/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2023, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */
#pragma once

#include <mrpt/core/Stringifyable.h>
#include <mrpt/poses/CPose3D.h>
#include <mrpt/poses/CPose3DPDF.h>

namespace mrpt
{
namespace poses
{
class CPosePDF;
class CPosePDFGaussian;
class CPose3DQuatPDFGaussian;

/** Declares a class that represents a Probability Density function (PDF) of a
 * 3D pose \f$ p(\mathbf{x}) = [x ~ y ~ z ~ yaw ~ pitch ~ roll]^t \f$.
 *
 *   This class implements that PDF using a mono-modal Gaussian distribution.
 * See mrpt::poses::CPose3DPDF for more details.
 *
 *  Uncertainty of pose composition operations (\f$ y = x \oplus u \f$) is
 * implemented in the method "CPose3DPDFGaussian::operator+=".
 *
 *  For further details on implemented methods and the theory behind them,
 *  see <a
 * href="http://www.mrpt.org/6D_poses:equivalences_compositions_and_uncertainty"
 * >this report</a>.
 *
 * \sa CPose3D, CPose3DPDF, CPose3DPDFParticles
 * \ingroup poses_pdf_grp
 */
class CPose3DPDFGaussian : public CPose3DPDF, public mrpt::Stringifyable
{
	DEFINE_SERIALIZABLE(CPose3DPDFGaussian, mrpt::poses)

   protected:
	/** Assures the symmetry of the covariance matrix (eventually certain
	 * operations in the math-coprocessor lead to non-symmetric matrixes!)
	 */
	void enforceCovSymmetry();

   public:
	/** Default constructor
	 */
	CPose3DPDFGaussian();

	/** Constructor
	 */
	explicit CPose3DPDFGaussian(const CPose3D& init_Mean);

	/** Uninitialized constructor: leave all fields uninitialized - Call with
	 * UNINITIALIZED_POSE as argument
	 */
	CPose3DPDFGaussian(TConstructorFlags_Poses constructor_dummy_param);

	/** Constructor  */
	CPose3DPDFGaussian(
		const CPose3D& init_Mean, const mrpt::math::CMatrixDouble66& init_Cov);

	/** Constructor from a Gaussian 2D pose PDF (sets to 0 the missing variables
	 * z,pitch, and roll).
	 */
	explicit CPose3DPDFGaussian(const CPosePDFGaussian& o);

	/** Constructor from a 6D pose PDF described as a Quaternion
	 */
	explicit CPose3DPDFGaussian(const CPose3DQuatPDFGaussian& o);

	/** The mean value
	 */
	CPose3D mean;

	/** The 6x6 covariance matrix
	 */
	mrpt::math::CMatrixDouble66 cov;

	inline const CPose3D& getPoseMean() const { return mean; }
	inline CPose3D& getPoseMean() { return mean; }
	/** Returns an estimate of the pose, (the mean, or mathematical expectation
	 * of the PDF).
	 * \sa getCovariance
	 */
	void getMean(CPose3D& mean_pose) const override { mean_pose = mean; }
	/** Returns an estimate of the pose covariance matrix (6x6 cov matrix) and
	 * the mean, both at once.
	 * \sa getMean
	 */
	std::tuple<cov_mat_t, type_value> getCovarianceAndMean() const override
	{
		return {this->cov, this->mean};
	}

	std::string asString() const override;

	/** Copy operator, translating if necesary (for example, between particles
	 * and gaussian representations)
	 */
	void copyFrom(const CPose3DPDF& o) override;

	/** Copy operator, translating if necesary (for example, between particles
	 * and gaussian representations)
	 */
	void copyFrom(const CPosePDF& o);

	/** Copy from a 6D pose PDF described as a Quaternion
	 */
	void copyFrom(const CPose3DQuatPDFGaussian& o);

	/** Save the PDF to a text file, containing the 3D pose in the first line,
	 * then the covariance matrix in next 3 lines.
	 */
	bool saveToTextFile(const std::string& file) const override;

	/** this = p (+) this. This can be used to convert a PDF from local
	 * coordinates to global, providing the point (newReferenceBase) from which
	 *   "to project" the current pdf. Result PDF substituted the currently
	 * stored one in the object.
	 */
	void changeCoordinatesReference(const CPose3D& newReferenceBase) override;

	/** Draws a single sample from the distribution
	 */
	void drawSingleSample(CPose3D& outPart) const override;

	/** Draws a number of samples from the distribution, and saves as a list of
	 * 1x6 vectors, where each row contains a (x,y,phi) datum.
	 */
	void drawManySamples(
		size_t N,
		std::vector<mrpt::math::CVectorDouble>& outSamples) const override;

	/** Bayesian fusion of two points gauss. distributions, then save the result
	 *in this object.
	 *  The process is as follows:<br>
	 *		- (x1,S1): Mean and variance of the p1 distribution.
	 *		- (x2,S2): Mean and variance of the p2 distribution.
	 *		- (x,S): Mean and variance of the resulting distribution.
	 *
	 *    \f$ S = (S_1^{-1} + S_2^{-1})^{-1} \f$
	 *    \f$ x = S ( S_1^{-1} x_1 + S_2^{-1} x_2 ) \f$
	 */
	void bayesianFusion(const CPose3DPDF& p1, const CPose3DPDF& p2) override;

	/** Returns a new PDF such as: NEW_PDF = (0,0,0) - THIS_PDF
	 */
	void inverse(CPose3DPDF& o) const override;

	/** Unary - operator, returns the PDF of the inverse pose.  */
	inline CPose3DPDFGaussian operator-() const
	{
		CPose3DPDFGaussian p(UNINITIALIZED_POSE);
		this->inverse(p);
		return p;
	}

	/** Makes: thisPDF = thisPDF + Ap, where "+" is pose composition (both the
	 * mean, and the covariance matrix are updated).
	 */
	void operator+=(const CPose3D& Ap);

	/** Makes: thisPDF = thisPDF + Ap, where "+" is pose composition (both the
	 * mean, and the covariance matrix are updated).
	 */
	void operator+=(const CPose3DPDFGaussian& Ap);

	/** Makes: thisPDF = thisPDF - Ap, where "-" is pose inverse composition
	 * (both the mean, and the covariance matrix are updated).
	 */
	void operator-=(const CPose3DPDFGaussian& Ap);

	/** Evaluates the PDF at a given point.
	 */
	double evaluatePDF(const CPose3D& x) const;

	/** Evaluates the ratio PDF(x) / PDF(MEAN), that is, the normalized PDF in
	 * the range [0,1].
	 */
	double evaluateNormalizedPDF(const CPose3D& x) const;

	/** Computes the Mahalanobis distance between the centers of two Gaussians.
	 *  The variables with a variance exactly equal to 0 are not taken into
	 * account in the process, but
	 *   "infinity" is returned if the corresponding elements are not exactly
	 * equal.
	 */
	double mahalanobisDistanceTo(const CPose3DPDFGaussian& theOther);

	/** Returns a 3x3 matrix with submatrix of the covariance for the variables
	 * (x,y,yaw) only.
	 */
	void getCovSubmatrix2D(mrpt::math::CMatrixDouble& out_cov) const;

};	// End of class def.
/** Pose composition for two 3D pose Gaussians  \sa CPose3DPDFGaussian::operator
 * +=  */
inline CPose3DPDFGaussian operator+(
	const CPose3DPDFGaussian& x, const CPose3DPDFGaussian& u)
{
	CPose3DPDFGaussian res(x);
	res += u;
	return res;
}

/** Pose composition for two 3D pose Gaussians  \sa CPose3DPDFGaussian::operator
 * -=  */
inline CPose3DPDFGaussian operator-(
	const CPose3DPDFGaussian& x, const CPose3DPDFGaussian& u)
{
	CPose3DPDFGaussian res(x);
	res -= u;
	return res;
}

/** Dumps the mean and covariance matrix to a text stream.
 */
std::ostream& operator<<(std::ostream& out, const CPose3DPDFGaussian& obj);

bool operator==(const CPose3DPDFGaussian& p1, const CPose3DPDFGaussian& p2);

}  // namespace poses

/** Global variables to change the run-time behaviour of some MRPT classes
 * within mrpt-base.
 *  See each variable for the description of what classes it affects.
 */
namespace global_settings
{
/** If set to true (false), a Scaled Unscented Transform is used instead of a
 *linear approximation with Jacobians.
 * Affects to:
 *		- CPose3DPDFGaussian::CPose3DPDFGaussian( const CPose3DQuatPDFGaussian
 *&o)
 */
void USE_SUT_QUAT2EULER_CONVERSION(bool value);
bool USE_SUT_QUAT2EULER_CONVERSION();
}  // namespace global_settings

}  // namespace mrpt
