<?php 

namespace common\library;

class ZM_Geohash{
	
	private $coding="0123456789bcdefghjkmnpqrstuvwxyz";
	private $codingMap=array();


	public function getGeohash(){
		return $this->codingMap;
	}


	public function getDistance($lat1,$lng1,$lat2,$lng2)
	{
	//地球半径
	$R = 6378137;
	//将角度转为狐度
	$radLat1 = deg2rad($lat1);
	$radLat2 = deg2rad($lat2);
	$radLng1 = deg2rad($lng1);
	$radLng2 = deg2rad($lng2);
	//结果
	$s = acos(cos($radLat1)*cos($radLat2)*cos($radLng1-$radLng2)+sin($radLat1)*sin($radLat2))*$R;
	//精度
	$s = round($s* 10000)/10000;
	return round($s);
	}


	public function init_codingMap()
	{
		for($i=0; $i<32; $i++)
		{
			$this->codingMap[substr($this->coding,$i,1)]=str_pad(decbin($i), 5, "0", STR_PAD_LEFT);
		}
	}


	public function decode($hash)
	{
		$binary="";
		$hl=strlen($hash);
		for($i=0; $i<$hl; $i++){
			$binary.=$this->codingMap[substr($hash,$i,1)];
		}
		$bl=strlen($binary);
		$blat="";
		$blong="";
		for ($i=0; $i<$bl; $i++)
		{
			if ($i%2)
			$blat=$blat.substr($binary,$i,1);
			else
			$blong=$blong.substr($binary,$i,1);
		}
		$lat=$this->binDecode($blat,-90,90);
		$long=$this->binDecode($blong,-180,180);
		$latErr=$this->calcError(strlen($blat),-90,90);
		$longErr=$this->calcError(strlen($blong),-180,180);
		$latPlaces=max(1, -round(log10($latErr))) - 1;
		$longPlaces=max(1, -round(log10($longErr))) - 1;
		$lat=round($lat, $latPlaces);
		$long=round($long, $longPlaces);
		return array($lat,$long);
	}


	public function encode($lat,$long)
	{
		$plat=$this->precision($lat);
		$latbits=1;
		$err=45;
		while($err>$plat)
		{
			$latbits++;
			$err/=2;
		}
		$plong=$this->precision($long);
		$longbits=1;
		$err=90;
		while($err>$plong)
		{
			$longbits++;
			$err/=2;
		}
		$bits=max($latbits,$longbits);
		$longbits=$bits;
		$latbits=$bits;
		$addlong=1;
		while (($longbits+$latbits)%5 != 0)
		{
			$longbits+=$addlong;
			$latbits+=!$addlong;
			$addlong=!$addlong;
		}
		$blat=$this->binEncode($lat,-90,90, $latbits);
		$blong=$this->binEncode($long,-180,180,$longbits);
		$binary="";
		$uselong=1;
		while (strlen($blat)+strlen($blong))
		{
			if ($uselong)
			{
				$binary=$binary.substr($blong,0,1);
				$blong=substr($blong,1);
			}
			else
			{
				$binary=$binary.substr($blat,0,1);
				$blat=substr($blat,1);
			}
			$uselong=!$uselong;
		}
		$hash="";
		for ($i=0; $i<strlen($binary); $i+=5){
			$n=bindec(substr($binary,$i,5));
			
			$hash=$hash.$this->coding[$n];
		}
		return $hash;
	}


	private function calcError($bits,$min,$max)
	{
	$err=($max-$min)/2;
	while ($bits--)
	$err/=2;
	return $err;
	}


	private function precision($number)
	{
	$precision=0;
	$pt=strpos($number,'.');
	if ($pt!==false)
	{
		$precision=-(strlen($number)-$pt-1);
	}
	return pow(10,$precision)/2;
	}


	private function binEncode($number, $min, $max, $bitcount)
	{
		if ($bitcount==0)
			return "";
		$mid=($min+$max)/2;
		if ($number>$mid)
			return "1".$this->binEncode($number, $mid, $max,$bitcount-1);
		else
			return "0".$this->binEncode($number, $min, $mid,$bitcount-1);
	}

	private function binDecode($binary, $min, $max)
	{
		$mid=($min+$max)/2;
		if (strlen($binary)==0)
		return $mid;
		$bit=substr($binary,0,1);
		$binary=substr($binary,1);
		if ($bit==1)
		return $this->binDecode($binary, $mid, $max);
		else
		return $this->binDecode($binary, $min, $mid);
	}
}?>