#include <conio.h>
#include <stdio.h>
#include <c64.h>
#include <joystick.h>
#include <stdint.h>

struct screen {
	unsigned char grid[25][40];
};

enum direction {
	UP,
	DOWN,
	LEFT,
	RIGHT,
};

struct player {
	char x;
	char y;
	enum direction dir;
	unsigned char joy;
	unsigned char prev_joy;
	unsigned char next_char;
};

#define SCREEN (*(struct screen*) 0x0400)
#define SCREEN_AT(x, y) (SCREEN.grid[y][x])

#define MAX_PLAYERS 2

#define EMPTY  '\x20'
#define PLAYER '\x71'

#define CHR_V  '\x42'+128
#define CHR_H  '\x43'+128

#define CHR_DR '\xed'+128
#define CHR_RD '\xee'+128
#define CHR_UR '\xf0'+128
#define CHR_RU '\xfd'+128

static void update_player(struct player *p) {
	/* has direction been changed? */
	if (p->joy == p->prev_joy) {
		if (p->dir == DOWN || p->dir == UP) {
			p->next_char = CHR_V;
		} else if (p->dir == LEFT || p->dir == RIGHT) {
			p->next_char = CHR_H;
		}
		return;
	}

	if (JOY_UP(p->joy) && p->dir != DOWN) {
		switch (p->dir) {
			case RIGHT: p->next_char = CHR_RU; break;
			case LEFT:  p->next_char = CHR_DR; break;
		}
		p->dir = UP;
	} else if (JOY_DOWN(p->joy) && p->dir != UP) {
		switch (p->dir) {
			case RIGHT: p->next_char = CHR_RD; break;
			case LEFT:  p->next_char = CHR_UR; break;
		}
		p->dir = DOWN;
	} else if (JOY_LEFT(p->joy) && p->dir != RIGHT) {
		switch (p->dir) {
			case UP:   p->next_char = CHR_RD; break;
			case DOWN: p->next_char = CHR_RU; break;
		}
		p->dir = LEFT;
	} else if (JOY_RIGHT(p->joy) && p->dir != LEFT) {
		switch (p->dir) {
			case UP:   p->next_char = CHR_UR; break;
			case DOWN: p->next_char = CHR_DR; break;
		}
		p->dir = RIGHT;
	}
	p->prev_joy = p->joy;
}

static char move_player(struct player *p) {
	int res = 1;
	SCREEN_AT(p->x, p->y) = p->next_char;

	switch (p->dir) {
		case UP:    p->y--; break;
		case DOWN:  p->y++; break;
		case LEFT:  p->x--; break;
		case RIGHT: p->x++; break;
	}

	if (SCREEN_AT(p->x, p->y) != EMPTY || p->x < 0 || p->x >= 40 || p->y < 0 || p->y >= 25) {
		res = 0;
	}
	SCREEN_AT(p->x, p->y) = PLAYER;

	return res;
}

static void play_game(char n_players) {
	uint16_t busy_wait = 300;

	struct player players[MAX_PLAYERS] = {
		{  5, 12, RIGHT, 0, 0, CHR_H },
		{ 35, 12, LEFT,  0, 0, CHR_H },
	};

	clrscr();

	while(1) {
		char i;
		uint16_t n;

		for (i=0; i<n_players; i++) {
			if (!move_player(&players[i])) {
				return;
			}
		}

		/* "sleep" for a bit, but keep reading joystick changes */
		for (n=0; n<busy_wait; n++) {
			for (i=0; i<n_players; i++) {
				char tmp = joy_read(i);
				if (tmp) {
					players[i].joy = tmp;
				}
			}
		}

		for (i=0; i<n_players; i++) {
			update_player(&players[i]);
		}
	}
}

int main() {
	joy_install(joy_static_stddrv);

	/* use uppercase character set */
	*((unsigned char*)0xD018) = 0x14;

	while(1) {
		play_game(2);
		printf("game over!");
	}
}