import java.util.ArrayList;
import java.awt.Color;

public class Screen {
        public int[][] map;
        public int mapWidth, mapHeight, width, height;
        public ArrayList textures;

        public Screen(int[][] m, ArrayList tex, int w, int h) {
            map = m;
            textures = tex;
            width = w;
            height = h;
        }

        public int[] update(Camera camera, int[] pixels) {
            for(int n=0; n<pixels.length/2; n++) {
                if(pixels[n] != Color.DARK_GRAY.getRGB()) pixels[n] = Color.DARK_GRAY.getRGB();
            }
            for(int i=pixels.length/2; i<pixels.length; i++) {
                if(pixels[i] != Color.gray.getRGB()) pixels[i] = Color.gray.getRGB();
            }

            for(int x=0; x<width; x=x+1) {
                double cameraX = 2 * x / (double)(width) -1;
                double rayDirX = camera.xDir + camera.xPlane * cameraX;
                double rayDirY = camera.yDir + camera.yPlane * cameraX;
                //Map position
                int mapX = (int)camera.xPos;
                int mapY = (int)camera.yPos;
                //length of ray from current position to next x or y-side
                double sideDistX;
                double sideDistY;
                //Length of ray from one side to next in map
                double deltaDistX = Math.sqrt(1 + (rayDirY*rayDirY) / (rayDirX*rayDirX));
                double deltaDistY = Math.sqrt(1 + (rayDirX*rayDirX) / (rayDirY*rayDirY));
                double perpWallDist;
                //Direction to go in x and y
                int stepX, stepY;
                boolean hit = false;//was a wall hit
                int side=0;//was the wall vertical or horizontal

              //Figure out the step direction and initial distance to a side
                if (rayDirX < 0)
                {
                    stepX = -1;
                    sideDistX = (camera.xPos - mapX) * deltaDistX;
                }
                else
                {
                    stepX = 1;
                    sideDistX = (mapX + 1.0 - camera.xPos) * deltaDistX;
                }
                if (rayDirY < 0)
                {
                    stepY = -1;
                    sideDistY = (camera.yPos - mapY) * deltaDistY;
                }
                else
                {
                    stepY = 1;
                    sideDistY = (mapY + 1.0 - camera.yPos) * deltaDistY;
                }

              //Loop to find where the ray hits a wall
                while(!hit) {
                    //Jump to next square
                    if (sideDistX < sideDistY)
                    {
                        sideDistX += deltaDistX;
                        mapX += stepX;
                        side = 0;
                    }
                    else
                    {
                        sideDistY += deltaDistY;
                        mapY += stepY;
                        side = 1;
                    }
                    //Check if ray has hit a wall
                    if(map[mapX][mapY] > 0) hit = true;
                }

              //Calculate distance to the point of impact
                if(side==0)
                    perpWallDist = Math.abs((mapX - camera.xPos + (1 - stepX) / 2) / rayDirX);
                else
                    perpWallDist = Math.abs((mapY - camera.yPos + (1 - stepY) / 2) / rayDirY);
                //Now calculate the height of the wall based on the distance from the camera
                int lineHeight;
                if(perpWallDist > 0) lineHeight = Math.abs((int)(height / perpWallDist));
                else lineHeight = height;
                //calculate lowest and highest pixel to fill in current stripe
                int drawStart = -lineHeight/2+ height/2;
                if(drawStart < 0)
                    drawStart = 0;
                int drawEnd = lineHeight/2 + height/2;
                if(drawEnd >= height)
                    drawEnd = height - 1;


              //add a texture
                int texNum = map[mapX][mapY] - 1;
                double wallX;//Exact position of where wall was hit
                if(side==1) {//If its a y-axis wall
                    wallX = (camera.xPos + ((mapY - camera.yPos + (1 - stepY) / 2) / rayDirY) * rayDirX);
                } else {//X-axis wall
                    wallX = (camera.yPos + ((mapX - camera.xPos + (1 - stepX) / 2) / rayDirX) * rayDirY);
                }
                wallX-=Math.floor(wallX);
                //x coordinate on the texture
                int texX = (int)(wallX * (textures.get(texNum).SIZE));
                if(side == 0 && rayDirX > 0) texX = textures.get(texNum).SIZE - texX - 1;
                if(side == 1 && rayDirY < 0) texX = textures.get(texNum).SIZE - texX - 1;

              //calculate y coordinate on texture
                for(int y=drawStart; y<drawEnd; y++) {
                    int texY = (((y*2 - height + lineHeight) << 6) / lineHeight) / 2;
                    int color;
                    if(side==0) color = textures.get(texNum).pixels[texX + (texY * textures.get(texNum).SIZE)];
                    else color = (textures.get(texNum).pixels[texX + (texY * textures.get(texNum).SIZE)]>>1) & 8355711;//Make y sides darker
                    pixels[x + y*(width)] = color;
                }

            }
        }
}