package ru.landrafhomyak.utility.reference_counter

import kotlinx.atomicfu.AtomicLong
import kotlinx.atomicfu.atomic
import kotlinx.atomicfu.update
import ru.landgrafhomyak.utility.highlevel_try_finally.safeAutoClose1
import ru.landgrafhomyak.utility.highlevel_try_finally.safeAutoClose2

internal class CloseableReferenceCounter(private val _errMessage: String) {
	private val _value: AtomicLong = atomic(0L)

	fun throwClosed() {
		throw IllegalStateException(this._errMessage)
	}

	fun incref() {
		this._value.update { o ->
			if (o < 0) this.throwClosed()
			return@update o + 1
		}
	}

	inline fun <R> tryIncref(block: () -> R): R {
		this.incref()
		return safeAutoClose2(onError = this::decref, action = block)
	}

	fun checkNotClosed() {
		if (this._value.value < 0) this.throwClosed()
	}

	fun decref() {
		this._value.update(Long::dec)
	}

	fun close(errExistRefs: String) {
		val state = this._value.compareAndExchange(0, -1)
		when {
			state > 0 -> throw IllegalStateException(errExistRefs)
			state < 0 -> this.throwClosed()
		}
	}

	inline fun <R> withRef(protected: () -> R): R {
		this.incref()
		return safeAutoClose1(finally = this::decref, action = protected)
	}

	private fun AtomicLong.compareAndExchange(expected: Long, newValue: Long): Long {
		while (true) {
			val old = this@compareAndExchange.value
			if (old != expected) return old
			if (this@compareAndExchange.compareAndSet(old, newValue)) return old
		}
	}
}