#pragma once

#include <string>
#include <shared_mutex>
#include <fstream>
#include "../../../core/world/forward.h"
#include "../../../core/world/Voxel.hpp"
#include "../../../core/data/mem.hpp"
#include "../../../core/utils/zctx.hpp"
#include "../../../core/data/math.hpp"

namespace world::server {
    ///Group of chunks saved as a single file only pointer
    class FileRegion {
    public:
        FileRegion(const std::string& folderPath, const area_<region_pos> &pos);
        ~FileRegion();

        template<typename D>
        void averages(D &out) {
            std::shared_lock lock(mutex);
            out.resize(index.size() * (sizeof(region_chunk_pos) + sizeof(Voxel)));
            data::in_view in((uint8_t*)out.data(), out.size());
            for(const auto& r: index) {
                if (r.second.average.has_value()) {
                    in.write((const uint8_t*)&r.first, sizeof(r.first));
                    in.write((const uint8_t*)&r.second.average.value(), sizeof(r.second.average.value()));
                }
            }
            out.resize(in.cur);
        }
        bool read(const region_chunk_pos &pos, const zstd::read_ctx& ctx, std::vector<char> &out);
        void write(const region_chunk_pos &pos, const zstd::write_ctx& ctx, const std::string_view &in, const std::optional<Voxel>& average);

    private:
        struct to_save {
            region_chunk_pos pos;
            std::unique_ptr<std::vector<char>> data;
            std::optional<Voxel> average;
        };
        void save(std::optional<to_save> added);

        std::string path;
        //TODO: use tickets to remove unused regions

        enum Flags: unsigned char {
            ZERO = 0,
            HAS_AVERAGE = 1 << 0,
            EMPTY = 1 << 1
        };

        std::shared_mutex mutex;
        std::ifstream file;
        struct node {
            node(const std::optional<Voxel>& a, ushort s, std::streampos o):
                average(a), size(s), offset(o) { }
            std::optional<Voxel> average;
            ushort size;
            std::streampos offset;
        };
        robin_hood::unordered_map<region_chunk_pos, node> index;

        void load();
    };
}