#include <stdio.h>
#include <stdbool.h>
#include "helpers.c"

#define WIDTH 60
#define HEIGHT 40
#define DEBUG false

unsigned int startLength = 0;
unsigned int startApples = 0;

unsigned int currentTick;
int snake[WIDTH*HEIGHT];
unsigned int snakeLength;
unsigned int snakeX;
unsigned int snakeY;
int snakeDirX;
int snakeDirY;
unsigned int numApples;

void spawnApple();
void tick();
void draw();

// start_game
// ==========
void start_game(int len, int n_apples)
{
	if (startLength == 0)
		startLength = len;
	if (startApples == 0)
		startApples = n_apples;

	// Initialize variables
	currentTick = 0;
	snakeLength = len;
	numApples = n_apples;

	nib_init();

	// Initialize the snake array
	// Set every cell to a time value greater than the snake length
	for (unsigned int i = 0; i < WIDTH*HEIGHT; ++i) {
		snake[i] = snakeLength;
	}

	// Place the snake head in the middle
	snakeX = WIDTH / 2;
	snakeY = HEIGHT / 2;
	snakeDirX = 0;
	snakeDirY = -1;

	// Place the initial snake segments, downwards or something
	for (unsigned int i = 0; i < snakeLength; ++i) {
		unsigned int x = snakeX % WIDTH;
		unsigned int y = (snakeY + i) % HEIGHT;
		snake[x + y*WIDTH] = i;
	}

	// Place apples
	srand(time(0));
	for (unsigned int i = 0; i < numApples; ++i) {
		spawnApple();
	}
	
	while (true) {
		tick();
		draw();
	}
}

// spawnApple
// ==========
void spawnApple()
{
	unsigned int x = rand() % WIDTH;
	unsigned int y = rand() % HEIGHT;
	while (snake[x + y*WIDTH] < snakeLength) {
		x = rand() % WIDTH;
		y = rand() % HEIGHT;
	}
	snake[x + y*WIDTH] = -1;
}

// tick
// ====
void tick()
{
	currentTick++;
	// Increment cell times
	// --------------------
	for (unsigned int i = 0; i < WIDTH*HEIGHT; ++i) {
		int val = snake[i];
		
		if (val < 0) {
			// Apple lifetime
			/* snake[i]--; */
		} else if (val >= 0 && val <= snakeLength) {
			// Other cells
			snake[i]++;
		}
	}

	// Input
	// -----
	int key = nib_poll_kbd();
	if (key == 'w' && snakeDirY != 1) {
		snakeDirX = 0;
		snakeDirY = -1;
	}
	if (key == 's' && snakeDirY != -1) {
		snakeDirX = 0;
		snakeDirY = 1;
	}
	if (key == 'a' && snakeDirX != 1) {
		snakeDirX = -1;
		snakeDirY = 0;
	}
	if (key == 'd' && snakeDirX != -1) {
		snakeDirX = 1;
		snakeDirY = 0;
	}
	
	// Move snake
	// ----------
	snakeX = (snakeX + snakeDirX + WIDTH) % WIDTH;
	snakeY = (snakeY + snakeDirY + HEIGHT) % HEIGHT;

	// Collision
	// ---------
	// On collision with self
	int val = snake[snakeX + snakeY*WIDTH];
	if (val < snakeLength && val >= 0) {
		//nib_end();
		start_game(startLength, startApples);
	}
	// ON collision with apple
	if (val < 0) {
		// Spawn a new apple somewhere
		spawnApple();
		// Increase our length!
		snakeLength++;
	}
	
	// Update world
	// ------------
	snake[snakeX + snakeY*WIDTH] = 0;
}

// draw
// ====
void draw()
{
	char body[] = "NIBBLES";

	for (int y = -1; y <= HEIGHT; ++y) {
		for (int x = -1; x <= WIDTH; ++x) {
			// Draw a border outside the playing field
			if (x == -1 || y == -1 || x == WIDTH || y == HEIGHT) {
				unsigned int screenX = x + 1;
				unsigned int screenY = y + 1;
				nib_put_scr(screenX, screenY, '#');
			} else {
				int snakeVal = snake[x + y*WIDTH];
				unsigned int screenX = x + 1;
				unsigned int screenY = y + 1;
	
				// If the `DEBUG` flag is set, draw the raw ASCII-value for debugging purposes
				if (DEBUG) {
					nib_put_scr(screenX, screenY, '0' + snakeVal);
					continue;
				}

				// If the value is greater than `0` and less than `snakeLength`, it's part of the snake
				if (snakeVal >= 0 && snakeVal < snakeLength) {
					if (x == snakeX && y == snakeY) {
						// Draw the head
						nib_put_scr(screenX, screenY, '@');
					} else {
						// Draw the body
						nib_put_scr(screenX, screenY, body[(snakeVal - 1) % 7]);
					}
				} else if (snakeVal < 0) {
					// If the value is less than `0`, it's an apple
					nib_put_scr(screenX, screenY, 'o');
				} else {
					// Otherwise it's empty.
					nib_put_scr(screenX, screenY, ' ');
				}
			}
		}
	}
}