//********************************************************************//
//* F. PERMADI MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE      *//
//* SUITABILITY OF                                                   *//
//* THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT       *//
//* LIMITED                                                          *//
//* TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A      *//
//* PARTICULAR PURPOSE                                               *//
//********************************************************************//
import java.awt.*;
import java.applet.*;

//*******************************************************************//
//* main class
//*******************************************************************//
public class Rayc extends Applet implements Runnable
{
  // this is Java's stuff 
  Thread fThread;

  // size of tile (wall height)
  static final int TILE_SIZE = 64;
  static final int WALL_HEIGHT = 64;
  static final int PROJECTIONPLANEWIDTH = 320;
  static final int PROJECTIONPLANEHEIGHT = 200;
  static final int ANGLE60 = PROJECTIONPLANEWIDTH;
  static final int ANGLE30 = (ANGLE60/2);
  static final int ANGLE15 = (ANGLE30/2);
  static final int ANGLE90 = (ANGLE30*3);
  static final int ANGLE180 = (ANGLE90*2);
  static final int ANGLE270 = (ANGLE90*3);
  static final int ANGLE360 = (ANGLE60*6);
  static final int ANGLE0 = 0;
  static final int ANGLE5 = (ANGLE30/6);
  static final int ANGLE10 = (ANGLE5*2);

  // trigonometric tables
  float fSinTable[];
  float fISinTable[];
  float fCosTable[];
  float fICosTable[];
  float fTanTable[];
  float fITanTable[];
  float fFishTable[];
  float fXStepTable[];
  float fYStepTable[];

  // offscreen buffer
  Image fOffscreenImage;
  Graphics fOffscreenGraphics;

  // player's attributes
  int fPlayerX = 100;
  int fPlayerY = 160;
  int fPlayerArc = ANGLE0;
  int fPlayerDistanceToTheProjectionPlane = 277;
  int fPlayerHeight =32;
  int fPlayerSpeed = 16;
  int fProjectionPlaneYCenter = PROJECTIONPLANEHEIGHT/2;
  // the following variables are used to keep the player coordinate in the overhead map
  int fPlayerMapX, fPlayerMapY, fMinimapWidth;

  // movement flag
  boolean fKeyUp=false;
  boolean fKeyDown=false;
  boolean fKeyLeft=false;
  boolean fKeyRight=false;

  // 2 dimensional map
  byte fMap[];
  static final byte W=1;                                // wall
  static final byte O=0;                                // opening
  static final int MAP_WIDTH=12;
  static final int MAP_HEIGHT=12;

  //*******************************************************************//
  //* Convert arc to radian
  //*******************************************************************//
  float arcToRad(float arcAngle)
  {
     return ((float)(arcAngle*Math.PI)/(float)ANGLE180);    
  }

  //*******************************************************************//
  //* Create tigonometric values to make the program runs faster.
  //*******************************************************************//
  public void createTables()
  {
    int i;
    float radian;
    fSinTable = new float[ANGLE360+1];
    fISinTable = new float[ANGLE360+1];
    fCosTable = new float[ANGLE360+1];
    fICosTable = new float[ANGLE360+1];
    fTanTable = new float[ANGLE360+1];
    fITanTable = new float[ANGLE360+1];
    fFishTable = new float[ANGLE60+1];
    fXStepTable = new float[ANGLE360+1];
    fYStepTable = new float[ANGLE360+1];

    for (i=0; i<=ANGLE360;i++)
    {
      // get the radian value (the last addition is to avoid division by 0, try removing
          // that and you'll see a hole in the wall when a ray is at 0, 90, 180, or 270 degree)
      radian = arcToRad(i) + (float)(0.0001);
      fSinTable[i]=(float)Math.sin(radian);
      fISinTable[i]=(1.0F/(fSinTable[i]));
      fCosTable[i]=(float)Math.cos(radian);
      fICosTable[i]=(1.0F/(fCosTable[i]));
      fTanTable[i]=(float)Math.tan(radian);
      fITanTable[i]=(1.0F/fTanTable[i]);

        //  you can see that the distance between xi is the same
        //  if we know the angle
        //  _____|_/next xi______________
        //       |
        //  ____/|next xi_________   slope = tan = height / dist between xi's
        //     / |
        //  __/__|_________  dist between xi = height/tan where height=tile size
        // old xi|
        //                  distance between xi = x_step[view_angle];
        //
        //
        // facine left
      // facing left
      if (i>=ANGLE90 && i<ANGLE270)
      {
        fXStepTable[i] = (float)(TILE_SIZE/fTanTable[i]);
        if (fXStepTable[i]>0)
          fXStepTable[i]=-fXStepTable[i];
      }
      // facing right
      else
      {
        fXStepTable[i] = (float)(TILE_SIZE/fTanTable[i]);
        if (fXStepTable[i]<0)
          fXStepTable[i]=-fXStepTable[i];
      }

      // FACING DOWN
      if (i>=ANGLE0 && i<ANGLE180)
      {
        fYStepTable[i] = (float)(TILE_SIZE*fTanTable[i]);
        if (fYStepTable[i]<0)
          fYStepTable[i]=-fYStepTable[i];
      }
      // FACING UP
      else
      {
        fYStepTable[i] = (float)(TILE_SIZE*fTanTable[i]);
        if (fYStepTable[i]>0)
          fYStepTable[i]=-fYStepTable[i];
      }
    }

    for (i=-ANGLE30; i<=ANGLE30; i++)
    {
        radian = arcToRad(i);
        // we don't have negative angle, so make it start at 0
        // this will give range 0 to 320
        fFishTable[i+ANGLE30] = (float)(1.0F/Math.cos(radian));
    }

        // CERATE A SIMPLE MAP
        byte[] map=
        {
                W,W,W,W,W,W,W,W,W,W,W,W,
                W,O,O,O,O,O,O,O,O,O,O,W,
                W,O,O,O,O,O,O,O,O,O,O,W,
                W,O,O,O,O,O,O,O,W,O,O,W,
                W,O,O,W,O,W,O,O,W,O,O,W,
                W,O,O,W,O,W,W,O,W,O,O,W,
                W,O,O,W,O,O,W,O,W,O,O,W,
                W,O,O,O,W,O,W,O,W,O,O,W,
                W,O,O,O,W,O,W,O,W,O,O,W,
                W,O,O,O,W,W,W,O,W,O,O,W,
                W,O,O,O,O,O,O,O,O,O,O,W,
                W,W,W,W,W,W,W,W,W,W,W,W
        };
        fMap=map;
  }

  //*******************************************************************//
  //* Called when program starts
  //*******************************************************************//
  public void start()
  {
    createTables();
    fThread=new Thread(this);
    fThread.start();
  }

  //*******************************************************************//
  //* Running thread
  //*******************************************************************//
  public void run()
  {
        requestFocus();
        // create offscreen buffer
    fOffscreenImage=createImage(size().width, size().height);
    fOffscreenGraphics=fOffscreenImage.getGraphics();

    while(true)
    {
          // rotate left
      if (fKeyLeft)
      {
        if ((fPlayerArc-=ANGLE10)<ANGLE0)
          fPlayerArc+=ANGLE360;
      }
          // rotate right
      else if (fKeyRight)
      {
        if ((fPlayerArc+=ANGLE10)>=ANGLE360)
          fPlayerArc-=ANGLE360;
      }

          //  _____     _
          // |\ arc     |
          // |  \       y
          // |    \     |
      //            -
          // |--x--|  
          //
          //  sin(arc)=y/diagonal
          //  cos(arc)=x/diagonal   where diagonal=speed
      float playerXDir=fCosTable[fPlayerArc];
      float playerYDir=fSinTable[fPlayerArc];

          // move forward
      if (fKeyUp)
      {
        fPlayerX+=(int)(playerXDir*fPlayerSpeed);
        fPlayerY+=(int)(playerYDir*fPlayerSpeed);
      }
          // move backward
      else if (fKeyDown)
      {
        fPlayerX-=(int)(playerXDir*fPlayerSpeed);
        fPlayerY-=(int)(playerYDir*fPlayerSpeed);
      }

      render();
      try
      {
        Thread.sleep(50);
      }
      catch (Exception sleepProblem)
      {
        showStatus("Sleep problem");
      }
    }
  }

  //*******************************************************************//
  //* Draw background image
  //*******************************************************************//
  public void drawBackground()
  {
    // sky
        int c=25;
        int r;
        for (r=0; r<PROJECTIONPLANEHEIGHT/2; r+=10)
        {
                fOffscreenGraphics.setColor(new Color(c, 125, 225));
                fOffscreenGraphics.fillRect(0, r, PROJECTIONPLANEWIDTH, 10);
                c+=20;
        }
        // ground
        c=22;
        for (; r<PROJECTIONPLANEHEIGHT; r+=15)
        {
                fOffscreenGraphics.setColor(new Color(c, 20, 20));
                fOffscreenGraphics.fillRect(0, r, PROJECTIONPLANEWIDTH, 15);
                c+=15;
        }
  }

  //*******************************************************************//
  //* Draw map on the right side
  //*******************************************************************//
  public void drawOverheadMap()
  {
        fMinimapWidth=5;
    for (int u=0; u<MAP_WIDTH; u++)
    {
      for (int v=0; v<MAP_HEIGHT; v++)
      {
        if (fMap[v*MAP_WIDTH+u]==W)
        {
                  fOffscreenGraphics.setColor(Color.cyan);
        }
                else
        {
                  fOffscreenGraphics.setColor(Color.black);
        }
            fOffscreenGraphics.fillRect(PROJECTIONPLANEWIDTH+(u*fMinimapWidth),
                        (v*fMinimapWidth), fMinimapWidth, fMinimapWidth);
      }
    }
        fPlayerMapX=PROJECTIONPLANEWIDTH+(int)(((float)fPlayerX/(float)TILE_SIZE) * fMinimapWidth);
        fPlayerMapY=(int)(((float)fPlayerY/(float)TILE_SIZE) * fMinimapWidth);
  }

  //*******************************************************************//
  //* Draw ray on the overhead map (for illustartion purpose)
  //* This is not part of the ray-casting process
  //*******************************************************************//
  public void drawRayOnOverheadMap(float x, float y)
  {
        fOffscreenGraphics.setColor(Color.yellow);
        // draw line from the player position to the position where the ray
        // intersect with wall
        fOffscreenGraphics.drawLine(fPlayerMapX, fPlayerMapY, 
                (int)(PROJECTIONPLANEWIDTH+((float)(x*fMinimapWidth)/(float)TILE_SIZE)),
                (int)(((float)(y*fMinimapWidth)/(float)TILE_SIZE)));
        // draw a red line indication the player's direction
        fOffscreenGraphics.setColor(Color.red);
    fOffscreenGraphics.drawLine(fPlayerMapX, fPlayerMapY, 
      (int)(fPlayerMapX+fCosTable[fPlayerArc]*10),
          (int)(fPlayerMapY+fSinTable[fPlayerArc]*10));
  }

  //*******************************************************************//
  //* Renderer
  //*******************************************************************//
  public void render()
  {
        drawBackground();
        drawOverheadMap();

    int verticalGrid;        // horizotal or vertical coordinate of intersection
    int horizontalGrid;      // theoritically, this will be multiple of TILE_SIZE
                             // , but some trick did here might cause
                             // the values off by 1
    int distToNextVerticalGrid; // how far to the next bound (this is multiple of
    int distToNextHorizontalGrid; // tile size)
    float xIntersection;  // x and y intersections
    float yIntersection;
    float distToNextXIntersection;
    float distToNextYIntersection;

    int xGridIndex;        // the current cell that the ray is in
    int yGridIndex;

    float distToVerticalGridBeingHit;      // the distance of the x and y ray intersections from
    float distToHorizontalGridBeingHit;      // the viewpoint

    int castArc, castColumn;

    castArc = fPlayerArc;
        // field of view is 60 degree with the point of view (player's direction in the middle)
        // 30  30
        //    ^
        //  \ | /
        //   \|/
        //    v
        // we will trace the rays starting from the leftmost ray
        castArc-=ANGLE30;
        // wrap around if necessary
    if (castArc < 0)
    {
      castArc=ANGLE360 + castArc;
    }

    for (castColumn=0; castColumn<PROJECTIONPLANEWIDTH; castColumn+=5)
    {
          // ray is between 0 to 180 degree (1st and 2nd quadrant)
          // ray is facing down
      if (castArc > ANGLE0 && castArc < ANGLE180)
      {
                // truncuate then add to get the coordinate of the FIRST grid (horizontal
                // wall) that is in front of the player (this is in pixel unit)
                // ROUND DOWN
        horizontalGrid = (fPlayerY/TILE_SIZE)*TILE_SIZE  + TILE_SIZE;

        // compute distance to the next horizontal wall
        distToNextHorizontalGrid = TILE_SIZE;

        float xtemp = fITanTable[castArc]*(horizontalGrid-fPlayerY);
                // we can get the vertical distance to that wall by
                // (horizontalGrid-GLplayerY)
                // we can get the horizontal distance to that wall by
                // 1/tan(arc)*verticalDistance
                // find the x interception to that wall
        xIntersection = xtemp + fPlayerX;
      }
      // else, the ray is facing up
      else
      {
        horizontalGrid = (fPlayerY/TILE_SIZE)*TILE_SIZE;
        distToNextHorizontalGrid = -TILE_SIZE;

        float xtemp = fITanTable[castArc]*(horizontalGrid - fPlayerY);
        xIntersection = xtemp + fPlayerX;

        horizontalGrid--;
      }
          // LOOK FOR HORIZONTAL WALL
      if (castArc==ANGLE0 || castArc==ANGLE180)
      {
        distToHorizontalGridBeingHit=9999999F;//Float.MAX_VALUE;
      }
      // else, move the ray until it hits a horizontal wall
      else
      {
        distToNextXIntersection = fXStepTable[castArc];
        while (true)
        {
          xGridIndex = (int)(xIntersection/TILE_SIZE);
          // in the picture, yGridIndex will be 1
          yGridIndex = (horizontalGrid/TILE_SIZE);

          if ((xGridIndex>=MAP_WIDTH) ||
            (yGridIndex>=MAP_HEIGHT) ||
            xGridIndex<0 || yGridIndex<0)
          {
            distToHorizontalGridBeingHit = Float.MAX_VALUE;
            break;
          }
          else if ((fMap[yGridIndex*MAP_WIDTH+xGridIndex])!=O)
          {
            distToHorizontalGridBeingHit  = (xIntersection-fPlayerX)*fICosTable[castArc];
            break;
          }
          // else, the ray is not blocked, extend to the next block
          else
          {
            xIntersection += distToNextXIntersection;
            horizontalGrid += distToNextHorizontalGrid;
          }
        }
      }


      // FOLLOW X RAY
      if (castArc < ANGLE90 || castArc > ANGLE270)
      {
        verticalGrid = TILE_SIZE + (fPlayerX/TILE_SIZE)*TILE_SIZE;
        distToNextVerticalGrid = TILE_SIZE;

        float ytemp = fTanTable[castArc]*(verticalGrid - fPlayerX);
        yIntersection = ytemp + fPlayerY;
      }
      // RAY FACING LEFT
      else
      {
        verticalGrid = (fPlayerX/TILE_SIZE)*TILE_SIZE;
        distToNextVerticalGrid = -TILE_SIZE;

        float ytemp = fTanTable[castArc]*(verticalGrid - fPlayerX);
        yIntersection = ytemp + fPlayerY;

        verticalGrid--;
      }
          // LOOK FOR VERTICAL WALL
      if (castArc==ANGLE90||castArc==ANGLE270)
      {
        distToVerticalGridBeingHit = 9999999;//Float.MAX_VALUE;
      }
      else
      {
        distToNextYIntersection = fYStepTable[castArc];
        while (true)
        {
          // compute current map position to inspect
          xGridIndex = (verticalGrid/TILE_SIZE);
          yGridIndex = (int)(yIntersection/TILE_SIZE);

          if ((xGridIndex>=MAP_WIDTH) ||
            (yGridIndex>=MAP_HEIGHT) ||
            xGridIndex<0 || yGridIndex<0)
          {
            distToVerticalGridBeingHit = Float.MAX_VALUE;
            break;
          }
          else if ((fMap[yGridIndex*MAP_WIDTH+xGridIndex])!=O)
          {
            distToVerticalGridBeingHit =(yIntersection-fPlayerY)*fISinTable[castArc];
            break;
          }
          else
          {
            yIntersection += distToNextYIntersection;
            verticalGrid += distToNextVerticalGrid;
          }
        }
      }

          // DRAW THE WALL SLICE
          float scaleFactor;
          float dist;
      int topOfWall;   // used to compute the top and bottom of the sliver that
      int bottomOfWall;   // will be the staring point of floor and ceiling
      // determine which ray strikes a closer wall.
      // if yray distance to the wall is closer, the yDistance will be shorter than
          // the xDistance
      if (distToHorizontalGridBeingHit < distToVerticalGridBeingHit)
          {
                // the next function call (drawRayOnMap()) is not a part of raycating rendering part, 
                // it just draws the ray on the overhead map to illustrate the raycasting process
            drawRayOnOverheadMap(xIntersection, horizontalGrid);
        dist=distToHorizontalGridBeingHit;
        fOffscreenGraphics.setColor(Color.gray);
      }
      // else, we use xray instead (meaning the vertical wall is closer than
      //   the horizontal wall)
          else
          {
                // the next function call (drawRayOnMap()) is not a part of raycating rendering part, 
                // it just draws the ray on the overhead map to illustrate the raycasting process
            drawRayOnOverheadMap(verticalGrid, yIntersection);
        dist=distToVerticalGridBeingHit;
        fOffscreenGraphics.setColor(Color.darkGray);
          }

          // correct distance (compensate for the fishbown effect)
      dist /= fFishTable[castColumn];
          // projected_wall_height/wall_height = fPlayerDistToProjectionPlane/dist;
          int projectedWallHeight=(int)(WALL_HEIGHT*(float)fPlayerDistanceToTheProjectionPlane/dist);
      bottomOfWall = fProjectionPlaneYCenter+(int)(projectedWallHeight*0.5F);
      topOfWall = PROJECTIONPLANEHEIGHT-bottomOfWall;
          if (bottomOfWall>=PROJECTIONPLANEHEIGHT)
                bottomOfWall=PROJECTIONPLANEHEIGHT-1;
          //fOffscreenGraphics.drawLine(castColumn, topOfWall, castColumn, bottomOfWall);
          fOffscreenGraphics.fillRect(castColumn, topOfWall, 5, projectedWallHeight);
 
          // TRACE THE NEXT RAY
          castArc+=5;
          if (castArc>=ANGLE360)
                castArc-=ANGLE360;
    }

        // blit to screen
    paint(getGraphics());
  }

  //*******************************************************************//
  //* Called when leaving the page.
  //*******************************************************************//
  public void stop()
  {
        if((fThread != null) && fThread.isAlive())
        {
      fThread.stop();
      fThread = null;
        }
  }

  //*******************************************************************//
  //* Called everytime applet need painting or whenever repaint is
  //*   called.
  //*******************************************************************//
  public void paint(Graphics g)
  {
    if (fOffscreenImage!=null)
      g.drawImage(fOffscreenImage, 0, 0, this);
  }

  //*******************************************************************//
  //* Detect keypress
  //*******************************************************************//
  public boolean keyDown(Event evt, int key)
  {
    switch (key)
    {
      case Event.UP:
      case 'i':
      case 'I':
        fKeyUp=true;
        break;
      case Event.DOWN:
      case 'k':
      case 'K':
        fKeyDown=true;
        break;
      case Event.LEFT:
      case 'j':
      case 'J':
        fKeyLeft=true;
        break;
      case Event.RIGHT:
      case 'l':
      case 'L':
        fKeyRight=true;
        break;
      default:
    }
    return true;
  }

  //*******************************************************************//
  //* Detect key release
  //*******************************************************************//
  public boolean keyUp(Event evt, int key)
  {
    switch (key)
    {
      case Event.UP:
      case 'i':
      case 'I':
        fKeyUp=false;
        break;
      case Event.DOWN:
      case 'k':
      case 'K':
        fKeyDown=false;
        break;
      case Event.LEFT:
      case 'j':
      case 'J':
        fKeyLeft=false;
        break;
      case Event.RIGHT:
      case 'l':
      case 'L':
        fKeyRight=false;
        break;
      default:
    }
    return true;
  }
}