// Photon.h -- written 16 Mar 1996 by Max Hailperin <max@gac.edu>
//
// Declares the class Photon, which is the "heart" of the Photon game.
//
// Its primary responsibility is mediating between the
// graphical user interface script on the one hand and the Obstacles and Ball
// on the other hand.
//
// It keeps track of all the Obstacles in the field, and of the Ball, and
// when asked by the user interface to do a time step makes use of those
// other objects.
//
// Conversely, it keeps track of the underlying TCL interpreter and its drawing
// canvas, so that when an Obstacle or Ball wants to draw itself on the canvas
// (for example), it can do so with the Photon object's help.

#ifndef PHOTON_H
#define PHOTON_H

#include <tcl.h>

class Ball;
class Obstacle;

class Photon {
public:
  // createCmd is installed as the TCL command called photon, used so that
  // the user interface script (written in TCL) can create a new Photon game
  static int createCmd(ClientData, Tcl_Interp *, int argc, char *argv[]);

  // the next two member functions let an Obstacle or Ball get the TCL
  // interpreter and canvas, for drawing etc.
  Tcl_Interp *interpreter() {return interp;}
  const char *canvas() {return cnvs;}
   
  // to actually do anything in the interpreter, you can eval a script
  // or as a shortcut you can use the draw command, which prepends the
  // canvas's name
  int eval(char *script) {return Tcl_Eval(interp, script);}
  int draw(const char *scriptTail);

  // mapX and mapY translate coordinates from the system used in the program
  // to real pixel coordinates, as needed for drawing on the canvas; the
  // program's coordinate system has integer coordinates at the centers of
  // the playing field's cells, with (0,0) being the center of the lower
  // left cell; pixel coordinates have (0,0) at the top left w/ a reversed y-axis
  int mapX(float x) {return int((x+0.5f)*fieldWidthPixels/fieldWidth);}
  int mapY(float y)
    {return int((fieldHeight-y-0.5f)*fieldHeightPixels/fieldHeight);}

  // moveObstacle moves the obstacle in a particular cell to another
  // cell, which must be unoccupied; this doesn't update the canvas display
  // at all, it just changes the record of what's where; see moveCanvasItem
  void moveObstacle(int oldX, int oldY, int newX, int newY);
  
  // moveCanvasItem moves a particular visual item on the canvas to a
  // new location; the old and new locations are give in the standard
  // cell coordinate system (*not* pixels); this can be used by an Obstacle
  // or Ball to move its visual representation, but other record keeping
  // will need doing as well -- see e.g. moveObstacle
  int moveCanvasItem(int id, int oldX, int oldY, int newX, int newY);

  // deleteCanvasItem does what it says
  int deleteCanvasItem(int id);

  // pickTargetLocation finds a cell with no Obstacle or Ball in it
  void pickTargetLocation(int &x, int &y);

private:
  enum Command {none, neg, pos, erase};
  int doTimeStep(Command);
  static int cmd(ClientData thePhoton, Tcl_Interp *interp,
                 int argc, char *argv[]);
  static void deleteProc(ClientData thePhoton);
  Photon(Tcl_Interp *theInterp, char *canvas);
  int okForTarget(int x, int y);
  ~Photon();
  Tcl_Interp *interp;
  char *cnvs;
  int tclCode;
  Ball *ball;
  enum {fieldWidth=30, fieldHeight=30};
  int fieldWidthPixels, fieldHeightPixels;
  Obstacle *field[fieldWidth][fieldHeight];
};

#endif