var topoKey = 'BGMCCPGOZNKXPZC';var topoRequests = new Array();
var topoLastIndex = 0;

var topoUrlChars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.!*()';
var topoUrlCharsLength = topoUrlChars.length;
var topoUrlCharsSqrt = Math.floor( Math.sqrt( topoUrlCharsLength ) );
var topoUrlMaxCoordinates = 280;

function topoToFeets( altitude )
{
  return altitude * 3.28084;
}

function topoParseAngle( value )
{
  var str = ( '' + value ).toUpperCase();
  var arr = str.match(/N|S|E|W|[\+\-]|\d*(\.)?\d+/g);
  var sign = 1.0;
  var divider = 1.0;
  var result  = 0.0;
  for ( var i = 0; i < arr.length; i++ )
  {
    if ( ( arr[ i ] == 'N' ) ||
	 ( arr[ i ] == 'E' ) ||	
	 ( arr[ i ] == '+' ) )
   {
     sign = 1.0;
   }
   else if ( ( arr[ i ] == 'S' ) ||
	     ( arr[ i ] == 'W' ) ||
	     ( arr[ i ] == '-' ) )
   {
     sign = -1.0;
   }
   else  // it is a number
   {
     result  = result + arr[ i ] / divider;
     divider = divider * 60;
   }
  }
  return Math.round(result*sign*10000)/10000;
}

function topoEncodeCoordinates( coordinates )
{
  var result = '';
  for ( var j = 0; j < coordinates.length; j++ )
  {
    var lat = topoParseAngle( coordinates[ j ][ 0 ] );
    var lon = topoParseAngle( coordinates[ j ][ 1 ] );
    if ( lat < 0.0 )
       lat = 180 + lat;
    lat = lat / 180.0;
    lat = lat - Math.floor( lat );
    if ( lon < 0.0 )
       lon = 360 + lon;
    lon = lon / 360;
    lon = lon - Math.floor( lon );
    for ( var i = 0; i < 3; i++ )
    {
       lat = lat * topoUrlCharsLength;
       var index = Math.floor( lat );
       lat = lat - index;
       result = result + topoUrlChars.substring( index, index+1 );
       lon = lon * topoUrlCharsLength;
       var index = Math.floor( lon );
       lon = lon - index;
       result = result + topoUrlChars.substring( index, index+1 );
    }
    lat = lat * topoUrlCharsSqrt;
    lon = lon * topoUrlCharsSqrt;
    var index = Math.floor( lat ) * topoUrlCharsSqrt + Math.floor( lon );
    result = result + topoUrlChars.substring( index, index+1 );
  }
  return result;
}

function topoQuietTimeout( id )
{
  topoRequests[ id ] = null;
}

function topoTimeout( id )
{
  var request = topoRequests[ id ];
  topoRequests[ id ] = null;
  if ( request )
  {
    var topoScript = document.getElementById('topoScript' + id);
    var topHead = document.getElementsByTagName('head').item(0);
    topHead.removeChild(topoScript);

    for ( var i = 0; i < request.length; i++ )
      if ( request[ i ] )
	{
	  if ( request[ i ][ 1 ] )
            request[ i ][ 0 ]( null, request[ i ][ 1 ] ); // null parameter means timeout
	  else
            request[ i ][ 0 ]( null ); // null parameter means timeout
        }
  }
}

function topoCall( id, altitudes )
{
  var request = topoRequests[ id ];
  topoRequests[ id ] = null;
  if ( request )
  {
    var topoScript = document.getElementById('topoScript' + id);
    var topHead = document.getElementsByTagName('head').item(0);
    topHead.removeChild(topoScript);

    if ( request.length == altitudes.length )
      for ( var i = 0; i < request.length; i++ )
        if ( request[ i ] )
	  {
  	    if ( request[ i ][ 1 ] )
              request[ i ][ 0 ]( altitudes[ i ], request[ i ][ 1 ] );
	    else
              request[ i ][ 0 ]( altitudes[ i ] );
	  }
  }
}

function topoGetAltitudes( quadruples, timeout )
{
  var topHead = document.getElementsByTagName('head').item(0);
  var maxURLlength = 2048 - 50; // 50 is for safety
  var url = 'https://topocoding.com/api/altitude_v1.php?key=' + topoKey + '&id=';
  var args = '';
  var requests = new Array();
  for ( var i = 0; i < quadruples.length; i++ )
  {
    args = args + topoEncodeCoordinates( new Array( [ quadruples[ i ][ 0 ], quadruples[ i ][ 1 ] ] ) );
    requests[ requests.length ] = [ quadruples[ i ][ 2 ], quadruples[ i ][ 3 ] ];
    if ( ( ( url.length + args.length ) > maxURLlength ) ||
	 ( ( i + 1 ) == quadruples.length ) )
    {
      var scriptNr = 0;
      do {
	scriptNr = topoLastIndex + 1;
	topoLastIndex++;
      } while ( scriptNr != topoLastIndex );  // thread-safe
      topoRequests[ scriptNr ] = requests;
      var topoScript = document.createElement('script');
      topoScript.src = url + scriptNr + '&l=' + args;
      topoScript.id = 'topoScript' + scriptNr;
      if ( timeout )
        setTimeout( function(){ topoTimeout(scriptNr); }, timeout );
      else
        setTimeout( function(){ topoQuietTimeout(scriptNr); }, 10000 );
      topHead.appendChild(topoScript);
      args = '';
      requests = new Array();
    }
  }
}

function topoGetAltitude( lat, lon, action, context, timeout )
{
    topoGetAltitudes( new Array( [ lat, lon, action, context ] ), timeout );
}

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

function topoComputeIntermediate(lat1,lon1,lat2,lon2,fraction,dist)
{
  if ( !dist )
    dist = topoComputeDistance( lat1,lon1,lat2,lon2 );

  var R = 6378.137;

  lat1 = lat1 / 180 * Math.PI;
  lon1 = lon1 / 180 * Math.PI;
  lat2 = lat2 / 180 * Math.PI;
  lon2 = lon2 / 180 * Math.PI;
  dist = dist / R;

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

  lat = lat * 180 / Math.PI;
  lon = lon * 180 / Math.PI;
  return new Array( lat, lon );
}

function topoFindIndexOfNearestSmaller( arr, value )
{
  var left = 0;
  var right = arr.length - 1;
  while ( left < right )
    {
      var mid = Math.floor( ( left + right ) / 2.0 );
      if ( arr[ mid ] > value )
        right = mid;
      else
        left = mid + 1;
    }
  return left - 1;
}

function topoResampleCoordinates( coordinates )
{
  if ( coordinates.length <= topoUrlMaxCoordinates )
    return coordinates;

  var uniqueCoordinates = new Array();
  uniqueCoordinates[ 0 ] = coordinates[ 0 ];
  for ( var i = 1; i < coordinates.length; i++ )  
    if ( ( coordinates[ i ][ 0 ] != coordinates[ i - 1 ][ 0 ] ) ||
         ( coordinates[ i ][ 1 ] != coordinates[ i - 1 ][ 1 ] ) )
    {
      uniqueCoordinates[ uniqueCoordinates.length ] = coordinates[ i ];
    }

  var distances = new Array();
  distances[ 0 ] = 0.0;
  var cummulativeDistance = 0.0;
  for ( var i = 1; i < uniqueCoordinates.length; i++ )
  {
    cummulativeDistance = cummulativeDistance + topoComputeDistance( uniqueCoordinates[ i - 1 ][ 0 ],
								     uniqueCoordinates[ i - 1 ][ 1 ],
							  	     uniqueCoordinates[ i ][ 0 ],
							  	     uniqueCoordinates[ i ][ 1 ] );
    distances[ i ] = cummulativeDistance;
  }

  var points = new Array();
  for ( var i = 0; i < topoUrlMaxCoordinates; i++ )
  {
    var lookDistance = i / ( topoUrlMaxCoordinates - 1 ) * cummulativeDistance;
    var smallerIndex = topoFindIndexOfNearestSmaller( distances, lookDistance );

    if ( smallerIndex == ( uniqueCoordinates.length - 1 ) )
      {
        points[ i ] = uniqueCoordinates[ smallerIndex ];
      }
    else
      {
	var distLR = distances[ smallerIndex + 1 ] - distances[ smallerIndex ];
	var fraction = ( lookDistance - distances[ smallerIndex ] ) / distLR;
	points[ i ] =  topoComputeIntermediate( uniqueCoordinates[ smallerIndex ][ 0 ],
				 		uniqueCoordinates[ smallerIndex ][ 1 ],
						uniqueCoordinates[ smallerIndex + 1 ][ 0 ],
						uniqueCoordinates[ smallerIndex + 1 ][ 1 ],
						fraction,
						distLR );
      }
  }
  return points;
}

function topoDrawGraph( divElement, coordinates, width, height, english )
{ 
  while (divElement.firstChild)
    divElement.removeChild(divElement.firstChild);
  if ( coordinates.length < 2 )
    return;
  var resampledCoordinates = topoResampleCoordinates( coordinates );
  var code = topoEncodeCoordinates( resampledCoordinates );
  var whu = '';
  if ( width )
    whu = whu + '&w=' + width;
  if ( height )
    whu = whu + '&h=' + height;
  if ( english )
    whu = whu + '&u=e';
  divElement.innerHTML = 
    '<img src=https://topocoding.com/api/profile_v1.php?key=' + topoKey + whu + '&l=' + code + '>';
}