@file:OptIn(ExperimentalContracts::class)

package ru.landgrafhomyak.utility.closeable_state

import kotlin.contracts.ExperimentalContracts
import ru.landgrafhomyak.utility.closeable_state.internal.AtomicLong
import ru.landgrafhomyak.utility.closeable_state.internal.Misc
import ru.landgrafhomyak.utility.closeable_state.internal.compareAndExchange
import ru.landgrafhomyak.utility.closeable_state.internal.get
import ru.landgrafhomyak.utility.closeable_state.internal.newAtomicLong
import ru.landgrafhomyak.utility.closeable_state.internal.update

public open class UsagesCounter : CloseableState.AllowsConcurrency {
	private val _value: AtomicLong = newAtomicLong(0L)

	public constructor()

	public fun getCurrentUsagesCount(): Long = this._value.get()

	public open override fun throwClosed(): Nothing {
		throw IllegalStateException("Object is closed")
	}

	public open override fun throwInUse(): Nothing {
		throw IllegalStateException("Failed close object because it is in use")
	}


	public final override val isClosed: Boolean get() = this._value.get() < 0

	public final override fun assertNotClosed() {
		if (this._value.get() < 0) this.throwClosed()
	}

	@ManualStateManipulation
	public final override fun startUsage() {
		this._value.update { o ->
			if (o < 0) this.throwClosed()
			return@update o + 1
		}
	}

	@ManualStateManipulation
	public final override fun finishUsage() {
		this._value.update(Long::dec)
	}

	@ManualStateManipulation
	public final override fun close() {
		val state = this._value.compareAndExchange(0, Misc.CLOSED_STATE_VALUE)
		when {
			state > 0 -> this.throwInUse()
			state < 0 -> this.throwClosed()
		}
	}

	override fun toString(): String {
		val cached = this._value.get()
		@Suppress("LiftReturnOrAssignment")
		if (cached < 0)
			return "<closeable usages counter [closed]>"
		else
			return "<closeable usages counter [${cached}]>"
	}
}