/*
 *  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 <type_traits>

namespace Catch {
namespace Detail {

    double max(double lhs, double rhs);

    class Approx {
    public:
        explicit Approx ( double value );

        static Approx custom();

        template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
        Approx operator()( T const& 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 const& 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 = static_cast<double>(lhs);
            bool relativeOK = std::fabs(lhs_v - rhs.m_value) < rhs.m_epsilon * (rhs.m_scale + (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 const& 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 const& rhs ) {
            return !operator==( rhs, lhs );
        }

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

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

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

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

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

        std::string toString() const;

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

template<>
struct StringMaker<Catch::Detail::Approx> {
    static std::string convert(Catch::Detail::Approx const& value);
};

} // end namespace Catch

#endif // TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED