// Circular Queues offer a quick to store FIFO data with a maximum size.

// Conserves memory as we only store up to our capacity

// It is opposed to a queue which could continue to grow if input outpaces output

// Doesn’t use dynamic memory so No memory leaks

class CircularQueue {

constructor(maxLength) {

this.queue = []

this.front = 0

this.rear = 0

this.maxLength = maxLength

}

// ADD ELEMENTS TO QUEUE

enqueue(value) {

if (this.checkOverflow()) return

if (this.checkEmpty()) {

this.front += 1

this.rear += 1

} else {

if (this.rear === this.maxLength) {

this.rear = 1

} else this.rear += 1

}

this.queue[this.rear] = value

}

// REMOVES ELEMENTS

dequeue() {

if (this.checkEmpty()) {

// UNDERFLOW

return

}

const y = this.queue[this.front]

this.queue[this.front] = '*'

if (!this.checkSingleelement()) {

if (this.front === this.maxLength) this.front = 1

else {

this.front += 1

}

}

return y // Returns the removed element and replaces it with a star

}

// checks if the queue is empty or not

checkEmpty() {

if (this.front === 0 && this.rear === 0) {

return true

}

}

checkSingleelement() {

if (this.front === this.rear && this.rear !== 0) {

this.front = this.rear = 0

return true

}

}

// Checks if max capacity of queue has been reached or not

checkOverflow() {

if (

(this.front === 1 && this.rear === this.maxLength) ||

this.front === this.rear + 1

) {

// CIRCULAR QUEUE OVERFLOW

return true

}

}

// Prints the entire array ('*' represents blank space)

display(output = (value) => console.log(value)) {

for (let index = 1; index < this.queue.length; index++) {

output(this.queue[index])

}

}

// Displays the length of queue

length() {

return this.queue.length - 1

}

// Display the top most value of queue

peek() {

return this.queue[this.front]

}

}

export { CircularQueue }