#pragma once

#include <memory>
#include <type_traits>
#include "Test.hpp"

namespace smart_pointer {
class exception : std::exception {
    using base_class = std::exception;
    using base_class::base_class;
};

template<typename T, typename Allocator>
class SmartPointer {
    ENABLE_CLASS_TESTS;

 public:
    using value_type = T;

    SmartPointer(value_type *value = nullptr) {
        if (value != nullptr)
            core = new Core(value);
        else
            core = nullptr;
    }

    // copy constructor
    SmartPointer(const SmartPointer &rhs) {
        core = rhs.core;

        if (core != nullptr)
            core->Increment();
    }

    // move constructor
    SmartPointer(SmartPointer &&rhs) {
        core = rhs.core;
        rhs.core = nullptr;
    }

    // copy assigment
    SmartPointer &operator=(const SmartPointer &rhs) {
        SmartPointer &lhs = *this;
        lhs.core = rhs.core;

        if (lhs.core != nullptr)
            lhs.core->Increment();

        return *this;
    }

    // move assigment
    SmartPointer &operator=(SmartPointer &&rhs) {
        SmartPointer &lhs = *this;
        lhs.core = rhs.core;
        rhs.core = nullptr;

        return *this;
    }

    //
    SmartPointer &operator=(value_type *rhs) {
        SmartPointer &lhs = *this;

        if (lhs.core != nullptr)
            lhs.core->Decrement();

        lhs = SmartPointer(rhs);

        return *this;
    }

    ~SmartPointer() {
        if (core != nullptr) {
            core->Decrement();

            if (core->CountOwners() == 0)
                delete core;
        }
    }

    // return reference to the object of class/type T
    // if SmartPointer contains nullptr throw `SmartPointer::exception`
    value_type &operator*() {
        if (!*this)
            throw smart_pointer::exception();

        return *(core->Value());
    }

    const value_type &operator*() const {
        if (!*this)
            throw smart_pointer::exception();

        return *(core->Value());
    }

    // return pointer to the object of class/type T
    value_type *operator->() const {
        if (*this)
            return core->Value();

        return nullptr;
    }

    value_type *get() const {
        if (*this)
            return core->Value();

        return nullptr;
    }

    // if pointer == nullptr => return false
    operator bool() const {
        return core != nullptr;
    }

    // if pointers points to the same address or both null => true
    template<typename U, typename AnotherAllocator>
    bool operator==(const SmartPointer<U, AnotherAllocator> &rhs) const {
        const SmartPointer &lhs = *this;

        if (!lhs && !rhs)
            return true;

        if (!std::is_same<T, U>::value)
            return false;

        return reinterpret_cast<U *>(lhs.get()) == rhs.get();
    }

    // if pointers points to the same address or both null => false
    template<typename U, typename AnotherAllocator>
    bool operator!=(const SmartPointer<U, AnotherAllocator> &rhs) const {
        const SmartPointer &lhs = *this;

        if (!lhs && !rhs)
            return false;

        if (!std::is_same<T, U>::value)
            return true;

        return reinterpret_cast<U *>(lhs.get()) != rhs.get();
    }

    // if smart pointer contains non-nullptr => return count owners
    // if smart pointer contains nullptr => return 0
    std::size_t count_owners() const {
        if (core != nullptr)
            return core->CountOwners();

        return 0;
    }

 private:
    class Core {
    public:
        explicit Core(value_type *value) : value_(value) {
            Increment();
        }

        value_type *Value() {
            return value_;
        }

        value_type *Value() const {
            return value_;
        }

        void Increment() {
            count_owners_++;
        }

        void Decrement() {
            count_owners_--;
        }

        std::size_t CountOwners() const {
            return count_owners_;
        }

    private:
        value_type *value_;
        std::size_t count_owners_ = 0;
    };

    Core *core;
};
}