#pragma once

#include "../stl_alias.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; }

    // f(group_index, element_index_in_group, elemenet)
    template <typename F>
    inline void foreach (F&& f) const
    {
        for (uint32_t group_idx = 0; group_idx < size(); ++group_idx) {
            for (uint32_t elem_idx = 0; elem_idx < start_indices[group_idx + 1] - start_indices[group_idx]; ++elem_idx) {
                f(group_idx, elem_idx, index_group[start_indices[group_idx] + elem_idx]);
            }
        }
    }

    // f(group_index, group_start_index, group_end_index)
    template <typename F>
    inline void group_foreach(F&& f) const
    {
        for (uint32_t group_idx = 0; group_idx < size(); ++group_idx) {
            f(group_idx, start_indices[group_idx], start_indices[group_idx + 1]);
        }
    }

    // f(element_index_in_group, element)
    template <typename F>
    inline void loop_on_group(uint32_t group_idx, F&& f) const
    {
        for (uint32_t elem_idx = 0; elem_idx < start_indices[group_idx + 1] - start_indices[group_idx]; ++elem_idx) {
            f(elem_idx, index_group[start_indices[group_idx] + elem_idx]);
        }
    }
};