/*
    * Copyright (C) 2015 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.ar.epipolar.estimators;
  
  import com.irurueta.ar.epipolar.FundamentalMatrix;
  import com.irurueta.geometry.Point2D;
  import com.irurueta.geometry.estimators.LockedException;
  import com.irurueta.geometry.estimators.NotReadyException;
  import com.irurueta.numerical.robust.LMedSRobustEstimator;
  import com.irurueta.numerical.robust.LMedSRobustEstimatorListener;
  import com.irurueta.numerical.robust.RobustEstimator;
  import com.irurueta.numerical.robust.RobustEstimatorException;
  import com.irurueta.numerical.robust.RobustEstimatorMethod;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Finds the best fundamental matrix for provided collections of matched 2D
   * points using LMedS algorithm.
   */
  public class LMedSFundamentalMatrixRobustEstimator extends FundamentalMatrixRobustEstimator {
  
      /**
       * Default value to be used for stop threshold. Stop threshold can be used
       * to keep the algorithm iterating in case that best estimated threshold
       * using median of residuals is not small enough. Once a solution is found
       * that generates a threshold below this value, the algorithm will stop.
       * The stop threshold can be used to prevent the LMedS algorithm iterating
       * too many times in cases where samples have a very similar accuracy.
       * For instance, in cases where proportion of outliers is very small (close
       * to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
       * iterate for a long time trying to find the best solution when indeed
       * there is no need to do that if a reasonable threshold has already been
       * reached.
       * Because of this behaviour the stop threshold can be set to a value much
       * lower than the one typically used in RANSAC, and yet the algorithm could
       * still produce even smaller thresholds in estimated results.
       */
      public static final double DEFAULT_STOP_THRESHOLD = 1e-3;
  
      /**
       * Minimum allowed stop threshold value.
       */
      public static final double MIN_STOP_THRESHOLD = 0.0;
  
      /**
       * Threshold to be used to keep the algorithm iterating in case that best
       * estimated threshold using median of residuals is not small enough. Once
       * a solution is found that generates a threshold below this value, the
       * algorithm will stop.
       * The stop threshold can be used to prevent the LMedS algorithm iterating
       * too many times in cases where samples have a very similar accuracy.
       * For instance, in cases where proportion of outliers is very small (close
       * to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
       * iterate for a long time trying to find the best solution when indeed
       * there is no need to do that if a reasonable threshold has already been
       * reached.
       * Because of this behaviour the stop threshold can be set to a value much
       * lower than the one typically used in RANSAC, and yet the algorithm could
       * still produce even smaller thresholds in estimated results.
       */
      private double stopThreshold;
  
      /**
       * Constructor.
       *
       * @param fundMatrixEstimatorMethod method for non-robust fundamental matrix
       *                                  estimator.
       */
      public LMedSFundamentalMatrixRobustEstimator(final FundamentalMatrixEstimatorMethod fundMatrixEstimatorMethod) {
          super(fundMatrixEstimatorMethod);
          stopThreshold = DEFAULT_STOP_THRESHOLD;
      }
  
      /**
       * Constructor.
       *
       * @param fundMatrixEstimatorMethod method for non-robust fundamental matrix
       *                                  estimator.
       * @param listener                  listener to be notified of events such as when estimation
       *                                  starts, ends or its progress significantly changes.
       */
      public LMedSFundamentalMatrixRobustEstimator(
              final FundamentalMatrixEstimatorMethod fundMatrixEstimatorMethod,
              final FundamentalMatrixRobustEstimatorListener listener) {
         super(fundMatrixEstimatorMethod, listener);
         stopThreshold = DEFAULT_STOP_THRESHOLD;
     }
 
     /**
      * Constructor.
      *
      * @param fundMatrixEstimatorMethod method for non-robust fundamental matrix
      *                                  estimator.
      * @param leftPoints                2D points on left view.
      * @param rightPoints               2D points on right view.
      * @throws IllegalArgumentException if provided list of points do not have
      *                                  the same length or their length is less than 7 points.
      */
     public LMedSFundamentalMatrixRobustEstimator(
             final FundamentalMatrixEstimatorMethod fundMatrixEstimatorMethod,
             final List<Point2D> leftPoints, final List<Point2D> rightPoints) {
         super(fundMatrixEstimatorMethod, leftPoints, rightPoints);
         stopThreshold = DEFAULT_STOP_THRESHOLD;
     }
 
     /**
      * Constructor.
      *
      * @param fundMatrixEstimatorMethod method for non-robust fundamental matrix
      *                                  estimator.
      * @param leftPoints                2D points on left view.
      * @param rightPoints               2D points on right view.
      * @param listener                  listener to be notified of events such as when estimation
      *                                  starts, ends or its progress significantly changes.
      * @throws IllegalArgumentException if provided list of points do not have
      *                                  the same length or their length is less than 7 points.
      */
     public LMedSFundamentalMatrixRobustEstimator(
             final FundamentalMatrixEstimatorMethod fundMatrixEstimatorMethod,
             final List<Point2D> leftPoints, final List<Point2D> rightPoints,
             final FundamentalMatrixRobustEstimatorListener listener) {
         super(fundMatrixEstimatorMethod, leftPoints, rightPoints, listener);
         stopThreshold = DEFAULT_STOP_THRESHOLD;
     }
 
     /**
      * Constructor.
      */
     public LMedSFundamentalMatrixRobustEstimator() {
         this(DEFAULT_FUNDAMENTAL_MATRIX_ESTIMATOR_METHOD);
     }
 
     /**
      * Constructor.
      *
      * @param listener listener to be notified of events such as when estimation
      *                 starts, ends or its progress significantly changes.
      */
     public LMedSFundamentalMatrixRobustEstimator(final FundamentalMatrixRobustEstimatorListener listener) {
         this(DEFAULT_FUNDAMENTAL_MATRIX_ESTIMATOR_METHOD, listener);
     }
 
     /**
      * Constructor.
      *
      * @param leftPoints  2D points on left view.
      * @param rightPoints 2D points on right view.
      * @throws IllegalArgumentException if provided list of points do not have
      *                                  the same length or their length is less than 7 points.
      */
     public LMedSFundamentalMatrixRobustEstimator(final List<Point2D> leftPoints, final List<Point2D> rightPoints) {
         this(DEFAULT_FUNDAMENTAL_MATRIX_ESTIMATOR_METHOD, leftPoints, rightPoints);
     }
 
     /**
      * Constructor.
      *
      * @param leftPoints  2D points on left view.
      * @param rightPoints 2D points on right view.
      * @param listener    listener to be notified of events such as when estimation
      *                    starts, ends or its progress significantly changes.
      * @throws IllegalArgumentException if provided list of points do not have
      *                                  the same length or their length is less than 7 points.
      */
     public LMedSFundamentalMatrixRobustEstimator(final List<Point2D> leftPoints, final List<Point2D> rightPoints,
                                                  final FundamentalMatrixRobustEstimatorListener listener) {
         this(DEFAULT_FUNDAMENTAL_MATRIX_ESTIMATOR_METHOD, leftPoints, rightPoints, listener);
     }
 
     /**
      * Returns threshold to be used to keep the algorithm iterating in case that
      * best estimated threshold using median of residuals is not small enough.
      * Once a solution is found that generates a threshold below this value, the
      * algorithm will stop.
      * The stop threshold can be used to prevent the LMedS algorithm iterating
      * too many times in cases where samples have a very similar accuracy.
      * For instance, in cases where proportion of outliers is very small (close
      * to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
      * iterate for a long time trying to find the best solution when indeed
      * there is no need to do that if a reasonable threshold has already been
      * reached.
      * Because of this behaviour the stop threshold can be set to a value much
      * lower than the one typically used in RANSAC, and yet the algorithm could
      * still produce even smaller thresholds in estimated results.
      *
      * @return stop threshold to stop the algorithm prematurely when a certain
      * accuracy has been reached.
      */
     public double getStopThreshold() {
         return stopThreshold;
     }
 
     /**
      * Sets threshold to be used to keep the algorithm iterating in case that
      * best estimated threshold using median of residuals is not small enough.
      * Once a solution is found that generates a threshold below this value, the
      * algorithm will stop.
      * The stop threshold can be used to prevent the LMedS algorithm iterating
      * too many times in cases where samples have a very similar accuracy.
      * For instance, in cases where proportion of outliers is very small (close
      * to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
      * iterate for a long time trying to find the best solution when indeed
      * there is no need to do that if a reasonable threshold has already been
      * reached.
      * Because of this behaviour the stop threshold can be set to a value much
      * lower than the one typically used in RANSAC, and yet the algorithm could
      * still produce even smaller thresholds in estimated results.
      *
      * @param stopThreshold stop threshold to stop the algorithm prematurely
      *                      when a certain accuracy has been reached.
      * @throws IllegalArgumentException if provided value is zero or negative.
      * @throws LockedException          if robust estimator is locked because an
      *                                  estimation is already in progress.
      */
     public void setStopThreshold(final double stopThreshold) throws LockedException {
         if (isLocked()) {
             throw new LockedException();
         }
         if (stopThreshold <= MIN_STOP_THRESHOLD) {
             throw new IllegalArgumentException();
         }
 
         this.stopThreshold = stopThreshold;
     }
 
     /**
      * Estimates a radial distortion using a robust estimator and
      * the best set of matched 2D points found using the robust estimator.
      *
      * @return a radial distortion.
      * @throws LockedException          if robust estimator is locked because an
      *                                  estimation is already in progress.
      * @throws NotReadyException        if provided input data is not enough to start
      *                                  the estimation.
      * @throws RobustEstimatorException if estimation fails for any reason
      *                                  (i.e. numerical instability, no solution available, etc).
      */
     @Override
     public FundamentalMatrix estimate() throws LockedException, NotReadyException, RobustEstimatorException {
         if (isLocked()) {
             throw new LockedException();
         }
         if (!isReady()) {
             throw new NotReadyException();
         }
 
         final var innerEstimator = new LMedSRobustEstimator<FundamentalMatrix>(new LMedSRobustEstimatorListener<>() {
 
             // subset of left points
             private final List<Point2D> subsetLeftPoints = new ArrayList<>();
 
             // subset of right points
             private final List<Point2D> subsetRightPoints = new ArrayList<>();
 
             @Override
             public int getTotalSamples() {
                 return leftPoints.size();
             }
 
             @Override
             public int getSubsetSize() {
                 return getMinRequiredPoints();
             }
 
             @Override
             public void estimatePreliminarSolutions(
                     final int[] samplesIndices, final List<FundamentalMatrix> solutions) {
 
                 subsetLeftPoints.clear();
                 subsetRightPoints.clear();
                 for (final var samplesIndex : samplesIndices) {
                     subsetLeftPoints.add(leftPoints.get(samplesIndex));
                     subsetRightPoints.add(rightPoints.get(samplesIndex));
                 }
 
                 nonRobustEstimate(solutions, subsetLeftPoints, subsetRightPoints);
             }
 
             @Override
             public double computeResidual(final FundamentalMatrix currentEstimation, final int i) {
                 final var leftPoint = leftPoints.get(i);
                 final var rightPoint = rightPoints.get(i);
                 return residual(currentEstimation, leftPoint, rightPoint);
             }
 
             @Override
             public boolean isReady() {
                 return LMedSFundamentalMatrixRobustEstimator.this.isReady();
             }
 
             @Override
             public void onEstimateStart(final RobustEstimator<FundamentalMatrix> estimator) {
                 if (listener != null) {
                     listener.onEstimateStart(LMedSFundamentalMatrixRobustEstimator.this);
                 }
             }
 
             @Override
             public void onEstimateEnd(final RobustEstimator<FundamentalMatrix> estimator) {
                 if (listener != null) {
                     listener.onEstimateEnd(LMedSFundamentalMatrixRobustEstimator.this);
                 }
             }
 
             @Override
             public void onEstimateNextIteration(
                     final RobustEstimator<FundamentalMatrix> estimator, final int iteration) {
                 if (listener != null) {
                     listener.onEstimateNextIteration(LMedSFundamentalMatrixRobustEstimator.this, iteration);
                 }
             }
 
             @Override
             public void onEstimateProgressChange(
                     final RobustEstimator<FundamentalMatrix> estimator, final float progress) {
                 if (listener != null) {
                     listener.onEstimateProgressChange(LMedSFundamentalMatrixRobustEstimator.this, progress);
                 }
             }
         });
 
         try {
             locked = true;
             inliersData = null;
             innerEstimator.setConfidence(confidence);
             innerEstimator.setMaxIterations(maxIterations);
             innerEstimator.setProgressDelta(progressDelta);
             innerEstimator.setStopThreshold(stopThreshold);
             final var result = innerEstimator.estimate();
             inliersData = innerEstimator.getInliersData();
             return attemptRefine(result);
         } catch (final com.irurueta.numerical.LockedException e) {
             throw new LockedException(e);
         } catch (final com.irurueta.numerical.NotReadyException e) {
             throw new NotReadyException(e);
         } finally {
             locked = false;
         }
     }
 
     /**
      * Returns method being used for robust estimation.
      *
      * @return method being used for robust estimation.
      */
     @Override
     public RobustEstimatorMethod getMethod() {
         return RobustEstimatorMethod.LMEDS;
     }
 
     /**
      * 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.
      */
     @Override
     protected double getRefinementStandardDeviation() {
         final var inliersData = (LMedSRobustEstimator.LMedSInliersData) getInliersData();
         return inliersData.getEstimatedThreshold();
     }
 }