/* +------------------------------------------------------------------------+
   |                     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/math/CMatrixD.h>
#include <mrpt/poses/CPose3D.h>
#include <mrpt/poses/CPose3DPDF.h>
#include <mrpt/poses/CPosePDF.h>

namespace mrpt::poses
{
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$ as a
 * Gaussian described by its mean and its inverse covariance matrix.
 *
 *   This class implements that PDF using a mono-modal Gaussian distribution in
 * "information" form (inverse covariance matrix).
 *
 *  Uncertainty of pose composition operations (\f$ y = x \oplus u \f$) is
 * implemented in the method "CPose3DPDFGaussianInf::operator+=".
 *
 * \note Read also: "A tutorial on SE(3) transformation parameterizations and
 * on-manifold optimization", in \cite blanco_se3_tutorial
 *
 * \sa CPose3D, CPose3DPDF, CPose3DPDFParticles, CPose3DPDFGaussian
 * \ingroup poses_pdf_grp
 */
class CPose3DPDFGaussianInf : public CPose3DPDF
{
	// This must be added to any CSerializable derived class:
	DEFINE_SERIALIZABLE(CPose3DPDFGaussianInf, mrpt::poses)
	using self_t = CPose3DPDFGaussianInf;

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

   public:
	/** @name Data fields
		@{   */

	/** The mean value */
	CPose3D mean;
	/** The inverse of the 6x6 covariance matrix */
	mrpt::math::CMatrixDouble66 cov_inv;

	/** @} */

	inline const CPose3D& getPoseMean() const { return mean; }
	inline CPose3D& getPoseMean() { return mean; }
	/** Default constructor - mean: all zeros, inverse covariance=all zeros ->
	 * so be careful! */
	CPose3DPDFGaussianInf();

	/** Constructor with a mean value, inverse covariance=all zeros -> so be
	 * careful! */
	explicit CPose3DPDFGaussianInf(const CPose3D& init_Mean);

	/** Uninitialized constructor: leave all fields uninitialized - Call with
	 * UNINITIALIZED_POSE as argument */
	CPose3DPDFGaussianInf(TConstructorFlags_Poses constructor_dummy_param);

	/** Constructor with mean and inv cov. */
	CPose3DPDFGaussianInf(
		const CPose3D& init_Mean,
		const mrpt::math::CMatrixDouble66& init_CovInv);

	/** Constructor from a 6D pose PDF described as a Quaternion */
	explicit CPose3DPDFGaussianInf(const CPose3DQuatPDFGaussian& o);

	void getMean(CPose3D& mean_pose) const override { mean_pose = mean; }

	bool isInfType() const override { return true; }

	std::tuple<cov_mat_t, type_value> getCovarianceAndMean() const override
	{
		return {cov_inv.inverse_LLt(), this->mean};
	}

	/** Returns the information (inverse covariance) matrix (a STATE_LEN x
	 * STATE_LEN matrix) \sa getMean, getCovarianceAndMean */
	void getInformationMatrix(mrpt::math::CMatrixDouble66& inf) const override
	{
		inf = cov_inv;
	}

	/** 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 CPose3DPDFGaussianInf operator-() const
	{
		CPose3DPDFGaussianInf 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 CPose3DPDFGaussianInf& Ap);
	/** Makes: thisPDF = thisPDF - Ap, where "-" is pose inverse composition
	 * (both the mean, and the covariance matrix are updated) */
	void operator-=(const CPose3DPDFGaussianInf& 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;
	/** Returns a 3x3 matrix with submatrix of the inverse covariance for the
	 * variables (x,y,yaw) only */
	void getInvCovSubmatrix2D(mrpt::math::CMatrixDouble& out_cov) 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 CPose3DPDFGaussianInf& theOther);

};	// End of class def.
bool operator==(
	const CPose3DPDFGaussianInf& p1, const CPose3DPDFGaussianInf& p2);
/** Pose composition for two 3D pose Gaussians  \sa CPose3DPDFGaussian::operator
 * +=  */
CPose3DPDFGaussianInf operator+(
	const CPose3DPDFGaussianInf& x, const CPose3DPDFGaussianInf& u);
/** Pose composition for two 3D pose Gaussians  \sa
 * CPose3DPDFGaussianInf::operator -=  */
CPose3DPDFGaussianInf operator-(
	const CPose3DPDFGaussianInf& x, const CPose3DPDFGaussianInf& u);
/** Dumps the mean and covariance matrix to a text stream. */
std::ostream& operator<<(std::ostream& out, const CPose3DPDFGaussianInf& obj);

}  // namespace mrpt::poses
