#include "twi.h"
#include "ssd1306.h"
#include "sevenseg.h"
#include "adc.h"
#include "iopins.h"
#include <avr/interrupt.h>

const uint16_t adc_target16_acceptable = 900;
const uint16_t adc_target16 = 972;
//const uint8_t adc_target8 = 243;

static bool g_pwm_on = false;

static volatile uint16_t tick_counter = 0;
static volatile bool tick_counter_changed = false;

// Tick
ISR(INT0_vect)
{
    tick_counter++;
    tick_counter_changed = true;
}

static void init_isr() {
    as_input(D2);

    // using INT0 - arduino pin D2
    EICRA = _BV(ISC01) | _BV(ISC00); // rising edge
    EIMSK = _BV(INT0);
}

static void init_pwm_out() {
    // Output is OC0A
    as_output(D5);

    // initialize the timer
    // Fast PWM mode, Output to OC0A

    // clock is 16MHz, presc /64, counting to 80 -> freq 3125Hz
    // Duty cycle = appx. 60%

    OCR0A = 80;
    OCR0B = 46;
    TCCR0A = _BV(WGM00) | _BV(WGM01);
    TCCR0B = _BV(CS01) | _BV(CS00) | _BV(WGM02);
}

static void pwm_on() {
    TCCR0A |= _BV(COM0B1);
    g_pwm_on = true;
}

static void pwm_off() {
    TCCR0A &= ~_BV(COM0B1);
    g_pwm_on = false;
}

void main() {
    TWI_Init();
    adc_init();

    init_pwm_out();

    ssd1306_128x32_i2c_init();
    ssd1306_clearScreen();

    struct SevenSeg sseg = {
        .x0 = 0,
        .y0 = 0,
        .charwidth = 17,
        .thick = 3,
        //.charwidth = 16,
        //.thick = 1,
        .spacing = 4,
    };

    init_isr();
    sei();

    // TODO show loading icon
    sseg_number(&sseg, 0, 5, 0);

    // request ADC meas
    adc_async_start_measure_word(0);

//    uint16_t cnt = 0;
    uint16_t analog;
    uint16_t count_boost_fail = 0;
    for (;;) {
        if (adc_async_ready()) {
            analog = adc_async_get_result_word();
            adc_async_start_measure_word(0);

            bool good_voltage = analog >= adc_target16;

            if (g_pwm_on) {
                if (good_voltage) {
                    pwm_off();
                    count_boost_fail = 0;
                } else {
                    count_boost_fail++;
                }
            }
            else if (!good_voltage) {
                pwm_on();
            }

            // If fail to reach target voltage in reasonable time,
            // show weak battery icon and stop trying.
            if (count_boost_fail > 50000 && analog < adc_target16_acceptable) {
                // TODO weak battery icon
                sseg_number(&sseg, 9999, 5, 0);
                pwm_off();

                for(;;) {}
            }

            // TODO synchronization?
            if (tick_counter_changed) {
                tick_counter_changed = false;
                sseg_number(&sseg, tick_counter, 5, 0);
            }

//            if (++cnt > 10000) {
//                sseg_number(&sseg, analog, 5, 0);
//                cnt = 0;
//            }
        }
    }
}