// Copyright (c) 2007 topocoding.com
// This software, or any portion of it, can be only used for resolving and processing data from topocoding.com server.
// Other use is subject to the terms and conditions of your written agreement with topocoding.com service providers.
// If you do not have such an agreement, then such a use of this material is strictly prohibited.
// This software is provided "as is", without express or implied warranty of any kind.

// ================ Numeric functions follow =========================

function topoToFeets($meters)
{
  return $meters * 3.28084;
}

function topoComputeDistance($lat1,$lon1,$lat2,$lon2)
{
  $lat1 = $lat1 / 180 * pi();
  $lon1 = $lon1 / 180 * pi();
  $lat2 = $lat2 / 180 * pi();
  $lon2 = $lon2 / 180 * pi();
  $dlon = $lon2 - $lon1;
  $dlat = $lat2 - $lat1;
  $a = sin($dlat/2) * sin($dlat/2) + cos($lat1) * cos($lat2) * sin($dlon/2) * sin($dlon/2);
  $c = 2 * atan2(sqrt($a), sqrt(1-$a));
  $R = 6378.137;
  return $R * $c;
}

function topoComputeIntermediate($lat1,$lon1,$lat2,$lon2,$fraction,$dist = -1.0 )
{
  if ( $dist <= 0.0 )
    $dist = topoComputeDistance($lat1,$lon1,$lat2,$lon2);

  $R = 6378.137;

  $lat1 = $lat1 / 180 * pi();
  $lon1 = $lon1 / 180 * pi();
  $lat2 = $lat2 / 180 * pi();
  $lon2 = $lon2 / 180 * pi();
  $dist = $dist / $R;

  $A=sin((1-$fraction)*$dist)/sin($dist);
  $B=sin($fraction*$dist)/sin($dist);
  $x = $A*cos($lat1)*cos($lon1) +  $B*cos($lat2)*cos($lon2);
  $y = $A*cos($lat1)*sin($lon1) +  $B*cos($lat2)*sin($lon2);
  $z = $A*sin($lat1)           +  $B*sin($lat2);
  $lat=atan2($z,sqrt($x*$x+$y*$y));
  $lon=atan2($y,$x);

  $lat = $lat * 180 / pi();
  $lon = $lon * 180 / pi();
  return array( $lat, $lon, $dist * $fraction * $R );
}

// =========== Server access functions follow ================

function topoEncodeCoordinates( $coordinates )
{
  $result = '';

  $topoUrlChars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.!*()';
  $topoUrlCharsLength = strlen( $topoUrlChars );
  $topoUrlCharsSqrt = floor( sqrt( $topoUrlCharsLength ) );
  $topoUrlMaxCoordinates = 280;
  
  if ( sizeof( $coordinates ) > $topoUrlMaxCoordinates )
    die( 'Too many points to fit into the safe URL length limit.' );

  for ( $j = 0; $j < sizeof( $coordinates); $j++ )
  {
    $lat = $coordinates[ $j ][ 0 ];
    $lon = $coordinates[ $j ][ 1 ];
    if ( $lat < 0.0 )
       $lat = 180 + $lat;
    $lat = $lat / 180.0;
    $lat = $lat - floor( $lat );
    if ( $lon < 0.0 )
       $lon = 360 + $lon;
    $lon = $lon / 360;
    $lon = $lon - floor( $lon );
    for ( $i = 0; $i < 3; $i++ )
    {
       $lat = $lat * $topoUrlCharsLength;
       $index = floor( $lat );
       $lat = $lat - $index;
       $result = $result . substr( $topoUrlChars, $index, 1 );
       $lon = $lon * $topoUrlCharsLength;
       $index = floor( $lon );
       $lon = $lon - $index;
       $result = $result . substr( $topoUrlChars, $index, 1 );
    }
    $lat = $lat * $topoUrlCharsSqrt;
    $lon = $lon * $topoUrlCharsSqrt;
    $index = floor( $lat ) * $topoUrlCharsSqrt + floor( $lon );
    $result = $result . substr( $topoUrlChars, $index, 1 );
  }
  return $result;
}


function topoGetAltitudes( $coordinates )
{
   global $topoKey;
   $url = 'http://topocoding.com/api/altitude_v1.php?id=x&key=' . $topoKey . '&l=' . topoEncodeCoordinates( $coordinates );
   $content = '';
   if ( ini_get( 'allow_url_fopen' ) == '1' )
   {
     $content = file_get_contents( $url );
   }
   else if ( function_exists( 'curl_init' ) )
   {
     $ch = curl_init();
     curl_setopt ( $ch, CURLOPT_URL, $url );
     curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, 1 );
     curl_setopt ( $ch, CURLOPT_CONNECTTIMEOUT, 5 );
     $content = curl_exec( $ch );
     curl_close( $ch );
   }
   else
   {
     // see also http://www.php-mysql-tutorial.com/php-tutorial/php-read-remote-file.php
     die( 'No method to read from remote server was found.' );
   }
   if ($content !== false) {
     $tmp0 = explode( '[', $content );
     if ( $tmp0[ 0 ] == 'topoCall(x,' )
     {
       $tmp1 = explode( ']', $tmp0[ 1 ] );
       return explode(',',$tmp1[ 0 ]);
     }
     else
     {
       die( $content );
     }
   } else {
     die( 'Unable to resolve altitudes.' );
   }
}