#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>

#include <sys/time.h>
#include <time.h>

#define MAX_BUF 64

struct timespec diff(struct timespec start, struct timespec end)
{
	struct timespec temp;
	if ((end.tv_nsec-start.tv_nsec)<0) {
		temp.tv_sec = end.tv_sec-start.tv_sec-1;
		temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
	} else {
		temp.tv_sec = end.tv_sec-start.tv_sec;
		temp.tv_nsec = end.tv_nsec-start.tv_nsec;
	}
	return temp;
}

int main( int argc, char** argv )
{
    struct pollfd fdset[2];

    int nfds = 2;
    int gpio_fd, timeout, rc;
    char buf[MAX_BUF];
    int len;
    int number=0;
    struct timespec now_ts, then_ts, diff_ts;
    bool firstInt; // the next interrupt is the first of the sequence
    

    gpio_fd = open( "/sys/class/gpio/gpio15_pb2/value", O_RDONLY | O_NONBLOCK );
    timeout = 500;
    

    clock_gettime(CLOCK_MONOTONIC, &then_ts);
    
    firstInt=true;    

    while (1) {

	memset((void*)fdset, 0, sizeof(fdset));
	memset((void*)buf,0,sizeof(buf));

	fdset[0].fd = 0;
	fdset[0].events = POLLIN;
     
	fdset[1].fd = gpio_fd;
	fdset[1].events = POLLPRI;

	rc = poll(fdset, nfds, timeout);      

	if (rc < 0) {
		fprintf(stderr,"\npoll() failed!\n");
		return -1;
	}
	
        // scaduto il timeout senza interrupt
	if (rc == 0) {
		// printf(".");
		if (number > 0) {
        		printf("%d\n\n", number % 10);
        		number=0;
                }
	}
            
	if (fdset[1].revents & POLLPRI) {
                clock_gettime(CLOCK_MONOTONIC, &now_ts);
                // printf("%d %d - ", now_ts.tv_sec, now_ts.tv_nsec);
                diff_ts = diff(then_ts, now_ts);
                then_ts = now_ts;
	        lseek(fdset[1].fd,0,SEEK_SET);
		len = read(fdset[1].fd, buf, MAX_BUF);
//		printf("\npoll() GPIO %d interrupt occurred\n", 34);
                strtok(buf,"\n");

                int sec=diff_ts.tv_sec;
                float msec=diff_ts.tv_nsec/1000000.0;


                printf("value [%s] sec %d msec %f\n",buf,sec,msec);
                
                if (firstInt || msec > 90) number++;
                firstInt=false;
	}

	if (fdset[0].revents & POLLIN) {
		(void)read(fdset[0].fd, buf, 1);
		fprintf(stderr, "\npoll() stdin read 0x%2.2X\n", (unsigned int) buf[0]);
	}

        fflush(stdout);
    }
    

}