#include <stdio.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <sys/stat.h>
#include <sys/sem.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>

struct sembuf p = {0,-1,SEM_UNDO};
struct sembuf v = {0,1,SEM_UNDO};
struct sembuf wait = {0,0,SEM_UNDO};


struct sembuf p1 = {1,-1,SEM_UNDO};
struct sembuf v1 = {1,1,SEM_UNDO};
struct sembuf wait1 = {1,0,SEM_UNDO};

struct sembuf p2 = {2,-1,SEM_UNDO};
struct sembuf v2 = {2,1,SEM_UNDO};
struct sembuf wait2 = {2,0,SEM_UNDO};

union semun
{
    int val;
    struct semid_ds *buf;
    ushort *array;
} sem;

struct sembuf sop;

int semdec(int sid, int n)
{
    sop.sem_num = n;
    sop.sem_op = -1;
    semop(sid, &sop, 1);
}

int seminc(int sid, int n)
{
    sop.sem_num = n;
    sop.sem_op = 1;
    semop(sid, &sop, 1);
}

int waits(int sid, int n)
{
    sop.sem_num = n;
    sop.sem_op = 0;
    semop(sid, &sop, 1);
}

void sleepbw(int ms)
{
    usleep(ms*1000);
}

int main()
{

    key_t key = 11;

    int semid = semget (key,1,0777|IPC_CREAT);

    printf("Semaphore created (%d)\n",semid);
    if (semid < 0)
    {
        exit(0);
    }

    int size = 2 * sizeof(int);

    int iterations = 3;
    sem.array = (ushort*)malloc(sizeof(ushort)*3);
    sem.array[0] = 1;
    sem.array[1] = 1;
    sem.array[2] = 1;
    sop.sem_flg = SEM_UNDO;

    semctl(semid, 3, SETALL, sem);
    semdec(semid,0);

    int pid = fork();

    if (pid != 0)
    {
        printf("Process 1 (%d)\n",getpid());
        int shmid = shmget(key,size, 0777| IPC_CREAT);
        char *addr = shmat(shmid,0,0);
        printf("Process 1 (%d) attached shared memory (shmid = %d,size = %d)\n",getpid(),shmid,size);
        int pid1 = fork();
        if (pid1!=0)
        {
            for (int i = 0; i < iterations; ++i)
            {
                sleepbw(3);
                printf("Process 1 waiting\n");
                waits(semid,0);
                seminc(semid, 0);
                strcat(addr, "1 ");
                strcat(addr, "1 ");
                printf("Process 1 executed\n");
                semdec(semid, 0);
                sleepbw(15);
            }

            shmdt(addr);
        }
        else
        {
            printf("Process 3 (%d)\n",getpid());

            int shmid = shmget(key,size,0);
            char *addr = shmat (shmid, 0,0);
            printf("Process 3 (%d) attached shared memory (shmid = %d,size = %d)\n",getpid(),shmid,size);
            for (int i = 0; i < iterations; ++i)
            {
                sleepbw(6);
                printf("Process 3 waiting\n");
                waits(semid,0);
                seminc(semid, 0);
                strcat(addr, "3 ");
                printf("Process 3 executed\n");
                semdec(semid, 0);
                sleepbw(15);
            }
            char buff[512];
            strcpy(buff,addr);
            //int file = open("text.txt",O_RDWR | O_TRUNC | O_CREAT, S_IREAD | S_IWRITE);

            //printf("Process 3 (%d) OPEN FILE\n",getpid());

            //int check = write(file, buff, 2 * size);
            //if(check == 2 * size)
            printf("Process 3 (%d) has wrote %s\n",getpid(),buff);

            shmdt(addr);
            shmctl(shmid,IPC_RMID, NULL);
            exit(0);
        }
    }
    else
    {
        printf("Process 2 (%d) \n",getpid());
        int shmid = shmget(key,size,0);
        char *addr = shmat (shmid, 0,0);
        printf("Process 2 (%d) attached shared memory (shmid = %d,size = %d)\n",getpid(),shmid,size);
        for (int i = 0; i < iterations; ++i)
        {
            printf("Process 2 waiting\n");
            waits(semid,0);
            seminc(semid, 0);
            strcat(addr, "2 ");
            printf("Process 2 executed\n");
            semdec(semid, 0);
            sleepbw(15);
        }
        shmdt(addr);
        exit(0);
    }
    /*
    if (pid == 0)
    {
        printf("Process 2 (%d) START\n",getpid());

        int shmid = shmget(key,size,0);
        char *addr = shmat (shmid, 0,0);
        printf("Process 2 (%d) attached shared memory (shmid = %d,size = %d)\n",getpid(),shmid,size);

        for(int i = 0; i<interations; i++)
        {
            semop(semid, &wait,1);
            semop(semid, &v,1);
            printf("Process 2 (%d) blocked semaphore\n",getpid());

            strcat(addr, "2 ");

            semop(semid, &p,1);
            printf("Process 2 (%d) released semaphore\n", getpid());
            usleep(200000);
        }
        shmdt(addr);

    } else {
        int shmid = shmget(key,size, 0777| IPC_CREAT);
        char *addr = shmat(shmid,0,0);
        printf("Process 1 (%d) attached shared memory (shmid = %d,size = %d)\n",getpid(),shmid,size);

        for(int i = 0; i < interations; i++)
        {
            usleep(100000);
            semop(semid, &wait,1);
            semop(semid, &v,1);
            printf("Process 1 (%d) blocked semaPHore\n",getpid());

            strcat(addr,"1 ");
            strcat(addr,"1 ");
            semop(semid, &p, 1);
            printf("Process 1 (%d) released semaphore\n", getpid());

            usleep(100000);
        }

        char buff[128];
        strcpy(buff,addr);

        shmdt(addr);
        shmctl(shmid,IPC_RMID, NULL);
        printf("Process 2 (%d) deleted shared memory\n",getpid());

        if(fork() == 0)
        {
            printf("Process 3 (%d) START\n",getpid());
            int file = open("text.txt",O_RDWR | O_TRUNC | O_CREAT, S_IREAD | S_IWRITE);

            printf("Process 3(%d) OPEN FILE\n",getpid());

            int check = write(file, buff, 2 * size);
            if(check == 2 * size) printf("Process 3 (%d) has wrote %s\n",getpid(),buff);
        }
        exit(0);
    }
    */
    return (0);
}