/**
    @class FindRefAltLatLon.cpp
    @author Brian Magill
    @creation date 6/4/2007

	$Date:$
    $Revision:$

    @copyright
     (©) Copyright 2006 by GATS Inc.
     11864 Canon Blvd., Suite 101, Newport News, VA 23606

     All Rights Reserved. No part of this software or publication may be
     reproduced, stored in a retrieval system, or transmitted, in any form
     or by any means, electronic, mechanical, photocopying, recording, or
     otherwise without the prior written permission of GATS Inc.
        
    @brief Finds the latitude and longitude at the 83 km tangent altitude
*/

#include "FindRefAltLatLon.h"
#include <stdexcept>

using namespace std;


pair <double, double> 
FindRefAltLatLon::operator() (valarray<double> const &tanAlt, 
                              valarray<double> const &tanLat,
                              valarray<double> const &tanLon) const                            
{
pair <double, double> result;
unsigned long i;
bool sunSet = false;

if (tanAlt.size() == 0)
    throw runtime_error("FindRefAltLatLon::Error, altitude array must contain data!");

if (tanAlt.size() != tanLat.size() )
    throw runtime_error("FindRefAltLatLon::Error, altitude and latitude array sizes differ");
    
if (tanAlt.size() != tanLon.size() )
    throw runtime_error("FindRefAltLatLon::Error, altitude and longitude array sizes differ");

if (tanAlt.max() < altRef )
    throw runtime_error("FindRefAltLatLon::Error, minimum tangent altitude is greater than reference altitude");

if (altRef < tanAlt.min())
    throw runtime_error("FindRefAltLatLon::Error, maximum tangent altitude is less than than reference altitude");

if (tanAlt[0] > tanAlt.min())
    sunSet = true;

if (sunSet)
    for(i = 0; i < tanAlt.size(); i++)
        {
        if (tanAlt[i] <= altRef)
            {
            result = pair<double, double>(tanLat[i], tanLon[i]);
            break;
            }
        }
else
    for(i = 0; i < tanAlt.size(); i++)
        {
        if (tanAlt[i] >= altRef)
            {
            result = pair<double, double>(tanLat[i], tanLon[i]);
            break;
            }
        }
    
return result;
};