#include <TinyDebug.h>

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/eeprom.h>
#include <avr/sleep.h>
#include <math.h>

#define F_CPU 1200000UL  // ATtiny13 operates at 1.2 MHz

#define PWM1_PIN PB0  // OC0A
#define PWM2_PIN PB1  // OC0B
#define BUTTON_PIN PB2

#define SHORT_PRESS_THRESHOLD (uint16_t)(50)  // ~170 ms
#define LONG_PRESS_THRESHOLD (uint16_t)(1000)  // ~5 seconds
#define PWM1_ON_DURATION (uint32_t)(1000)  // 15 minutes in 3.6ms ticks
#define PWM1_FADE_STEPTIME (uint16_t)(50)  // Nr of 3.6ms ticks before a next fadeing step is made
#define PWM2_FADE_STEPTIME (uint16_t)(50)  // Nr of 3.6ms ticks before a next fadeing step is made

uint32_t button_press_time = 0;
uint16_t pwm1_counter = 0;
uint8_t pwm1_stepCount = 0;
uint8_t pwm2_stepCount = 0;
int16_t pwm1_duty_cycle = 0;  //Need 16bit for calculation in decay to be handled
int16_t pwm2_duty_cycle = 128;  //Need 16bit for calculation in decay to be handled
volatile uint8_t timer_interrupt_flag = 0;
uint8_t button_history = 0xFF;
uint16_t press_count = 0;
uint8_t StepUp = 1;

uint8_t EEMEM stored_pwm2_duty_cycle;

ISR(TIM0_OVF_vect) {
    timer_interrupt_flag = 1;
}

void handle_pwm1() {
  if (pwm1_duty_cycle>0) {
    pwm1_counter = pwm1_counter+1;
    if (pwm1_counter > PWM1_ON_DURATION) {
      pwm1_stepCount = pwm1_stepCount+1;
      if (pwm1_stepCount > PWM1_FADE_STEPTIME) {
        pwm1_duty_cycle = pwm1_duty_cycle - max(1,pwm1_duty_cycle/12);  // Logarithmic decay
        if (pwm1_duty_cycle < 0) { pwm1_duty_cycle=0; }
          OCR0A = pwm1_duty_cycle; 
        pwm1_counter = PWM1_ON_DURATION+1; //Limit max count
        pwm1_stepCount = 0;
      }
    }
  } else {
    pwm1_counter=0;
    pwm1_stepCount = 0;    
  }
}

void handle_pwm2() {
  pwm2_stepCount++;
  if (pwm2_stepCount > PWM2_FADE_STEPTIME) {  
    if (StepUp) {
      pwm2_duty_cycle = pwm2_duty_cycle + max(1,pwm2_duty_cycle/5);  // Logarithmic increase    
    } else {
      pwm2_duty_cycle = (pwm2_duty_cycle * 255) / 271;  // Logarithmic decay    
    }    
    if (pwm2_duty_cycle <= 0) {
      StepUp = 1;
      pwm2_duty_cycle = 0;    
    } else if (pwm2_duty_cycle >= 255) {
      StepUp = 0;
      pwm2_duty_cycle = 255;    
    }
    OCR0B = pwm2_duty_cycle;
    pwm2_stepCount = 0;
  }
}

void toggle_pwm1() {
  if (pwm1_duty_cycle == 0) {
    pwm1_duty_cycle = 255;
    pwm1_counter = 0;
  } else {
    pwm1_duty_cycle = 0;
  }
  OCR0A = pwm1_duty_cycle;  
}


int main() {

  // Setup
  Debug.begin();
  DDRB |= (1 << PWM1_PIN) | (1 << PWM2_PIN);  // PWM pins as output
  DDRB &= ~(1 << BUTTON_PIN);  // Button pin as input
  PORTB |= (1 << BUTTON_PIN);  // Enable pull-up resistor
  // Configure Timer0 for Fast PWM mode, prescaler 8
  TCCR0A = (1 << WGM00) | (1 << COM0A1) | (1 << COM0B1);  // Fast PWM mode
  TCCR0B = (1 << CS01) ;  // Prescaler 8
  TIMSK = (1 << TOIE0);  // Enable Timer0 overflow interrupt
  pwm2_duty_cycle = eeprom_read_byte(&stored_pwm2_duty_cycle);
  OCR0B = pwm2_duty_cycle;  
  OCR0A = pwm1_duty_cycle; 

  sei();    // Enable global interrupts

  while(1) {  
    OCR0A = 255;                                                                                   
    OCR0B = 0;     
    _delay_ms(1000);
    OCR0A = 0;
    OCR0B = 255;  
    _delay_ms(1000);
  }
}