using System;
using System.Drawing;
using System.Windows.Forms;

namespace Simulation  {

/// <summary>
/// Draws directed edges between the SimNode's in the simulation model.
/// </summary>
public class SimConnector {
   /// <summary> The beginning SimNode for the connector. </summary>
   private SimNode startNode;
   /// <summary> The ending SimNode for the connector. </summary>
   private SimNode stopNode ;
   /// <summary> boolean, true if edge direction is left to right. </summary>
   private bool leftRight;
   /// <summary> space between SimNode edge and any vertical line segments. </summary>
   private int gap = 25;
   /// <summary> half space of the gap, used to draw the arrow ends. </summary>
   private int halfGap;
   /// <summary> Point [] holds 4 line segments of any edge. </summary>
   private Point[] line = new Point[4];
   /// <summary> Point [] holds locations use to draw arrow ends. </summary>
   private Point[] end = new Point[3];
 
   /// <summary>
   /// Create a connector between two SimNodes.
   /// </summary>
   /// <param name="start"> edge is directed from start SimNode.</param>
   /// <param name="end"> edge is directed to end SimNode.</param>
   /// <param name="leftToRight"> direction of edge, true for left to right.</param>
              
   public SimConnector (SimNode start, SimNode end, bool leftToRight) {
      startNode = start;
      stopNode = end; 
      leftRight = leftToRight; 
      halfGap = gap / 4;
      }
 
   /// <summary>
   /// Show the connector on the screen
   /// </summary>
   /// <param name="pea"> drawing context.</param>
   public void draw(PaintEventArgs pea) {
     Graphics grfx = pea.Graphics;                 // get the graphics context for display.
     bool startDirection = startNode.LeftRight;    // direction of start SimNode.
     bool stopDirection = stopNode.LeftRight;      // direction of stop SimNode.
     int x1, y1, y2, back;                         // locations of line seqments of directed edge.
     back = line[3].X - halfGap;
      
      if ( startDirection && stopDirection && leftRight) {
         // startNode output and connection are left to right
         line[0] = startNode.RightConnector;
         line[3] = stopNode.LeftConnector;
         x1 = line[0].X + gap;
         y1 = line[0].Y;
         y2 = line[3].Y;    
         line[1] = new Point(x1, y1);
         line[2] = new Point(x1, y2);
         back = line[3].X - halfGap;   } 
      if (startDirection && (! stopDirection) && (! leftRight)) {
         // startNode leftToRight, but connection and stopNode are right to left
         line[0] = startNode.RightConnector;
         line[3] = stopNode.RightConnector;
         x1 = line[0].X + gap;
         y1 = line[0].Y;
         y2 = line[3].Y;     
         line[1] = new Point(x1, y1);
         line[2] = new Point(x1, y2); 
         back = line[3].X + halfGap;     }
      if ( (! startDirection) && (! stopDirection) && (! leftRight)) {
         // startNode, stopNode, and connection all right to left  
         line[0] = startNode.LeftConnector;
         line[3] = stopNode.RightConnector; 
         x1 = line[0].X - gap;
         y1 = line[0].Y;
         y2 = line[3].Y;             
         line[1] = new Point(x1, y1);
         line[2] = new Point(x1, y2); 
         back = line[3].X + halfGap;     }
      if ((! startDirection) && stopDirection && (! leftRight)) {
         //startNode right to left, stopNode left to right, and connection right to left 
         line[0] = startNode.LeftConnector;
         line[3] = stopNode.LeftConnector; 
         x1 = line[0].X - gap;
         y1 = line[0].Y;
         y2 = line[3].Y;                      
         line[1] = new Point(x1, y1);
         line[2] = new Point(x1, y2); 
         back = line[3].X - halfGap;     }
      
      grfx.DrawLines(Pens.Black, line);
      
      // set points for arrow end
      end[0] = line[3];
      end[1] = new Point(back, line[3].Y - halfGap);
      end[2] = new Point(back, line[3].Y + halfGap);
      grfx.FillPolygon(Brushes.Black, end);
      }
   }
}