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

#define SHM_SIZE 20

union semun
{
	int val;
	struct semid_ds *buf;
	unsigned short int *array;
	struct seminfo *__buf;
};


int semlock(int semid)
{
	struct sembuf opr;

    	opr.sem_num =  0;
    	opr.sem_op  = -1;        // blokowanie
    	opr.sem_flg =  0;        // operacja blokujaca

	if (semop(semid, &opr, 1) == -1)
	{
    		warn("Blad blokowania semafora!");
    		return 0;
	}
	else
	{
		return 1;
	}
}

int semunlock(int semid)
{
	struct sembuf opr;

    	opr.sem_num = 0;
    	opr.sem_op  = 1;
    	opr.sem_flg = 0;

	if (semop(semid, &opr, 1) == -1)
	{
	    warn("Blad odblokowania semafora!");
    	return 0;
    }else return 1;
}

int verification(FILE *fl, char fileName[20])
{
	char temp='a';
	int number, line=-1, space=0;

	if (access(fileName, R_OK)!=0)
	{
		printf("Can not read data from file.\n");
		fclose(fl);
		return 0;
	}

	fscanf(fl, "%d", &number);

	while(!feof(fl))
	{
		fscanf(fl, "%c", &temp);
		if (temp == '\n') line++;
		if (temp == ' ') space++;
	}

	if (line != number+1 || space != number*2)
	{
		printf("The program structure is not correct.\n");

		fclose(fl);
		return 0;
	}

	printf("Plik sprawdzony.\n");
	fclose(fl);
	return 1;
}

int main(void)
{
	FILE *f = NULL;
	FILE *fOut;
	char fileName[20];
	int number, i, pdes[2], shmid, semid1, semid2;
	union semun ctl;
	float A, B, C, delta, x1, x2;
	float *shm, *s;
	key_t key, key1, key2;

	if ((key = ftok(".", 'A')) == -1) errx(1, "Blad tworzenia klucza!");
	if ((shmid = shmget(key, SHM_SIZE, IPC_CREAT | 0666)) < 0) errx(2, "Blad tworzenia segmentu pamieci dzielonej!");
	if ((shm = shmat(shmid, NULL, 0)) == (float *) -1) errx(3, "Blad przylaczania pamieci dzielonej!");

	if ((key1 = ftok(".", 'A')) == -1) errx(1, "Blad tworzenia klucza!");
	if ((semid1 = semget(key1, 1, IPC_CREAT | 0600)) == -1) errx(2, "Blad tworzenia semafora!");
	ctl.val = 1;
    if (semctl(semid1, 0, SETVAL, ctl) == -1) errx(3, "Blad ustawiania semafora!");

	if ((key2 = ftok(".", 'B')) == -1) errx(1, "Blad tworzenia klucza!");
	if ((semid2 = semget(key2, 1, IPC_CREAT | 0600)) == -1) errx(2, "Blad tworzenia semafora!");
    ctl.val = 1;
    if (semctl(semid2, 0, SETVAL, ctl) == -1) errx(3, "Blad ustawiania semafora!");

	semlock(semid2);

	printf("Enter the name of the input file: ");

	while(f==NULL)
	{
		scanf("%s", fileName);
		f = fopen(fileName, "r");

		if (f == NULL) printf("Nie ma takiego pliku!\n\nSprobuj ponownie: ");
	}

	if (!verification(f, fileName)) return 0;

	f = fopen(fileName, "r");
	fOut = fopen("wynik.txt", "w");

	fscanf(f, "%d", &number);

	pipe(pdes);

	if(fork())
	{
		s=shm;
		for (i=0; i<number; i++)
		{
			semlock(semid1);
			sleep(1);
			fscanf(f,"%f", &A);
			fscanf(f,"%f", &B);
			fscanf(f,"%f", &C);

			*s++ = A;
			*s++ = B;
			*s++ = C;
			semunlock(semid2);
		}
		while(*s != '*') sleep(1);

		shmdt(shm);
		shmctl(shmid, IPC_RMID, NULL);
	}else
	{
		s=shm;
		for (i=0; i<number; i++)
		{
			semlock(semid2);
			A = *s++;
			B = *s++;
			C = *s++;

			delta = B*B - 4*A*C;

			if (delta < 0)
			{
				fprintf(fOut, "(%.1f)x^2 + (%.1f)x + (%.1f) = 0 - brak rozwiazan\n", A, B, C);
			}
			else if (delta == 0)
			{
				x1 = -B/2*A;
				fprintf(fOut, "(%.1f)x^2 + (%.1f)x + (%.1f) = 0 - x0=%.1f\n", A, B, C, x1);
			}
			else
			{
				x1 = (-B-sqrt(delta))/(2*A);
				x2 = (-B+sqrt(delta))/(2*A);
				fprintf(fOut, "(%.1f)x^2 + (%.1f)x + (%.1f) = 0 - x1=%.1f x2=%.1f\n", A, B, C, x1, x2);
			}
			semunlock(semid1);
		}
		*s = '*';
		shmdt(shm);
		printf("Wypisano dane do wynik.txt\n\n");
	}
	sleep(1);
	fclose(f);
	fclose(fOut);

	return 0;
}