#include <GLFW/glfw3.h>
#include <stdio.h>
#include <math.h>

// TODO: move to implicit map definition with level editor in future
#define MAP_HEIGHT 20
#define MAP_WIDTH 20
int world_map[MAP_HEIGHT][MAP_WIDTH] = {
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 0, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 4, 0, 1},
    {1, 0, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 4, 0, 1},
    {1, 0, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 4, 0, 1},
    {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
};

// TODO: move player code to dedicated file after complication demands it
// TODO: implement y-shearing to allow players to look vertically
typedef struct {
	float pos_x, pos_y;
	float dir_x, dir_y;
	float plane_x, plane_y;
	float move_speed;
	float rot_speed;
} Player;

typedef struct {
	unsigned char r, g, b;
} ColorRGB;

// honest- this function can from chatgpt- cross-reference this with other raycasting guides
void raycast(Player *player) {
    	int screen_width = 800;
    	int screen_height = 600;

    	for (int x = 0; x < screen_width; ++x) {
        	// Calculate ray position and direction
        	double camera_x = 2.0 * x / (double)screen_width - 1; // x-coordinate in camera space
        	double ray_dir_x = player->dir_x + player->plane_x * camera_x;
        	double ray_dir_y = player->dir_y + player->plane_y * camera_x;

        	// Which box of the map we're in
        	int map_x = (int)player->pos_x;
        	int map_y = (int)player->pos_y;

        	// Length of ray from one x or y-side to next x or y-side
        	double delta_dist_x = fabs(1 / ray_dir_x);
        	double delta_dist_y = fabs(1 / ray_dir_y);

        	// Length of ray from current position to next x or y-side
        	double side_dist_x;
        	double side_dist_y;

        	// Direction to step in x or y-direction (either +1 or -1)
        	int step_x;
        	int step_y;

        	// Was a wall hit?
        	int hit = 0;
        	// Was the wall hit a wall facing north, east-west, or south?
        	int side;
        	if (ray_dir_x < 0) {
            		step_x = -1;
            		side_dist_x = (player->pos_x - map_x) * delta_dist_x;
        	} else {
            		step_x = 1;
            		side_dist_x = (map_x + 1.0 - player->pos_x) * delta_dist_x;
        	}
        	if (ray_dir_y < 0) {
            		step_y = -1;
            		side_dist_y = (player->pos_y - map_y) * delta_dist_y;
        	} else {
            		step_y = 1;
            		side_dist_y = (map_y + 1.0 - player->pos_y) * delta_dist_y;
        	}

        	// Perform DDA
        	while (hit == 0) {
            		// Jump to next map square
            		if (side_dist_x < side_dist_y) {
                		side_dist_x += delta_dist_x;
                		map_x += step_x;
                		side = (ray_dir_x > 0) ? 0 : 2;
            		} else {
                		side_dist_y += delta_dist_y;
                		map_y += step_y;
                		side = 1;
            		}
            		// Check if ray has hit a wall
            		if (world_map[map_x][map_y] > 0) { hit = 1; }
        	}

		// calculate distance projected on camera direction
		double perp_wall_dist;
		if (side == 0 || side == 2) { perp_wall_dist = (map_x - player->pos_x + (1 - step_x) / 2) / ray_dir_x; }
		else           { perp_wall_dist = (map_y - player->pos_y + (1 - step_y) / 2) / ray_dir_y; }

		// fog effect
		float fog_distance = 20.0f;
		float scale_factor = 1.0f - perp_wall_dist / fog_distance;
		if (scale_factor < 0.0f) { scale_factor = 0.0f; }
		
		// calculate height of line on screen
		int line_height = (int)(screen_height / perp_wall_dist);
		int draw_start = -line_height / 2 + screen_height / 2;
		if (draw_start < 0) { draw_start = 0; }
		int draw_end = line_height / 2 + screen_height / 2;
		if (draw_end >= screen_height)  { draw_end = screen_height - 1; }


		// colors :)

		// TODO: currently, this effects both inside and outside faces
		// which creates some awkward coloring issues with the outer walls.
		// this may not be an issue in the final release, depending how walls
		// are handled, but worth noting now.
		ColorRGB color;
		if (world_map[map_x][map_y] == 1)	color = (ColorRGB){.r = 255, .g = 255, .b = 255};
		else if (world_map[map_x][map_y] == 2)	color = (ColorRGB){.r = 255, .g = 0, .b = 0};
		else if (world_map[map_x][map_y] == 3)	color = (ColorRGB){.r = 0, .g = 255, .b = 0};
		else if (world_map[map_x][map_y] == 4)	color = (ColorRGB){.r = 0, .g = 0, .b = 255};
		else					color = (ColorRGB){.r = 0, .g = 0, .b = 0};

		if (side == 1) {
			color.r /= 2;
			color.g /= 2;
			color.b /= 2;
		} else if (side == 2) {
			color.r /= 4;
			color.g /= 4;
			color.b /= 4;
		}

		// scale brightness in accordance with distance (for fog)
		color.r *= scale_factor;
		color.g *= scale_factor;
		color.b *= scale_factor;

		// TODO: recommended to put this in its own function or something at some point,
		// as it deals with library calls outside of this function's scope
		glBegin(GL_LINES);
		glColor3ub(color.r, color.g, color.b);
		glVertex2i(x, draw_start);
		glVertex2i(x, draw_end);
		glEnd();
    	}
}

int main(int argc, char *argv[]) {
	GLFWwindow* window;

	// init player
	Player player;
	player.pos_y = 2.0f;
	player.pos_x = 2.0f;
	player.dir_x = 1.0f; // facing right
	player.dir_y = 0.0f; // facing right
	player.plane_x = 0.0f; // FOV related
	player.plane_y = 0.66f; // FOV related
	player.move_speed = 0.05f;
	player.rot_speed = 0.1f;

	// initiate glfw library
	if (!glfwInit()){
		printf("Failed to initiate GLFW.\n");
		return -1;
	}

	// create glfw window
	window = glfwCreateWindow(800, 600, "raycaster", NULL, NULL);
	if (!window){
		printf("Failed to create GLFW window.\n");
		glfwTerminate();
		return -1;
	}

	// make window current
	glfwMakeContextCurrent(window);

	// setup orthographic projection camera
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0.0, 800, 600, 0.0, -1.0, 1.0);
	glMatrixMode(GL_MODELVIEW);

	// TODO: move timers into a header
	double last_time = glfwGetTime();
	int nb_frames = 0;
	// TODO: render FPS with freetype or something as opposed to updating title
	char title[200];

	while (!glfwWindowShouldClose(window)) {

		// timing section
		double current_time = glfwGetTime();
		nb_frames++;
		if (current_time - last_time >= 1.0) {
			sprintf(title, "FPS: %d", nb_frames);
			glfwSetWindowTitle(window, title);
			nb_frames = 0;
			last_time += 1.0;
		}

		// clear window
		glClear(GL_COLOR_BUFFER_BIT);
		glLoadIdentity();

		// main raycast function
		raycast(&player);

		// movement and camera rotation
		// TODO: eventually translate movement from a header
		if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS) {
			player.pos_x += player.dir_x * player.move_speed;
			player.pos_y += player.dir_y * player.move_speed;
		}
		if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS) {
			player.pos_x -= player.dir_x * player.move_speed;
			player.pos_y -= player.dir_y * player.move_speed;
		}
		if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS) {
			// this changes where we're casting our rays
			double old_dir_x = player.dir_x;
			player.dir_x = player.dir_x * cos(-player.rot_speed) - player.dir_y * sin(-player.rot_speed);
			player.dir_y = old_dir_x * sin(-player.rot_speed) + player.dir_y * cos(-player.rot_speed);
			// this updates perspective
			double old_plane_x = player.plane_x;
			player.plane_x = player.plane_x * cos(-player.rot_speed) - player.plane_y * sin(-player.rot_speed);
			player.plane_y = old_plane_x * sin(-player.rot_speed) + player.plane_y * cos(-player.rot_speed);
		}
		if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS) {
			double old_dir_x = player.dir_x;
			player.dir_x = player.dir_x * cos(player.rot_speed) - player.dir_y * sin(player.rot_speed);
			player.dir_y = old_dir_x * sin(player.rot_speed) + player.dir_y * cos(player.rot_speed);
			double old_plane_x = player.plane_x;
			player.plane_x = player.plane_x * cos(player.rot_speed) - player.plane_y * sin(player.rot_speed);
			player.plane_y = old_plane_x * sin(player.rot_speed) + player.plane_y * cos(player.rot_speed);
		}


		glfwSwapBuffers(window);
		glfwPollEvents();

	}

	glfwTerminate();
	printf("Terminating program...\n");
	return 0;
}