: Collection<T>): Boolean = wrappedSet.addAll(elements).alsoNotifyObservers()
override fun remove(element: T): Boolean = wrappedSet.remove(element).alsoNotifyObservers()
override fun removeAll(elements: Collection<T>): Boolean = wrappedSet.removeAll(elements).alsoNotifyObservers()
override fun retainAll(elements: Collection<T>): Boolean = wrappedSet.retainAll(elements).alsoNotifyObservers()
override fun clear() = wrappedSet.clear().alsoNotifyObservers()
private fun <T> T.alsoNotifyObservers(): T {
observers.forEach { it.invoke(this@ObservableMutableSet) }
return this@alsoNotifyObservers
}
companion object {
fun <T> from(setToWrap: MutableSet<T>): ObservableMutableSet<T> = ObservableMutableSet(setToWrap)
}
}
fun <T> MutableSet<T>.toObservableMutableSet(): ObservableMutableSet<T> = ObservableMutableSet.from(this)