/*
 *  Created by Phil on 28/04/2011.
 *  Copyright 2010 Two Blue Cubes Ltd. All rights reserved.
 *
 *  Distributed under the Boost Software License, Version 1.0. (See accompanying
 *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 */
#ifndef TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED
#define TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED

#include "catch_tostring.h"

#include <cmath>
#include <limits>

#include <type_traits>

namespace Catch {
namespace Detail {

    class Approx {
    public:
        explicit Approx ( double value )
        :   m_epsilon( std::numeric_limits<float>::epsilon()*100 ),
            m_margin( 0.0 ),
            m_scale( 1.0 ),
            m_value( value )
        {}

        Approx( Approx const& other ) = default;

        static Approx custom() {
            return Approx( 0 );
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        Approx operator()( T value ) {
            Approx approx( static_cast<double>(value) );
            approx.epsilon( m_epsilon );
            approx.margin( m_margin );
            approx.scale( m_scale );
            return approx;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        explicit Approx( T value ): Approx(static_cast<double>(value))
        {}


        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator == ( const T& lhs, Approx const& rhs ) {
            // Thanks to Richard Harris for his help refining this formula
            auto lhs_v = double(lhs);
            bool relativeOK = std::fabs(lhs_v - rhs.m_value) < rhs.m_epsilon * (rhs.m_scale + (std::max)(std::fabs(lhs_v), std::fabs(rhs.m_value)));
            if (relativeOK) {
                return true;
            }
            return std::fabs(lhs_v - rhs.m_value) < rhs.m_margin;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator == ( Approx const& lhs, const T& rhs ) {
            return operator==( rhs, lhs );
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator != ( T lhs, Approx const& rhs ) {
            return !operator==( lhs, rhs );
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator != ( Approx const& lhs, T rhs ) {
            return !operator==( rhs, lhs );
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator <= ( T lhs, Approx const& rhs ) {
            return double(lhs) < rhs.m_value || lhs == rhs;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator <= ( Approx const& lhs, T rhs ) {
            return lhs.m_value < double(rhs) || lhs == rhs;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator >= ( T lhs, Approx const& rhs ) {
            return double(lhs) > rhs.m_value || lhs == rhs;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        friend bool operator >= ( Approx const& lhs, T rhs ) {
            return lhs.m_value > double(rhs) || lhs == rhs;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        Approx& epsilon( T newEpsilon ) {
            m_epsilon = double(newEpsilon);
            return *this;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        Approx& margin( T newMargin ) {
            m_margin = double(newMargin);
            return *this;
        }

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        Approx& scale( T newScale ) {
            m_scale = double(newScale);
            return *this;
        }


        std::string toString() const {
            std::ostringstream oss;
            oss << "Approx( " << Catch::toString( m_value ) << " )";
            return oss.str();
        }

    private:
        double m_epsilon;
        double m_margin;
        double m_scale;
        double m_value;
    };
}

template<>
inline std::string toString<Detail::Approx>( Detail::Approx const& value ) {
    return value.toString();
}

} // end namespace Catch

#endif // TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED