catch2/include/internal/catch_decomposer.h

/*
 *  Created by Phil Nash on 8/8/2017.
 *  Copyright 2017 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_DECOMPOSER_H_INCLUDED
#define TWOBLUECUBES_CATCH_DECOMPOSER_H_INCLUDED

#include "catch_tostring.h"
#include "catch_stringref.h"

#include <ostream>

namespace Catch {

    struct ITransientExpression {
        virtual auto isBinaryExpression() const -> bool = 0;
        virtual auto getResult() const -> bool = 0;
        virtual void streamReconstructedExpression( std::ostream &os ) const = 0;
    };

    void formatReconstructedExpression( std::ostream &os, std::string const& lhs, std::string const& op, std::string const& rhs );

    template<typename LhsT, typename RhsT>
    class BinaryExpr  : public ITransientExpression {
        bool m_result;
        LhsT m_lhs;
        std::string m_op;
        RhsT m_rhs;

        auto isBinaryExpression() const -> bool override { return true; }
        auto getResult() const -> bool override { return m_result; }

        void streamReconstructedExpression( std::ostream &os ) const override {
            formatReconstructedExpression
                    ( os, Catch::Detail::stringify( m_lhs ), m_op, Catch::Detail::stringify( m_rhs ) );
        }

    public:
        BinaryExpr( bool comparisionResult, LhsT lhs, StringRef op, RhsT rhs )
        :   m_result( comparisionResult ),
            m_lhs( lhs ),
            m_op( op.c_str() ),
            m_rhs( rhs )
        {}
    };

    template<typename LhsT>
    class UnaryExpr : public ITransientExpression {
        LhsT m_lhs;

        auto isBinaryExpression() const -> bool override { return false; }
        auto getResult() const -> bool override { return m_lhs ? true : false; }

        void streamReconstructedExpression( std::ostream &os ) const override {
            os << Catch::Detail::stringify( m_lhs );
        }

    public:
        UnaryExpr( LhsT lhs ) : m_lhs( lhs ) {}
    };


    // Specialised comparison functions to handle equality comparisons between ints and pointers (NULL deduces as an int)
    template<typename LhsT, typename RhsT>
    auto compareEqual( LhsT lhs, RhsT&& rhs ) -> bool { return lhs == rhs; };
    template<typename T>
    auto compareEqual( T* const& lhs, int rhs ) -> bool { return lhs == reinterpret_cast<void const*>( rhs ); };
    template<typename T>
    auto compareEqual( int lhs, T* const& rhs ) -> bool { return reinterpret_cast<void const*>( lhs ) == rhs; };

    template<typename LhsT, typename RhsT>
    auto compareNotEqual( LhsT lhs, RhsT&& rhs ) -> bool { return lhs != rhs; };
    template<typename T>
    auto compareNotEqual( T* const& lhs, int rhs ) -> bool { return lhs != reinterpret_cast<void const*>( rhs ); };
    template<typename T>
    auto compareNotEqual( int lhs, T* const& rhs ) -> bool { return reinterpret_cast<void const*>( lhs ) != rhs; };


    template<typename LhsT>
    class ExprLhs {
        LhsT m_lhs;
    public:
        ExprLhs( LhsT lhs ) : m_lhs( lhs ) {}

        template<typename RhsT>
        auto operator == ( RhsT&& rhs ) -> BinaryExpr<LhsT, RhsT&> const {
            return BinaryExpr<LhsT, RhsT&>( compareEqual( m_lhs, rhs ), m_lhs, "==", rhs );
        }
        auto operator == ( bool rhs ) -> BinaryExpr<LhsT, bool> const {
            return BinaryExpr<LhsT, bool>( m_lhs == rhs, m_lhs, "==", rhs );
        }

        template<typename RhsT>
        auto operator != ( RhsT&& rhs ) -> BinaryExpr<LhsT, RhsT&> const {
            return BinaryExpr<LhsT, RhsT&>( compareNotEqual( m_lhs, rhs ), m_lhs, "!=", rhs );
        }
        auto operator != ( bool rhs ) -> BinaryExpr<LhsT, bool> const {
            return BinaryExpr<LhsT, bool>( m_lhs != rhs, m_lhs, "!=", rhs );
        }

        template<typename RhsT>
        auto operator > ( RhsT&& rhs ) -> BinaryExpr<LhsT, RhsT&> const {
            return BinaryExpr<LhsT, RhsT&>( m_lhs > rhs, m_lhs, ">", rhs );
        }
        template<typename RhsT>
        auto operator < ( RhsT&& rhs ) -> BinaryExpr<LhsT, RhsT&> const {
            return BinaryExpr<LhsT, RhsT&>( m_lhs < rhs, m_lhs, "<", rhs );
        }
        template<typename RhsT>
        auto operator >= ( RhsT&& rhs ) -> BinaryExpr<LhsT, RhsT&> const {
            return BinaryExpr<LhsT, RhsT&>( m_lhs >= rhs, m_lhs, ">=", rhs );
        }
        template<typename RhsT>
        auto operator <= ( RhsT&& rhs ) -> BinaryExpr<LhsT, RhsT&> const {
            return BinaryExpr<LhsT, RhsT&>( m_lhs <= rhs, m_lhs, "<=", rhs );
        }

        auto makeUnaryExpr() const -> UnaryExpr<LhsT> {
            return UnaryExpr<LhsT>( m_lhs );
        }
    };

    void handleExpression( ITransientExpression const& expr );

    template<typename T>
    void handleExpression( ExprLhs<T> const& expr ) {
        handleExpression( expr.makeUnaryExpr() );
    }

    struct Decomposer {
        template<typename T>
        auto operator <= ( T& lhs ) -> ExprLhs<T&> {
            return ExprLhs<T&>( lhs );
        }
        template<typename T>
        auto operator <= ( T const& lhs ) -> ExprLhs<T const&> {
            return ExprLhs<T const&>( lhs );
        }
        auto operator <=( bool value ) -> ExprLhs<bool> {
            return ExprLhs<bool>( value );
        }
    };

} // end namespace Catch

#endif // TWOBLUECUBES_CATCH_DECOMPOSER_H_INCLUDED