/*
    * Copyright (C) 2017 Alberto Irurueta Carro (alberto@irurueta.com)
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *         http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.irurueta.geometry.refiners;
  
  import com.irurueta.algebra.Matrix;
  import com.irurueta.geometry.*;
  import com.irurueta.geometry.estimators.LockedException;
  import com.irurueta.geometry.estimators.NotReadyException;
  import com.irurueta.numerical.EvaluationException;
  import com.irurueta.numerical.GradientEstimator;
  import com.irurueta.numerical.fitting.LevenbergMarquardtMultiDimensionFitter;
  import com.irurueta.numerical.fitting.LevenbergMarquardtMultiDimensionFunctionEvaluator;
  import com.irurueta.numerical.robust.InliersData;
  
  import java.util.BitSet;
  import java.util.List;
  
  /**
   * Refines a 3D metric transformation by taking into account an initial
   * estimation, inlier point matches and their residuals.
   * This class can be used to find a solution that minimizes error of inliers in
   * LMSE terms.
   * Typically, a refiner is used by a robust estimator, however it can also be
   * useful in some other situations.
   */
  @SuppressWarnings("DuplicatedCode")
  public class MetricTransformation3DRefiner extends
          PairMatchesAndInliersDataRefiner<MetricTransformation3D, Point3D, Point3D> {
  
      /**
       * Point to be reused when computing residuals.
       */
      private final Point3D residualTestPoint = Point3D.create(CoordinatesType.HOMOGENEOUS_COORDINATES);
  
      /**
       * Quaternion to be reused for refinement computations.
       */
      private Quaternion quaternion = new Quaternion();
  
      /**
       * Standard deviation used for Levenberg-Marquardt fitting during
       * refinement.
       * Returned value gives an indication of how much variance each residual
       * has.
       * Typically, this value is related to the threshold used on each robust
       * estimation, since residuals of found inliers are within the range of
       * such threshold.
       */
      private double refinementStandardDeviation;
  
      /**
       * Constructor.
       */
      public MetricTransformation3DRefiner() {
      }
  
      /**
       * Constructor.
       *
       * @param initialEstimation           initial estimation to be set.
       * @param keepCovariance              true if covariance of estimation must be kept after
       *                                    refinement, false otherwise.
       * @param inliers                     set indicating which of the provided matches are inliers.
       * @param residuals                   residuals for matched samples.
       * @param numInliers                  number of inliers on initial estimation.
       * @param samples1                    1st set of paired samples.
       * @param samples2                    2nd set of paired samples.
       * @param refinementStandardDeviation standard deviation used for
       *                                    Levenberg-Marquardt fitting.
       */
      public MetricTransformation3DRefiner(
              final MetricTransformation3D initialEstimation, final boolean keepCovariance,
              final BitSet inliers, final double[] residuals, final int numInliers,
              final List<Point3D> samples1, final List<Point3D> samples2, final double refinementStandardDeviation) {
          super(initialEstimation, keepCovariance, inliers, residuals, numInliers, samples1, samples2);
          this.refinementStandardDeviation = refinementStandardDeviation;
      }
  
      /**
       * Constructor.
       *
       * @param initialEstimation           initial estimation to be set.
       * @param keepCovariance              true if covariance of estimation must be kept after
       *                                    refinement, false otherwise.
       * @param inliersData                 inlier data, typically obtained from a robust
       *                                    estimator.
      * @param samples1                    1st set of paired samples.
      * @param samples2                    2nd set of paired samples.
      * @param refinementStandardDeviation standard deviation used for
      *                                    Levenberg-Marquardt fitting.
      */
     public MetricTransformation3DRefiner(
             final MetricTransformation3D initialEstimation, final boolean keepCovariance,
             final InliersData inliersData, final List<Point3D> samples1, final List<Point3D> samples2,
             final double refinementStandardDeviation) {
         super(initialEstimation, keepCovariance, inliersData, samples1, samples2);
         this.refinementStandardDeviation = refinementStandardDeviation;
     }
 
     /**
      * Gets standard deviation used for Levenberg-Marquardt fitting during
      * refinement.
      * Returned value gives an indication of how much variance each residual
      * has.
      * Typically, this value is related to the threshold used on each robust
      * estimation, since residuals of found inliers are within the range of
      * such threshold.
      *
      * @return standard deviation used for refinement.
      */
     public double getRefinementStandardDeviation() {
         return refinementStandardDeviation;
     }
 
     /**
      * Sets standard deviation used for Levenberg-Marquardt fitting during
      * refinement.
      * Returned value gives an indication of how much variance each residual
      * has.
      * Typically, this value is related to the threshold used on each robust
      * estimation, since residuals of found inliers are within the range of such
      * threshold.
      *
      * @param refinementStandardDeviation standard deviation used for
      *                                    refinement.
      * @throws LockedException if estimator is locked.
      */
     public void setRefinementStandardDeviation(final double refinementStandardDeviation) throws LockedException {
         if (isLocked()) {
             throw new LockedException();
         }
         this.refinementStandardDeviation = refinementStandardDeviation;
     }
 
     /**
      * Refines provided initial estimation.
      *
      * @return refines estimation.
      * @throws NotReadyException if not enough input data has been provided.
      * @throws LockedException   if estimator is locked because refinement is
      *                           already in progress.
      * @throws RefinerException  if refinement fails for some reason (e.g. unable
      *                           to converge to a result).
      */
     @Override
     public MetricTransformation3D refine() throws NotReadyException, LockedException, RefinerException {
         final var result = new MetricTransformation3D();
         refine(result);
         return result;
     }
 
     /**
      * Refines provided initial estimation.
      * This method always sets a value into provided result instance regardless
      * of the fact that error has actually improved in LMSE terms or not.
      *
      * @param result instance where refined estimation will be stored.
      * @return true if result improves (error decreases) in LMSE terms respect
      * to initial estimation, false if no improvement has been achieved.
      * @throws NotReadyException if not enough input data has been provided.
      * @throws LockedException   if estimator is locked because refinement is
      *                           already in progress.
      * @throws RefinerException  if refinement fails for some reason (e.g. unable
      *                           to converge to a result).
      */
     @Override
     public boolean refine(final MetricTransformation3D result) throws NotReadyException, LockedException,
             RefinerException {
         if (isLocked()) {
             throw new LockedException();
         }
         if (!isReady()) {
             throw new NotReadyException();
         }
 
         locked = true;
 
         if (listener != null) {
             listener.onRefineStart(this, initialEstimation);
         }
 
         final var initialTotalResidual = totalResidual(initialEstimation);
 
         try {
             // parameters: rotation angle + scale + translation
             final var initParams = new double[1 + Quaternion.N_PARAMS
                     + EuclideanTransformation3D.NUM_TRANSLATION_COORDS];
             // copy rotation values
             if (initialEstimation.getRotation().getType() == Rotation3DType.QUATERNION) {
                 quaternion = (Quaternion) initialEstimation.getRotation();
             } else {
                 quaternion = initialEstimation.getRotation().toQuaternion();
             }
             quaternion.normalize();
 
             // copy values
             initParams[0] = initialEstimation.getScale();
             initParams[1] = quaternion.getA();
             initParams[2] = quaternion.getB();
             initParams[3] = quaternion.getC();
             initParams[4] = quaternion.getD();
 
             System.arraycopy(initialEstimation.getTranslation(), 0, initParams, Quaternion.N_PARAMS + 1,
                     EuclideanTransformation3D.NUM_TRANSLATION_COORDS);
 
             // output values to be fitted/optimized will contain residuals
             final var y = new double[numInliers];
             // input values will contain 2 sets of 2D points to compute residuals
             final var nDims = 2 * Point3D.POINT3D_HOMOGENEOUS_COORDINATES_LENGTH;
             final var x = new Matrix(numInliers, nDims);
             final var nSamples = inliers.length();
             var pos = 0;
             for (var i = 0; i < nSamples; i++) {
                 if (inliers.get(i)) {
                     // sample is inlier
                     final var inputPoint = samples1.get(i);
                     final var outputPoint = samples2.get(i);
                     inputPoint.normalize();
                     outputPoint.normalize();
                     x.setElementAt(pos, 0, inputPoint.getHomX());
                     x.setElementAt(pos, 1, inputPoint.getHomY());
                     x.setElementAt(pos, 2, inputPoint.getHomZ());
                     x.setElementAt(pos, 3, inputPoint.getHomW());
                     x.setElementAt(pos, 4, outputPoint.getHomX());
                     x.setElementAt(pos, 5, outputPoint.getHomY());
                     x.setElementAt(pos, 6, outputPoint.getHomZ());
                     x.setElementAt(pos, 7, outputPoint.getHomW());
 
                     y[pos] = residuals[i];
                     pos++;
                 }
             }
 
             final var evaluator = new LevenbergMarquardtMultiDimensionFunctionEvaluator() {
 
                 private final Point3D inputPoint = Point3D.create(CoordinatesType.HOMOGENEOUS_COORDINATES);
 
                 private final Point3D outputPoint = Point3D.create(CoordinatesType.HOMOGENEOUS_COORDINATES);
 
                 private final MetricTransformation3D transformation = new MetricTransformation3D();
 
                 private final GradientEstimator gradientEstimator = new GradientEstimator(params -> {
                     // copy values
                     transformation.setScale(params[0]);
                     quaternion.setA(params[1]);
                     quaternion.setB(params[2]);
                     quaternion.setC(params[3]);
                     quaternion.setD(params[4]);
                     transformation.setRotation(quaternion);
 
                     System.arraycopy(params, 1 + Quaternion.N_PARAMS, transformation.getTranslation(), 0,
                             EuclideanTransformation3D.NUM_TRANSLATION_COORDS);
 
                     return residual(transformation, inputPoint, outputPoint);
                 });
 
                 @Override
                 public int getNumberOfDimensions() {
                     return nDims;
                 }
 
                 @Override
                 public double[] createInitialParametersArray() {
                     return initParams;
                 }
 
                 @Override
                 public double evaluate(final int i, final double[] point, final double[] params,
                                        final double[] derivatives) throws EvaluationException {
                     inputPoint.setHomogeneousCoordinates(point[0], point[1], point[2], point[3]);
                     outputPoint.setHomogeneousCoordinates(point[4], point[5], point[6], point[7]);
 
                     // copy values
                     transformation.setScale(params[0]);
                     quaternion.setA(params[1]);
                     quaternion.setB(params[2]);
                     quaternion.setC(params[3]);
                     quaternion.setD(params[4]);
                     transformation.setRotation(quaternion);
 
                     System.arraycopy(params, 1 + Quaternion.N_PARAMS, transformation.getTranslation(), 0,
                             EuclideanTransformation3D.NUM_TRANSLATION_COORDS);
 
                     final var y = residual(transformation, inputPoint, outputPoint);
                     gradientEstimator.gradient(params, derivatives);
 
                     return y;
                 }
             };
 
             final var fitter = new LevenbergMarquardtMultiDimensionFitter(evaluator, x, y,
                     getRefinementStandardDeviation());
 
             fitter.fit();
 
             // obtain estimated params
             final var params = fitter.getA();
 
             // update transformation
             result.setScale(params[0]);
             quaternion.setA(params[1]);
             quaternion.setB(params[2]);
             quaternion.setC(params[3]);
             quaternion.setD(params[4]);
             result.setRotation(quaternion);
             System.arraycopy(params, 1 + Quaternion.N_PARAMS, result.getTranslation(), 0,
                     EuclideanTransformation3D.NUM_TRANSLATION_COORDS);
 
             if (keepCovariance) {
                 // keep covariance
                 covariance = fitter.getCovar();
             }
 
             final var finalTotalResidual = totalResidual(result);
             final var errorDecreased = finalTotalResidual < initialTotalResidual;
 
             if (listener != null) {
                 listener.onRefineEnd(this, initialEstimation, result, errorDecreased);
             }
 
             return errorDecreased;
 
         } catch (final Exception e) {
             throw new RefinerException(e);
         } finally {
             locked = false;
         }
     }
 
     /**
      * Computes the residual between the Euclidean transformation and a pair or
      * matched points.
      *
      * @param transformation a transformation.
      * @param inputPoint     input 3D point.
      * @param outputPoint    output 3D point.
      * @return residual.
      */
     private double residual(final MetricTransformation3D transformation, final Point3D inputPoint,
                             final Point3D outputPoint) {
         inputPoint.normalize();
         outputPoint.normalize();
 
         transformation.transform(inputPoint, residualTestPoint);
         return residualTestPoint.distanceTo(outputPoint);
     }
 
     /**
      * Computes total residual among all provided inlier samples.
      *
      * @param transformation a transformation.
      * @return total residual.
      */
     private double totalResidual(final MetricTransformation3D transformation) {
         var result = 0.0;
 
         final var nSamples = inliers.length();
         for (var i = 0; i < nSamples; i++) {
             if (inliers.get(i)) {
                 // sample is inlier
                 final var inputPoint = samples1.get(i);
                 final var outputPoint = samples2.get(i);
                 inputPoint.normalize();
                 outputPoint.normalize();
                 result += residual(transformation, inputPoint, outputPoint);
             }
         }
 
         return result;
     }
 }