pilotclient/src/blackmisc/range.h

/* Copyright (C) 2013 VATSIM Community / authors
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! \file

#ifndef BLACKMISC_RANGE_H
#define BLACKMISC_RANGE_H

#include "indexvariantmap.h"
#include "iterator.h"
#include "predicates.h"
#include <QtGlobal>
#include <algorithm>
#include <type_traits>
#include <iterator>

namespace BlackMisc
{

    template <class> class CRange;

    /*!
     * Any container class with begin and end iterators can inherit from this CRTP class
     * to gain some useful algorithms as member functions.
     * \tparam Derived The most derived container class inheriting from this instantiation.
     * \tparam CIt the const_iterator of Derived.
     */
    template <class Derived, class CIt>
    class CRangeBase
    {
    public:
        /*!
         * Return a new container generated by applying some transformation function to all elements of this one.
         */
        template <class F>
        inline auto transform(F function) const
            -> CRange<Iterators::TransformIterator<CIt, F>>;

        /*!
         * \brief Return a copy containing only those elements for which a given predicate returns true.
         */
        template <class Predicate>
        inline auto findBy(Predicate p) const
            -> CRange<Iterators::ConditionalIterator<CIt, Predicate>>;

        /*!
         * \brief Return a copy containing only those elements matching some particular key/value pair(s).
         * \param k0 A pointer to a member function of T.
         * \param v0 A value to compare against the value returned by k0.
         * \param keysValues Zero or more additional pairs of { pointer to member function of T, value to compare it against }.
         */
        template <class K0, class V0, class... KeysValues>
        inline auto findBy(K0 k0, V0 v0, KeysValues... keysValues) const
            -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...))>>;

        /*!
         * \brief Return a copy containing only those elements matching a given value map.
         */
        inline auto findBy(CIndexVariantMap valueMap) const
            -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::Equals(std::move(valueMap)))>>;

        /*!
         * \brief Return true if there is an element for which a given predicate returns true.
         */
        template <class Predicate>
        bool containsBy(Predicate p) const
        {
            return std::any_of(derived().cbegin(), derived().cend(), p);
        }

        /*!
         * \brief Return true if there is an element equal to given object. Uses the most efficient implementation available in the derived container.
         */
        template <class T>
        bool contains(const T &object) const
        {
            return derived().find(object) != derived().cend();
        }

        /*!
         * \brief Return a copy containing only those elements matching some particular key/value pair(s).
         * \param k0 A pointer to a member function of T.
         * \param v0 A value to compare against the value returned by k0.
         * \param keysValues Zero or more additional pairs of { pointer to member function of T, value to compare it against }.
         */
        template <class K0, class V0, class... KeysValues>
        bool contains(K0 k0, V0 v0, KeysValues... keysValues) const
        {
            return containsBy(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...));
        }

    private:
        Derived &derived() { return static_cast<Derived &>(*this); }
        const Derived &derived() const { return static_cast<const Derived &>(*this); }
    };

    /*!
     * A range is a conceptual container which does not contain any elements of its own,
     * but is constructed from a begin iterator and an end iterator of another container.
     *
     * By using iterator wrappers, it is possible to use CRange to iterate over the results of predicate methods without copying elements.
     *
     * \warning Remember that the iterators in the range refer to elements in the original container,
     *          so take care that the original container remains valid and does not invalidate its iterators
     *          during the lifetime of the range.
     */
    template <class I>
    class CRange : public CRangeBase<CRange<I>, I>
    {
    public:
        //! STL compatibility
        //! @{
        typedef typename std::iterator_traits<I>::value_type key_type;
        typedef typename std::iterator_traits<I>::value_type value_type;
        typedef value_type &reference;
        typedef const value_type &const_reference;
        typedef value_type *pointer;
        typedef const value_type *const_pointer;
        typedef I const_iterator;
        typedef I iterator;
        typedef typename std::iterator_traits<I>::difference_type difference_type;
        //! @}

        //! Constructor.
        CRange(I begin, I end) : m_begin(begin), m_end(end) { check(begin, end); }

        //! Begin and end iterators.
        //! @{
        const_iterator begin() const { return m_begin; }
        const_iterator cbegin() const { return m_begin; }
        const_iterator end() const { return m_end; }
        const_iterator cend() const { return m_end; }
        //! @}

        //! Implicit conversion to any container of value_type which supports push_back. This will copy elements.
        template <class T, class = typename std::enable_if<std::is_convertible<value_type, typename T::value_type>::value>::type>
        operator T() const
        {
            T container;
            std::copy(begin(), end(), std::back_inserter(container));
            return container;
        }

        //! Returns true if the range is empty.
        //! @{
        bool empty() const { return begin() == end(); }
        bool isEmpty() const { return empty(); }
        //! @}

        //! Returns the element at the beginning of the range. Undefined if the range is empty.
        const_reference front() const { return *begin(); }

        //! Returns the element at the beginning of the range, or a default value if the range is empty.
        const_reference frontOrDefault() const
        {
            static const value_type def;
            return empty() ? def : *begin();
        }

        //! Returns the element at the beginning of the range, or a default value if the range is empty.
        value_type frontOrDefault(value_type def) const
        {
            return empty() ? def : *begin();
        }

    private:
        I m_begin;
        I m_end;

        void check(...) {};
        template <class I2, class F> void check(Iterators::ConditionalIterator<I2, F> begin, Iterators::ConditionalIterator<I2, F> end)
        {
            begin.checkEnd(end);
        }
    };

    /*!
     * Streaming operators for CRange to qDebug.
     */
    //! @{
    template <class I>
    QDebug operator <<(QDebug d, const CRange<I> &range)
    {
        for (const auto &v : range) { d << v; }
        return d;
    }
    template <class I>
    QNoDebug operator <<(QNoDebug d, const CRange<I> &)
    {
        return d;
    }
    //! @}

    /*!
     * Returns a CRange constructed from begin and end iterators of deduced types.
     * \param begin The begin iterator.
     * \param end The end iterator, which can be any iterator type convertible to I.
     */
    template <class I, class I2>
    auto makeRange(I begin, I2 end) -> CRange<I>
    {
        return { begin, static_cast<I>(end) };
    }

    /*!
     * Returns a CRange constructed from the begin and end iterators of the given container.
     *
     * The returned CRange may or may not be const, depending on the constness of the container.
     */
    template <class T>
    auto makeRange(T &&container) -> CRange<decltype(container.begin())>
    {
        return { container.begin(), container.end() };
    }

    /*!
     * Returns a const CRange constructed from the cbegin and cend iterators of the given container.
     */
    template <class T>
    auto makeConstRange(T &&container) -> CRange<decltype(container.cbegin())>
    {
        return { container.cbegin(), container.cend() };
    }

    /*
     * Member functions of CRangeBase template defined out of line, because they depend on CRange etc.
     */
    template <class Derived, class CIt>
    template <class F>
    auto CRangeBase<Derived, CIt>::transform(F function) const
        -> CRange<Iterators::TransformIterator<CIt, F>>
    {
        return makeRange(Iterators::makeTransformIterator(derived().cbegin(), function), derived().cend());
    }

    template <class Derived, class CIt>
    template <class Predicate>
    auto CRangeBase<Derived, CIt>::findBy(Predicate p) const
        -> CRange<Iterators::ConditionalIterator<CIt, Predicate>>
    {
        return makeRange(makeConditionalIterator(derived().cbegin(), derived().cend(), p), derived().cend());
    }

    template <class Derived, class CIt>
    template <class K0, class V0, class... KeysValues>
    auto CRangeBase<Derived, CIt>::findBy(K0 k0, V0 v0, KeysValues... keysValues) const
        -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...))>>
    {
        return findBy(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...));
    }

    template <class Derived, class CIt>
    auto CRangeBase<Derived, CIt>::findBy(CIndexVariantMap valueMap) const
        -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::Equals(std::move(valueMap)))>>
    {
        return findBy(BlackMisc::Predicates::Equals(std::move(valueMap)));
    }

}

#endif // guard