// Priority Queue Item
class PQi {

    constructor(item, priority) {
        this.item = item;
        this.priority = priority;
    }

}

// Priority Queue
class PQ {
    constructor() {
        this.items = [];
    }

    enqueue(item, priority) {
        const pqi = new PQi(item, priority);
        let added = false;

        for(let i = 0; i < this.items.length; ++i) {
            if(priority < this.items[i].priority) {
                this.items.splice(i, 0, pqi);
                added = true;
                break;
            }
        }

        if(!added) { // then priority is highest, just add at end of array
            this.items.push(pqi);
        }
    }

    dequeue() {
        return this.items.shift();
    }

    changePriority(item, newPriority) {
        for(let i = 0; i < this.items.length; ++i) {
            if(item === this.items[i].item) {
                this.items.splice(i, 1);
                break;
            }
        }
        this.enqueue(item, newPriority);
    }

    isEmpty() {
        return this.items.length === 0;
    }

    peekFirst() {
        return this.items[0];
    }

    peekLast() {
        return this.items[this.items.length-1];
    }
}