LibreTube/app/src/main/java/com/github/libretube/api/ResettableLazy.kt

package com.github.libretube.api

import java.util.*
import kotlin.reflect.KProperty

class ResettableLazyManager {
    // we synchronize to make sure the timing of a reset() call and new inits do not collide
    private val managedDelegates = LinkedList<Resettable>()

    fun register(managed: Resettable) {
        synchronized(managedDelegates) {
            managedDelegates.add(managed)
        }
    }

    fun reset() {
        synchronized(managedDelegates) {
            managedDelegates.forEach { it.reset() }
            managedDelegates.clear()
        }
    }
}

interface Resettable {
    fun reset()
}

class ResettableLazy<PROPTYPE>(val manager: ResettableLazyManager, val init: () -> PROPTYPE) :
    Resettable {
    @Volatile
    var lazyHolder = makeInitBlock()

    operator fun getValue(thisRef: Any?, property: KProperty<*>): PROPTYPE {
        return lazyHolder.value
    }

    override fun reset() {
        lazyHolder = makeInitBlock()
    }

    private fun makeInitBlock(): Lazy<PROPTYPE> {
        return lazy {
            manager.register(this)
            init()
        }
    }
}

fun <PROPTYPE> resettableLazy(manager: ResettableLazyManager, init: () -> PROPTYPE):
        ResettableLazy<PROPTYPE> {
    return ResettableLazy(manager, init)
}

fun resettableManager(): ResettableLazyManager = ResettableLazyManager()