#include <avr/io.h>
#include <avr/wdt.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#define DUTY 15
#define LED_PIN PB0
//#define ONTIME 7210
//#define OFFTIME 10094
//#define ONTIME 213
//#define OFFTIME 425
#define ONTIME 1
#define OFFTIME 1

#define BODS 7                     //BOD Sleep bit in MCUCR
#define BODSE 2                    //BOD Sleep enable bit in MCUCR

#define N_1 (_BV(CS00))
#define N_8 (_BV(CS01))
#define N_64 (_BV(CS01) | _BV(CS00))
#define N_256 (_BV(CS02))
#define N_1024 (_BV(CS02) | _BV(CS00))

static void setPrescaler(uint8_t mode) {
  cli();
  CLKPR = bit(CLKPCE);
  CLKPR = mode;
  sei();
}
uint8_t onoff = 1;
volatile uint16_t seccount = 0;
volatile uint16_t lastsec = 0;
uint8_t daycount = 0;


static void pwm_init(void) {
  DDRB |= _BV(PB0);                   // set PWM pin as OUTPUT
  TCCR0A |= _BV(WGM01) | _BV(WGM00);  // set timer mode to FAST PWM
  TCCR0A |= _BV(COM0A1);              // connect PWM signal to pin (AC0A => PB0)
}

/* When timer is set to Fast PWM Mode, the freqency can be
calculated using equation: F = F_CPU / (N * 256) 
Posible frequencies (@1.2MHz):
 -> F(N_1) = 4.687kHz
 -> F(N_8) = 585Hz
 -> F(N_64) = 73Hz
 -> F(N_256) = 18Hz
 -> F(N_1024) = 4Hz */
static void pwm_set_frequency(uint32_t N) {
  TCCR0B = (TCCR0B & ~((1 << CS02) | (1 << CS01) | (1 << CS00))) | N;  // set prescaler
}

static void pwm_set_duty(uint8_t duty) {
  OCR0A = duty;  // set the OCRnx
}

static void pwm_stop(void) {
  TCCR0B &= ~((1 << CS02) | (1 << CS01) | (1 << CS00));  // stop the timer
}

ISR(WDT_vect) {
  cli();
  seccount++;
  // set prescaler to 5s and enable Watchdog Timer
  WDTCR |= (1 << WDCE);
  WDTCR = (1 << WDTIE) | (0 << WDE) | (1 << WDP3) | (0 << WDP2) | (0 << WDP1) | (0 << WDP0);
  sei();                // enable global interrupts
  if(!onoff && (seccount > OFFTIME))
  {
    onoff=1;
    seccount=0;
    lastsec=0;
    pwm_set_frequency(N_8);
    pwm_init();
    pwm_set_duty(DUTY);
    // goToSleep(true);
    return;        
  }
  if(onoff && seccount > ONTIME){
    onoff=0;
    seccount=0;
    lastsec=0;
    pwm_stop();
    // goToSleep(false);    
  }
}

void setup() {
  /* setup */
  pinMode(LED_PIN, OUTPUT);
  setPrescaler(4);
  pwm_set_frequency(N_8);
  pwm_init();
  pwm_set_duty(DUTY);
  onoff=1;  
  seccount = 0;
  cli();
  WDTCR |= (1 << WDCE);
  WDTCR = (1 << WDTIE) | (0 << WDE) | (1 << WDP3) | (0 << WDP2) | (0 << WDP1) | (0 << WDP0);
  sei();                // enable global interrupts
}

void goToSleep(bool withInterrupt)
{
    byte adcsra, mcucr1, mcucr2;

    set_sleep_mode(SLEEP_MODE_IDLE);
    sleep_enable();
    MCUCR &= ~(_BV(ISC01) | _BV(ISC00));      //INT0 on low level
    if(withInterrupt){
      GIMSK |= _BV(INT0);                     //enable INT0
    }
    adcsra = ADCSRA;                          //save ADCSRA
    ADCSRA &= ~_BV(ADEN);                     //disable ADC
    cli();                                    //stop interrupts to ensure the BOD timed sequence executes as required
    mcucr1 = MCUCR | _BV(BODS) | _BV(BODSE);  //turn off the brown-out detector
    mcucr2 = mcucr1 & ~_BV(BODSE);            //if the MCU does not have BOD disable capability,
    MCUCR = mcucr1;                           //  this code has no effect
    MCUCR = mcucr2;
    sei();                                    //ensure interrupts enabled so we can wake up again
    sleep_cpu();                              //go to sleep
    sleep_disable();                          //wake up here
    ADCSRA = adcsra;                          //restore ADCSRA
}

void loop() {

}