/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   render.c                                           :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: mcolonna <mcolonna@student.42.fr>          +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2024/10/14 14:55:05 by greg              #+#    #+#             */
/*   Updated: 2024/10/15 13:52:35 by mcolonna         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "algo.h"

static void calculate_perpwalldist3(int x,
	double *raydirX, double *raydirY,
	double *deltadistX, double *deltadistY)
{
	double	ray_direction = 2 * x / (double)SCREEN_WIDTH - 1;
	double dirX;
	double dirY;
	double planeX;
	double planeY;
	vector_from_rotation(&dirX, &dirY, g_ray.rot, 1);
	vector_from_rotation(&planeX, &planeY, g_ray.rot + PI / 2, 1);
	*raydirX = dirX + planeX * ray_direction;
	*raydirY = dirY + planeY * ray_direction;
	*deltadistX = (raydirX == 0) ? 1e30 : fabs(1 / *raydirX);
	*deltadistY = (raydirY == 0) ? 1e30 : fabs(1 / *raydirY);
}

static void	calculate_perpwalldist2(int x,
	double *sidedistX, double *sidedistY,
	double *deltadistX, double *deltadistY,
	int *stepX, int *stepY)
{
	int mapX = (int)g_ray.posX;
	int mapY = (int)g_ray.posY;
	double raydirX;
	double raydirY;

	calculate_perpwalldist3(x, &raydirX, &raydirY, deltadistX, deltadistY);
	if (raydirX < 0)
	{
		*stepX = -1;
		*sidedistX = (g_ray.posX - mapX) * *deltadistX;
	}
	else
	{
		*stepX = 1;
		*sidedistX = (mapX + 1.0 - g_ray.posX) * *deltadistX;
	}
	if (raydirY < 0)
	{
		*stepY = -1;
		*sidedistY = (g_ray.posY - mapY) * *deltadistY;
	}
	else
	{
		*stepY = 1;
		*sidedistY = (mapY + 1.0 - g_ray.posY) * *deltadistY;
	}
}

/// @brief Calculate the distance of the wall perpendicularly to the camera
///        plane.
///
/// @param x Ray direction x between 0 and 1. 
/// @return Result.
static double	calculate_perpwalldist(int x)
{
	int mapX = (int)g_ray.posX;
	int mapY = (int)g_ray.posY;
	bool side;
	double sidedistX;
	double sidedistY;
	double deltadistX;
	double deltadistY;
	int stepX;
	int stepY;
	calculate_perpwalldist2(x, &sidedistX, &sidedistY, &deltadistX, &deltadistY, &stepX, &stepY);
	while(worldMap[mapX][mapY] != 1)
	{
		// jump to next map square, either in x-direction, or in y-direction
		if(sidedistX < sidedistY)
		{
			sidedistX += deltadistX;
			mapX += stepX;
			side = false;
		}
		else
		{
			sidedistY += deltadistY;
			mapY += stepY;
			side = true;
		}
	}
	double	perpwalldist;
	if(!side) 
		perpwalldist = (sidedistX - deltadistX);
	else
		perpwalldist = (sidedistY - deltadistY);
	return (perpwalldist);
}

/// @brief Draw a vertical line according to the ray direction x.
///
/// @param x Ray direction x between 0 and 1.
static void	draw_vertical_line(int x, u_int32_t *img_data)
{
	double perpwalldist = calculate_perpwalldist(x);
	int lineHeight = (int)(SCREEN_HEIGHT / perpwalldist);
	int	drawStart = -lineHeight / 2 + SCREEN_HEIGHT / 2;
	if(drawStart < 0)
		drawStart = 0;
	int drawEnd = lineHeight / 2 + SCREEN_HEIGHT / 2;
	if(drawEnd >= SCREEN_HEIGHT)
		drawEnd = SCREEN_HEIGHT - 1;
	int y = 0;
	while (y < drawStart)
	{
		img_data[y * SCREEN_WIDTH + x] = COLOR_CEILING;
		y++;
	}
	while (y < drawEnd)
	{
		img_data[y * SCREEN_WIDTH + x] = COLOR_WALL;
		y++;
	}
	while (y < SCREEN_HEIGHT)
	{
		img_data[y * SCREEN_WIDTH + x] = COLOR_FLOOR;
		y++;
	}
}

int render(u_int32_t *img_data)
{
	int x; // px
	
	// clear image data
	ft_bzero(img_data, SCREEN_WIDTH * SCREEN_HEIGHT * sizeof(int)); // TODO why
	
	// 1
	double dirX, dirY, planeX, planeY;
	vector_from_rotation(&dirX, &dirY, g_ray.rot, 1);
	vector_from_rotation(&planeX, &planeY, g_ray.rot + PI/2, FOV);

	x = 0;
	while (x < SCREEN_WIDTH)
	{
		draw_vertical_line(x, img_data);
		x++;
	}

	return (0);
}