#pragma once

#include "container/stl_alias.hpp"
#include "iterator/counting_iterator.hpp"

struct flat_index_group {
    stl_vector_mp<uint32_t> index_group{};   /// a list of indices in the group
    stl_vector_mp<uint32_t> start_indices{}; /// a list of start indices for each group in the flat index group

    inline size_t size() const { return start_indices.size() - 1; }

    struct group_index_looper {
        auto begin() const { return counting_iterator<uint32_t>{0}; }

        auto end() const { return counting_iterator<uint32_t>{static_cast<uint32_t>(parent_group.size())}; }

        const flat_index_group& parent_group{};
    };

    auto group_indices() const { return group_index_looper{*this}; }

    struct group_looper {
        auto begin() const
        {
            return std::next(parent_group.index_group.begin(), *(parent_group.start_indices.begin() + group_idx));
        }

        auto end() const
        {
            return std::next(parent_group.index_group.begin(), *(parent_group.start_indices.begin() + group_idx + 1));
        }

        const flat_index_group& parent_group{};
        const uint32_t          group_idx{};
    };

    auto group(uint32_t group_idx) const { return group_looper{*this, group_idx}; }

    inline auto group_index_iter_begin() const { return counting_iterator<uint32_t>{0}; }

    inline auto group_index_iter_end() const { return counting_iterator<uint32_t>{static_cast<uint32_t>(size())}; }

    inline auto group_begin(uint32_t group_idx) const
    {
        return std::next(index_group.begin(), *(start_indices.begin() + group_idx));
    }

    inline auto group_end(uint32_t group_idx) const
    {
        return std::next(index_group.begin(), *(start_indices.begin() + group_idx + 1));
    }
};