/**
 * \file main.c
 * \brief Simple gaming board
 *
 * \subsection Copyright
 * Copyright (c) 2013-2022 Michael Buesch <m@bues.ch>
 *
 * \subsection License
 * Licensed under the terms of the GNU General Public License version 2.
 */

#include "main.h"
#include "ks0108.h"
#include "output_extender.h"
#include "util.h"
#include "shr3.h"
#include "buzzer.h"
#if GAMEID == GAMEID_TETRIS
# include "tetris.h"
#endif

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


/** Systemtimer tick-Merker. */
static uint8_t timer_tick;
/** Tasterereignisse. */
static struct button_event_queue button_events;
/** Tasten-Autofire. */
static uint8_t button_autofire_count[NR_BTN];
/** Schnittstelle zur Spiellogik. */
static struct game_interface *game_interface;
/** Seed fuer Zufallszahlengenerator. */
static uint32_t EEMEM ee_rng_seed = RNG_SEED;

/** \brief	Taster Hardware auslesen.
 *
 * \return	Gibt die Tasterbits zurueck.
 *		Gesetztes Bit -> Taster gedrueckt.
 *		Geloeschtes Bit -> Taster nicht gedrueckt.
 */
static uint8_t buttons_state_get(void)
{
	return PINC ^ 0xFF;
}

/** \brief	Taster initialisieren. */
static void buttons_init(void)
{
	DDRC &= ~((1 << DDC0) | (1 << DDC1) | (1 << DDC2) |
		  (1 << DDC3) | (1 << DDC4) | (1 << DDC5));
	PORTC |= (1 << PC0) | (1 << PC1) | (1 << PC2) |
		 (1 << PC3) | (1 << PC4) | (1 << PC5);
}

/** \brief	Tasterereignisse bearbeiten. */
static void handle_button_events(void)
{
	struct button_event event;
	uint8_t sreg;

	sreg = irq_disable_save();
	while (button_events.nr_events) {
		/* Ereignis aus dem Ringpuffer entnehmen. */
		event = button_events.events[button_events.read_index];
		button_events.read_index++;
		if (button_events.read_index >= ARRAY_SIZE(button_events.events))
			button_events.read_index = 0;
		button_events.nr_events--;

		irq_restore(sreg);

		/* Tastenereignis an das Spiel uebergeben. */
		game_interface->handle_button(&event);

		sreg = irq_disable_save();
	}
	irq_restore(sreg);
}

/** \brief	Tasterereignis in Ringpuffer ablegen.
 *
 * \param button	Die logische Taster-ID-Nummer.
 *
 * \param action	Die logische Taster-Action-ID-Nummer.
 *
 * \param allocation	Anzahl der Bufferplaetze, die im Ringpuffer frei sein muessen.
 */
static void button_ringbuf_put(enum button button,
			       enum button_action action,
			       uint8_t allocation)
{
	struct button_event *ev;
	uint8_t sreg;

	sreg = irq_disable_save();

	if (allocation <= ARRAY_SIZE(button_events.events) &&
	    button_events.nr_events <= ARRAY_SIZE(button_events.events) - allocation) {
		/* Ereignis in Ringpuffer schreiben. */
		ev = &button_events.events[button_events.write_index];
		button_events.write_index++;
		if (button_events.write_index >= ARRAY_SIZE(button_events.events))
			button_events.write_index = 0;
		button_events.nr_events++;
		ev->button = button;
		ev->action = action;
	}

	irq_restore(sreg);
}

/** \brief	Tasterereignis pruefen und in Ringpuffer ablegen.
 *
 * \param state		Der Hardwarestatus des Tasters.
 *
 * \param pos_edge	Der Hardwarestatus des Tasters: Steigende Flanke.
 *
 * \param neg_edge	Der Hardwarestatus des Tasters: Fallende Flanke.
 *
 * \param mask		Die Bitmaske des Tasters.
 *
 * \param button	Die logische Taster-ID-Nummer.
 */
static void check_button_event(uint8_t state,
			       uint8_t pos_edge,
			       uint8_t neg_edge,
			       uint8_t mask,
			       enum button button)
{
	uint8_t autofire_delay;

	autofire_delay = game_interface->get_autofire_delay(button);

	if (autofire_delay > 0) {
		/* Autofire-Modus. */
		if (state & mask) {
			if (button_autofire_count[button] == 0) {
				button_ringbuf_put(button, BTNACT_PRESSED, 2);
				button_ringbuf_put(button, BTNACT_RELEASED, 1);
				button_autofire_count[button] = autofire_delay - 1;
			} else {
				button_autofire_count[button]--;
			}
		} else {
			button_autofire_count[button] = 0;
		}
	} else {
		/* Flankenmodus. */
		if (pos_edge & mask)
			button_ringbuf_put(button, BTNACT_PRESSED, 1);
		if (neg_edge & mask)
			button_ringbuf_put(button, BTNACT_RELEASED, 1);
		button_autofire_count[button] = 0;
	}
}

/** \brief	Tasterhardware auslesen. */
static void buttons_hardware_read(void)
{
	uint8_t state, pos_edge, neg_edge;
	static uint8_t prev_state;

	/* Tasterhardware auslesen. */
	state = buttons_state_get();

	/* Ungenutzte Bits loeschen */
	state &= ((1 << BTNBIT_UP) | (1 << BTNBIT_LEFT) |
		  (1 << BTNBIT_RIGHT) | (1 << BTNBIT_DOWN) |
		  (1 << BTNBIT_A) | (1 << BTNBIT_B));

	/* Flankenerkennung. */
	pos_edge = state & ~prev_state;
	neg_edge = ~state & prev_state;
	prev_state = state;

	/* "UP" Taster auswerten. */
	check_button_event(state, pos_edge, neg_edge, (1 << BTNBIT_UP), BTN_UP);

	/* "LEFT" Taster auswerten. */
	check_button_event(state, pos_edge, neg_edge, (1 << BTNBIT_LEFT), BTN_LEFT);

	/* "RIGHT" Taster auswerten. */
	check_button_event(state, pos_edge, neg_edge, (1 << BTNBIT_RIGHT), BTN_RIGHT);

	/* "DOWN" Taster auswerten. */
	check_button_event(state, pos_edge, neg_edge, (1 << BTNBIT_DOWN), BTN_DOWN);

	/* "A" Taster auswerten. */
	check_button_event(state, pos_edge, neg_edge, (1 << BTNBIT_A), BTN_A);

	/* "B" Taster auswerten. */
	check_button_event(state, pos_edge, neg_edge, (1 << BTNBIT_B), BTN_B);
}

/** \brief	Systemtimer - 100Hz. */
ISR(TIMER2_COMP_vect)
{
	mb();

	/* Systemtick inkrementieren. */
	timer_tick++;
	/* Taster auslesen und verarbeiten. */
	buttons_hardware_read();
	/* Periodische Summerfunktion aufrufen. */
	buzzer_100hz_tick();

	mb();
}

/** \brief	Systemtimer initialisieren. */
static void systemtimer_init(void)
{
	/* Timer 2 auf 100 Hz Interrupt initialisieren. */
	OCR2 = 156;
	TCNT2 = 0;
	TCCR2 = (1 << WGM21) | (1 << CS20) | (1 << CS21) | (1 << CS22);
	TIMSK |= (1 << OCIE2);
}

/** \brief	Zufallszahlengenerator initialisieren. */
static void rng_init(void)
{
	uint32_t seed;

	seed = eeprom_read_dword(&ee_rng_seed);
	eeprom_update_dword(&ee_rng_seed, seed + 1u);
	shr3_init(seed);
}

/** \brief	Hauptprogramm. */
int main(void)
{
	uint8_t nr_ticks;

	irq_disable();

	/* System initialisieren. */
	rng_init();
	extout_init();
	ks0108_init();
	buttons_init();
	systemtimer_init();
	buzzer_init();

	/* Spiel initialisieren. */
#if GAMEID == GAMEID_TETRIS
	game_interface = &tetris_game_interface;
#else
# error "Unknown game type."
#endif
	game_interface->init();

	irq_enable();
	while (1) {
		/* Tasten verarbeiten und ggf. an Spiel uebergeben. */
		handle_button_events();

		/* Tick-Merker auslesen */
		irq_disable();
		nr_ticks = timer_tick;
		timer_tick = 0;
		irq_enable();

		/* Ticks an Spiel uebergeben. */
		while (nr_ticks--)
			game_interface->do_100hz_tick();

		/* Periodische Aufgaben durchfuehren. */
		game_interface->periodic_work();
	}
}