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

#define ENVELOP "envelop.txt"

void moveFromLeft2Right(FILE * sd, char shape[], double fps);

int main(int argc, char* argv[]) {
    pid_t pid;
    int pfd[2];
    int i, status;
    FILE * sd;
    
    /*
     * Create a pipe.
     */
    if (pipe(pfd) < 0) {
        perror("pipe");
        exit(1);
    }

    /*
     * Create a child process.
     */
    if ((pid = fork()) < 0) {
        perror("fork");
        exit(1);
    }

    /*
     * The child process executes "gnuplot".
     */
    if (pid == 0) {
        /*
         * Attach standard input of this child process to read from the pipe.
         */
        dup2(pfd[0], 0);
        close(pfd[1]);  /* close the write end off the pipe */

        execlp("gnuplot", "gnuplot", 0);
        perror("exec");
        _exit(127);
    }

    /*
     * We won't be reading from the pipe.
     */
    close(pfd[0]);
    sd = fdopen(pfd[1], "w");

    moveFromLeft2Right(sd, ENVELOP, atof(argv[1]));

    /*getchar();*/
    fprintf(sd, "\n exit"); fflush(sd);
      /*
       * Close the pipe and wait for the child
       * to exit.
       */
    fclose(sd);
    waitpid(pid, &status, 0);
    
      /*
       * Exit with a status of 0, indicating that
       * everything went fine.
     */
    exit(0);
}

static void	keepGoing(int signal)
{
  return;
}

#define scanTime 20  /* in seconds*/
#define boardWidth 1000

void moveFromLeft2Right(FILE * sd, char* shape, double fps) 
{
  struct itimerval it_val;
  int x, delta_x;
  
  it_val.it_interval.tv_sec=(int)(1/fps);
  it_val.it_interval.tv_usec= 1000000*(1/fps - (int)(1/fps));
  it_val.it_value=it_val.it_interval;
  setitimer(ITIMER_REAL, &it_val, NULL);
  signal(SIGALRM, keepGoing);
  delta_x= (boardWidth-10)/(scanTime*fps);  /*assume shape`s  width = 10*/
  fprintf(sd, "set xrange [0:%i]\n set yrange[0:20]\n", boardWidth);  
/*  fprintf(sd, "plot \"%s\" using ($1):($2) with lines lt 1\n", shape); fflush(sd);
  printf("Ajuste tamaņo de ventana y presione enter\n"); fflush(stdout);
  getchar();
  */
  for (x=0 ; x< boardWidth; x+=delta_x) {
    pause();
    fprintf(sd, "plot \"%s\" using ($1+%i):($2+%i) with lines lt 1\n", shape, x, 5);
    fflush(sd);
  }
}