#include<stdio.h>
#include<stdlib.h>  //exit
#include<unistd.h>  //sleep
#include<signal.h>  //signal

#define STOP          SIGBUS
#define START         SIGILL
#define DATA_SAVED    SIGUSR1
#define CEZAR_OFFSET  5
#define BUFFER_SIZE   100

volatile int read_data = 0;
volatile int save_data = 1;

const char* FILENAME = "data";

int pid_producent;
int pid_konsument;

void sig_handler(int sig)
{
    switch(sig)
    {
        case STOP:
            signal(DATA_SAVED, SIG_IGN);
        break;
        case START:
            signal(DATA_SAVED, sig_handler);
        break;
        case DATA_SAVED:
            read_data = 1;
        break;
        default:

        break;
    }
}

void zero_table(unsigned char* tab, int s)
{
    for(int i = 0; i < s; i++)
        tab[i] = 0;
}

void producent()
{
    FILE *file;
    unsigned char BUFFER[BUFFER_SIZE];
    printf("PID producent: %d\n", getpid());

    while(1)
    {
        zero_table(BUFFER, BUFFER_SIZE);
        scanf("%s", BUFFER);

        if((file=fopen(FILENAME, "w"))==NULL){
            printf("BĹ‚Ä…d odczytu pliku");
            exit(1);
        }

        for(int i=0; i<BUFFER_SIZE; i++)
            fputc(BUFFER[i], file);

        fclose(file);

        save_data = 0;

        kill(pid_konsument, DATA_SAVED);
    }

    return;
}

void cezar(unsigned char* data, int size)
{
    for(int i = 0; i < size; i++)
        data[i] = (data[i] + CEZAR_OFFSET) % 255;
}

void konsument()
{
    FILE *file;
    unsigned char BUFFER[BUFFER_SIZE];
    printf("PID konsument: %d\n", getpid());

    while(1)
    {
        if(read_data)
        {
            zero_table(BUFFER, BUFFER_SIZE);

            if((file=fopen(FILENAME, "r"))==NULL){
                printf("BĹ‚Ä…d odczytu pliku");
                exit(1);
            }

            int letter;
            for(int i=0; i<BUFFER_SIZE; i++)
            {
                if((letter = fgetc(file))!=EOF)
                    BUFFER[i] = letter;
                else break;
            }

            fclose(file);

            cezar(BUFFER, BUFFER_SIZE);

            for(int i = 0; i < BUFFER_SIZE; i++)
                putc(BUFFER[i], stderr);
            printf("\n");

            read_data = 0;
        }else sleep(1);
    }

    return;
}

int main(void){

    signal(START, sig_handler);
    signal(STOP, sig_handler);
    signal(DATA_SAVED, sig_handler);

    pid_konsument = fork();

    if(pid_konsument == 0)
        konsument();

    pid_producent = fork();

    if(pid_producent == 0)
        producent();

    printf("PID rodzic: %d\n", getpid());

    signal(START, SIG_IGN);
    signal(STOP, SIG_IGN);
    signal(DATA_SAVED, SIG_IGN);

    while(1)
        sleep(1);

    return 0;
}