//          Copyright Joakim Karlsson & Kim Gräsman 2010-2012.
// 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 SNOWHOUSE_EQUALSWITHDELTACONSTRAINT_H
#define SNOWHOUSE_EQUALSWITHDELTACONSTRAINT_H

#include "expressions/expression.h"

namespace snowhouse
{
    template <typename ExpectedType, typename DeltaType>
    struct EqualsWithDeltaConstraint :
        Expression<EqualsWithDeltaConstraint<ExpectedType, DeltaType>>
    {
        EqualsWithDeltaConstraint(
            const ExpectedType& expected, const DeltaType& delta):
            m_expected(expected),
            m_delta(delta)
        {
        }

        template <typename ActualType>
        bool operator()(const ActualType& actual) const
        {
            return ((m_expected <= (actual + m_delta)) &&
                    (m_expected >= (actual - m_delta)));
        }

        ExpectedType m_expected;
        DeltaType m_delta;
    };

    template <typename ExpectedType, typename DeltaType>
    inline EqualsWithDeltaConstraint<ExpectedType, DeltaType> EqualsWithDelta(
        const ExpectedType& expected, const DeltaType& delta)
    {
        return EqualsWithDeltaConstraint<ExpectedType, DeltaType>(
            expected, delta);
    }

    template <typename ExpectedType, typename DeltaType>
    struct Stringizer<EqualsWithDeltaConstraint<ExpectedType, DeltaType>>
    {
        static std::string ToString(
            const EqualsWithDeltaConstraint<ExpectedType, DeltaType>&
                constraint)
        {
            std::ostringstream builder;
            builder << "equal to "
                    << snowhouse::Stringize(constraint.m_expected) << " (+/- "
                    << snowhouse::Stringize(constraint.m_delta) << ")";

            return builder.str();
        }
    };
}

#endif
