#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

/*
 * main method
 *
 * @args
*/
main(int argc, char* argv[])
{
  int fd[2], pid, i;
  char pipeBuffer[1024];

  //print error and exit program if no arguments were specified
  if(argc != 2)
  {
    printf("Usage: my_program <filname of textfile>\n");
    exit(0);
  }

  //create a pipe
  if(pipe(fd) == -1)
  {
    perror("pipe");
    exit(EXIT_FAILURE);
  }

  //create a fork
  if((pid = fork()) == -1) //if fork failed
  {
    perror("fork");
    exit(EXIT_FAILURE);
  }

  if(pid == 0) //child created
  {
    close(fd[1]); //close unused write end

    int letterCounter = 0;
    int counter = 0;
    printf("\n");

    //read letters from the pipe
    while(read(fd[0], pipeBuffer, 1) > 0)
    {
      if(isalpha(pipeBuffer[counter]))
      {
        letterCounter++;
        printf("%c", pipeBuffer[counter]);
      }

      counter++;
    }

    printf("\n\nChild counting letters: %d\n\n", letterCounter);


    close(fd[0]); //close finished read end
    _exit(EXIT_SUCCESS);
  }
  else //parent
  {
    close(fd[0]); //close unused read end

    //store file contents in a buffer
    char fileBuffer[1024];
    FILE *fp = fopen(argv[1], "r");
    int c;
    int count = 0;

    while((c = fgetc(fp)) != EOF)
    {
      fileBuffer[count] = c;
      printf("%d %c\n", count, fileBuffer[count]);
      count++;
    }
    fclose(fp);

    printf("write return: %d\n", write(fd[1], fileBuffer, count)); //write to the pipe
    write(fd[1], fileBuffer, count);

    close(fd[1]); //close finished write end
    wait(NULL); //prevent zombies
    exit(EXIT_SUCCESS);
  }
}