package bhylu.lessons.k_mutex

import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.launch
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.sync.Mutex
import kotlinx.coroutines.sync.withLock

class SharedDesk(private val capacity: Int) {
    init { require(capacity >= 0) }
    private val mutex = Mutex()
    private var used = 0
    suspend fun hireOne(): Boolean = mutex.withLock {
        if (used >= capacity) false else { used++; true }
    }
    suspend fun hired(): Int = mutex.withLock { used }
}

fun main() {
    runBlocking {
        val desk = SharedDesk(5)
        val results = BooleanArray(20)
        val jobs = List(20) { index -> launch(Dispatchers.Default) { results[index] = desk.hireOne() } }
        jobs.forEach { it.join() }
        println(results.count { it })
        println(desk.hired())
    }
}