#include <iostream>
#include <memory>
#include <ranges>

#include <QStandardItem>
#include <QStandardItemModel>

namespace
{
    using std::views::iota;

    constexpr int arbitraryNumberOfChildren = 3;

    constexpr auto numberOfBytesInAPointer = sizeof(std::uintptr_t);
    constexpr auto numberOfNibblesInAByte = 2;
    constexpr auto numberOfCharactersProceedingAHexadecimalNumber = 2;
    constexpr auto numberOfFormatCharactersForPointer = numberOfBytesInAPointer * numberOfNibblesInAByte + numberOfCharactersProceedingAHexadecimalNumber;

    static void PrintChildren_(auto& item)
    {
        std::cout << std::format("  {}'s children", item->text().toStdString()) << std::endl;
        for (int i : iota(0, arbitraryNumberOfChildren))
        {
            std::cout << std::format("    {:#0{}x}", reinterpret_cast<std::uintptr_t>(item->child(i)), numberOfFormatCharactersForPointer) << std::endl;
        }
    };

    static void AddChildrenToItem_(auto& item)
    {
        for ([[maybe_unused]] int i : iota(0, arbitraryNumberOfChildren))
        {
            item->appendRow(new QStandardItem());
        }
    };
}

int main()
{
    std::cout << "Code in question: secondParent's children are null" << std::endl;
    {
        auto firstParent = std::make_unique<QStandardItem>("firstParent");
        auto secondParent = std::make_unique<QStandardItem>("secondParent");

        AddChildrenToItem_(firstParent);
        PrintChildren_(firstParent);

        std::cout << "Swapping children" << std::endl;
        for (int i : iota(0, arbitraryNumberOfChildren))
        {
            secondParent->setChild(i, firstParent->takeChild(i));
        }
        PrintChildren_(secondParent);
    }
    std::cout << std::endl;

    std::cout << "Workaround 1: Ensure the firstParent has a model before taking its children" << std::endl;
    {
        auto model = std::make_unique<QStandardItemModel>();
        auto firstParent = model->invisibleRootItem();
        firstParent->setText("firstParent");
        auto secondParent = std::make_unique<QStandardItem>("secondParent");

        AddChildrenToItem_(firstParent);
        PrintChildren_(firstParent);

        std::cout << "Swapping children" << std::endl;
        for (int i : iota(0, arbitraryNumberOfChildren))
        {
            secondParent->setChild(i, firstParent->takeChild(i));
        }
        PrintChildren_(secondParent);
    }
    std::cout << std::endl;

    std::cout << "Workaround 2: Use takeColumn" << std::endl;
    {
        auto firstParent = std::make_unique<QStandardItem>("firstParent");
        auto secondParent = std::make_unique<QStandardItem>("secondParent");

        AddChildrenToItem_(firstParent);
        PrintChildren_(firstParent);

        std::cout << "Swapping children" << std::endl;
        secondParent->insertColumn(0, firstParent->takeColumn(0));
        PrintChildren_(secondParent);
    }
    std::cout << std::endl;
}