#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main()
{
    int fds[2][2], result;
    // fds[0] parent -> child
    // fds[1] child -> parent

    size_t size;
    char resstring[14];

    for (int i = 0; i < 2; ++i)
    {
        if (pipe(fds[i]) < 0)
        {
            printf("Can\'t open pipe\n");
            exit(-1);
        }
    }

    result = fork();

    if (result < 0)
    {
        printf("Can\'t fork child\n");
        exit(-1);
    }
    else if (result > 0)
    {
        /* Parent process */
        close(fds[0][0]);
        close(fds[1][1]);

        size = write(fds[0][1], "Hello, world!", 14);
        if (size != 14)
        {
            printf("Parent: Can\'t write all string to pipe\n");
            exit(-1);
        }
        size = read(fds[1][0], resstring, 14);
        if (size < 0)
        {
            printf("Parent: Can\'t read string from pipe\n");
            exit(-1);
        }
        printf("Parent: resstring:%s\n", resstring);
    }
    else
    {
        /* Child process */
        close(fds[0][1]);
        close(fds[1][0]);

        size = read(fds[0][0], resstring, 14);

        if (size < 0)
        {
            printf("Child: Can\'t read string from pipe\n");
            exit(-1);
        }
        printf("Child: resstring:%s\n", resstring);
        size = write(fds[1][1], resstring, 14);
        if (size != 14)
        {
            printf("Child: Can\'t write all string to pipe\n");
            exit(-1);
        }
    }

    for(int i = 0; i < 2; ++i){
        close(fds[i][0]);
        close(fds[i][1]);
    }

    return 0;
}