#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/wait.h>

#define MAXSIZE 8192

/* A program to illustrate how pipe works.  The parent process reads
 * from stdin in a loop and writes each line it reads to the pipe.  The
 * child process reads from the pipe and prints each line is reads to
 * standard output.  Extra print statements are included so you can see
 * what each process is doing.
 *
 * Notes:
 *  - to close standard input from the shell type ctrl-D
 *  - You will save yourself some grief if you read the same number of bytes
 *  from the pipe as were written to the pipe. This is especially important
 *  if you are working with binary data.
*/

int main() {
    char line[MAXSIZE];
    int fd[2];
    // create a pipe
    if (pipe(fd) == -1) {
        perror("pipe");
    }

    int r = fork();

    if (r > 0) {
        // Parent reads from stdin, and writes to child
        // close the read file descriptor since parent will write to pipe
        close(fd[0]);

        printf("Enter a line > ");
        while (fgets(line, MAXSIZE, stdin) != NULL) {

            printf("[%d] writing to pipe\n", getpid());
            if (write(fd[1], line, MAXSIZE) == -1) {
                perror("write to pipe");
            }

            printf("[%d] finished writing\n", getpid());
            printf("Enter a line > ");
        }

        close(fd[1]);
        printf("[%d] stdin has been closed, waiting for child\n", getpid());

        int status;
        if (wait(&status) != -1)  {
            if (WIFEXITED(status)) {
                printf("[%d] Child exited with %d\n", getpid(),
                        WEXITSTATUS(status));
            } else {
                printf("[%d] Child exited abnormally\n", getpid());
            }
        }

    } else if (r == 0) {
        close(fd[1]);
        printf("[%d] child\n", getpid());
        // Child will read from parent
        char other[MAXSIZE];

        while (read(fd[0], other, MAXSIZE) > 0) {
            printf("[%d] child received %s", getpid(), other);
            sleep(2);
        }
        printf("[%d] child finished reading", getpid());
        close(fd[0]);
        exit(0);

    } else {
        perror("fork");
        exit(1);
    }

    return 0;
}