#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

const char *path = "/tmp/fifo-server-432423";
char path_pid_1[500];
char path_pid_2[500];
const char *suf_1 = "-1-";
const char *suf_2 = "-2-";
int m_fifo, m_w, m_r;

void handle_error(char *txt)
{
    close(m_w);
    close(m_r);
    perror(txt);
    exit(1);
}

int main()
{
    int p;
    if (access(path, F_OK) == 0)
        unlink(path);

    if ((m_fifo = mkfifo(path, 0600)) == -1)
        handle_error("main mkfifo");

    if ((m_r = open(path, O_RDONLY)) == -1 || (m_w = open(path, O_WRONLY)) == -1)
    {
        unlink(path);
        handle_error("main open");
    }

    printf("otwieranie kolejki\n");
    while (1)
    {
        pid_t client_pid;
        read(m_r, (void *)&client_pid, sizeof(pid_t));
        int pid;
        int db_w, db_r;
        if ((pid = fork()) == -1)
            handle_error("fork");
        if (pid == 0)
        {
            char pid_str[20];
            strcpy(path_pid_1, path);
            strcpy(path_pid_2, path);
            strcpy(path_pid_1, strcat(path_pid_1, suf_1));
            strcpy(path_pid_2, strcat(path_pid_2, suf_2));
            sprintf(pid_str, "%d", client_pid);
            strcpy(path_pid_1, strcat(path_pid_1, pid_str));
            strcpy(path_pid_2, strcat(path_pid_2, pid_str));

            if ((db_r = open(path_pid_1, O_RDONLY)) == -1)
                handle_error("db_r open");
            if ((db_w = open(path_pid_2, O_WRONLY)) == -1)
                handle_error("db_w open");

            double db;
            read(db_r, (void *)&db, sizeof(double));
            printf("%f\n", db);
            db *= 2;
            write(db_w, (void *)&db, sizeof(double));
            printf("%f\n", db);
            close(db_r);
            close(db_w);
            return;
        }
    }

    return 0;
}