// ----------------------------------------------------------------------------
// -                        Open3D: www.open3d.org                            -
// ----------------------------------------------------------------------------
// The MIT License (MIT)
//
// Copyright (c) 2018 www.open3d.org
//
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#pragma once

#include <Eigen/Core>
#include <memory>
#include <vector>

#include "Open3D/Geometry/Geometry.h"
#include "Open3D/Geometry/KDTreeSearchParam.h"
#include "Open3D/Registration/Feature.h"

namespace flann {
template <typename T>
class Matrix;
template <typename T>
struct L2;
template <typename T>
class Index;
}  // namespace flann

namespace open3d {
namespace geometry {

/// \class KDTreeFlann
///
/// \brief KDTree with FLANN for nearest neighbor search.
class KDTreeFlann {
public:
    /// \brief Default Constructor.
    KDTreeFlann();
    /// \brief Parameterized Constructor.
    ///
    /// \param data Provides set of data points for KDTree construction.
    KDTreeFlann(const Eigen::MatrixXd &data);
    /// \brief Parameterized Constructor.
    ///
    /// \param geometry Provides geometry from which KDTree is constructed.
    KDTreeFlann(const Geometry &geometry);
    /// \brief Parameterized Constructor.
    ///
    /// \param feature Provides a set of features from which the KDTree is
    /// constructed.
    KDTreeFlann(const registration::Feature &feature);
    ~KDTreeFlann();
    KDTreeFlann(const KDTreeFlann &) = delete;
    KDTreeFlann &operator=(const KDTreeFlann &) = delete;

public:
    /// Sets the data for the KDTree from a matrix.
    ///
    /// \param data Data points for KDTree Construction.
    bool SetMatrixData(const Eigen::MatrixXd &data);
    /// Sets the data for the KDTree from geometry.
    ///
    /// \param geometry Geometry for KDTree Construction.
    bool SetGeometry(const Geometry &geometry);
    /// Sets the data for the KDTree from the feature data.
    ///
    /// \param feature Set of features for KDTree construction.
    bool SetFeature(const registration::Feature &feature);

    template <typename T>
    int Search(const T &query,
               const KDTreeSearchParam &param,
               std::vector<int> &indices,
               std::vector<double> &distance2) const;

    template <typename T>
    int SearchKNN(const T &query,
                  int knn,
                  std::vector<int> &indices,
                  std::vector<double> &distance2) const;

    template <typename T>
    int SearchRadius(const T &query,
                     double radius,
                     std::vector<int> &indices,
                     std::vector<double> &distance2) const;

    template <typename T>
    int SearchHybrid(const T &query,
                     double radius,
                     int max_nn,
                     std::vector<int> &indices,
                     std::vector<double> &distance2) const;

private:
    /// \brief Sets the KDTree data from the data provided by the other methods.
    ///
    /// Internal method that sets all the members of KDTree by data provided by
    /// features, geometry, etc.
    bool SetRawData(const Eigen::Map<const Eigen::MatrixXd> &data);

protected:
    std::vector<double> data_;
    std::unique_ptr<flann::Matrix<double>> flann_dataset_;
    std::unique_ptr<flann::Index<flann::L2<double>>> flann_index_;
    size_t dimension_ = 0;
    size_t dataset_size_ = 0;
};

}  // namespace geometry
}  // namespace open3d