/* +------------------------------------------------------------------------+
   |                     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/CMatrixFixed.h>
#include <mrpt/poses/CPosePDF.h>

namespace mrpt::poses
{
class CPose3DPDF;
class CPoint2DPDFGaussian;

/** Declares a class that represents a Probability Density  function (PDF) of a
 * 2D pose \f$ p(\mathbf{x}) = [x ~ y ~ \phi ]^t \f$.
 *
 *   This class implements that PDF using a mono-modal Gaussian distribution.
 * See mrpt::poses::CPosePDF for more details.
 *
 * \sa CPose2D, CPosePDF, CPosePDFParticles
 * \ingroup poses_pdf_grp
 */
class CPosePDFGaussian : public CPosePDF
{
	DEFINE_SERIALIZABLE(CPosePDFGaussian, mrpt::poses)
	DEFINE_SCHEMA_SERIALIZABLE()

   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 */
	CPose2D mean;
	/** The 3x3 covariance matrix */
	mrpt::math::CMatrixDouble33 cov;

	/** @} */

	inline const CPose2D& getPoseMean() const { return mean; }
	inline CPose2D& getPoseMean() { return mean; }
	/** Default constructor
	 */
	CPosePDFGaussian();

	/** Constructor
	 */
	explicit CPosePDFGaussian(const CPose2D& init_Mean);

	/** Constructor
	 */
	CPosePDFGaussian(
		const CPose2D& init_Mean, const mrpt::math::CMatrixDouble33& init_Cov);

	/** Copy constructor, including transformations between other PDFs */
	explicit CPosePDFGaussian(const CPosePDF& o) { copyFrom(o); }
	/** Copy constructor, including transformations between other PDFs */
	explicit CPosePDFGaussian(const CPose3DPDF& o) { copyFrom(o); }

	void getMean(CPose2D& mean_pose) const override { mean_pose = mean; }

	std::tuple<cov_mat_t, type_value> getCovarianceAndMean() const override
	{
		return {cov, mean};
	}

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

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

	/** Save PDF's particles to a text file, containing the 2D 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;

	/** 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 CPose2D& newReferenceBase);

	/** Rotate the covariance matrix by replacing it by \f$
	 * \mathbf{R}~\mathbf{COV}~\mathbf{R}^t \f$, where \f$ \mathbf{R} = \left[
	 * \begin{array}{ccc} \cos\alpha & -\sin\alpha & 0 \\ \sin\alpha &
	 * \cos\alpha & 0 \\ 0 & 0 & 1 \end{array}\right] \f$.
	 */
	void rotateCov(const double ang);

	/** Set \f$ this = x1 \ominus x0 \f$ , computing the mean using the "-"
	 * operator and the covariances through the corresponding Jacobians (For
	 * 'x0' and 'x1' being independent variables!). */
	void inverseComposition(
		const CPosePDFGaussian& x, const CPosePDFGaussian& ref);

	/** Set \f$ this = x1 \ominus x0 \f$ , computing the mean using the "-"
	 * operator and the covariances through the corresponding Jacobians (Given
	 * the 3x3 cross-covariance matrix of variables x0 and x1). */
	void inverseComposition(
		const CPosePDFGaussian& x1, const CPosePDFGaussian& x0,
		const mrpt::math::CMatrixDouble33& COV_01);

	/** Draws a single sample from the distribution
	 */
	void drawSingleSample(CPose2D& outPart) const override;

	/** Draws a number of samples from the distribution, and saves as a list of
	 * 1x3 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 CPosePDF& p1, const CPosePDF& p2,
		const double minMahalanobisDistToDrop = 0) override;

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

	/** Makes: thisPDF = thisPDF + Ap, where "+" is pose composition (both the
	 * mean, and the covariance matrix are updated). */
	void operator+=(const CPose2D& Ap);

	/** Evaluates the PDF at a given point. */
	double evaluatePDF(const CPose2D& x) const;

	/** Evaluates the ratio PDF(x) / PDF(MEAN), that is, the normalized PDF in
	 * the range [0,1]. */
	double evaluateNormalizedPDF(const CPose2D& x) const;

	/** Computes the Mahalanobis distance between the centers of two Gaussians.
	 */
	double mahalanobisDistanceTo(const CPosePDFGaussian& theOther);

	/** Substitutes the diagonal elements if (square) they are below some given
	 * minimum values (Use this before bayesianFusion, for example, to avoid
	 * inversion of singular matrixes, etc...)  */
	void assureMinCovariance(double minStdXY, double minStdPhi);

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

	/** Makes: thisPDF = thisPDF - Ap, where "-" is pose inverse composition
	 * (both the mean, and the covariance matrix are updated) */
	inline void operator-=(const CPosePDFGaussian& ref)
	{
		this->inverseComposition(*this, ref);
	}

	/** Returns the PDF of the 2D point \f$ g = q \oplus l\f$ with "q"=this pose
	 * and "l" a point without uncertainty */
	void composePoint(
		const mrpt::math::TPoint2D& l, CPoint2DPDFGaussian& g) const;

};	// End of class def.

/** Pose compose operator: RES = A (+) B , computing both the mean and the
 * covariance */
CPosePDFGaussian operator+(
	const CPosePDFGaussian& a, const CPosePDFGaussian& b);

/** Pose inverse compose operator: RES = A (-) B , computing both the mean and
 * the covariance */
CPosePDFGaussian operator-(
	const CPosePDFGaussian& a, const CPosePDFGaussian& b);

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

/** Returns the Gaussian distribution of \f$ \mathbf{C} \f$, for \f$ \mathbf{C}
 * = \mathbf{A} \oplus \mathbf{B} \f$. */
poses::CPosePDFGaussian operator+(
	const mrpt::poses::CPose2D& A, const mrpt::poses::CPosePDFGaussian& B);

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

}  // namespace mrpt::poses
