#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <utmp.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <pwd.h>
#include <unistd.h>
#include <errno.h>
#include <queue>
#include <string>

using namespace std;

// Shared memory sizes
#define SHM_M_SIZE		5000
#define SHM_PID_SIZE	500

// Semaphores Keys
#define SEM1			10
#define SEM2			11
// MessageQueue Keys
#define MQKEY			101
// Shared Memory Keys
#define SHM1			10
#define SHM2			11

// queue for storing the messages
queue<string> msg_queue;

void down(int sem_id, int sub_sem_id)
{
	struct sembuf sop;
	sop.sem_num = sub_sem_id;
	sop.sem_op = -1;
	sop.sem_flg = 0;
	semop(sem_id,&sop,1);
}

void up(int sem_id, int sub_sem_id)
{
	struct sembuf sop;
	sop.sem_num = sub_sem_id;
	sop.sem_op = 1;
	sop.sem_flg = 0;
	semop(sem_id,&sop,1);
}

void upn(int sem_id, int sub_sem_id,int n)
{
	struct sembuf sop;
	sop.sem_num = sub_sem_id;
	sop.sem_op = n;
	sop.sem_flg = 0;
	semop(sem_id,&sop,1);
}

void ctrl_c_handler(int dummy = 0)
{
	// read the message and push it in the message queue

}

int main()
{
	// check if server exists by checking ser.txt file
	if( access( "ser.txt", F_OK ) == -1 )
	{
		// server doesn't exist
		perror("Server doesn't exists!!");
		exit(1);
	}
	// Get the IPC resources
	// Semaphores
	int sem1,sem2;
	sem1 = semget(SEM1, 1, IPC_CREAT|0666);		// Semaphore to provide mutual exclusion to the shared PID Array
	sem2 = semget(SEM2, 1, IPC_CREAT|0666);		// Semaphore to provide mutual exclusion to the shared message segment
	// Message Queue
	int mq;
	mq = msgget(MQKEY,IPC_CREAT|0666);			// Message queue to transfer messages to all the available MIDs
	// Shared Memory
	int shm1,shm2;
	// shm1 is shared PID array
	if((shm1 = shmget(SHM1, SHM_PID_SIZE,IPC_CREAT|0666)) == -1)
	{
		perror("Shared PID array was not created!");
		exit(1);
	}
	// shm2 is shared message section
	if((shm2 = shmget(SHM2, SHM_M_SIZE,IPC_CREAT|0666)) == -1)
	{
		perror("Shared Message Segment was not created!");
		exit(1);
	}


	return 0;
}