#include <iostream>
#include <memory>

void changeInt(int n);
void changeIntPointer(int* pN);
void changeIntReference(int& n);

void createInt(int* pI);
void createInt(int** ppI);

int main()
{
    int i = 1;
    int* pI = nullptr;
    pI = &i;
    *pI = 10;
    std::cout << "i = " << i << std::endl;
    pI = new int;
    pI = new int(); // CAUTION - created a memory leak
    pI = new int(10); // CAUTION - created a memory leak
    delete pI;
    pI = nullptr;

    changeInt(i);
    changeIntPointer(&i);
    changeIntReference(i);

    // const
    // const int ci = 10; // integer is constant
    // const int* pCi = new int(0); // pointer to a constant integer
    // pCi = new int(0);
    // *pCi = 0;
    // int const * pic = new int(0); // pointer to a constant integer
    // pic = new int(0);
    // *pic = 0;
    // const int const * pcic = new int(0); // pointer to a constant integer
    // pcic = new int(0);
    // *pcic = 0;
    // int * const cpi = new int(0); // constant pointer to an integer
    // cpi = new int(0);
    // *cpi = 0;
    // int const * const cpic = new int(0); // constant pointer to a constant integer
    // cpic = new int(0);
    // *cpic = 0;
    // const int * const cpci = new int(0); // constant pointer to a constant integer
    // cpci = new int(0);
    // *cpci = 0;
    // const int const * const cpcic = new int(0); // constant pointer to a constant integer
    // cpcic = new int(0);
    // *cpcic = 0;

    createInt(pI);
    createInt(&pI);

    if (pI != nullptr) {
        delete pI;
        pI = nullptr;
    }

    std::unique_ptr<int> upI = std::make_unique<int>(0);
    // std::unique_ptr<int> upI2 = upI; // don't work
    std::unique_ptr<int> upI2 = std::make_unique<int>(*upI);

    std::shared_ptr<int> spI = std::make_shared<int>(0);
    std::shared_ptr<int> spI2 = spI;
    spI.reset();

    std::weak_ptr<int> wpI = spI2;
    if (wpI.expired()) {
        std::cout << "wpI is expired" << std::endl;
    }
    else {
        std::cout << "wpI is not expired" << std::endl;
        std::shared_ptr<int> spI3 = wpI.lock();
    }

    spI2.reset();

    if (wpI.expired()) {
        std::cout << "wpI is expired" << std::endl;
    }
    else {
        std::cout << "wpI is not expired" << std::endl;
    }

    return 0;
}

void changeInt(int n) {
    n *= 2;
}

void changeIntPointer(int* pN) {
    if (pN == nullptr) return;
    *pN *= 2;
}

void changeIntReference(int& n) {
    n *= 2;
}

void createInt(int* pI) {
    pI = new int(0);
}

void createInt(int** ppI) {
    if (ppI == nullptr) return;
    *ppI = new int(0);
}