#include<stdio.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include "sem.h"
#include<stdlib.h>

#define N 3
#define BUFSIZE 1
#define PERMS 0666 //0666 - To grant read and write permissions

int *buffer, *num_order;
int nextp=0,nextc=0;
int emptyShelf, orderOnShelf, pizzaOnShelf, mutex;

void waiter_as_producer()
{
    nextp = 0, (*num_order) = 0;
    int order, *add;
    char cont;
    printf("\nShould we take order today (y or n): ");
    scanf("\n%c", &cont);
    if (cont != 'y') return;

    while(cont != 'n' && nextp < N)
    {

        (*num_order)++;
        printf("Enter order number: ");
        scanf("\n%d", (buffer + nextp));
    nextp++;
        printf("More customers (y or n): ");
        scanf("\n%c", &cont);
        if (cont == 'n')
        {
            printf("\nStop serving customers right now. Passing orders to cooker:");
            break;
        }
    }
    printf("\nThere are total of %d order(s)\n", (*num_order));

}

void waiter_as_consumer()
{
    int max, order, i = 0;
    max = *(num_order);

    if (max == 0)
    {
    printf("\nNo order made on shelf yet.");
        return;
    }
    printf("\nHey, thanks cooker.");
    printf("\nOkay. Let me deliver pizza to all customers right now.");
    for(; i < max; i++)
    {
        order = *(buffer + i);
        printf("\nPizza order #%d is ready.", order);
    }
    printf("\nI am done!");
}

void cooker_as_consumer()
{
    int order, max;
    nextc = 0;
    max = *(num_order);

    if (max == 0)
    {
       printf("\nNo pizza order.");
       return;
    }
    for(; nextc < max; nextc++)
    {
        order = *(buffer + nextc);
        printf("\nRoger, waiter. I am processing order #%d", order);
    }
    printf("\nI finished cooking.");
}

int main()
{
     int shmid, shmid_num;
     int pid;
     if((shmid=shmget(1000,BUFSIZE,IPC_CREAT | PERMS)) < 0)
     {
      printf("\n unable to create shared memory");
      return;
     }

     if((shmid_num=shmget(1001, BUFSIZE, IPC_CREAT | PERMS)) < 0)
     {
        printf("\n unable to create shared memory for num_order");
        return;
     }

     if((buffer=(int*)shmat(shmid,(char*)0,0)) == (int*)-1)
     {
      printf("\n Shared memory allocation error\n");
      exit(1);
     }

     if((num_order=(int*)shmat(shmid_num, (char*)0,0)) == (int*)-1)
     {
        printf("\n Shared memory allocation for num_order encountered error\n");
        exit(1);
     }

     if((mutex=semget(IPC_PRIVATE,1,PERMS | IPC_CREAT)) == -1)
     {
       printf("\n can't create mutex semaphore");
       exit(1);
     }

     if((emptyShelf=semget(IPC_PRIVATE,1,PERMS | IPC_CREAT)) == -1)
     {
      printf("\n can't create emptyShelf semaphore");
      exit(1);
     }

     if((orderOnShelf=semget(IPC_PRIVATE,1,PERMS | IPC_CREAT)) == -1)
     {
      printf("\ncan't create orderOnShelf semaphore");
      exit(1);
     }

     if((pizzaOnShelf=semget(IPC_PRIVATE, 1, PERMS | IPC_CREAT)) == -1)
     {
      printf("\ncan't create pizzaOnShelf semaphore");
      exit(1);
     }

     // Create the semaphore
     sem_create(mutex,1);
     sem_create(emptyShelf,N);
     sem_create(orderOnShelf,0);
     sem_create(pizzaOnShelf,0);


    //forking a child
     if((pid=fork()) < 0)
     {
      printf("\n Error in process creation");
      exit(1);
     }

    //Producer process
     if(pid > 0)
     {
    while(1)
    {
          P(emptyShelf); // waiter as P finds no items on shelf;
          P(mutex); // has permission to use the shelf
          waiter_as_producer();
          V(mutex); // cooker now can use the shelf
          V(orderOnShelf); // cooker now can pickup orders

          wait();
          P(pizzaOnShelf);
          P(mutex);
          waiter_as_consumer();
          V(mutex);
          V(emptyShelf);
    }
     }
        if(pid == 0)
        {
     while(1)
    {
         P(orderOnShelf); // make sure there is an order on shelf
         P(mutex); //permission to work
         cooker_as_consumer(); // take order and put pizza on shelf
         V(mutex); //release permission
         V(pizzaOnShelf); // pizza is now on shelf
     wait();
     wait();
    }
      }
}