Stamp.h

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#pragma once

 
#include <type_traits>
 
#include <EmrysFilter/Core/Macros.h>
 
namespace Emrys::internal
{

class Stamp
{
public:
 
    Stamp() = default;

    Stamp(Stamp const &) noexcept {}

    Stamp(Stamp && other) noexcept
    {
        other.touchShape();
    }

    Stamp &
    operator=(Stamp const &) noexcept
    {
        touchShape();
        return *this;
    }

    Stamp &
    operator=(Stamp && other) noexcept
    {
        touchShape();
        other.touchShape();
        return *this;
    }

    void
    touchValues() noexcept
    {
        ++m_values;
    }

    void
    touchShape() noexcept
    {
        ++m_values;
        ++m_shape;
    }

    [[nodiscard]] unsigned
    values() const noexcept
    {
        return m_values;
    }

    [[nodiscard]] unsigned
    shape() const noexcept
    {
        return m_shape;
    }
 
private:
 
    unsigned m_values = 0;  
    unsigned m_shape = 0;   
};

template <typename Source>
class ValuesCheck
{
public:

    explicit ValuesCheck(Source const & source)
        : m_source{&source}
        , m_seen{source.m_stamp.values()}
    {}

    [[nodiscard]] Source const &
    get() const
    {
        EMRYS_FILTER_ASSERT(
            m_source->m_stamp.values() == m_seen && "the parameters changed while a view of them was alive"
        );
        return *m_source;
    }
 
private:
 
    Source const * m_source;  
    unsigned m_seen;          
};

template <typename Source>
class ShapeCheck
{
public:

    explicit ShapeCheck(Source const & source)
        : m_source{&source}
        , m_seen{source.m_stamp.shape()}
    {}

    [[nodiscard]] Source const &
    get() const
    {
        EMRYS_FILTER_ASSERT(
            m_source->m_stamp.shape() == m_seen
            && "the parameters changed size or structure while a marginal of them was alive"
        );
        return *m_source;
    }
 
private:
 
    Source const * m_source;  
    unsigned m_seen;          
};

class CallbackGuard
{
public:

    explicit CallbackGuard(Stamp const & stamp) noexcept
        : m_stamp{&stamp}
        , m_seen{stamp.values()}
    {}

    void
    check() const
    {
        EMRYS_FILTER_ASSERT(m_stamp->values() == m_seen && "the parameters changed inside their own callback");
    }
 
private:
 
    [[maybe_unused]] Stamp const * m_stamp;  
    unsigned m_seen;                         
};

template <typename View>
class ViewHolder
{
public:

    explicit ViewHolder(View const & view)
        : m_view{view}
    {}

    [[nodiscard]] View const &
    get() const
    {
        return m_view;
    }
 
private:
 
    View m_view;  
};

template <typename Source>
using HolderFor = std::conditional_t<Source::IsParams, ShapeCheck<Source>, ViewHolder<Source>>;
 
}  // namespace Emrys::internal