package bluej.graph;

import bluej.pkgmgr.Package;
import bluej.pkgmgr.target.Target;
import javafx.scene.input.KeyCode;
import threadchecker.OnThread;
import threadchecker.Tag;




| A strategy to move graph selections with keyboard input.
|
| @author fisker
|
@OnThread(Tag.FXPlatform)
public class TraverseStrategyImpl
implements TraverseStrategy{     
   private double calcDistance(Target vertex1, Target vertex2)
   {
      if (vertex1 == null || vertex2 == null) {            
         return Double.POSITIVE_INFINITY;         
         }
      int x1 = vertex1.getX() + vertex1.getWidth() / 2;
      int y1 = vertex1.getY() + vertex1.getHeight() / 2;
      int x2 = vertex2.getX() + vertex2.getWidth() / 2;
      int y2 = vertex2.getY() + vertex2.getHeight() / 2;
      double d = Math.sqrt(Math.pow((x2 - x1), 2) + Math.pow((y2 - y1), 2));
       
      return d;     
      }

   
   


| Given a currently selected vertex and a key press, decide which vertex
| should be selected next.
|
| @param graph  The graph we're looking at.
| @param currentVertex  The currently selected vertex.
| @param key  The key that was pressed.
| @return     A vertex that should be selected now.
|
public Target findNextVertex(Package graph, Target currentVertex, KeyCode key)
   {
      int currentVertexCenterX = currentVertex.getX() + currentVertex.getWidth() / 2;
      int currentVertexCenterY = currentVertex.getY() + currentVertex.getHeight() / 2;
       
      int x;
       
      int y;
       
      double closest = Double.POSITIVE_INFINITY;
       
      double currentDistance;
       
      Target closestVertex = null;
       
      boolean left, right, up, down, notSelf, inRightRegion;
       
      for (Target v : graph.getVertices()) {
         x = v.getX() + v.getWidth() / 2 - currentVertexCenterX;
         y = v.getY() + v.getHeight() / 2 - currentVertexCenterY;
           
         left = key == KeyCode.LEFT && y >= x && y <= -x;
           
         right = key == KeyCode.RIGHT && y <= x && y >= -x;
           
         up = key == KeyCode.UP && y <= x && y <= -x;
           
         down = key == KeyCode.DOWN && y >= x && y >= -x;
           
         notSelf = currentVertex != v;
         inRightRegion = (left || right || up || down) && notSelf;

         if (inRightRegion) {
            if (closestVertex == null) {                    
               closestVertex = v;
               closest = calcDistance(v, currentVertex);                 
               }
            if (closest > (currentDistance = calcDistance(v, currentVertex))) {                    
               closest = currentDistance;
                   
               closestVertex = v;                 
               }              
            }          
         }
      if (closestVertex == null) {            
         closestVertex = currentVertex;         
         }
       
      return closestVertex;     
      } 
   }