#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/power.h>
#include <avr/sleep.h>
#include <avr/wdt.h>
#include <util/delay.h>

#include "logging.h"

#define N_STEPS 5
static unsigned char steps[] = { 60, 85, 121, 171, 242 };
static unsigned char intensity = 0;

static void timer_init()
{
	power_timer1_enable();

	DDRB |= _BV(PB4);

	// TCCR1 = _BV(CS10); // clk/1 = 1 MHz
	TCCR1 = _BV(CS11) | _BV(CS13); // clk/512 = 2 kHz
	GTCCR = _BV(COM1B1) | _BV(PWM1B);
	OCR1C = 255;
	OCR1B = steps[0];
	TIMSK = _BV(OCIE1B) | _BV(TOIE1);
}

volatile unsigned char adc_type, adc_drop;

ISR(TIM1_OVF_vect)
{
	adc_drop = 2;
	adc_type = 1;
	ADCSRA |= _BV(ADSC);
}

ISR(TIM1_COMPB_vect)
{
	adc_drop = 2;
	adc_type = 0;
	ADCSRA |= _BV(ADSC);
}

static void set_pwm(unsigned char pwm)
{
	OCR1B = pwm;
}

static void adc_init()
{
	power_adc_enable();

	ADCSRA = _BV(ADEN) | _BV(ADPS1) | _BV(ADPS0) | _BV(ADIE); // clk/8 = 125 kHz
	ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0); // 1.1V ref., PB3 single-ended
	DIDR0 = _BV(ADC3D);
}

volatile uint16_t batt_on, batt_off;

ISR(ADC_vect)
{
	uint16_t adcw = ADCW;

	if (adc_drop) {
		adc_drop--;
		ADCSRA |= _BV(ADSC);
		return;
	}

	if (adc_type == 0) {
		if (batt_off) {
			batt_off += adcw - (batt_off >> 5);
		} else {
			batt_off = adcw << 5;
		}
	} else {
		if (batt_on) {
			batt_on += adcw - (batt_on >> 5);
		} else {
			batt_on = adcw << 5;
		}
	}
}

static void status_led_init()
{
	DDRB |= _BV(PB2);
	PORTB &= ~_BV(PB2);
}

static void status_led_on()
{
	PORTB |= _BV(PB2);
}

static void status_led_off()
{
	PORTB &= ~_BV(PB2);
}

static unsigned char status_led_is_on()
{
	return PORTB & _BV(PB2) ? 1 : 0;
}

static void buttons_init()
{
	DDRB &= ~(_BV(PB0) | _BV(PB1)); // set as input
	PORTB |= _BV(PB0) | _BV(PB1);	// internal pull-up

        GIMSK &= ~_BV(PCIE); // disable pin-change IRQs
        PCMSK = 0; // disable pin-change IRQs on all pins of port B
}

static void buttons_susp()
{
	buttons_init();

	GIMSK |= _BV(PCIE);
	PCMSK |= _BV(PCINT0) | _BV(PCINT1);
}

static unsigned char buttons_pressed()
{
	return (
		(PINB & _BV(PB0) ? 0 : 1)
		|
		(PINB & _BV(PB1) ? 0 : 2)
	);
}

#define WAKEUP_POLL 100	// msec
#define WAKEUP_LIMIT 5	// times WAKEUP_POLL

static unsigned char buttons_wait_for_release()
{
	uint16_t wake_count = 0;

	do {
		if (++wake_count > WAKEUP_LIMIT)
			status_led_on(); // inform the user

		_delay_ms(WAKEUP_POLL);
	} while (buttons_pressed());

	status_led_off();

	return wake_count > WAKEUP_LIMIT;
}

ISR(PCINT0_vect)
{
        // empty - let it wake us from sleep, but do nothing else
}

static void wdt_init()
{
	WDTCR = _BV(WDIE) | _BV(WDP1); // interrupt mode, 64 ms
}

static void wdt_susp()
{
	wdt_disable();
}

static void hw_setup()
{
	power_all_disable();

	timer_init();
	adc_init();
	status_led_init();
	wdt_init();
}

static void hw_suspend()
{
	ADCSRA &= ~_BV(ADEN); // disable ADC
	TCCR1 = 0; // disable T/C 1

	status_led_init();
	buttons_susp();
	wdt_susp();

	power_all_disable();
}

static volatile unsigned char wdt_timer_fired;

ISR(WDT_vect) {
	wdt_timer_fired = 1;
}

static void power_down()
{
	hw_suspend();

	do {
		// G'night
		set_sleep_mode(SLEEP_MODE_PWR_DOWN);
		sleep_enable();
		sleep_bod_disable();
		sei();
		sleep_cpu();

		// G'morning
		cli();
		sleep_disable();

		// allow wakeup by long button-press only
	} while (!buttons_wait_for_release());

	// OK, wake up now
	hw_setup();
}

static void button_one_pressed()
{
	if (intensity > 0) {
		set_pwm(steps[--intensity]);
	} else {
		power_down();
	}
}

static void button_two_pressed()
{
	if (intensity < N_STEPS-1) {
		set_pwm(steps[++intensity]);
	}
}

static unsigned char button_state, button_state_time;

static void timer_check_buttons()
{
	unsigned char newstate = buttons_pressed();

	if (newstate == button_state) {
		if (newstate && button_state_time < 4)
			++button_state_time;
		return;
	}

	if (newstate) {
		button_state = newstate;
		button_state_time = 0;
		return;
	}

	// just released
	switch (button_state) {
	case 1:	button_one_pressed();
		break;
	case 2: button_two_pressed();
		break;
	default: // ignore when both are preseed
		break;
	}

	button_state = newstate;
}

static unsigned char blink_on_time, blink_off_time, n_blinks;
static unsigned char blink_counter;

static void timer_blink()
{
	if (blink_counter) {
		blink_counter--;
	} else if (status_led_is_on()) {
		status_led_off();
		blink_counter = blink_off_time;
	} else if (n_blinks) {
		--n_blinks;
		status_led_on();
		blink_counter = blink_on_time;
	} else {
		n_blinks = intensity + 1;
		blink_on_time = 0;
		blink_off_time = 2;
		blink_counter = 10;
#if 0
		log_byte(0xbb);
		log_byte(batt_on >> 7);
		log_byte(batt_off >> 7);
#endif
	}
}

int main()
{
	log_init();

	power_down();

	sei();

	// we try to be completely IRQ-driven, so just wait for IRQs here
	while(1) {
		cli();
		set_sleep_mode(SLEEP_MODE_IDLE);
		sleep_enable();
		// keep BOD active, no sleep_bod_disable();
		sei();
		sleep_cpu();
		sleep_disable();

		if (wdt_timer_fired) {
			wdt_timer_fired = 0;
			timer_check_buttons();
			timer_blink();
			log_flush();
		}
	}
}