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

/*--------- STRUCTURE DECLARATION ----------*/
struct node
{
    int val;
    struct node* next;
};
typedef struct node NODE;

struct queue
{
    NODE *front;
    NODE *rear;
};
typedef struct queue QUEUE;

/*---------------------- FUNCTIONS -----------------------*/
NODE* newnode(void)
{
    NODE* pnode;
    pnode = (NODE*)malloc(sizeof(NODE));
    if(pnode!=NULL) pnode->next = NULL; //(*pnode).next=NULL;
    return pnode;
}
/*--------------------------------------------------------*/
QUEUE* createqueue(void)
{
    QUEUE* q = (QUEUE*)malloc(sizeof(QUEUE));
    q->front= NULL; 
    q->rear = NULL;
    return q;
}

/*-------------- INSERT A VALUE IN THE END OF QUEUE--------*/
void enqueue(QUEUE *q, int val)
{
    NODE* nnode = newnode();
    nnode->val = val;

    if (q->front == NULL)
    {
        q->front = nnode; q->rear = nnode;
    }
    else
    {
        q->rear->next = nnode;
        q->rear = nnode;
    }
    
}
/*---------- REMOVE THE FIRST VALUE OF QUEUE -----------*/
int dequeue(QUEUE* q)
{
    NODE *t=q->front;
    int val = t->val;

    q->front = q->front->next; 
    free(t);
    return val;
}

/*--------------------------------------------------------*/
int peek(QUEUE *q)
{
   return q->front->val;
}
/*--------------------------------------------------------*/
void displayqueue(QUEUE *queue)
{
    NODE* pnode;
    pnode = queue->front;
    if (pnode == NULL)  printf("The queue is empty\n");
    else 
        while(pnode!=NULL)
    {   
        printf("%u (%d) ->%u\n", (int)pnode, pnode->val, (int)pnode->next);
        pnode = pnode->next;
    }
}

/*---------------- FIND A NODE INCLUDING A SPECIFIC VALUE ---------*/
NODE* findnode(QUEUE *q, int val)
{
    NODE* pnode = q->front;
    while (pnode)
    {
        if (val == pnode->val) break;
        pnode = pnode->next;
    }
    return pnode;
}

/*--------PRESS ENTER-------*/
void  press_enter()
{
    printf("Press ENTER to continue");
    getchar();
    while (getchar() != '\n');
}
/*------------------------------------------------------------*/
int main(int argc, char* argv[])
{   
    QUEUE *queue=createqueue();
    int key, val;
    NODE* pnode;
     
    do
    {
        system("cls");
        printf("1.Enqueue\n");
        printf("2.Dequeue\n");
        printf("3.Search node\n");
        printf("4.Print Queue\n");
        printf("5.Peek\n");
        printf("0.Exit\n");
        key = getchar();
        switch (key)
        {
        case '1':printf("val:"); scanf("%i", &val);
            enqueue(queue, val);
            break;
        case '2':printf("Value %d removed from the front of queue\n",
                         dequeue(queue));
            break;
        case '3':printf("val:"); scanf("%i", &val);
            pnode = findnode(queue, val);
            if (pnode)printf("%i found in address %u\n", val, (int)pnode);
            else printf("Value not found\n");
            break;
        case '4':displayqueue(queue);
            break;
        case '5':printf("Val %i on the top of queue\n",peek(queue));
            break;
        case '0':break;
        };
        press_enter();
    } while (key != '0');
    return 1;
}