#include <stdio.h>
#include <stdlib.h>

#define SIZE 4

int queue[SIZE]; // |0|1|2|3|

int head = -1;
int tail = -1;


void initialise() {
    head = -1;
    tail = -1;

    for (int i = 0; i < SIZE; i++) {
        queue[i] = 0;
    }
}


int isFull() {
    if ( ( head == tail + 1 ) )
    {
        return 1;
    }
    else if ((head == 0 && tail == SIZE - 1)) {
        return 1;
    }
    else {
        return 0;
    }
}

int isEmpty() {
    if (head == -1) {
        return 1;
    }
    else {
        return 0;
    }
}

void push(int number) {
    if (head == -1) {
        head = 0;
        tail = (tail + 1) % SIZE;
        queue[tail] = number;
        //printf("ATM->Head is at position:%d\n", head);
        //printf("ATM->Tail is at position:%d\n", tail);

    }
    else if (head != -1) {
        if (isFull()) {
            head = (head + 1) % SIZE;
            tail = (tail + 1) % SIZE;
            queue[tail] = number;
            //printf("ATM->Head is at position:%d\n", head);
            //printf("ATM->Tail is at position:%d\n", tail);
        }

        else {
            tail = (tail + 1) % SIZE;
            queue[tail] = number;
            //printf("ATM->Head is at position:%d\n", head);
            //printf("ATM->Tail is at position:%d\n", tail);
        }

        /*
        else if(head != -1){
            if(isFull() && tail>head){
                printf("Tail reached head!\n");
                head = (head + 1)% SIZE;
                tail = (tail + 1) % SIZE;
                queue[tail] = number;
                printf("ATM->Head is at position:%d\n", head);
                printf("ATM->Tail is at position:%d\n", tail);
            }
            else if(tail<head){
                head = (head + 1) % SIZE;
                queue[tail-1] = number;
            }
            else {
                tail = (tail + 1) % SIZE;
                queue[tail] = number;
                printf("ATM->Head is at position:%d\n", head);
                printf("ATM->Tail is at position:%d\n", tail);
            }
        }
        */
    }
}

void pop() {

    if (head == -1)
    {
        printf("Queue Underflow\n");
        return;
    }
    printf("Element deleted from queue is : %d\n", queue[head]);
    queue[head] = 0;
    if (head == tail) /* queue has only one element */
    {
        head = -1;
        tail = -1;
    }
    else
    {
        if (head == SIZE - 1)
            head = 0;
        else
            head = head + 1;
    }

    /*
    int delete;

    if (head == -1) {
        printf("Queue is empty! Don't have anything to pop!\n");
    }
    else if(head==tail) {
        queue[head] = 0 ;
        head = -1;
        tail = -1;
        printf("ATM->Head is at position:%d\n", head);
        printf("ATM->Tail is at position:%d\n", tail);
    }
    else if (head != tail) {

        if (tail > head) {

            if (tail == head + 1) {
                queue[head] = 0;
                head = tail;
                printf("ATM->Head is at position:%d\n", head);
                printf("ATM->Tail is at position:%d\n", tail);
            }

            else {
                queue[head] = 0;
                head = (head + 1) % SIZE;
                printf("ATM->Head is at position:%d\n", head);
                printf("ATM->Tail is at position:%d\n", tail);
            }
        }
        else{
            if (head == tail + 1) {
                queue[head] = 0;
                if (head == tail) {
                    head = (head + 1) % SIZE;
                }


        printf("ATM->Head is at position:%d\n", head);
        printf("ATM->Tail is at position:%d\n", tail);
            }
            else {
                queue[head] = 0;
                head = (head + 1) % SIZE;
                printf("ATM->Head is at position:%d\n", head);
                printf("ATM->Tail is at position:%d\n", tail);
            }
        }
    }
    */

}

void display() {
    for (int i = 0; i < SIZE; i++) {
        printf("queue[%d] = %d \n", i, queue[i]);
    }
    printf("ATM->Head is at position:%d\n", head);
    printf("ATM->Tail is at position:%d\n", tail);
}

int main() {

    //case 1
    int numberPush;

    int choice;

    do
    {
        printf("\n\t---MENU---\n");
        printf("\n\t---1.PUSH---\n");
        printf("\n\t---2.POP---\n");
        printf("\n\t---3.EMPTY---\n");
        printf("\n\t---4.FULL---\n");
        printf("\n\t---5.INITILIASE---\n");
        printf("\n\t---6.DISPLAY---\n");
        printf("\n\t---7.EXIT---\n");

        printf("Choose an option:");
        scanf("%d", &choice);

        switch (choice)
        {
        case 1: {
            printf("Push:");
            scanf("%d",&numberPush);
            push(numberPush);
            break;
        }
        case 2: {
            pop();
            break;
        }

        case 3: {
            if (isEmpty() == 1) {
                printf("Empty!All the positions are empty!\n");
            }
            else {
                printf("Not empty! We have elements!\n");
            }
            break;
        }

        case 4: {
            if (isFull() == 1) {
                printf("Full! Each position has an element stored!\n");
            }
            else {
                printf("Not each position has an element stored!\n");
            }
            break;
        }

        case 5: {
            initialise();
            printf("The list has been initialized!\n");
            break;
        }

        case 6: {
            display();
            break;
        }

        default:
            printf("Program quited!\n");
            break;
        }

    } while (choice>0 && choice<7);

    return 0;
}