#ifndef libslic3r_SeamPlacer_hpp_
#define libslic3r_SeamPlacer_hpp_

#include <optional>
#include <vector>
#include <memory>
#include <atomic>

#include "libslic3r/libslic3r.h"
#include "libslic3r/ExtrusionEntity.hpp"
#include "libslic3r/Polygon.hpp"
#include "libslic3r/PrintConfig.hpp"
#include "libslic3r/BoundingBox.hpp"
#include "libslic3r/AABBTreeIndirect.hpp"
#include "libslic3r/KDTreeIndirect.hpp"

namespace Slic3r {

class PrintObject;
class ExtrusionLoop;
class Print;
class Layer;

namespace EdgeGrid {
class Grid;
}

namespace SeamPlacerImpl {

// ************  FOR BACKPORT COMPATIBILITY ONLY ***************
// Angle from v1 to v2, returning double atan2(y, x) normalized to <-PI, PI>.
template<typename Derived, typename Derived2> inline double angle(const Eigen::MatrixBase<Derived> &v1, const Eigen::MatrixBase<Derived2> &v2)
{
    static_assert(Derived::IsVectorAtCompileTime && int(Derived::SizeAtCompileTime) == 2, "angle(): first parameter is not a 2D vector");
    static_assert(Derived2::IsVectorAtCompileTime && int(Derived2::SizeAtCompileTime) == 2, "angle(): second parameter is not a 2D vector");
    auto v1d = v1.template cast<double>();
    auto v2d = v2.template cast<double>();
    return atan2(cross2(v1d, v2d), v1d.dot(v2d));
}
// ***************************

struct GlobalModelInfo;
struct SeamComparator;

enum class EnforcedBlockedSeamPoint {
    Blocked  = 0,
    Neutral  = 1,
    Enforced = 2,
};

// struct representing single perimeter loop
struct Perimeter
{
    size_t start_index{};
    size_t end_index{}; // inclusive!
    size_t seam_index{};
    float  flow_width{};

    // During alignment, a final position may be stored here. In that case, finalized is set to true.
    // Note that final seam position is not limited to points of the perimeter loop. In theory it can be any position
    // Random position also uses this flexibility to set final seam point position
    bool  finalized           = false;
    Vec3f final_seam_position = Vec3f::Zero();
};

// Struct over which all processing of perimeters is done. For each perimeter point, its respective candidate is created,
// then all the needed attributes are computed and finally, for each perimeter one point is chosen as seam.
// This seam position can be then further aligned
struct SeamCandidate
{
    SeamCandidate(const Vec3f &pos, Perimeter &perimeter, float local_ccw_angle, EnforcedBlockedSeamPoint type)
        : position(pos), perimeter(perimeter), visibility(0.0f), overhang(0.0f), embedded_distance(0.0f), local_ccw_angle(local_ccw_angle), type(type), central_enforcer(false)
    {}
    const Vec3f position;
    // pointer to Perimeter loop of this point. It is shared across all points of the loop
    Perimeter &perimeter;
    float      visibility;
    float      overhang;
    // distance inside the merged layer regions, for detecting perimeter points which are hidden indside the print (e.g. multimaterial join)
    // Negative sign means inside the print, comes from EdgeGrid structure
    float                    embedded_distance;
    float                    local_ccw_angle;
    EnforcedBlockedSeamPoint type;
    bool                     central_enforcer; // marks this candidate as central point of enforced segment on the perimeter - important for alignment
};

struct SeamCandidateCoordinateFunctor
{
    SeamCandidateCoordinateFunctor(const std::vector<SeamCandidate> &seam_candidates) : seam_candidates(seam_candidates) {}
    const std::vector<SeamCandidate> &seam_candidates;
    float                             operator()(size_t index, size_t dim) const { return seam_candidates[index].position[dim]; }
};
} // namespace SeamPlacerImpl

struct PrintObjectSeamData
{
    using SeamCandidatesTree = KDTreeIndirect<3, float, SeamPlacerImpl::SeamCandidateCoordinateFunctor>;

    struct LayerSeams
    {
        Slic3r::deque<SeamPlacerImpl::Perimeter>   perimeters;
        std::vector<SeamPlacerImpl::SeamCandidate> points;
        std::unique_ptr<SeamCandidatesTree>        points_tree;
    };
    // Map of PrintObjects (PO) -> vector of layers of PO -> vector of perimeter
    std::vector<LayerSeams> layers;
    // Map of PrintObjects (PO) -> vector of layers of PO -> unique_ptr to KD
    // tree of all points of the given layer

    void clear() { layers.clear(); }
};

class SeamPlacer
{
public:
    // Number of samples generated on the mesh. There are sqr_rays_per_sample_point*sqr_rays_per_sample_point rays casted from each samples
    static constexpr size_t raycasting_visibility_samples_count = 30000;
    static constexpr size_t fast_decimation_triangle_count_target = 16000;
    //square of number of rays per sample point
    static constexpr size_t sqr_rays_per_sample_point = 5;

    // snapping angle - angles larger than this value will be snapped to during seam painting
    static constexpr float sharp_angle_snapping_threshold = 55.0f * float(PI) / 180.0f;
    // overhang angle for seam placement that still yields good results, in degrees, measured from vertical direction
    //BBS
    static constexpr float overhang_angle_threshold = 45.0f * float(PI) / 180.0f;

    // determines angle importance compared to visibility ( neutral value is 1.0f. )
    static constexpr float angle_importance_aligned = 0.6f;
    static constexpr float angle_importance_nearest = 1.0f; // use much higher angle importance for nearest mode, to combat the visibility info noise

    // For long polygon sides, if they are close to the custom seam drawings, they are oversampled with this step size
    static constexpr float enforcer_oversampling_distance = 0.2f;

    // When searching for seam clusters for alignment:
    // following value describes, how much worse score can point have and still be picked into seam cluster instead of original seam point on the same layer
    static constexpr float seam_align_score_tolerance = 0.3f;
    // seam_align_tolerable_dist_factor - how far to search for seam from current position, final dist is seam_align_tolerable_dist_factor * flow_width
    static constexpr float seam_align_tolerable_dist_factor = 4.0f;
    // minimum number of seams needed in cluster to make alignment happen
    static constexpr size_t seam_align_minimum_string_seams = 6;
    // millimeters covered by spline; determines number of splines for the given string
    static constexpr size_t seam_align_mm_per_segment = 4.0f;

    // The following data structures hold all perimeter points for all PrintObject.
    std::unordered_map<const PrintObject *, PrintObjectSeamData> m_seam_per_object;

    void init(const Print &print, std::function<void(void)> throw_if_canceled_func);

    void place_seam(const Layer *layer, ExtrusionLoop &loop, bool external_first, const Point &last_pos) const;

private:
    void gather_seam_candidates(const PrintObject *po, const SeamPlacerImpl::GlobalModelInfo &global_model_info, const SeamPosition configured_seam_preference);
    void calculate_candidates_visibility(const PrintObject *po, const SeamPlacerImpl::GlobalModelInfo &global_model_info);
    void calculate_overhangs_and_layer_embedding(const PrintObject *po);
    void align_seam_points(const PrintObject *po, const SeamPlacerImpl::SeamComparator &comparator);
    std::vector<std::pair<size_t, size_t>> find_seam_string(const PrintObject *po, std::pair<size_t, size_t> start_seam, const SeamPlacerImpl::SeamComparator &comparator) const;
    std::optional<std::pair<size_t, size_t>> find_next_seam_in_layer(const std::vector<PrintObjectSeamData::LayerSeams> &layers,
                                                                     const Vec3f &                                       projected_position,
                                                                     const size_t                                        layer_idx,
                                                                     const float                                         max_distance,
                                                                     const SeamPlacerImpl::SeamComparator &              comparator) const;
};

} // namespace Slic3r

#endif // libslic3r_SeamPlacer_hpp_