#include "assets/prefetch_lookups/pose_prefetch_lookup.hpp"

#include <algorithm>

 pose_prefetch_lookup::find_directory(
	const std::filesystem::path& directory
) {
	const auto dir_it = m_directory_lookup.find(directory);
	const auto dir_match = dir_it != m_directory_lookup.end();
	auto offset = index_type{};

	if (dir_match)
	{
		for (index_type i{}; i != dir_match; ++i)
		{
			offset += m_directory_indices[offset];
		}
	}

	return { std::make_pair(dir_it, offset), dir_match };
}

std::pair<pose_prefetch_lookup::index_iterator, dynamic_pose_store::id_type> pose_prefetch_lookup::find_index(
	directory_iterator directory_it,
	index_type index
) {
	const auto [ dir_it, dir_offset ] = directory_it;

	const auto index_count = m_directory_indices[dir_offset];
	const auto indices_begin = m_directory_indices.begin() + dir_offset + 1;
	const auto indices_end = indices_begin + index_count;

	const auto it = std::upper_bound(indices_begin, indices_end, index);
	const auto is_match = it != indices_begin and *std::prev(it) == index;

	auto match = dynamic_pose_store::id_type{};

	if (is_match)
	{
		const auto dir_index = dir_it->second;
		const auto id_index = it - m_directory_indices.begin() - match - dir_index;
		match = m_pose_ids[id_index];
	}

	return { it, match };
}

pose_prefetch_lookup::directory_iterator pose_prefetch_lookup::emplace_dir(
	directory_iterator directory_it,
	const std::filesystem::path& directory
) {
	auto [ dir_it, dir_offset ] = directory_it;

	dir_it = m_directory_lookup.emplace_hint(dir_it, directory, m_directory_lookup.size());
	dir_offset = m_directory_indices.size();
	m_directory_indices.push_back(1);

	return { dir_it, dir_offset };
}

void pose_prefetch_lookup::emplace(
	const std::filesystem::path& directory,
	index_type index,
	dynamic_pose_store::id_type id
) {
	auto [ directory_it, dir_match ] = find_directory(directory);

	if (not dir_match) [[unlikely]]
	{
		directory_it = emplace_dir(directory_it, directory);
	}

 	emplace_hint_dir(
		directory_it,
		index,
		id
	);
}


void pose_prefetch_lookup::emplace_hint_dir(
	directory_iterator directory_it,
	const index_type index,
	const dynamic_pose_store::id_type id
) {

	const auto [ index_it, match ] = find_index(
		directory_it,
		index
	);

	if (match) [[unlikely]]
	{
		const auto dir_index = directory_it.first->second;
		const auto id_index = index_it - m_directory_indices.begin() - dir_index;
		m_pose_ids[id_index] = match; // TODO I guess I should warn?!?
	}
	else [[likely]]
	{
		emplace_hint_dir_index(
			directory_it,
			index_it,
			index,
			id
		);
	}
}

void pose_prefetch_lookup::emplace_hint_dir_index(
	directory_iterator directory_it,
	index_iterator index_it,
	index_type index,
	const dynamic_pose_store::id_type id
) {
	const auto [ dir_it, dir_offset ] = directory_it;
	const auto dir_index = dir_it->second;

	index_it = m_directory_indices.emplace(index_it, index);
	++m_directory_indices[dir_offset];

	const auto id_index = index_it - m_directory_indices.begin() - dir_index;
	const auto id_it = m_pose_ids.begin() + id_index;

	m_pose_ids.insert(id_it, id);
}