#pragma once

#if !defined(MIJIN_UTIL_ITERATORS_HPP_INCLUDED)
#define MIJIN_UTIL_ITERATORS_HPP_INCLUDED 1

#include <cstddef>
#include <tuple>

namespace mijin
{
template<typename TIdx, typename TIterator>
struct EnumeratingIterator
{
    TIdx idx;
    TIterator base;

    EnumeratingIterator(TIdx idx_, TIterator base_) noexcept : idx(idx_), base(base_) {}
    EnumeratingIterator(const EnumeratingIterator&) noexcept = default;

    EnumeratingIterator& operator=(const EnumeratingIterator&) noexcept = default;

    auto operator*() const noexcept
    {
        return std::tie(idx, *base);
    }

    EnumeratingIterator& operator++() noexcept
    {
        ++idx;
        ++base;
        return *this;
    }

    EnumeratingIterator operator++(int) noexcept
    {
        EnumeratingIterator copy(*this);
        ++(*this);
        return copy;
    }

    EnumeratingIterator& operator--() noexcept
    {
        --idx;
        --base;
        return *this;
    }

    EnumeratingIterator operator--(int) noexcept
    {
        EnumeratingIterator copy(*this);
        --(*this);
        return copy;
    }

    bool operator==(const EnumeratingIterator& other) const noexcept
    {
        return base == other.base; // note: ignoring idx so we don't have to find it out for end()
    }

    bool operator!=(const EnumeratingIterator& other) const noexcept
    {
        return base != other.base; // note: ignoring idx so we don't have to find it out for end()
    }
};
template<typename TIdx, typename TIterator>
EnumeratingIterator(TIdx, TIterator) -> EnumeratingIterator<TIdx, TIterator>;

template<typename TIdx, typename TIterable>
struct Enumeratable
{
    TIterable& base;

    auto begin() const noexcept
    {
        return EnumeratingIterator(TIdx(0), base.begin());
    }

    auto end() const noexcept
    {
        return EnumeratingIterator(TIdx(0), base.end());
    }
};

template<typename TIdx = std::size_t, typename TIterable>
Enumeratable<TIdx, TIterable> enumerate(TIterable& iterable)
{
    return {iterable};
}
} // namespace mijin

#endif // MIJIN_UTIL_ITERATORS_HPP_INCLUDED