#pragma once

#include <memory>
#include <sstream>
#include "Generator.hpp"
#include "Voxel.hpp"
#include "../data/geometry/Faces.hpp"
#include "../data/math.hpp"

/// Chunk length
namespace world {
    const auto CHUNK_LENGTH2 = CHUNK_LENGTH * CHUNK_LENGTH;
    const auto CHUNK_SIZE = CHUNK_LENGTH2 * CHUNK_LENGTH;

    constexpr auto RLE = true; //NOTE: only 2.7% gain after zstd
    using namespace geometry;
    /// World part as linear 3d voxel array
    class Chunk {
    public:
        Chunk() {}
        Chunk(const chunk_pos& pos, Generator& rnd);
        Chunk(std::istream& str, bool rle = RLE);
        ~Chunk();

        /// Update voxels
        /// @return if modified neighbors to update
        std::optional<Faces> update();

        // Notify for render
        inline void invalidate(Faces faces) {
            upToDate = false;
            toUpdate = toUpdate | faces;
            modified = true;
        }
        // Get voxel from index
        inline const Voxel& get(chunk_voxel_idx idx) const {
            return voxels[idx];
        }
        // Get voxel from position
        inline const Voxel& getAt(const chunk_voxel_pos& pos) const {
            return get(glm::toIdx(pos));
        }
        // Set voxel from index
        void set(chunk_voxel_idx idx, const Voxel& val);
        // Set voxel from position
        void setAt(const chunk_voxel_pos& pos, const Voxel& val) {
            set(glm::toIdx(pos), val);
        }
        // Break voxel
        std::optional<Item> replace(chunk_voxel_idx idx, const Voxel& val) {
            const auto res = voxels[idx];
            set(idx, val);
            return {Item{res.density(), res.material()}}; //TODO: materials break table
        }
        // Is player modified
        inline bool isModified() const { return modified; }
        // Write to file.
        void write(std::ostream& str, bool rle = RLE) const;

        static std::optional<chunk_voxel_idx> getNeighborIdx(chunk_voxel_idx idx, Face dir);

    private:
        /// Chunk data
        std::array<Voxel, CHUNK_SIZE> voxels;
        /// Require update
        bool upToDate = true;
        /// Neighbors to update
        Faces toUpdate = Faces::None;
        /// Modified by player
        bool modified = false;
    };

    /// Chunk full of air
    static const std::shared_ptr<const Chunk> EMPTY_CHUNK = std::make_shared<Chunk>();
}