<?php

class Tile {

	// The point (x,y) for this tile
	var $p;
	// The coord (lat,lon) for this tile
	var $co;
	// Zoom level for this tile
	var $z;

	// ...Constants...
	var $PI = 3.1415926535;
	var $tileSize = 256;
	var $pixelsPerLonDegree = Array();
	var $pixelsPerLonRadian = Array();
	var $numTiles = Array();
	var $bitmapOrigo = Array();
	// Note: These variable names are based on the variables names found in the
	//       Google maps.*.js code.
	var $c = 256;
	var $bc;
	var $Wa;

	// Fill in the constants array
	function fillinconstants() {
		$this->bc = 2*$this->PI;
		$this->Wa = $this->PI/180;
	
		for($d = 17; $d >= 0; --$d) {
  			$this->pixelsPerLonDegree[$d] = $this->c / 360;
  			$this->pixelsPerLonRadian[$d] = $this->c / $this->bc;
  			$e = $this->c / 2;
  			$this->bitmapOrigo[$d] = new p($e,$e);
  			$this->numTiles[$d] = $this->c / 256;
  			$this->c *= 2;
		}
	}

	function Tile($latitude, $longitude, $zoomLevel) {
		$this->fillInConstants();
		$this->z = $zoomLevel;
		$this->p = $this->getTileCoordinate($latitude, $longitude, $zoomLevel);
		$this->co = $this->getLatLong($latitude, $longitude, $zoomLevel);
	}

	function getTileCoord() {
		return $this->p;
	}

	function getTileLatLong() {
		return $this->co;
	}

	function getKeyholeString() {
		$s = "";
		$myX = $this->p->x;
		$myY = $this->p->y;
		
		for($i = 17; $i > $this->z; $i--) {
			$rx = (fmod($myX, 2));
			$myX = floor($myX / 2);
			$ry = (fmod($myY, 2));
			$myY = floor($myY / 2);
			$s = $this->getKeyholeDirection($rx, $ry).$s;
		}
		return 't'.$s;
	}

	function getKeyholeDirection($x, $y) {
		if($x == 1) {
			if($y == 1) {
				return 's';
			} else if($y == 0) {
				return 'r';
			}
		} else if($x == 0) {
			if($y == 1) {
				return 't';
			} else if($y == 0) {
				return 'q';
			}
		}

		return '';
	}
		
	function getBitmapCoordinate($a, $b, $c) {
  		$d = new p(0,0);

  		$d->x = floor($this->bitmapOrigo[$c]->x + $b * $this->pixelsPerLonDegree[$c]);
  		$e = sin($a * $this->Wa);

  		if($e > 0.9999) {
    		$e = 0.9999;
  		}

  		if($e < -0.9999) {
    		$e = -0.9999;
  		}

  		$d->y = floor($this->bitmapOrigo[$c]->y + 0.5 * log((1 + $e) / (1 - $e)) * -1*($this->pixelsPerLonRadian[$c]));
  		return $d;
	}

	function getTileCoordinate($a, $b, $c) {
  		$d = $this->getBitmapCoordinate($a, $b, $c);
  		$d->x = floor($d->x / $this->tileSize);
  		$d->y = floor($d->y / $this->tileSize);

  		return $d;
	}

	function getLatLong($a, $b, $c) {
		$d = new p(0, 0);
		$e = $this->getBitmapCoordinate($a, $b, $c);
  		$a = $e->x;
		$b = $e->y;

		$d->x = ($a - $this->bitmapOrigo[$c]->x) / $this->pixelsPerLonDegree[$c];
		$e = ($b - $this->bitmapOrigo[$c]->y) / (-1*$this->pixelsPerLonRadian[$c]);
		$d->y = (2 * atan(exp($e)) - $this->PI / 2) / $this->Wa;
		return $d;
	}
}

// A simple PHP class that represents a point
class p {
	var $x;
  	var $y;
  	
	function p($x,$y) {
    	$this->x = $x;
    	$this->y = $y;
  	}
}
?>