#include "../avr-i2c-slave/I2CSlave.h"
#include <util/delay.h>
#include <avr/io.h>
#include <avr/interrupt.h>

#define I2C_ADDR 0x30

volatile uint8_t challenge = 0; // Use 0 as 'challenge not sent' condition
uint16_t time_open = 0;

uint8_t check_challenge(uint8_t arg) {
  return (arg >> 3);
}

void I2C_received(uint8_t received_data) {
  if (received_data == check_challenge(challenge)) { // Check validity of response
    // Open lock
    time_open = 5000;
  }
}

void I2C_requested() {
  challenge = (uint8_t)(TCNT1 & 0xff);
  I2C_transmitByte(challenge);
}

void setup() {
  // set received/requested callbacks
  I2C_setCallbacks(I2C_received, I2C_requested);
  // init I2C
  I2C_init(I2C_ADDR);
  // init output gpio
  DDRC = 0b00000100; // PC2
  TCNT1 = 0;
  TCCR1B |= (1 << CS10) | (1 << CS11); // No prescaling
}

int main() {
  setup();
  while (1) {
    if (time_open > 0) {
      PORTC |= 2 << 1;
      time_open -= 1;
    } else {
      PORTC = 0;
    }
    _delay_ms(1);
  }
}