// #include <vcc.h>
#include <stdio.h>

typedef unsigned char task ;

void init();
void delay(task, unsigned);
task tick();

unsigned ctickcount = 0; // clocked tick count
task delayedtask;  // delayed task id
unsigned delayed; // is there a delayed task to be woken in this clock cycle
unsigned odelayed; // is there a delayed task to be woken in next clock cycle
unsigned waketime; // time to wakeup delayed task
unsigned owaketime; // overflowed wake time

void init() {
  ctickcount = 0;
  delayedtask = 0;
  delayed = 0; // no task to be woken this cycle
  odelayed = 0; // no task to be woken next cycle
  waketime = 0;
  owaketime = 0;
}

void delay(task t, unsigned d) {
  unsigned p = 0;
  unsigned overflowed = 0;
  if (!(delayed || odelayed) && d <= 60) {
    delayedtask = t;
    p = ctickcount;
    while (d > 0) {
      if (p < 59)
        p++;
      else {
        p = 0;
        overflowed = 1;
      }
      d--;
	} 
    if (overflowed) {
      owaketime = p;
      odelayed = 1;
    }
    else {
      waketime = p;
      delayed = 1;
    }
  }
}

task tick() {
  if (ctickcount < 59)
    ctickcount++;
  else {
    ctickcount = 0;
    delayed = odelayed;
    odelayed = 0;
    waketime = owaketime;
  }
  if (waketime == ctickcount) {
    delayed = 0;
    return delayedtask;
  }
  else {
    return 0;
  }
}