// Copyright (C) 2020 The Qt Company Ltd.
// Copyright (C) 2019 Intel Corporation
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#ifndef QLIST_H
#define QLIST_H

#include <QtCore/qarraydatapointer.h>
#include <QtCore/qnamespace.h>
#include <QtCore/qhashfunctions.h>
#include <QtCore/qiterator.h>
#include <QtCore/qcontainertools_impl.h>

#include <functional>
#include <limits>
#include <initializer_list>
#include <type_traits>

QT_BEGIN_NAMESPACE

namespace QtPrivate {
   template <typename V, typename U> qsizetype indexOf(const QList<V> &list, const U &u, qsizetype from) noexcept;
   template <typename V, typename U> qsizetype lastIndexOf(const QList<V> &list, const U &u, qsizetype from) noexcept;
}

template <typename T> struct QListSpecialMethodsBase
{
protected:
    ~QListSpecialMethodsBase() = default;

    using Self = QList<T>;
    Self *self() { return static_cast<Self *>(this); }
    const Self *self() const { return static_cast<const Self *>(this); }

public:
    template <typename AT = T>
    qsizetype indexOf(const AT &t, qsizetype from = 0) const noexcept;
    template <typename AT = T>
    qsizetype lastIndexOf(const AT &t, qsizetype from = -1) const noexcept;

    template <typename AT = T>
    bool contains(const AT &t) const noexcept
    {
        return self()->indexOf(t) != -1;
    }
};
template <typename T> struct QListSpecialMethods : QListSpecialMethodsBase<T>
{
protected:
    ~QListSpecialMethods() = default;
public:
    using QListSpecialMethodsBase<T>::indexOf;
    using QListSpecialMethodsBase<T>::lastIndexOf;
    using QListSpecialMethodsBase<T>::contains;
};
template <> struct QListSpecialMethods<QByteArray>;
template <> struct QListSpecialMethods<QString>;

#if !defined(QT_STRICT_QLIST_ITERATORS) && (QT_VERSION >= QT_VERSION_CHECK(6, 6, 0)) && !defined(Q_OS_WIN)
#define QT_STRICT_QLIST_ITERATORS
#endif

#ifdef Q_QDOC // define QVector for QDoc
template<typename T> class QVector : public QList<T> {};
#endif

template <typename T>
class QList
#ifndef Q_QDOC
    : public QListSpecialMethods<T>
#endif
{
    using Data = QTypedArrayData<T>;
    using DataOps = QArrayDataOps<T>;
    using DataPointer = QArrayDataPointer<T>;
    class DisableRValueRefs {};

    DataPointer d;

    template <typename V, typename U> friend qsizetype QtPrivate::indexOf(const QList<V> &list, const U &u, qsizetype from) noexcept;
    template <typename V, typename U> friend qsizetype QtPrivate::lastIndexOf(const QList<V> &list, const U &u, qsizetype from) noexcept;

public:
    using Type = T;
    using value_type = T;
    using pointer = T *;
    using const_pointer = const T *;
    using reference = T &;
    using const_reference = const T &;
    using size_type = qsizetype;
    using difference_type = qptrdiff;
#ifndef Q_QDOC
    using parameter_type = typename DataPointer::parameter_type;
    using rvalue_ref = typename std::conditional<DataPointer::pass_parameter_by_value, DisableRValueRefs, T &&>::type;
#else  // simplified aliases for QDoc
    using parameter_type = const T &;
    using rvalue_ref = T &&;
#endif

    class const_iterator;
    class iterator {
        friend class QList<T>;
        friend class const_iterator;
        T *i = nullptr;
#ifdef QT_STRICT_QLIST_ITERATORS
        inline constexpr explicit iterator(T *n) : i(n) {}
#endif

    public:
        using difference_type = qsizetype;
        using value_type = T;
        // libstdc++ shipped with gcc < 11 does not have a fix for defect LWG 3346
#if __cplusplus >= 202002L && (!defined(_GLIBCXX_RELEASE) || _GLIBCXX_RELEASE >= 11)
        using iterator_concept = std::contiguous_iterator_tag;
        using element_type = value_type;
#endif
        using iterator_category = std::random_access_iterator_tag;
        using pointer = T *;
        using reference = T &;

        inline constexpr iterator() = default;
#ifndef QT_STRICT_QLIST_ITERATORS
        inline constexpr explicit iterator(T *n) : i(n) {}
#endif
        inline T &operator*() const { return *i; }
        inline T *operator->() const { return i; }
        inline T &operator[](qsizetype j) const { return *(i + j); }
        inline constexpr bool operator==(iterator o) const { return i == o.i; }
        inline constexpr bool operator!=(iterator o) const { return i != o.i; }
        inline constexpr bool operator<(iterator other) const { return i < other.i; }
        inline constexpr bool operator<=(iterator other) const { return i <= other.i; }
        inline constexpr bool operator>(iterator other) const { return i > other.i; }
        inline constexpr bool operator>=(iterator other) const { return i >= other.i; }
        inline constexpr bool operator==(const_iterator o) const { return i == o.i; }
        inline constexpr bool operator!=(const_iterator o) const { return i != o.i; }
        inline constexpr bool operator<(const_iterator other) const { return i < other.i; }
        inline constexpr bool operator<=(const_iterator other) const { return i <= other.i; }
        inline constexpr bool operator>(const_iterator other) const { return i > other.i; }
        inline constexpr bool operator>=(const_iterator other) const { return i >= other.i; }
        inline constexpr bool operator==(pointer p) const { return i == p; }
        inline constexpr bool operator!=(pointer p) const { return i != p; }
        inline iterator &operator++() { ++i; return *this; }
        inline iterator operator++(int) { auto copy = *this; ++*this; return copy; }
        inline iterator &operator--() { --i; return *this; }
        inline iterator operator--(int) { auto copy = *this; --*this; return copy; }
        inline qsizetype operator-(iterator j) const { return i - j.i; }
#if QT_DEPRECATED_SINCE(6, 3) && !defined(QT_STRICT_QLIST_ITERATORS)
        QT_DEPRECATED_VERSION_X_6_3("Use operator* or operator-> rather than relying on "
                                    "the implicit conversion between a QList/QVector::iterator "
                                    "and a raw pointer")
        inline operator T*() const { return i; }

        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
        &operator+=(Int j) { i+=j; return *this; }
        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
        &operator-=(Int j) { i-=j; return *this; }
        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
        operator+(Int j) const { return iterator(i+j); }
        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, iterator>
        operator-(Int j) const { return iterator(i-j); }
        template <typename Int> friend std::enable_if_t<std::is_integral_v<Int>, iterator>
        operator+(Int j, iterator k) { return k + j; }
#else
        inline iterator &operator+=(qsizetype j) { i += j; return *this; }
        inline iterator &operator-=(qsizetype j) { i -= j; return *this; }
        inline iterator operator+(qsizetype j) const { return iterator(i + j); }
        inline iterator operator-(qsizetype j) const { return iterator(i - j); }
        friend inline iterator operator+(qsizetype j, iterator k) { return k + j; }
#endif
    };

    class const_iterator {
        friend class QList<T>;
        friend class iterator;
        const T *i = nullptr;
#ifdef QT_STRICT_QLIST_ITERATORS
        inline constexpr explicit const_iterator(const T *n) : i(n) {}
#endif

    public:
        using difference_type = qsizetype;
        using value_type = T;
        // libstdc++ shipped with gcc < 11 does not have a fix for defect LWG 3346
#if __cplusplus >= 202002L && (!defined(_GLIBCXX_RELEASE) || _GLIBCXX_RELEASE >= 11)
        using iterator_concept = std::contiguous_iterator_tag;
        using element_type = const value_type;
#endif
        using iterator_category = std::random_access_iterator_tag;
        using pointer = const T *;
        using reference = const T &;

        inline constexpr const_iterator() = default;
#ifndef QT_STRICT_QLIST_ITERATORS
        inline constexpr explicit const_iterator(const T *n) : i(n) {}
#endif
        inline constexpr const_iterator(iterator o): i(o.i) {}
        inline const T &operator*() const { return *i; }
        inline const T *operator->() const { return i; }
        inline const T &operator[](qsizetype j) const { return *(i + j); }
        inline constexpr bool operator==(const_iterator o) const { return i == o.i; }
        inline constexpr bool operator!=(const_iterator o) const { return i != o.i; }
        inline constexpr bool operator<(const_iterator other) const { return i < other.i; }
        inline constexpr bool operator<=(const_iterator other) const { return i <= other.i; }
        inline constexpr bool operator>(const_iterator other) const { return i > other.i; }
        inline constexpr bool operator>=(const_iterator other) const { return i >= other.i; }
        inline constexpr bool operator==(iterator o) const { return i == o.i; }
        inline constexpr bool operator!=(iterator o) const { return i != o.i; }
        inline constexpr bool operator<(iterator other) const { return i < other.i; }
        inline constexpr bool operator<=(iterator other) const { return i <= other.i; }
        inline constexpr bool operator>(iterator other) const { return i > other.i; }
        inline constexpr bool operator>=(iterator other) const { return i >= other.i; }
        inline constexpr bool operator==(pointer p) const { return i == p; }
        inline constexpr bool operator!=(pointer p) const { return i != p; }
        inline const_iterator &operator++() { ++i; return *this; }
        inline const_iterator operator++(int) { auto copy = *this; ++*this; return copy; }
        inline const_iterator &operator--() { --i; return *this; }
        inline const_iterator operator--(int) { auto copy = *this; --*this; return copy; }
        inline qsizetype operator-(const_iterator j) const { return i - j.i; }
#if QT_DEPRECATED_SINCE(6, 3) && !defined(QT_STRICT_QLIST_ITERATORS)
        QT_DEPRECATED_VERSION_X_6_3("Use operator* or operator-> rather than relying on "
                                    "the implicit conversion between a QList/QVector::const_iterator "
                                    "and a raw pointer")
        inline operator const T*() const { return i; }

        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
        &operator+=(Int j) { i+=j; return *this; }
        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
        &operator-=(Int j) { i-=j; return *this; }
        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
        operator+(Int j) const { return const_iterator(i+j); }
        template <typename Int> std::enable_if_t<std::is_integral_v<Int>, const_iterator>
        operator-(Int j) const { return const_iterator(i-j); }
        template <typename Int> friend std::enable_if_t<std::is_integral_v<Int>, const_iterator>
        operator+(Int j, const_iterator k) { return k + j; }
#else
        inline const_iterator &operator+=(qsizetype j) { i += j; return *this; }
        inline const_iterator &operator-=(qsizetype j) { i -= j; return *this; }
        inline const_iterator operator+(qsizetype j) const { return const_iterator(i + j); }
        inline const_iterator operator-(qsizetype j) const { return const_iterator(i - j); }
        friend inline const_iterator operator+(qsizetype j, const_iterator k) { return k + j; }
#endif
    };
    using Iterator = iterator;
    using ConstIterator = const_iterator;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;

private:
    void resize_internal(qsizetype i);
    bool isValidIterator(const_iterator i) const
    {
        const std::less<const T*> less = {};
        return !less(d->end(), i.i) && !less(i.i, d->begin());
    }
public:
    QList(DataPointer dd) noexcept
        : d(dd)
    {
    }

public:
    QList() = default;
    explicit QList(qsizetype size)
        : d(Data::allocate(size))
    {
        if (size)
            d->appendInitialize(size);
    }
    QList(qsizetype size, parameter_type t)
        : d(Data::allocate(size))
    {
        if (size)
            d->copyAppend(size, t);
    }

    inline QList(std::initializer_list<T> args)
        : d(Data::allocate(qsizetype(args.size())))
    {
        if (args.size())
            d->copyAppend(args.begin(), args.end());
    }

    QList<T> &operator=(std::initializer_list<T> args)
    {
        d = DataPointer(Data::allocate(qsizetype(args.size())));
        if (args.size())
            d->copyAppend(args.begin(), args.end());
        return *this;
    }
    template <typename InputIterator, QtPrivate::IfIsInputIterator<InputIterator> = true>
    QList(InputIterator i1, InputIterator i2)
    {
        if constexpr (!std::is_convertible_v<typename std::iterator_traits<InputIterator>::iterator_category, std::forward_iterator_tag>) {
            std::copy(i1, i2, std::back_inserter(*this));
        } else {
            const auto distance = std::distance(i1, i2);
            if (distance) {
                d = DataPointer(Data::allocate(qsizetype(distance)));
                // appendIteratorRange can deal with contiguous iterators on its own,
                // this is an optimization for C++17 code.
                if constexpr (std::is_same_v<std::decay_t<InputIterator>, iterator> ||
                              std::is_same_v<std::decay_t<InputIterator>, const_iterator>) {
                    d->copyAppend(i1.i, i2.i);
                } else {
                    d->appendIteratorRange(i1, i2);
               }
            }
        }
    }

    // This constructor is here for compatibility with QStringList in Qt 5, that has a QStringList(const QString &) constructor
    template<typename String, typename = std::enable_if_t<std::is_same_v<T, QString> && std::is_convertible_v<String, QString>>>
    inline explicit QList(const String &str)
    { append(str); }

    // compiler-generated special member functions are fine!

    void swap(QList &other) noexcept { d.swap(other.d); }

#ifndef Q_QDOC
    template <typename U = T>
    QTypeTraits::compare_eq_result_container<QList, U> operator==(const QList &other) const
    {
        if (size() != other.size())
            return false;
        if (begin() == other.begin())
            return true;

        // do element-by-element comparison
        return d->compare(data(), other.data(), size());
    }
    template <typename U = T>
    QTypeTraits::compare_eq_result_container<QList, U> operator!=(const QList &other) const
    {
        return !(*this == other);
    }

    template <typename U = T>
    QTypeTraits::compare_lt_result_container<QList, U> operator<(const QList &other) const
        noexcept(noexcept(std::lexicographical_compare<typename QList<U>::const_iterator,
                                                       typename QList::const_iterator>(
                            std::declval<QList<U>>().begin(), std::declval<QList<U>>().end(),
                            other.begin(), other.end())))
    {
        return std::lexicographical_compare(begin(), end(),
                                            other.begin(), other.end());
    }

    template <typename U = T>
    QTypeTraits::compare_lt_result_container<QList, U> operator>(const QList &other) const
        noexcept(noexcept(other < std::declval<QList<U>>()))
    {
        return other < *this;
    }

    template <typename U = T>
    QTypeTraits::compare_lt_result_container<QList, U> operator<=(const QList &other) const
        noexcept(noexcept(other < std::declval<QList<U>>()))
    {
        return !(other < *this);
    }

    template <typename U = T>
    QTypeTraits::compare_lt_result_container<QList, U> operator>=(const QList &other) const
        noexcept(noexcept(std::declval<QList<U>>() < other))
    {
        return !(*this < other);
    }
#else
    bool operator==(const QList &other) const;
    bool operator!=(const QList &other) const;
    bool operator<(const QList &other) const;
    bool operator>(const QList &other) const;
    bool operator<=(const QList &other) const;
    bool operator>=(const QList &other) const;
#endif // Q_QDOC

    qsizetype size() const noexcept { return d->size; }
    qsizetype count() const noexcept { return size(); }
    qsizetype length() const noexcept { return size(); }

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

    void resize(qsizetype size)
    {
        resize_internal(size);
        if (size > this->size())
            d->appendInitialize(size);
    }
    void resize(qsizetype size, parameter_type c)
    {
        resize_internal(size);
        if (size > this->size())
            d->copyAppend(size - this->size(), c);
    }

    inline qsizetype capacity() const { return qsizetype(d->constAllocatedCapacity()); }
    void reserve(qsizetype size);
    inline void squeeze();

    void detach() { d.detach(); }
    bool isDetached() const noexcept { return !d->isShared(); }

    inline bool isSharedWith(const QList<T> &other) const { return d == other.d; }

    pointer data() { detach(); return d->data(); }
    const_pointer data() const noexcept { return d->data(); }
    const_pointer constData() const noexcept { return d->data(); }
    void clear() {
        if (!size())
            return;
        if (d->needsDetach()) {
            // must allocate memory
            DataPointer detached(Data::allocate(d.allocatedCapacity()));
            d.swap(detached);
        } else {
            d->truncate(0);
        }
    }

    const_reference at(qsizetype i) const noexcept
    {
        Q_ASSERT_X(size_t(i) < size_t(d->size), "QList::at", "index out of range");
        return data()[i];
    }
    reference operator[](qsizetype i)
    {
        Q_ASSERT_X(size_t(i) < size_t(d->size), "QList::operator[]", "index out of range");
        // don't detach() here, we detach in data below:
        return data()[i];
    }
    const_reference operator[](qsizetype i) const noexcept { return at(i); }
    void append(parameter_type t) { emplaceBack(t); }
    void append(const_iterator i1, const_iterator i2);
    void append(rvalue_ref t)
    {
        if constexpr (DataPointer::pass_parameter_by_value) {
            Q_UNUSED(t);
        } else {
            emplaceBack(std::move(t));
        }
    }
    void append(const QList<T> &l)
    {
        append(l.constBegin(), l.constEnd());
    }
    void append(QList<T> &&l);
    void prepend(rvalue_ref t) {
        if constexpr (DataPointer::pass_parameter_by_value) {
            Q_UNUSED(t);
        } else {
            emplaceFront(std::move(t));
        }
    }
    void prepend(parameter_type t) { emplaceFront(t); }

    template<typename... Args>
    inline reference emplaceBack(Args &&... args);

    template <typename ...Args>
    inline reference emplaceFront(Args&&... args);

    iterator insert(qsizetype i, parameter_type t)
    { return emplace(i, t); }
    iterator insert(qsizetype i, qsizetype n, parameter_type t);
    iterator insert(const_iterator before, parameter_type t)
    {
        Q_ASSERT_X(isValidIterator(before),  "QList::insert", "The specified iterator argument 'before' is invalid");
        return insert(before, 1, t);
    }
    iterator insert(const_iterator before, qsizetype n, parameter_type t)
    {
        Q_ASSERT_X(isValidIterator(before),  "QList::insert", "The specified iterator argument 'before' is invalid");
        return insert(std::distance(constBegin(), before), n, t);
    }
    iterator insert(const_iterator before, rvalue_ref t)
    {
        Q_ASSERT_X(isValidIterator(before),  "QList::insert", "The specified iterator argument 'before' is invalid");
        return insert(std::distance(constBegin(), before), std::move(t));
    }
    iterator insert(qsizetype i, rvalue_ref t) {
        if constexpr (DataPointer::pass_parameter_by_value) {
            Q_UNUSED(i);
            Q_UNUSED(t);
            return end();
        } else {
            return emplace(i, std::move(t));
        }
    }

    template <typename ...Args>
    iterator emplace(const_iterator before, Args&&... args)
    {
        Q_ASSERT_X(isValidIterator(before),  "QList::emplace", "The specified iterator argument 'before' is invalid");
        return emplace(std::distance(constBegin(), before), std::forward<Args>(args)...);
    }

    template <typename ...Args>
    iterator emplace(qsizetype i, Args&&... args);
#if 0
    template< class InputIt >
    iterator insert( const_iterator pos, InputIt first, InputIt last );
    iterator insert( const_iterator pos, std::initializer_list<T> ilist );
#endif
    void replace(qsizetype i, parameter_type t)
    {
        Q_ASSERT_X(i >= 0 && i < d->size, "QList<T>::replace", "index out of range");
        DataPointer oldData;
        d.detach(&oldData);
        d.data()[i] = t;
    }
    void replace(qsizetype i, rvalue_ref t)
    {
        if constexpr (DataPointer::pass_parameter_by_value) {
            Q_UNUSED(i);
            Q_UNUSED(t);
        } else {
            Q_ASSERT_X(i >= 0 && i < d->size, "QList<T>::replace", "index out of range");
            DataPointer oldData;
            d.detach(&oldData);
            d.data()[i] = std::move(t);
        }
    }

    void remove(qsizetype i, qsizetype n = 1);
    void removeFirst() noexcept;
    void removeLast() noexcept;
    value_type takeFirst() { Q_ASSERT(!isEmpty()); value_type v = std::move(first()); d->eraseFirst(); return v; }
    value_type takeLast() { Q_ASSERT(!isEmpty()); value_type v = std::move(last()); d->eraseLast(); return v; }

    QList<T> &fill(parameter_type t, qsizetype size = -1);

#ifndef Q_QDOC
    using QListSpecialMethods<T>::contains;
    using QListSpecialMethods<T>::indexOf;
    using QListSpecialMethods<T>::lastIndexOf;
#else
    template <typename AT>
    qsizetype indexOf(const AT &t, qsizetype from = 0) const noexcept;
    template <typename AT>
    qsizetype lastIndexOf(const AT &t, qsizetype from = -1) const noexcept;
    template <typename AT>
    bool contains(const AT &t) const noexcept;
#endif

    template <typename AT = T>
    qsizetype count(const AT &t) const noexcept
    {
        return qsizetype(std::count(data(), data() + size(), t));
    }

    void removeAt(qsizetype i) { remove(i); }
    template <typename AT = T>
    qsizetype removeAll(const AT &t)
    {
        return QtPrivate::sequential_erase_with_copy(*this, t);
    }

    template <typename AT = T>
    bool removeOne(const AT &t)
    {
        return QtPrivate::sequential_erase_one(*this, t);
    }

    template <typename Predicate>
    qsizetype removeIf(Predicate pred)
    {
        return QtPrivate::sequential_erase_if(*this, pred);
    }

    T takeAt(qsizetype i) { T t = std::move((*this)[i]); remove(i); return t; }
    void move(qsizetype from, qsizetype to)
    {
        Q_ASSERT_X(from >= 0 && from < size(), "QList::move(qsizetype, qsizetype)", "'from' is out-of-range");
        Q_ASSERT_X(to >= 0 && to < size(), "QList::move(qsizetype, qsizetype)", "'to' is out-of-range");
        if (from == to) // don't detach when no-op
            return;
        detach();
        T * const b = d->begin();
        if (from < to)
            std::rotate(b + from, b + from + 1, b + to + 1);
        else
            std::rotate(b + to, b + from, b + from + 1);
    }

    // STL-style
    iterator begin() { detach(); return iterator(d->begin()); }
    iterator end() { detach(); return iterator(d->end()); }

    const_iterator begin() const noexcept { return const_iterator(d->constBegin()); }
    const_iterator end() const noexcept { return const_iterator(d->constEnd()); }
    const_iterator cbegin() const noexcept { return const_iterator(d->constBegin()); }
    const_iterator cend() const noexcept { return const_iterator(d->constEnd()); }
    const_iterator constBegin() const noexcept { return const_iterator(d->constBegin()); }
    const_iterator constEnd() const noexcept { return const_iterator(d->constEnd()); }
    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 erase(const_iterator begin, const_iterator end);
    inline iterator erase(const_iterator pos) { return erase(pos, pos+1); }

    // more Qt
    inline T& first() { Q_ASSERT(!isEmpty()); return *begin(); }
    inline const T &first() const noexcept { Q_ASSERT(!isEmpty()); return *begin(); }
    inline const T &constFirst() const noexcept { Q_ASSERT(!isEmpty()); return *begin(); }
    inline T& last() { Q_ASSERT(!isEmpty()); return *(end()-1); }
    inline const T &last() const noexcept { Q_ASSERT(!isEmpty()); return *(end()-1); }
    inline const T &constLast() const noexcept { Q_ASSERT(!isEmpty()); return *(end()-1); }
    inline bool startsWith(parameter_type t) const { return !isEmpty() && first() == t; }
    inline bool endsWith(parameter_type t) const { return !isEmpty() && last() == t; }
    QList<T> mid(qsizetype pos, qsizetype len = -1) const;

    QList<T> first(qsizetype n) const
    {
        Q_ASSERT(size_t(n) <= size_t(size()));
        return QList<T>(begin(), begin() + n);
    }
    QList<T> last(qsizetype n) const
    {
        Q_ASSERT(size_t(n) <= size_t(size()));
        return QList<T>(end() - n, end());
    }
    QList<T> sliced(qsizetype pos) const
    {
        Q_ASSERT(size_t(pos) <= size_t(size()));
        return QList<T>(begin() + pos, end());
    }
    QList<T> sliced(qsizetype pos, qsizetype n) const
    {
        Q_ASSERT(size_t(pos) <= size_t(size()));
        Q_ASSERT(n >= 0);
        Q_ASSERT(pos + n <= size());
        return QList<T>(begin() + pos, begin() + pos + n);
    }

    T value(qsizetype i) const { return value(i, T()); }
    T value(qsizetype i, parameter_type defaultValue) const;

    void swapItemsAt(qsizetype i, qsizetype j) {
        Q_ASSERT_X(i >= 0 && i < size() && j >= 0 && j < size(),
                    "QList<T>::swap", "index out of range");
        detach();
        qSwap(d->begin()[i], d->begin()[j]);
    }

    // STL compatibility
    inline void push_back(parameter_type t) { append(t); }
    void push_back(rvalue_ref t) { append(std::move(t)); }
    void push_front(rvalue_ref t) { prepend(std::move(t)); }
    inline void push_front(parameter_type t) { prepend(t); }
    void pop_back() noexcept { removeLast(); }
    void pop_front() noexcept { removeFirst(); }

    template <typename ...Args>
    reference emplace_back(Args&&... args) { return emplaceBack(std::forward<Args>(args)...); }

    inline bool empty() const noexcept
    { return d->size == 0; }
    inline reference front() { return first(); }
    inline const_reference front() const noexcept { return first(); }
    inline reference back() { return last(); }
    inline const_reference back() const noexcept { return last(); }
    void shrink_to_fit() { squeeze(); }

    // comfort
    QList<T> &operator+=(const QList<T> &l) { append(l); return *this; }
    QList<T> &operator+=(QList<T> &&l) { append(std::move(l)); return *this; }
    inline QList<T> operator+(const QList<T> &l) const &
    { QList n = *this; n += l; return n; }
    QList<T> operator+(const QList<T> &l) &&
    { return std::move(*this += l); }
    inline QList<T> operator+(QList<T> &&l) const &
    { QList n = *this; n += std::move(l); return n; }
    QList<T> operator+(QList<T> &&l) &&
    { return std::move(*this += std::move(l)); }
    inline QList<T> &operator+=(parameter_type t)
    { append(t); return *this; }
    inline QList<T> &operator<< (parameter_type t)
    { append(t); return *this; }
    inline QList<T> &operator<<(const QList<T> &l)
    { *this += l; return *this; }
    inline QList<T> &operator<<(QList<T> &&l)
    { *this += std::move(l); return *this; }
    inline QList<T> &operator+=(rvalue_ref t)
    { append(std::move(t)); return *this; }
    inline QList<T> &operator<<(rvalue_ref t)
    { append(std::move(t)); return *this; }

    // Consider deprecating in 6.4 or later
    static QList<T> fromList(const QList<T> &list) noexcept { return list; }
    QList<T> toList() const noexcept { return *this; }

    static inline QList<T> fromVector(const QList<T> &vector) noexcept { return vector; }
    inline QList<T> toVector() const noexcept { return *this; }

    template<qsizetype N>
    static QList<T> fromReadOnlyData(const T (&t)[N]) noexcept
    {
        return QList<T>({ nullptr, const_cast<T *>(t), N });
    }
};

template <typename InputIterator,
          typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
          QtPrivate::IfIsInputIterator<InputIterator> = true>
QList(InputIterator, InputIterator) -> QList<ValueType>;

template <typename T>
inline void QList<T>::resize_internal(qsizetype newSize)
{
    Q_ASSERT(newSize >= 0);

    if (d->needsDetach() || newSize > capacity() - d.freeSpaceAtBegin()) {
        d.detachAndGrow(QArrayData::GrowsAtEnd, newSize - d.size, nullptr, nullptr);
    } else if (newSize < size()) {
        d->truncate(newSize);
    }
}

template <typename T>
void QList<T>::reserve(qsizetype asize)
{
    // capacity() == 0 for immutable data, so this will force a detaching below
    if (asize <= capacity() - d.freeSpaceAtBegin()) {
        if (d->flags() & Data::CapacityReserved)
            return;  // already reserved, don't shrink
        if (!d->isShared()) {
            // accept current allocation, don't shrink
            d->setFlag(Data::CapacityReserved);
            return;
        }
    }

    DataPointer detached(Data::allocate(qMax(asize, size())));
    detached->copyAppend(d->begin(), d->end());
    if (detached.d_ptr())
        detached->setFlag(Data::CapacityReserved);
    d.swap(detached);
}

template <typename T>
inline void QList<T>::squeeze()
{
    if (!d.isMutable())
        return;
    if (d->needsDetach() || size() < capacity()) {
        // must allocate memory
        DataPointer detached(Data::allocate(size()));
        if (size()) {
            if (d.needsDetach())
                detached->copyAppend(d.data(), d.data() + d.size);
            else
                detached->moveAppend(d.data(), d.data() + d.size);
        }
        d.swap(detached);
    }
    // We're detached so this is fine
    d->clearFlag(Data::CapacityReserved);
}

template <typename T>
inline void QList<T>::remove(qsizetype i, qsizetype n)
{
    Q_ASSERT_X(size_t(i) + size_t(n) <= size_t(d->size), "QList::remove", "index out of range");
    Q_ASSERT_X(n >= 0, "QList::remove", "invalid count");

    if (n == 0)
        return;

    d.detach();
    d->erase(d->begin() + i, n);
}

template <typename T>
inline void QList<T>::removeFirst() noexcept
{
    Q_ASSERT(!isEmpty());
    d.detach();
    d->eraseFirst();
}

template <typename T>
inline void QList<T>::removeLast() noexcept
{
    Q_ASSERT(!isEmpty());
    d.detach();
    d->eraseLast();
}


template<typename T>
inline T QList<T>::value(qsizetype i, parameter_type defaultValue) const
{
    return size_t(i) < size_t(d->size) ? at(i) : defaultValue;
}

template <typename T>
inline void QList<T>::append(const_iterator i1, const_iterator i2)
{
    d->growAppend(i1.i, i2.i);
}

template <typename T>
inline void QList<T>::append(QList<T> &&other)
{
    Q_ASSERT(&other != this);
    if (other.isEmpty())
        return;
    if (other.d->needsDetach() || !std::is_nothrow_move_constructible_v<T>)
        return append(other);

    // due to precondition &other != this, we can unconditionally modify 'this'
    d.detachAndGrow(QArrayData::GrowsAtEnd, other.size(), nullptr, nullptr);
    Q_ASSERT(d.freeSpaceAtEnd() >= other.size());
    d->moveAppend(other.d->begin(), other.d->end());
}

template<typename T>
template<typename... Args>
inline typename QList<T>::reference QList<T>::emplaceFront(Args &&... args)
{
    d->emplace(0, std::forward<Args>(args)...);
    return *d.begin();
}


template <typename T>
inline typename QList<T>::iterator
QList<T>::insert(qsizetype i, qsizetype n, parameter_type t)
{
    Q_ASSERT_X(size_t(i) <= size_t(d->size), "QList<T>::insert", "index out of range");
    Q_ASSERT_X(n >= 0, "QList::insert", "invalid count");
    if (Q_LIKELY(n))
        d->insert(i, n, t);
    return begin() + i;
}

template <typename T>
template <typename ...Args>
typename QList<T>::iterator
QList<T>::emplace(qsizetype i, Args&&... args)
{
    Q_ASSERT_X(i >= 0 && i <= d->size, "QList<T>::insert", "index out of range");
    d->emplace(i, std::forward<Args>(args)...);
    return begin() + i;
}

template<typename T>
template<typename... Args>
inline typename QList<T>::reference QList<T>::emplaceBack(Args &&... args)
{
    d->emplace(d->size, std::forward<Args>(args)...);
    return *(end() - 1);
}

template <typename T>
typename QList<T>::iterator QList<T>::erase(const_iterator abegin, const_iterator aend)
{
    Q_ASSERT_X(isValidIterator(abegin), "QList::erase", "The specified iterator argument 'abegin' is invalid");
    Q_ASSERT_X(isValidIterator(aend), "QList::erase", "The specified iterator argument 'aend' is invalid");
    Q_ASSERT(aend >= abegin);

    qsizetype i = std::distance(constBegin(), abegin);
    qsizetype n = std::distance(abegin, aend);
    remove(i, n);

    return begin() + i;
}

template <typename T>
inline QList<T> &QList<T>::fill(parameter_type t, qsizetype newSize)
{
    if (newSize == -1)
        newSize = size();
    if (d->needsDetach() || newSize > capacity()) {
        // must allocate memory
        DataPointer detached(Data::allocate(d->detachCapacity(newSize)));
        detached->copyAppend(newSize, t);
        d.swap(detached);
    } else {
        // we're detached
        const T copy(t);
        d->assign(d.begin(), d.begin() + qMin(size(), newSize), t);
        if (newSize > size()) {
            d->copyAppend(newSize - size(), copy);
        } else if (newSize < size()) {
            d->truncate(newSize);
        }
    }
    return *this;
}

namespace QtPrivate {
template <typename T, typename U>
qsizetype indexOf(const QList<T> &vector, const U &u, qsizetype from) noexcept
{
    if (from < 0)
        from = qMax(from + vector.size(), qsizetype(0));
    if (from < vector.size()) {
        auto n = vector.begin() + from - 1;
        auto e = vector.end();
        while (++n != e)
            if (*n == u)
                return qsizetype(n - vector.begin());
    }
    return -1;
}

template <typename T, typename U>
qsizetype lastIndexOf(const QList<T> &vector, const U &u, qsizetype from) noexcept
{
    if (from < 0)
        from += vector.d->size;
    else if (from >= vector.size())
        from = vector.size() - 1;
    if (from >= 0) {
        auto b = vector.begin();
        auto n = vector.begin() + from + 1;
        while (n != b) {
            if (*--n == u)
                return qsizetype(n - b);
        }
    }
    return -1;
}
}

template <typename T>
template <typename AT>
qsizetype QListSpecialMethodsBase<T>::indexOf(const AT &t, qsizetype from) const noexcept
{
    return QtPrivate::indexOf(*self(), t, from);
}

template <typename T>
template <typename AT>
qsizetype QListSpecialMethodsBase<T>::lastIndexOf(const AT &t, qsizetype from) const noexcept
{
    return QtPrivate::lastIndexOf(*self(), t, from);
}

template <typename T>
inline QList<T> QList<T>::mid(qsizetype pos, qsizetype len) const
{
    qsizetype p = pos;
    qsizetype l = len;
    using namespace QtPrivate;
    switch (QContainerImplHelper::mid(d.size, &p, &l)) {
    case QContainerImplHelper::Null:
    case QContainerImplHelper::Empty:
        return QList();
    case QContainerImplHelper::Full:
        return *this;
    case QContainerImplHelper::Subset:
        break;
    }

    // Allocate memory
    DataPointer copied(Data::allocate(l));
    copied->copyAppend(data() + p, data() + p + l);
    return copied;
}

Q_DECLARE_SEQUENTIAL_ITERATOR(List)
Q_DECLARE_MUTABLE_SEQUENTIAL_ITERATOR(List)

template <typename T>
size_t qHash(const QList<T> &key, size_t seed = 0)
    noexcept(noexcept(qHashRange(key.cbegin(), key.cend(), seed)))
{
    return qHashRange(key.cbegin(), key.cend(), seed);
}

template <typename T, typename AT>
qsizetype erase(QList<T> &list, const AT &t)
{
    return QtPrivate::sequential_erase(list, t);
}

template <typename T, typename Predicate>
qsizetype erase_if(QList<T> &list, Predicate pred)
{
    return QtPrivate::sequential_erase_if(list, pred);
}

// ### Qt 7 char32_t
QList<uint> QStringView::toUcs4() const { return QtPrivate::convertToUcs4(*this); }

QT_END_NAMESPACE

#include <QtCore/qbytearraylist.h>
#include <QtCore/qstringlist.h>

#endif // QLIST_H
