#include <avr/io.h>
#include <string.h>
#include <util/delay.h>

#define	LED		13	/* built-in LED */
#define	BTN_UP		2
#define	BTN_DOWN	3
#define	BTN_PRINT	4
#define PIN_PRINT	5

#define BTNS_COUNT	3

#define UP		0
#define DOWN		1
#define PRINT		2

#define	DEBOUNCE_DELAY	100	/* ms */

#if 0	/* can't delay by dynamic steps like this */
#define PRINTING_PULSE_MIN	   5	/* 0.5us */
#define PRINTING_PULSE_MAX	 255	/* 25.5us */
#define PRINTING_PULSE_STEP	   5	/* 0.5us */
#define PRINTING_PULSE_DELAY	1000	/* 1ms -- better more and be safe */
#else
/* calculated for 16MHz -- 1 = 0.1875us */
#define PRINTING_PULSE_MIN	   4	/* 0.75us */
#define PRINTING_PULSE_MAX	 132	/* 24.75us */
#define PRINTING_PULSE_STEP	   4	/* 0.75us */
/* = 32 steps */
#endif

struct s_debounce {
	uint8_t state;		/** current state: pressed/not pressed */
	uint8_t previous_state;	/** previous state: pressed/not pressed */
	uint8_t lasting;	/** how long current state lasts */
};

/*
 * PLAN *
 * - step up/down pulse width (once per click)
 * - repeat printing while pressed
 *   = send a pulse (block the software) and end it
 *   = do not allow more pulses within a certain delay
 */
int main(void)
{
	/* calculate bits for the PINs */
	uint8_t led_pin  = _BV(LED % 8);
	uint8_t btn_pin[BTNS_COUNT];
	uint8_t print_pin = _BV(PIN_PRINT);

	struct s_debounce debounced[BTNS_COUNT];

	uint8_t printing_pulse = PRINTING_PULSE_MIN;
	/*uint16_t printing_delay = PRINTING_PULSE_DELAY;*/	/* init: can print */

	/* initialise arrays */
	memset(debounced, 0x0, BTNS_COUNT * sizeof(struct s_debounce));

	btn_pin[UP]	= _BV(BTN_UP);
	btn_pin[DOWN]	= _BV(BTN_DOWN);
	btn_pin[PRINT]	= _BV(BTN_PRINT);

	/* set LED's PIN to output (= 1); default is off */
	DDRB  |=  led_pin;
	PORTB &= ~led_pin;

	/* set the reading PINs to input (= 0) */
	DDRD &= ~btn_pin[UP] & ~btn_pin[DOWN] & ~btn_pin[PRINT];

	/* set the buttons to use the internal pull-up resistors */
	PORTD |= btn_pin[UP] | btn_pin[DOWN] | btn_pin[PRINT];

	/* set the printing PIN to output (= 1); default is off */
	DDRD  |=  print_pin;
	PORTD &= ~print_pin;

	for (;;) {
		/* UP and DOWN are mutually exclusive */
		/* BTN: increase pulse width */
		if (debounced[DOWN].state) {
			debounced[UP].state = PIND & btn_pin[UP];

			if (debounced[UP].state ==
			    debounced[UP].previous_state) {
				if (debounced[UP].lasting < DEBOUNCE_DELAY) {
					debounced[UP].lasting++;
				}
			} else {
				debounced[UP].lasting = 0;
			}

			if (debounced[UP].lasting == DEBOUNCE_DELAY) {
				/* button pushed => increase pulse width */
				if (!debounced[UP].state &&
				    printing_pulse < PRINTING_PULSE_MAX) {
					printing_pulse += PRINTING_PULSE_STEP;
				}

				/* prevent repeating the action */
				debounced[UP].lasting++;
			}

			debounced[UP].previous_state = debounced[UP].state;
		}

		/* BTN: decrease pulse width */
		if (debounced[UP].state) {
			debounced[DOWN].state = PIND & btn_pin[DOWN];

			if (debounced[DOWN].state ==
			    debounced[DOWN].previous_state) {
				if (debounced[DOWN].lasting < DEBOUNCE_DELAY) {
					debounced[DOWN].lasting++;
				}
			} else {
				debounced[DOWN].lasting = 0;
			}

			if (debounced[DOWN].lasting == DEBOUNCE_DELAY) {
				/* button pushed => decrease pulse */
				if (!debounced[DOWN].state &&
				    printing_pulse > PRINTING_PULSE_MIN) {
					printing_pulse -= PRINTING_PULSE_STEP;
				}

				/* prevent repeating the action */
				debounced[DOWN].lasting++;
			}

			debounced[DOWN].previous_state = debounced[DOWN].state;
		}

		/* BTN: print */
		/*if (printing_delay == PRINTING_PULSE_DELAY) {*/
			debounced[PRINT].state = PIND & btn_pin[PRINT];

			if (debounced[PRINT].state ==
			    debounced[PRINT].previous_state) {
				if (debounced[PRINT].lasting < DEBOUNCE_DELAY) {
					debounced[PRINT].lasting++;
				}
			} else {
				debounced[PRINT].lasting = 0;
			}

			if (debounced[PRINT].lasting == DEBOUNCE_DELAY) {
				/* button pushed => fire! */
				if (!debounced[PRINT].state) {
					PORTD |= print_pin;
					_delay_loop_1(printing_pulse);
					PORTD &= ~print_pin;
					/* make sure the nozzle gets its rest */
					/*printing_delay = 0;*/
				}
			}

			debounced[PRINT].previous_state = debounced[PRINT].state;
		/*
		} else {
			printing_delay++;
		}
		*/

		_delay_ms(1);
	}

	return 0;
}