#include <iostream>
#include <regex>
#include <sstream>
#include <filesystem>
#include <fstream>

using namespace std;

template<typename T>
class SinglyLinkedList
{
    public:
        SinglyLinkedList();
        SinglyLinkedList(const SinglyLinkedList& other);
        ~SinglyLinkedList();
        void push_back(T data);
        void push_front(T data);
        void pop_front();
        void clear();
        void build_empty(size_t sizeOfList);
        void insert(T data, int index);
        void removeAt(int index);
        void pop_back();
        int getSize(){ return size;}
        T operator[] (const int index);
    private:
        template<typename T>
        class Node
        {
        public:
            Node *pNext;
            T data;
            Node(T data = T(), Node *pNext = nullptr)
            {
                this->data = data;
                this->pNext = pNext;
            }
        };
        Node<T> *head;
        size_t size;
};

template<typename T>
SinglyLinkedList<T>::SinglyLinkedList()
{
    size = 0;
    head = nullptr;
}

template<typename T>
SinglyLinkedList<T>::SinglyLinkedList(const SinglyLinkedList& other) : SinglyLinkedList()
{
    Node<T> *current = other.head;
    while (current != nullptr)
    {
        push_back(current->data);
        current = current->pNext;
    }
}

//template<typename T>
//SinglyLinkedList<T>::SinglyLinkedList(const SinglyLinkedList& other) : SinglyLinkedList() {
//  for (auto current = other.head; current != nullptr; current = current->pNext) {
//      push_back(current->data);
//  }
//}

template<typename T>
SinglyLinkedList<T>::~SinglyLinkedList()
{
    clear();
}

template<typename T>
void SinglyLinkedList<T>::push_back(T data)
{
    if (head == nullptr)
    {
        head = new Node<T>(data);
    }
    else
    {
        Node<T> *current = this->head;
        while (current->pNext != nullptr)
        {
            current = current->pNext;
        }
        current->pNext = new Node<T>(data);
    }
    size++;
}

template<typename T>
void SinglyLinkedList<T>::pop_front()
{
    Node<T> *temp = head;
    head = head->pNext;
    delete temp;
    size--;
}

template<typename T>
T SinglyLinkedList<T>::operator[](const int index)
{
    size_t counter = 0;
    Node<T> *current = this->head;
    while (current != nullptr)
    {
        if (counter == index)
        {
            return current->data;
        }
        ++counter;
        current = current->pNext;
    }
}

template<typename T>
void SinglyLinkedList<T>::clear()
{
    while (size)
    {
        pop_front();
    }
}

template<typename T>
void SinglyLinkedList<T>::build_empty(size_t sizeOfList)
{
    for (size_t i = 0; i < sizeOfList; ++i)
    {
        push_back(T());
    }
}

template<typename T>
void SinglyLinkedList<T>::push_front(T data)
{
    head = new Node<T>(data, head);
    size++;
}

template<typename T>
void SinglyLinkedList<T>::insert(T data, int index)
{
    if (index == 0)
    {
        push_front(data);
    }
    else
    {
        Node<T>* previous = this->head;
        for (size_t i = 0; i < index - 1; ++i)
        {
            previous = previous->pNext;
        }
        Node<T> *newNode = new Node<T>(data, previous->pNext);
        previous->pNext = newNode;
        ++size;
    }
}

template<typename T>
void SinglyLinkedList<T>::removeAt(int index)
{
    if (index == 0)
    {
        pop_front();
    }
    else
    {
        Node<T> *previous = this->head;
        for (size_t i = 0; i < index - 1; ++i)
        {
            previous = previous->pNext;
        }
        Node<T> *temp = previous->pNext;
        previous->pNext = temp->pNext;
        delete temp;
        size--;
    }
}

template<typename T>
void SinglyLinkedList<T>::pop_back()
{
    removeAt(size - 1);
}

template<typename T>
int allEntryOfElement(T element, SinglyLinkedList<T> list)
{
    int counter = 0;
    for (size_t i = 0; i < list.getSize(); ++i)
    {
        if (element == list[i])
            counter++;
    }
    return counter;
}

bool isFileCorrect(string path)
{
    string inputline;
    regex regular("^(\\d+\\s*)+$");
    fstream fin(path, ios_base::in);
    bool isCorrect = true;
    while (!fin.eof() && isCorrect)
    {
        getline(fin, inputline);
        if (!(regex_match(inputline.c_str(), regular)))
            isCorrect = false;
    }
    fin.close();
    return isCorrect;
}

string readFilePath(bool flag)
{
    string path;
    bool isIncorrect;
    do
    {
        isIncorrect = false;
        cout << "Введите абсолютный путь к файлу: " << endl;
        cin >> path;
        if (!filesystem::exists(path))
        {
            cout << "Файл не найден. Проверьте введённый путь." << endl;
            isIncorrect = true;
        }
        else
        {
            if (flag && !isFileCorrect(path))
            {
                cout << "Ошибка при чтении файла! Проверьте данные и попробуйте ещё раз!" << endl;
                isIncorrect = true;
            }
        }

    } while (isIncorrect);
    return path;
}

template<typename T>
void getListFromFile(SinglyLinkedList<T> &list)
{
    bool flag = true;
    string path = readFilePath(flag);
    string inputline;
    cmatch res;
    regex reg("(\\d+)\\s*");
    fstream fin(path, std::ios_base::in);
    while (!fin.eof())
    {
        getline(fin, inputline);
        auto inputline_begin = sregex_iterator(inputline.begin(), inputline.end(), reg);
        auto inputline_end = sregex_iterator();
        for (auto i = inputline_begin; i != inputline_end; ++i)
        {
            list.push_back(stoi((*i).str()));
        }
    }
    fin.close();
}

int getMainMenuItem()
{
    bool isIncorrect;
    string inputLine;
    int item = 0;
    do
    {
        isIncorrect = false;
        try
        {
            cin >> inputLine;
            item = stoi(inputLine);
        }
        catch (...)
        {
            isIncorrect = true;
            cout << "Введите целое число!" << endl;
        }
        if ((item != 1) && (item != 2) && (item != 3) && !isIncorrect)
        {
            cout << "Выберете один из пунктов!\n";
            isIncorrect = true;
        }
    } while (isIncorrect);
    return item;
}

template<typename T>
void print(SinglyLinkedList<T> list)
{
    cout << "Ваш список:" << endl;
    for (size_t i = 0; i < list.getSize(); ++i)
    {
        cout << list[i] << " ";
    }
    cout << endl;
    showMenu(getMainMenuItem());
}

void showMenu(int menuItem)
{
    SinglyLinkedList<int> list;
    switch (menuItem)
    {
    case 1:
        getListFromFile(list);
        break;
    case 2:
        getListFromConsole(list);
        break;
    case 3:
        cout << "Введите размер списка\n";
        list.build_empty(readSizeOfEmptyList());
        break;
    }
    print(list);
}

int readSizeOfEmptyList()
{
    bool isIncorrect;
    string inputLine;
    int size;
    do
    {
        isIncorrect = false;
        try
        {
            cin >> inputLine;
            size = stoi(inputLine);
        }
        catch (...)
        {
            isIncorrect = true;
            cout << "Введите целое число!" << endl;
        }
        if (!isIncorrect && size < 1 && size > 2000000)
        {
            cout << "Введите положительное число до 2*10^6!\n";
            isIncorrect = true;
        }
    } while (isIncorrect);
    return size;
}

template<typename T>
void getListFromConsole(SinglyLinkedList<T>& list)
{
    //cout <<
}

void showMainMenu()
{
    int menuItem;
    cout << "Выберете один из пунктов меню :" << endl;
    cout << "1. Открыть список из файла." << endl;
    cout << "2. Создать новый список." << endl;
    cout << "3. Создать новый пустой список указанного размера." << endl;
    menuItem = getMainMenuItem();
    showMenu(menuItem);
}

int main()
{
    setlocale(LC_ALL, "ru");
    showMainMenu();
}