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/**
 * @file gravity_fusion.cpp
 * Fuse observations from the gravity vector to constrain roll
 * and pitch (a la complementary filter).
 *
 * @author Daniel M. Sahu <danielmohansahu@gmail.com>
 */

#include "ekf.h"
#include <ekf_derivation/generated/compute_gravity_innov_var_and_k_and_h.h>

#include <mathlib/mathlib.h>

void Ekf::controlGravityFusion(const imuSample &imu)
{
	// fuse gravity observation if our overall acceleration isn't too big
	const float gravity_scale = _accel_vec_filt.norm() / CONSTANTS_ONE_G;

	_control_status.flags.gravity_vector = (_params.imu_ctrl & static_cast<int32_t>(ImuCtrl::GravityVector))
					       && (((gravity_scale >= 0.9f && gravity_scale <= 1.1f)) || _control_status.flags.vehicle_at_rest)
					       && !isHorizontalAidingActive();

	// get raw accelerometer reading at delayed horizon and expected measurement noise (gaussian)
	const Vector3f measurement = imu.delta_vel / imu.delta_vel_dt - getAccelBias();
	const float measurement_var = sq(_params.gravity_noise);

	// calculate kalman gains and innovation variances
	Vector3f innovation; // innovation of the last gravity fusion observation (m/s**2)
	Vector3f innovation_variance;
	VectorState Kx, Ky, Kz; // Kalman gain vectors
	sym::ComputeGravityInnovVarAndKAndH(
		_state.vector(), P, measurement, measurement_var, FLT_EPSILON,
		&innovation, &innovation_variance, &Kx, &Ky, &Kz);

	// fill estimator aid source status
	resetEstimatorAidStatus(_aid_src_gravity);
	_aid_src_gravity.timestamp_sample = imu.time_us;
	measurement.copyTo(_aid_src_gravity.observation);

	for (auto &var : _aid_src_gravity.observation_variance) {
		var = measurement_var;
	}

	innovation.copyTo(_aid_src_gravity.innovation);
	innovation_variance.copyTo(_aid_src_gravity.innovation_variance);

	float innovation_gate = 1.f;
	setEstimatorAidStatusTestRatio(_aid_src_gravity, innovation_gate);

	const bool accel_clipping = imu.delta_vel_clipping[0] || imu.delta_vel_clipping[1] || imu.delta_vel_clipping[2];

	if (_control_status.flags.gravity_vector && !_aid_src_gravity.innovation_rejected && !accel_clipping) {
		// perform fusion for each axis
		_aid_src_gravity.fused = measurementUpdate(Kx, innovation_variance(0), innovation(0))
					 && measurementUpdate(Ky, innovation_variance(1), innovation(1))
					 && measurementUpdate(Kz, innovation_variance(2), innovation(2));

		if (_aid_src_gravity.fused) {
			_aid_src_gravity.time_last_fuse = imu.time_us;
		}
	}
}