list_invariants.hpp

#ifndef PASTELSYS_LIST_INVARIANTS_HPP
#define PASTELSYS_LIST_INVARIANTS_HPP

#include "pastel/sys/list/list_invariants.h"

#include <iterator>

namespace Pastel
{

    template <
        typename Settings,
        template <typename> class Customization>
    bool testInvariants(
        const List<Settings, Customization>& list)
    {
        if ((list.size() == 0) != list.empty())
        {
            // The size() is zero if and only if the list
            // is empty.
            return false;
        }

        if (std::distance(list.cbegin(), list.cend()) != list.size())
        {
            // The size() must equal the number of elements
            // in the list.
            return false;
        }

        if (!list.cend().isEnd())
        {
            // The end-node must be locally identifiable 
            // as an end-node.
            return false;
        }

        if (!list.cbegin().isBegin())
        {
            // The begin-node must be locally identifiable
            // as a begin-node.
            return false;
        }

        if (list.empty())
        {
            return true;
        }

        auto begin = list.cbegin();
        auto end = list.cend();

        if (!begin.prev().isEnd())
        {
            // The previous of the first node must
            // be the end-node.
            return false;
        }

        if (end.next() != end)
        {
            // The next of the end-node must be 
            // the end-node.
            return false;
        }

        auto iter = begin;
        while (iter != end)
        {
            if (iter.empty() ||
                iter.isEnd() ||
                (iter.isBegin() != (iter == begin)) ||
                !iter.isNormal())
            {
                // An iterator must not be null or end, 
                // and must be normal. An iterator is
                // begin if and only if it is the begin
                // iterator.
                return false;
            }

            if (iter != begin &&
                iter.prev().next() != iter)
            {
                // The next of the previous must
                // be the element itself.
                return false;
            }

            if (iter.next().prev() != iter)
            {
                // The previous of the next must
                // be the element itself.
                return false;
            }

            ++iter;
        }

        return true;
    }

}

#endif