#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/stat.h>

int stop = 0;
int finish = 0;

// Signal handling
void parent_sigusr()
{
    signal(SIGUSR1, parent_sigusr);
    stop = 1;
    // printf("parent stop %d\n", getpid());
}

void parent_sigcont()
{
    signal(SIGCONT, parent_sigcont);
    stop = 0;
    // printf("parent resume %d\n", getpid());
}

void parent_sigint()
{
    signal(SIGINT, parent_sigint);
    finish = 1;
    // printf("parent kill %d\n", getpid());
}

void child_sigusr()
{
    signal(SIGUSR1, child_sigusr);
    stop = 1;
    // printf("p %d stop\n", getpid());
}

void child_sigcont()
{
    signal(SIGCONT, child_sigcont);
    stop = 0;
    // printf("p %d resume\n", getpid());
}

void child_sigint()
{
    // printf("p %d kill\n", getpid());
    kill(getppid(), SIGINT);
    exit(0);
}

int main()
{
    pid_t wpid;
    char *fpath = "/tmp/fifopath";
    char *filepath = "/tmp/filepath.txt";
    FILE *fp_read;

    fp_read = fopen(filepath, "a+");

    int p1 = fork();
    if (p1 != 0) {
        // printf("p0 pid = %d\n", getpid());
        // printf("p1 pid = %d\n", p1);
        int p2 = fork();
        if (p2 != 0) {
            // printf("p2 pid = %d\n", p2);

            int p3 = fork();

            if (p3 != 0) {
                // printf("p3 pid = %d\n", p3);

                signal(SIGINT, parent_sigint);
                signal(SIGUSR1, parent_sigusr);
                signal(SIGCONT, parent_sigcont);

                int p_counter = 0;
                int stop_sent = 0;

                // Wait for all processes to finish
                while (1) {
                    while (stop == 1) {
                        // Means we need to stop - send info to children
                        if (stop_sent == 0) {
                            kill(p1, SIGUSR1);
                            kill(p2, SIGUSR1);
                            kill(p3, SIGUSR1);
                            stop_sent = 1;
                        }
                        pause();
                        // If we got SIGINT we need to exit the stop
                        if (finish == 1) {
                            break;
                        }
                        // We got a signal to continue so propagate to children
                        if (stop == 0) {
                            kill(p1, SIGCONT);
                            kill(p2, SIGCONT);
                            kill(p3, SIGCONT);
                        }
                    }
                    stop_sent = 0;
                    if (finish == 1) {
                        kill(p1, SIGINT);
                        kill(p2, SIGINT);
                        kill(p3, SIGINT);
                    }
                    finish = 0;
                    // Wait for children but without stopping execution
                    // so we can propagate signals
                    wpid = waitpid(-1, NULL, WNOHANG);
                    if (wpid != 0) {
                        finish = 1;
                        p_counter = p_counter + 1;
                        // If all children exit we exit
                        if (p_counter == 3) {
                            break;
                        }
                    }
                }
                fclose(fp_read);
                exit(0);
            } else {
                // P3
                signal(SIGINT, child_sigint);
                signal(SIGUSR1, child_sigusr);
                signal(SIGCONT, child_sigcont);

                char buff[2];
                int ok;
                int i = 0;
                while(1) {
                    while (stop == 1) {
                        kill(getppid(), SIGUSR1);
                        pause();
                        if (stop == 0) {
                            kill(getppid(), SIGCONT);
                        }
                    }

                    // Reading from a file
                    ok = fscanf(fp_read, "%2s", buff);
                    // ok > 0 means we read something
                    if (ok > 0) {
                        // print on the standard error
                        fprintf(stderr, "%s ", buff);
                        if (i == 14)
                            fprintf(stderr, "\n");
                        i = (i + 1) % 15;
                    }
                }
            }
        } else {
            // P2
            signal(SIGINT, child_sigint);
            signal(SIGUSR1, child_sigusr);
            signal(SIGCONT, child_sigcont);

            char read_c;
            char converted_c[3];
            int fd_read = open(fpath, O_RDONLY);
            FILE *fp_write;

            while(read(fd_read, (void *)&read_c, 1)) {
                while (stop == 1) {
                    // send to mother pid
                    kill(getppid(), SIGUSR1);
                    pause();
                    if (stop == 0) {
                        kill(getppid(), SIGCONT);
                    }
                }
                // Converting to hex
                sprintf((char*)(converted_c),"%02X", read_c);
                // Add ending character
                converted_c[2] = '\0';

                // open, write to file and close
                fp_write = fopen(filepath, "a");
                fprintf(fp_write, "%s", converted_c);
                fclose(fp_write);
            }
            exit(0);
        }
    } else {
        // P1
        signal(SIGINT, child_sigint);
        signal(SIGUSR1, child_sigusr);
        signal(SIGCONT, child_sigcont);

        int fd_write;
        mkfifo(fpath, 0666);
        // open fifo
        fd_write = open(fpath, O_WRONLY);

        char c;
        while ((c = getchar()) != EOF) {
            while (stop == 1) {
                // Notify P0 to STOP
                kill(getppid(), SIGUSR1);
                pause();
                if (stop == 0) {
                    kill(getppid(), SIGCONT);
                }
            }
            // write to fifo what we read from
            write(fd_write, (void *)&c, 1);
        }
        close(fd_write);
        exit(0);
    }

    return 0;
}