#include "cube3d.h"

static void	init_raycast(t_rcast *rcast, t_vec *ray)
{
	rcast->is_x = 0;
	rcast->wall_height = 0;
	// ray sign
	rcast->ray_sign_x = 1;
	if (ray->start.x < ray->end.x)
		rcast->ray_sign_x = -1;
	rcast->ray_sign_y = 1;
	if (ray->start.y < ray->end.y)
		rcast->ray_sign_y = -1;
	// cell position of ray
	rcast->cell_x = ray->start.x / CELL;
	rcast->cell_y = ray->start.y / CELL;
	// slope of ray
	rcast->slope_x = ray->end.x - ray->start.x;
	rcast->slope_y = ray->end.y - ray->start.y;
	// direction of next cell
	rcast->next_cell_x = -rcast->ray_sign_x;
	rcast->next_cell_y = -rcast->ray_sign_y;
	// ray steps in both axis
	rcast->ray_step_x = ft_abs(CELL * rcast->slope_y);
	rcast->ray_step_y = ft_abs(CELL * rcast->slope_x);
}

static void	init_first_step(t_rcast *rcast, t_vec *ray)
{
	// first next time ray cross grid
	rcast->first_next_x = ray->start.x % CELL;
	if (rcast->first_next_x && rcast->ray_sign_x < 0)
		rcast->first_next_x = CELL - rcast->first_next_x;
	if (!rcast->first_next_x && rcast->ray_sign_x < 0)
		rcast->first_next_x = CELL;
	rcast->first_next_y = ray->start.y % CELL;
	if (rcast->first_next_y && rcast->ray_sign_y < 0)
		rcast->first_next_y = CELL - rcast->first_next_y;
	if (!rcast->first_next_y && rcast->ray_sign_y < 0)
		rcast->first_next_y = CELL;
	rcast->next_x = ft_abs(rcast->first_next_x * rcast->slope_y);
	rcast->next_y = ft_abs(rcast->first_next_y * rcast->slope_x);
}

static void	next_cell(t_rcast *rcast)
{
	if (rcast->next_x > rcast->next_y)
	{
		rcast->cell_y += rcast->next_cell_y;
		rcast->next_y += rcast->ray_step_y;
		rcast->is_x = 0;
	}
	else
	{
		rcast->cell_x += rcast->next_cell_x;
		rcast->next_x += rcast->ray_step_x;
		rcast->is_x = 1;
	}
}

static void	calcul_ray_end(t_rcast *rcast, t_vec *ray)
{
	if (rcast->is_x)
	{
		ray->end.x = rcast->cell_x * CELL;
		if (rcast->ray_sign_x == 1)
			ray->end.x += CELL;
		if (rcast->slope_x)
		{
			rcast->ratio = (double)(ray->end.x - ray->start.x) / (double)rcast->slope_x;
			ray->end.y = ray->start.y + (double)rcast->slope_y * rcast->ratio;
		}
	}
	else
	{
		ray->end.y = rcast->cell_y * CELL;
		if (rcast->ray_sign_y == 1)
			ray->end.y += CELL;
		if (rcast->slope_y)
		{
			rcast->ratio = (double)(ray->end.y - ray->start.y) / (double)rcast->slope_y;
			ray->end.x = ray->start.x + (double)rcast->slope_x * rcast->ratio;
		}
	}
}

void	ray_intersect(t_game *game, t_rcast *rcast, t_vec *ray)
{
	ray->start.x = rcast->ray.start.x + game->plr.pos.x;
	ray->start.y = rcast->ray.start.y + game->plr.pos.y;
	ray->end.x = rcast->ray.end.x + game->plr.pos.x;
	ray->end.x += rcast->ray_nb * SCREEN_SIZE / SCREEN_DEF;
	ray->end.y = rcast->ray.end.y + game->plr.pos.y;
	rotate(&(game->plr), &(ray->end));
	init_raycast(rcast, ray);
	init_first_step(rcast, ray);
	// loop through grid
	while (!is_wall(game, rcast->cell_x, rcast->cell_y))
		next_cell(rcast);
	// end ray position
	calcul_ray_end(rcast, ray);
}