function createQueue() {
    const queue = []

    return {
        enqueue: function(item){
            queue.unshift(item)
        },
        dequeue: function(item){
            queue.pop(item)
        },
        isEmpty: function(){
            return queue.length === 0
        },
        peek: function(){
            return queue[queue.length - 1]
        },
        length: function(){
            return queue.length
        }

    }

}

const q = createQueue()
console.log(q.enqueue(1))
console.log(q.length())
console.log(q.enqueue(2))
console.log(q.length())



function createPriorityQueue(){

    const highPriorityQueue = createQueue()
    const lowPriorityQueue = createQueue()

    return{

        enqueue: function(item, highPriority = false){

            if(highPriority === true){
                return highPriorityQueue.enqueue(item)
            }
            return lowPriorityQueue.enqueue(item)

        },
        dequeue: function(){

            if(highPriorityQueue.isEmpty()){
                return lowPriorityQueue.dequeue()
            }
            return highPriorityQueue.dequeue()
        },

        peek: function(){
            if(highPriorityQueue.isEmpty()){
                return lowPriorityQueue.peek()
            }
            return highPriorityQueue.peek()
        },

        length: function(){
            return highPriorityQueue.length() + lowPriorityQueue.length()
        },

        isEmpty: function(){
            highPriorityQueue.isEmpty() && lowPriorityQueue.isEmpty()
        }
    }

}

const qPriority = createPriorityQueue()

qPriority.enqueue("first task")
qPriority.enqueue("second task")
qPriority.enqueue("third task")

console.log(qPriority.peek())

qPriority.dequeue()
console.log(qPriority.peek())

qPriority.enqueue("priority task", true)
console.log(qPriority.peek())