/* +------------------------------------------------------------------------+
   |                     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          |
   +------------------------------------------------------------------------+ */

#include "vision-precomp.h"	 // Precompiled headers
//
#include <cmath>
#include <iostream>
#include <vector>

//#include <mrpt/math/types_math.h>  // Eigen must be included first via MRPT to
// enable the plugin system
#include <Eigen/Dense>
#include <Eigen/SVD>
#include <Eigen/StdVector>
#include <unsupported/Eigen/Polynomials>

#include "rpnp.h"

mrpt::vision::pnp::rpnp::rpnp(
	Eigen::MatrixXd obj_pts_, Eigen::MatrixXd img_pts_, Eigen::MatrixXd cam_,
	int n0)
{
	obj_pts = obj_pts_;
	img_pts = img_pts_;
	cam_intrinsic = cam_;
	n = n0;

	// Store obj_pts as 3XN and img_projections as 2XN matrices
	P = obj_pts.transpose();
	Q = img_pts.transpose();

	for (int i = 0; i < n; i++)
		Q.col(i) = Q.col(i) / Q.col(i).norm();

	R.setZero();
	t.setZero();
}

bool mrpt::vision::pnp::rpnp::compute_pose(
	Eigen::Ref<Eigen::Matrix3d> R_, Eigen::Ref<Eigen::Vector3d> t_)
{
	// selecting an edge $P_{ i1 }P_{ i2 }$ by n random sampling
	int i1 = 0, i2 = 1;
	double lmin =
		Q(0, i1) * Q(0, i2) + Q(1, i1) * Q(1, i2) + Q(2, i1) * Q(2, i2);

	Eigen::MatrixXi rij(n, 2);

	R_ = Eigen::MatrixXd::Identity(3, 3);
	t_ = Eigen::Vector3d::Zero();

	for (int i = 0; i < n; i++)
		for (int j = 0; j < 2; j++)
			rij(i, j) = rand() % n;

	for (int ii = 0; ii < n; ii++)
	{
		int i = rij(ii, 0), j = rij(ii, 1);

		if (i == j) continue;

		double l = Q(0, i) * Q(0, j) + Q(1, i) * Q(1, j) + Q(2, i) * Q(2, j);

		if (l < lmin)
		{
			i1 = i;
			i2 = j;
			lmin = l;
		}
	}

	// calculating the rotation matrix of $O_aX_aY_aZ_a$.
	Eigen::Vector3d p1, p2, p0, x, y, z, dum_vec;

	p1 = P.col(i1);
	p2 = P.col(i2);
	p0 = (p1 + p2) / 2;

	x = p2 - p0;
	x /= x.norm();

	if (std::abs(x(1)) < std::abs(x(2)))
	{
		dum_vec << 0, 1, 0;
		z = x.cross(dum_vec);
		z /= z.norm();
		y = z.cross(x);
		y /= y.norm();
	}
	else
	{
		dum_vec << 0, 0, 1;
		y = dum_vec.cross(x);
		y /= y.norm();
		z = x.cross(y);
		x /= x.norm();
	}

	Eigen::Matrix3d R0;

	R0.col(0) = x;
	R0.col(1) = y;
	R0.col(2) = z;

	for (int i = 0; i < n; i++)
		P.col(i) = R0.transpose() * (P.col(i) - p0);

	// Dividing the n - point set into(n - 2) 3 - point subsets
	// and setting up the P3P equations

	Eigen::Vector3d v1 = Q.col(i1), v2 = Q.col(i2);
	double cg1 = v1.dot(v2);
	double sg1 = sqrt(1 - cg1 * cg1);
	double D1 = (P.col(i1) - P.col(i2)).norm();
	Eigen::MatrixXd D4(n - 2, 5);

	Eigen::VectorXd rowvec(5);
	for (int i = 0, j = 0; i < n; i++)
	{
		if (i == i1 || i == i2) continue;

		Eigen::Vector3d vi = Q.col(i);
		double cg2 = v1.dot(vi);
		double cg3 = v2.dot(vi);
		double sg2 = sqrt(1 - cg2 * cg2);
		double D2 = (P.col(i1) - P.col(i)).norm();
		double D3 = (P.col(i) - P.col(i2)).norm();

		// get the coefficients of the P3P equation from each subset.

		rowvec = getp3p(cg1, cg2, cg3, sg1, sg2, D1, D2, D3);
		D4.row(j) = rowvec;
		j += 1;

		if (j > n - 3) break;
	}

	Eigen::VectorXd D7(8), dumvec(8), dumvec1(5);
	D7.setZero();

	for (int i = 0; i < n - 2; i++)
	{
		dumvec1 = D4.row(i);
		dumvec = getpoly7(dumvec1);
		D7 += dumvec;
	}

	Eigen::PolynomialSolver<double, 7> psolve(D7.reverse());
	Eigen::VectorXcd comp_roots = psolve.roots().transpose();
	Eigen::VectorXd real_comp, imag_comp;
	real_comp = comp_roots.real();
	imag_comp = comp_roots.imag();

	Eigen::VectorXd::Index max_index;

	double max_real = real_comp.cwiseAbs().maxCoeff(&max_index);

	std::vector<double> act_roots_;

	int cnt = 0;

	for (int i = 0; i < imag_comp.size(); i++)
	{
		if (std::abs(imag_comp(i)) / max_real < 0.001)
		{
			act_roots_.push_back(real_comp(i));
			cnt++;
		}
	}

	double* ptr = &act_roots_[0];
	Eigen::Map<Eigen::VectorXd> act_roots(ptr, cnt);

	if (cnt == 0) { return false; }

	Eigen::VectorXd act_roots1(cnt);
	act_roots1 << act_roots.segment(0, cnt);

	std::vector<Eigen::Matrix3d> R_cum(cnt);
	std::vector<Eigen::Vector3d> t_cum(cnt);
	std::vector<double> err_cum(cnt);

	for (int i = 0; i < cnt; i++)
	{
		double root = act_roots(i);

		// Compute the rotation matrix

		double d2 = cg1 + root;

		Eigen::Vector3d unitx, unity, unitz;
		unitx << 1, 0, 0;
		unity << 0, 1, 0;
		unitz << 0, 0, 1;
		x = v2 * d2 - v1;
		x /= x.norm();
		if (std::abs(unity.dot(x)) < std::abs(unitz.dot(x)))
		{
			z = x.cross(unity);
			z /= z.norm();
			y = z.cross(x);
			y / y.norm();
		}
		else
		{
			y = unitz.cross(x);
			y /= y.norm();
			z = x.cross(y);
			z /= z.norm();
		}
		R.col(0) = x;
		R.col(1) = y;
		R.col(2) = z;

		// calculating c, s, tx, ty, tz

		Eigen::MatrixXd D(2 * n, 6);
		D.setZero();

		R0 = R.transpose();
		Eigen::VectorXd r(
			Eigen::Map<Eigen::VectorXd>(R0.data(), R0.cols() * R0.rows()));

		for (int j = 0; j < n; j++)
		{
			double ui = img_pts(j, 0), vi = img_pts(j, 1), xi = P(0, j),
				   yi = P(1, j), zi = P(2, j);
			D.row(2 * j) << -r(1) * yi + ui * (r(7) * yi + r(8) * zi) -
					r(2) * zi,
				-r(2) * yi + ui * (r(8) * yi - r(7) * zi) + r(1) * zi, -1, 0,
				ui, ui * r(6) * xi - r(0) * xi;

			D.row(2 * j + 1)
				<< -r(4) * yi + vi * (r(7) * yi + r(8) * zi) - r(5) * zi,
				-r(5) * yi + vi * (r(8) * yi - r(7) * zi) + r(4) * zi, 0, -1,
				vi, vi * r(6) * xi - r(3) * xi;
		}

		Eigen::MatrixXd DTD = D.transpose() * D;

		Eigen::EigenSolver<Eigen::MatrixXd> es(DTD);

		Eigen::VectorXd Diag = es.pseudoEigenvalueMatrix().diagonal();

		Eigen::MatrixXd V_mat = es.pseudoEigenvectors();

		Eigen::MatrixXd::Index min_index;

		Diag.minCoeff(&min_index);

		Eigen::VectorXd V = V_mat.col(min_index);

		V /= V(5);

		double c = V(0), s = V(1);
		t << V(2), V(3), V(4);

		// calculating the camera pose by 3d alignment
		Eigen::VectorXd xi, yi, zi;
		xi = P.row(0);
		yi = P.row(1);
		zi = P.row(2);

		Eigen::MatrixXd XXcs(3, n), XXc(3, n);
		XXc.setZero();

		XXcs.row(0) = r(0) * xi + (r(1) * c + r(2) * s) * yi +
			(-r(1) * s + r(2) * c) * zi + t(0) * Eigen::VectorXd::Ones(n);
		XXcs.row(1) = r(3) * xi + (r(4) * c + r(5) * s) * yi +
			(-r(4) * s + r(5) * c) * zi + t(1) * Eigen::VectorXd::Ones(n);
		XXcs.row(2) = r(6) * xi + (r(7) * c + r(8) * s) * yi +
			(-r(7) * s + r(8) * c) * zi + t(2) * Eigen::VectorXd::Ones(n);

		for (int ii = 0; ii < n; ii++)
			XXc.col(ii) = Q.col(ii) * XXcs.col(ii).norm();

		Eigen::Matrix3d R2;
		Eigen::Vector3d t2;

		Eigen::MatrixXd XXw = obj_pts.transpose();

		calcampose(XXc, XXw, R2, t2);

		R_cum[i] = R2;
		t_cum[i] = t2;

		for (int k = 0; k < n; k++)
			XXc.col(k) = R2 * XXw.col(k) + t2;

		Eigen::MatrixXd xxc(2, n);

		xxc.row(0) = XXc.row(0).array() / XXc.row(2).array();
		xxc.row(1) = XXc.row(1).array() / XXc.row(2).array();

		double res = ((xxc.row(0) - img_pts.col(0).transpose()).norm() +
					  (xxc.row(1) - img_pts.col(1).transpose()).norm()) /
			2;

		err_cum[i] = res;
	}

	int pos_cum =
		std::min_element(err_cum.begin(), err_cum.end()) - err_cum.begin();

	R_ = R_cum[pos_cum];
	t_ = t_cum[pos_cum];

	return true;
}

void mrpt::vision::pnp::rpnp::calcampose(
	Eigen::MatrixXd& XXc, Eigen::MatrixXd& XXw, Eigen::Matrix3d& R2,
	Eigen::Vector3d& t2)
{
	Eigen::MatrixXd X = XXc;
	Eigen::MatrixXd Y = XXw;
	Eigen::MatrixXd K =
		Eigen::MatrixXd::Identity(n, n) - Eigen::MatrixXd::Ones(n, n) * 1 / n;
	Eigen::VectorXd ux, uy;
	uy = X.rowwise().mean();
	ux = Y.rowwise().mean();

	// Need to verify sigmax2
	double sigmax2 =
		(((X * K).array() * (X * K).array()).colwise().sum()).mean();

	Eigen::MatrixXd SXY = Y * K * (X.transpose()) / n;

	Eigen::JacobiSVD<Eigen::MatrixXd> svd(
		SXY, Eigen::ComputeThinU | Eigen::ComputeThinV);

	Eigen::Matrix3d S = Eigen::MatrixXd::Identity(3, 3);
	if (SXY.determinant() < 0) S(2, 2) = -1;

	R2 = svd.matrixV() * S * svd.matrixU().transpose();

	double c2 = (svd.singularValues().asDiagonal() * S).trace() / sigmax2;
	t2 = uy - c2 * R2 * ux;

	Eigen::Vector3d x, y, z;
	x = R2.col(0);
	y = R2.col(1);
	z = R2.col(2);

	if ((x.cross(y) - z).norm() > 0.02) R2.col(2) = -R2.col(2);
}

Eigen::VectorXd mrpt::vision::pnp::rpnp::getpoly7(const Eigen::VectorXd& vin)
{
	Eigen::VectorXd vout(8);
	vout << 4 * pow(vin(0), 2), 7 * vin(1) * vin(0),
		6 * vin(2) * vin(0) + 3 * pow(vin(1), 2),
		5 * vin(3) * vin(0) + 5 * vin(2) * vin(1),
		4 * vin(4) * vin(0) + 4 * vin(3) * vin(1) + 2 * pow(vin(2), 2),
		3 * vin(4) * vin(1) + 3 * vin(3) * vin(2),
		2 * vin(4) * vin(2) + pow(vin(3), 2), vin(4) * vin(3);
	return vout;
}

Eigen::VectorXd mrpt::vision::pnp::rpnp::getp3p(
	double l1, double l2, double A5, double C1, double C2, double D1, double D2,
	double D3)
{
	double A1 = (D2 / D1) * (D2 / D1);
	double A2 = A1 * pow(C1, 2) - pow(C2, 2);
	double A3 = l2 * A5 - l1;
	double A4 = l1 * A5 - l2;
	double A6 = (pow(D3, 2) - pow(D1, 2) - pow(D2, 2)) / (2 * pow(D1, 2));
	double A7 = 1 - pow(l1, 2) - pow(l2, 2) + l1 * l2 * A5 + A6 * pow(C1, 2);

	Eigen::VectorXd vec(5);

	vec << pow(A6, 2) - A1 * pow(A5, 2), 2 * (A3 * A6 - A1 * A4 * A5),
		pow(A3, 2) + 2 * A6 * A7 - A1 * pow(A4, 2) - A2 * pow(A5, 2),
		2 * (A3 * A7 - A2 * A4 * A5), pow(A7, 2) - A2 * pow(A4, 2);

	return vec;
}
