/////////////////////////////////////////////////////////////////////////////// 
// 
// Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
// 
// This code is licensed under the MIT License (MIT). 
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
// THE SOFTWARE. 
// 
///////////////////////////////////////////////////////////////////////////////

#pragma once

#ifndef GSL_CONTRACTS_H
#define GSL_CONTRACTS_H

#include <exception>
#include <stdexcept>

//
// There are three configuration options for this GSL implementation's behavior
// when pre/post conditions on the GSL types are violated:
//
// 1. GSL_TERMINATE_ON_CONTRACT_VIOLATION: std::terminate will be called (default)
// 2. GSL_THROW_ON_CONTRACT_VIOLATION: a gsl::fail_fast exception will be thrown
// 3. GSL_UNENFORCED_ON_CONTRACT_VIOLATION: nothing happens  
//
#if !(defined(GSL_THROW_ON_CONTRACT_VIOLATION) ^ defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION) ^ defined(GSL_UNENFORCED_ON_CONTRACT_VIOLATION))
#define GSL_TERMINATE_ON_CONTRACT_VIOLATION 
#endif


#define GSL_STRINGIFY_DETAIL(x) #x
#define GSL_STRINGIFY(x) GSL_STRINGIFY_DETAIL(x)


//
// GSL.assert: assertions
//

namespace gsl
{
struct fail_fast
{
    virtual char const* what() const noexcept = 0;
};

namespace details
{
    template<typename E>
    struct contract_violation : public E, public fail_fast
    {
        explicit contract_violation(char const* const message) : E(message) {}
        virtual char const* what() const noexcept override
        {
            return E::what();
        }
    };
}
}

#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)

#define Expects(cond)  if (!(cond)) \
    throw gsl::details::contract_violation<std::logic_error>("GSL: Precondition failure at " __FILE__ ": " GSL_STRINGIFY(__LINE__));
#define Ensures(cond)  if (!(cond)) \
    throw gsl::details::contract_violation<std::runtime_error>("GSL: Postcondition failure at " __FILE__ ": " GSL_STRINGIFY(__LINE__));


#elif defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION)


#define Expects(cond)           if (!(cond)) std::terminate(); 
#define Ensures(cond)           if (!(cond)) std::terminate();


#elif defined(GSL_UNENFORCED_ON_CONTRACT_VIOLATION)

#define Expects(cond)           
#define Ensures(cond)           

#endif 


#endif // GSL_CONTRACTS_H