// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant reason:default

#ifndef QT5LINKEDLIST_H
#define QT5LINKEDLIST_H

#include <QtCore5Compat/qcore5global.h>

#include <QtCore/qiterator.h>
#include <QtCore/qrefcount.h>
#include <QtCore/qcontainertools_impl.h>
#include <QtCore/qdatastream.h>
#include <QtCore/qmetatype.h>
#include <QtCore/qtypeinfo.h>

#include <algorithm>
#include <initializer_list>
#include <iterator>
#include <list>

QT_BEGIN_NAMESPACE

struct Q_CORE5COMPAT_EXPORT QLinkedListData
{
    QLinkedListData *n, *p;
    QtPrivate::RefCount ref;
    int size;
    uint sharable : 1;

    static const QLinkedListData shared_null;
};

template<typename T>
struct QLinkedListNode
{
    inline QLinkedListNode(const T &arg) : t(arg) {}
    QLinkedListNode *n, *p;
    T t;
};

template<class T>
class QLinkedList
{
    typedef QLinkedListNode<T> Node;
    union {
        QLinkedListData *d;
        QLinkedListNode<T> *e;
    };

public:
    inline QLinkedList() noexcept : d(const_cast<QLinkedListData *>(&QLinkedListData::shared_null))
    {
    }
    inline QLinkedList(const QLinkedList<T> &l) : d(l.d)
    {
        d->ref.ref();
        if (!d->sharable)
            detach();
    }
    inline QLinkedList(std::initializer_list<T> list) : QLinkedList(list.begin(), list.end()) {}
    template<typename InputIterator, QtPrivate::IfIsInputIterator<InputIterator> = true>
    inline QLinkedList(InputIterator first, InputIterator last) : QLinkedList()
    {
        std::copy(first, last, std::back_inserter(*this));
    }
    ~QLinkedList();
    QLinkedList<T> &operator=(const QLinkedList<T> &);
    QLinkedList(QLinkedList<T> &&other) noexcept : d(other.d)
    {
        other.d = const_cast<QLinkedListData *>(&QLinkedListData::shared_null);
    }
    QLinkedList<T> &operator=(QLinkedList<T> &&other) noexcept
    {
        QLinkedList moved(std::move(other));
        swap(moved);
        return *this;
    }
    void swap(QLinkedList &other) noexcept { qt_ptr_swap(d, other.d); }
    bool operator==(const QLinkedList<T> &l) const;
    inline bool operator!=(const QLinkedList<T> &l) const { return !(*this == l); }

    inline int size() const { return d->size; }
    inline void detach()
    {
        if (d->ref.isShared())
            detach_helper2(this->e);
    }
    inline bool isDetached() const { return !d->ref.isShared(); }
    inline bool isSharedWith(const QLinkedList<T> &other) const { return d == other.d; }

    inline bool isEmpty() const { return d->size == 0; }

    void clear();

    void append(const T &);
    void prepend(const T &);
    T takeFirst();
    T takeLast();
    int removeAll(const T &t);
    bool removeOne(const T &t);
    bool contains(const T &t) const;
    int count(const T &t) const;

    class const_iterator;

    class iterator
    {
    public:
        typedef std::bidirectional_iterator_tag iterator_category;
        typedef qptrdiff difference_type;
        typedef T value_type;
        typedef T *pointer;
        typedef T &reference;
        Node *i;
        inline iterator() : i(nullptr) {}
        inline iterator(Node *n) : i(n) {}
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
        iterator(const iterator &other) noexcept : i(other.i) {}
        iterator &operator=(const iterator &other) noexcept
        {
            i = other.i;
            return *this;
        }
        iterator(iterator &&other) noexcept : i(other.i) {}
        iterator &operator=(iterator &&other) noexcept { return *this = other; }
#endif
        inline T &operator*() const { return i->t; }
        inline T *operator->() const { return &i->t; }
        inline bool operator==(const iterator &o) const { return i == o.i; }
        inline bool operator!=(const iterator &o) const { return i != o.i; }
        inline bool operator==(const const_iterator &o) const { return i == o.i; }
        inline bool operator!=(const const_iterator &o) const { return i != o.i; }
        inline iterator &operator++()
        {
            i = i->n;
            return *this;
        }
        inline iterator operator++(int)
        {
            Node *n = i;
            i = i->n;
            return n;
        }
        inline iterator &operator--()
        {
            i = i->p;
            return *this;
        }
        inline iterator operator--(int)
        {
            Node *n = i;
            i = i->p;
            return n;
        }
        inline iterator operator+(int j) const
        {
            Node *n = i;
            if (j > 0)
                while (j--)
                    n = n->n;
            else
                while (j++)
                    n = n->p;
            return n;
        }
        inline iterator operator-(int j) const { return operator+(-j); }
        inline iterator &operator+=(int j) { return *this = *this + j; }
        inline iterator &operator-=(int j) { return *this = *this - j; }
        friend inline iterator operator+(int j, iterator k) { return k + j; }
    };
    friend class iterator;

    class const_iterator
    {
    public:
        typedef std::bidirectional_iterator_tag iterator_category;
        typedef qptrdiff difference_type;
        typedef T value_type;
        typedef const T *pointer;
        typedef const T &reference;
        Node *i;
        inline const_iterator() : i(nullptr) {}
        inline const_iterator(Node *n) : i(n) {}
        inline const_iterator(iterator ci) : i(ci.i) {}
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
        const_iterator(const const_iterator &other) noexcept : i(other.i) {}
        const_iterator &operator=(const const_iterator &other) noexcept
        {
            i = other.i;
            return *this;
        }
        const_iterator(const_iterator &&other) noexcept : i(other.i) {}
        const_iterator &operator=(const_iterator &&other) noexcept { return *this = other; }
#endif
        inline const T &operator*() const { return i->t; }
        inline const T *operator->() const { return &i->t; }
        inline bool operator==(const const_iterator &o) const { return i == o.i; }
        inline bool operator!=(const const_iterator &o) const { return i != o.i; }
        inline const_iterator &operator++()
        {
            i = i->n;
            return *this;
        }
        inline const_iterator operator++(int)
        {
            Node *n = i;
            i = i->n;
            return n;
        }
        inline const_iterator &operator--()
        {
            i = i->p;
            return *this;
        }
        inline const_iterator operator--(int)
        {
            Node *n = i;
            i = i->p;
            return n;
        }
        inline const_iterator operator+(int j) const
        {
            Node *n = i;
            if (j > 0)
                while (j--)
                    n = n->n;
            else
                while (j++)
                    n = n->p;
            return n;
        }
        inline const_iterator operator-(int j) const { return operator+(-j); }
        inline const_iterator &operator+=(int j) { return *this = *this + j; }
        inline const_iterator &operator-=(int j) { return *this = *this - j; }
        friend inline const_iterator operator+(int j, const_iterator k) { return k + j; }
    };
    friend class const_iterator;

    // stl style
    typedef std::reverse_iterator<iterator> reverse_iterator;
    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

    inline iterator begin()
    {
        detach();
        return e->n;
    }
    inline const_iterator begin() const noexcept { return e->n; }
    inline const_iterator cbegin() const noexcept { return e->n; }
    inline const_iterator constBegin() const noexcept { return e->n; }
    inline iterator end()
    {
        detach();
        return e;
    }
    inline const_iterator end() const noexcept { return e; }
    inline const_iterator cend() const noexcept { return e; }
    inline const_iterator constEnd() const noexcept { return e; }

    reverse_iterator rbegin() { return reverse_iterator(end()); }
    reverse_iterator rend() { return reverse_iterator(begin()); }
    const_reverse_iterator rbegin() const noexcept { return const_reverse_iterator(end()); }
    const_reverse_iterator rend() const noexcept { return const_reverse_iterator(begin()); }
    const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(end()); }
    const_reverse_iterator crend() const noexcept { return const_reverse_iterator(begin()); }

    iterator insert(iterator before, const T &t);
    iterator erase(iterator pos);
    iterator erase(iterator first, iterator last);

    // more Qt
    typedef iterator Iterator;
    typedef const_iterator ConstIterator;
    inline int count() const { return d->size; }
    inline T &first()
    {
        Q_ASSERT(!isEmpty());
        return *begin();
    }
    inline const T &first() const
    {
        Q_ASSERT(!isEmpty());
        return *begin();
    }
    T &last()
    {
        Q_ASSERT(!isEmpty());
        return *(--end());
    }
    const T &last() const
    {
        Q_ASSERT(!isEmpty());
        return *(--end());
    }
    inline void removeFirst()
    {
        Q_ASSERT(!isEmpty());
        erase(begin());
    }
    inline void removeLast()
    {
        Q_ASSERT(!isEmpty());
        erase(--end());
    }
    inline bool startsWith(const T &t) const { return !isEmpty() && first() == t; }
    inline bool endsWith(const T &t) const { return !isEmpty() && last() == t; }

    // stl compatibility
    inline void push_back(const T &t) { append(t); }
    inline void push_front(const T &t) { prepend(t); }
    inline T &front() { return first(); }
    inline const T &front() const { return first(); }
    inline T &back() { return last(); }
    inline const T &back() const { return last(); }
    inline void pop_front() { removeFirst(); }
    inline void pop_back() { removeLast(); }
    inline bool empty() const { return isEmpty(); }
    typedef int size_type;
    typedef T value_type;
    typedef value_type *pointer;
    typedef const value_type *const_pointer;
    typedef value_type &reference;
    typedef const value_type &const_reference;
    typedef qptrdiff difference_type;

    static inline QLinkedList<T> fromStdList(const std::list<T> &list)
    {
        QLinkedList<T> tmp;
        std::copy(list.begin(), list.end(), std::back_inserter(tmp));
        return tmp;
    }
    inline std::list<T> toStdList() const
    {
        std::list<T> tmp;
        std::copy(constBegin(), constEnd(), std::back_inserter(tmp));
        return tmp;
    }

    // comfort
    QLinkedList<T> &operator+=(const QLinkedList<T> &l);
    QLinkedList<T> operator+(const QLinkedList<T> &l) const;
    inline QLinkedList<T> &operator+=(const T &t)
    {
        append(t);
        return *this;
    }
    inline QLinkedList<T> &operator<<(const T &t)
    {
        append(t);
        return *this;
    }
    inline QLinkedList<T> &operator<<(const QLinkedList<T> &l)
    {
        *this += l;
        return *this;
    }

private:
    void detach_helper();
    iterator detach_helper2(iterator);
    void freeData(QLinkedListData *);
};

#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606
template<typename InputIterator,
         typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
         QtPrivate::IfIsInputIterator<InputIterator> = true>
QLinkedList(InputIterator, InputIterator)->QLinkedList<ValueType>;
#endif

template<typename T>
inline QLinkedList<T>::~QLinkedList()
{
    if (!d->ref.deref())
        freeData(d);
}

template<typename T>
void QLinkedList<T>::detach_helper()
{
    detach_helper2(this->e);
}

template<typename T>
typename QLinkedList<T>::iterator QLinkedList<T>::detach_helper2(iterator orgite)
{
    // detach and convert orgite to an iterator in the detached instance
    bool isEndIterator = (orgite.i == this->e);
    union {
        QLinkedListData *d;
        Node *e;
    } x;
    x.d = new QLinkedListData;
    x.d->ref.initializeOwned();
    x.d->size = d->size;
    x.d->sharable = true;
    Node *original = e->n;
    Node *copy = x.e;
    Node *org = orgite.i;

    while (original != org) {
        QT_TRY
        {
            copy->n = new Node(original->t);
            copy->n->p = copy;
            original = original->n;
            copy = copy->n;
        }
        QT_CATCH(...)
        {
            copy->n = x.e;
            Q_ASSERT(!x.d->ref.deref()); // Don't trigger assert in free
            freeData(x.d);
            QT_RETHROW;
        }
    }
    iterator r(copy);
    while (original != e) {
        QT_TRY
        {
            copy->n = new Node(original->t);
            copy->n->p = copy;
            original = original->n;
            copy = copy->n;
        }
        QT_CATCH(...)
        {
            copy->n = x.e;
            Q_ASSERT(!x.d->ref.deref()); // Don't trigger assert in free
            freeData(x.d);
            QT_RETHROW;
        }
    }
    copy->n = x.e;
    x.e->p = copy;
    if (!d->ref.deref())
        freeData(d);
    d = x.d;
    if (!isEndIterator)
        ++r; // since we stored the element right before the original node.
    return r;
}

template<typename T>
void QLinkedList<T>::freeData(QLinkedListData *x)
{
    Node *y = reinterpret_cast<Node *>(x);
    Node *i = y->n;
    Q_ASSERT(x->ref.atomic.loadRelaxed() == 0);
    while (i != y) {
        Node *n = i;
        i = i->n;
        delete n;
    }
    delete x;
}

template<typename T>
void QLinkedList<T>::clear()
{
    *this = QLinkedList<T>();
}

template<typename T>
QLinkedList<T> &QLinkedList<T>::operator=(const QLinkedList<T> &l)
{
    if (d != l.d) {
        QLinkedListData *o = l.d;
        o->ref.ref();
        if (!d->ref.deref())
            freeData(d);
        d = o;
        if (!d->sharable)
            detach_helper();
    }
    return *this;
}

template<typename T>
bool QLinkedList<T>::operator==(const QLinkedList<T> &l) const
{
    if (d->size != l.d->size)
        return false;
    if (e == l.e)
        return true;
    Node *i = e->n;
    Node *il = l.e->n;
    while (i != e) {
        if (!(i->t == il->t))
            return false;
        i = i->n;
        il = il->n;
    }
    return true;
}

template<typename T>
void QLinkedList<T>::append(const T &t)
{
    detach();
    Node *i = new Node(t);
    i->n = e;
    i->p = e->p;
    i->p->n = i;
    e->p = i;
    d->size++;
}

template<typename T>
void QLinkedList<T>::prepend(const T &t)
{
    detach();
    Node *i = new Node(t);
    i->n = e->n;
    i->p = e;
    i->n->p = i;
    e->n = i;
    d->size++;
}

template<typename T>
int QLinkedList<T>::removeAll(const T &_t)
{
    detach();
    const T t = _t;
    Node *i = e->n;
    int c = 0;
    while (i != e) {
        if (i->t == t) {
            Node *n = i;
            i->n->p = i->p;
            i->p->n = i->n;
            i = i->n;
            delete n;
            c++;
        } else {
            i = i->n;
        }
    }
    d->size -= c;
    return c;
}

template<typename T>
bool QLinkedList<T>::removeOne(const T &_t)
{
    detach();
    iterator it = std::find(begin(), end(), _t);
    if (it != end()) {
        erase(it);
        return true;
    }
    return false;
}

template<typename T>
inline T QLinkedList<T>::takeFirst()
{
    T t = std::move(first());
    removeFirst();
    return t;
}

template<typename T>
inline T QLinkedList<T>::takeLast()
{
    T t = std::move(last());
    removeLast();
    return t;
}

template<typename T>
bool QLinkedList<T>::contains(const T &t) const
{
    Node *i = e;
    while ((i = i->n) != e)
        if (i->t == t)
            return true;
    return false;
}

template<typename T>
int QLinkedList<T>::count(const T &t) const
{
    Node *i = e;
    int c = 0;
    while ((i = i->n) != e)
        if (i->t == t)
            c++;
    return c;
}

template<typename T>
typename QLinkedList<T>::iterator QLinkedList<T>::insert(iterator before, const T &t)
{
    if (d->ref.isShared())
        before = detach_helper2(before);

    Node *i = before.i;
    Node *m = new Node(t);
    m->n = i;
    m->p = i->p;
    m->p->n = m;
    i->p = m;
    d->size++;
    return m;
}

template<typename T>
typename QLinkedList<T>::iterator QLinkedList<T>::erase(typename QLinkedList<T>::iterator afirst,
                                                        typename QLinkedList<T>::iterator alast)
{
    if (afirst == alast)
        return alast; // no-op
    if (!d->ref.isShared()) {
        do {
            erase(afirst++);
        } while (afirst != alast);
        return alast;
    }
    // When shared, don't detach; create a completely new QLinkedList and then swap()
    const const_iterator cafirst = afirst;
    const const_iterator calast = alast;
    QLinkedList l{cbegin(), cafirst};
    // QLinkedList has no range-insert :(
    iterator r;
    if (calast == cend()) {
        r = l.end();
    } else {
        // end() appears to be a sentinel, so need to get an actual iterator:
        auto it = calast;
        l.append(*it);
        ++it;
        r = std::prev(l.end());
        for (/* empty */; it != cend(); ++it)
            l.append(*it);
    }
    swap(l);
    return r;
}

template<typename T>
typename QLinkedList<T>::iterator QLinkedList<T>::erase(iterator pos)
{
    if (d->ref.isShared())
        pos = detach_helper2(pos);

    Node *i = pos.i;
    if (i != e) {
        Node *n = i;
        i->n->p = i->p;
        i->p->n = i->n;
        i = i->n;
        delete n;
        d->size--;
    }
    return i;
}

template<typename T>
QLinkedList<T> &QLinkedList<T>::operator+=(const QLinkedList<T> &l)
{
    detach();
    int n = l.d->size;
    d->size += n;
    Node *original = l.e->n;
    while (n--) {
        QT_TRY
        {
            Node *copy = new Node(original->t);
            original = original->n;
            copy->n = e;
            copy->p = e->p;
            copy->p->n = copy;
            e->p = copy;
        }
        QT_CATCH(...)
        {
            // restore the original list
            while (n++ < d->size)
                removeLast();
            QT_RETHROW;
        }
    }
    return *this;
}

template<typename T>
QLinkedList<T> QLinkedList<T>::operator+(const QLinkedList<T> &l) const
{
    QLinkedList<T> n = *this;
    n += l;
    return n;
}

Q_DECLARE_SEQUENTIAL_ITERATOR(LinkedList)
Q_DECLARE_MUTABLE_SEQUENTIAL_ITERATOR(LinkedList)

#ifndef QT_NO_DATASTREAM
template<typename T>
inline QDataStreamIfHasIStreamOperatorsContainer<QLinkedList<T>, T>
operator>>(QDataStream &s, QLinkedList<T> &l)
{
    return QtPrivate::readListBasedContainer(s, l);
}

template<typename T>
inline QDataStreamIfHasOStreamOperatorsContainer<QLinkedList<T>, T>
operator<<(QDataStream &s, const QLinkedList<T> &l)
{
    return QtPrivate::writeSequentialContainer(s, l);
}
#endif

template<typename T>
Q_DECLARE_TYPEINFO_BODY(QLinkedList<T>, Q_RELOCATABLE_TYPE);

QT_END_NAMESPACE

Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE(QLinkedList)

#endif // QT5LINKEDLIST_H