box

<?php

class box{
    public $w = 768;
    public $h = 512;
    public $sx = 101;
    public $sy = 62;
    public $bounce = [];
    public $bounceX0 = [];
    public $bounceY0 = [];
    public $bounceX1 = [];
    public $bounceY1 = [];
    const BL = 'BL', BR = 'BR', UL = 'UL', UR = 'UR';
    function w(){
        return $this->w - $this->sx;
    }
    function h(){
        return $this->h - $this->sy;
    }
    function crossX($prevX, $prevY, $pd, $y){
        // ax + b = y
        // a = 1
        $a = ($pd == box::UL || $pd == box::BR)?1:-1;
        $b = $prevY - $a * $prevX;
        return ($y - $b)/$a;
    }
    function crossY($prevX, $prevY, $pd, $x){
        // ax + b = y
        // a = 1
        $a = ($pd == box::UL || $pd == box::BR)?1:-1;
        $b = $prevY - $a * $prevX;
        return ($a*$x + $b);
    }
    function xInRange($x){
        return $this->w() >= $x && $x >= 0;
    }
    function yInRange($y){
        return $this->h() >= $y && $y >= 0;
    }
    function inCorner($x, $y){
        return ($this->h() == $y || $y == 0) && ($this->w() == $x || $x == 0);
    }
    function prevBounce($px, $py, $pd = null){
        $x = null;
        $y = null;
        $crossX = false;
        $w = $this->w();
        $h = $this->h();
        if ($px == 0 && $py == 0){
            $pd = box::UL;
        }
        if ($pd == box::UL || $pd == box::UR){
            $y = $h;
            $d = ($pd == box::UL)?box::BL:box::BR;
            $x = $this->crossX($px, $py, $pd, $y);
        }
        if ($pd == box::BL || $pd == box::BR){
            $y = 0;
            $d = ($pd == box::BL)?box::UL:box::UR;
            $x = $this->crossX($px, $py, $pd, $y);
        }
        $k = $x.'_'.$y.'_'.$d;
        //var_dump($pd.'<-'.$x.'x'.$y.'_'.$d.' '.$w.'x'.$h.($this->xInRange($x)?'t':'f').($this->yInRange($y)?'t':'f'));
        if (!$this->xInRange($x) || !$this->yInRange($y)){
            $crossX = false;
            if ($pd == box::UL || $pd == box::BL){ // from right to left
                $x = $w;
                $d = ($pd == box::UL)?box::UR:box::BR;
                $y = $this->crossY($px, $py, $pd, $x);
            }
            if ($pd == box::UR || $pd == box::BR){ // from left to right
                $x = 0;
                $d = ($pd == box::UR)?box::UL:box::BL;
                $y = $this->crossY($px, $py, $pd, $x);
            }
           // var_dump($pd.'<-'.$x.'x'.$y.'_'.$d.' '.$w.'x'.$h.($this->xInRange($x)?'t':'f').($this->yInRange($y)?'t':'f'));
        }
        $k = $x.'_'.$y.'_'.$d;
        //echo $k."\r\n";
        return [$x, $y, $d];
    }
    function multiBounce($px, $py, $pd = null, $n = 0){

        $k = $px.'_'.$py.'_'.$pd;
        echo $n.' '.$k."\r\n";
        if ($n > 0 && $this->inCorner($px, $py)){
            echo 'corner'."\r\n";
            //return [$this->bounceX0, $this->bounceY0, $this->bounceX1, $this->bounceY1];
        }
        if (isset($this->bounce[$k])){
            echo 'cycle'."\r\n";
            return [$this->bounceX0, $this->bounceY0, $this->bounceX1, $this->bounceY1];
            //$this->bounce,
        }
        $this->bounce[$k] = $n;
        if ($px == 0){
            $this->bounceX0[$py][] = $k;
        }
        if ($py == 0){
            $this->bounceY0[$px][] = $k;
        }
        if ($px == $this->w()){
            $this->bounceX1[$py][] = $k;
        }
        if ($py == $this->h()){
            $this->bounceY1[$px][] = $k;
        }
        list($x, $y, $d) = $this->prevBounce($px, $py, $pd);
        return $this->multiBounce($x, $y, $d, $n+1);
    }
}
$b = new box();
$b->multiBounce(404, 256, box::BR);
//var_dump($b->w()*2+$b->h()*2, );