/*
    * Copyright (C) 2018 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.navigation.indoor.radiosource;
  
  import com.irurueta.geometry.Point3D;
  import com.irurueta.navigation.LockedException;
  import com.irurueta.navigation.NotReadyException;
  import com.irurueta.navigation.indoor.RadioSource;
  import com.irurueta.navigation.indoor.RssiReadingLocated;
  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.List;
  
  /**
   * Robustly estimate 3D position, transmitted power and path-loss exponent of a radio source
   * (e.g. Wi-Fi access point or bluetooth beacon), by discarding outliers using LMedS
   * algorithm and assuming that the radio source emits isotropically following the
   * expression below:
   * Pr = Pt*Gt*Gr*lambda^2 / (4*pi*d)^2,
   * where Pr is the received power (expressed in mW),
   * Gt is the Gain of the transmission antenna
   * Gr is the Gain of the receiver antenna
   * d is the distance between emitter and receiver
   * and lambda is the wavelength and is equal to: lambda = c / f,
   * where c is the speed of light
   * and f is the carrier frequency of the radio signal.
   * Because usually information about the antenna of the radio source cannot be
   * retrieved (because many measurements are made on unknown access points where
   * physical access is not possible), this implementation will estimate the
   * equivalent transmitted power as: Pte = Pt * Gt * Gr.
   * If WifiReadings contain RSSI standard deviations, those values will be used,
   * otherwise it will be assumed an RSSI standard deviation of 1 dB.
   * Implementations of this class should be able to detect and discard outliers in
   * order to find the best solution.
   * <p>
   * IMPORTANT: When using this class estimation can be done using a
   * combination of radio source position, transmitted power and path loss
   * exponent. However enabling all three estimations usually achieves
   * inaccurate results. When using this class, estimation must be of at least
   * one parameter (position, transmitted power or path loss exponent) when
   * initial values are provided for the other two, and at most it should consist
   * of two parameters (either position and transmitted power, position and
   * path loss exponent or transmitted power and path loss exponent), providing an
   * initial value for the remaining parameter.
   *
   * @param <S> a {@link RadioSource} type.
   */
  @SuppressWarnings("Duplicates")
  public class LMedSRobustRssiRadioSourceEstimator3D<S extends RadioSource> extends RobustRssiRadioSourceEstimator3D<S> {
  
      /**
       * Default value to be used for stop threshold. Stop threshold can be used to
       * avoid keeping the algorithm unnecessarily 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-4;
  
      /**
       * 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 = DEFAULT_STOP_THRESHOLD;
 
     /**
      * Constructor.
      */
     public LMedSRobustRssiRadioSourceEstimator3D() {
         super();
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings Wi-Fi signal readings belonging to the same radio source.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(final List<? extends RssiReadingLocated<S, Point3D>> readings) {
         super(readings);
     }
 
     /**
      * Constructor.
      *
      * @param listener listener in charge of attending events raised by this instance.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings signal readings belonging to the same radio source.
      * @param listener listener in charge of attending events raised by this instance.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings,
             final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(readings, listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings        signal readings belonging to the same radio source.
      * @param initialPosition initial position to start the estimation of radio
      *                        source position.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings, final Point3D initialPosition) {
         super(readings, initialPosition);
     }
 
     /**
      * Constructor.
      *
      * @param initialPosition initial position to start the estimation of radio
      *                        source position.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(final Point3D initialPosition) {
         super(initialPosition);
     }
 
     /**
      * Constructor.
      *
      * @param initialPosition initial position to start the estimation of radio
      *                        source position.
      * @param listener        listener in charge of attending events raised by this instance.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final Point3D initialPosition, final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(initialPosition, listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings        signal readings belonging to the same radio source.
      * @param initialPosition initial position to start the estimation of radio
      *                        source position.
      * @param listener        listener in charge of attending events raised by this instance.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings, final Point3D initialPosition,
             final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(readings, initialPosition, listener);
     }
 
     /**
      * Constructor.
      *
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's)
      */
     public LMedSRobustRssiRadioSourceEstimator3D(final Double initialTransmittedPowerdBm) {
         super(initialTransmittedPowerdBm);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings                   signal readings belonging to the same radio source.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's)
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings, final Double initialTransmittedPowerdBm) {
         super(readings, initialTransmittedPowerdBm);
     }
 
     /**
      * Constructor.
      *
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @param listener                   listener in charge of attending events raised by this instance.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final Double initialTransmittedPowerdBm,
             final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(initialTransmittedPowerdBm, listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings                   signal readings belonging to the same radio source.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's)
      * @param listener                   listener in charge of attending events raised by this instance.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings,
             final Double initialTransmittedPowerdBm,
             final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(readings, initialTransmittedPowerdBm, listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings                   signal readings belonging to the same radio source.
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings,
             final Point3D initialPosition, final Double initialTransmittedPowerdBm) {
         super(readings, initialPosition, initialTransmittedPowerdBm);
     }
 
     /**
      * Constructor.
      *
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final Point3D initialPosition, final Double initialTransmittedPowerdBm) {
         super(initialPosition, initialTransmittedPowerdBm);
     }
 
     /**
      * Constructor.
      *
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @param listener                   in charge of attending events raised by this instance.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final Point3D initialPosition, final Double initialTransmittedPowerdBm,
             final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(initialPosition, initialTransmittedPowerdBm, listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings                   signal readings belonging to the same radio source.
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @param listener                   listener in charge of attending events raised by this instance.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings,
             final Point3D initialPosition, final Double initialTransmittedPowerdBm,
             final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(readings, initialPosition, initialTransmittedPowerdBm, listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings                   signal readings belonging to the same radio source.
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @param initialPathLossExponent    initial path loss exponent. A typical value is 2.0.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings, final Point3D initialPosition,
             final Double initialTransmittedPowerdBm, final double initialPathLossExponent) {
         super(readings, initialPosition, initialTransmittedPowerdBm, initialPathLossExponent);
     }
 
     /**
      * Constructor.
      *
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @param initialPathLossExponent    initial path loss exponent. A typical value is 2.0.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final Point3D initialPosition, final Double initialTransmittedPowerdBm,
             final double initialPathLossExponent) {
         super(initialPosition, initialTransmittedPowerdBm, initialPathLossExponent);
     }
 
     /**
      * Constructor.
      *
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @param initialPathLossExponent    initial path loss exponent. A typical value is 2.0.
      * @param listener                   listener in charge of attending events raised by this instance.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final Point3D initialPosition, final Double initialTransmittedPowerdBm,
             final double initialPathLossExponent, final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(initialPosition, initialTransmittedPowerdBm, initialPathLossExponent, listener);
     }
 
     /**
      * Constructor.
      * Sets signal readings belonging to the same radio source.
      *
      * @param readings                   signal readings belonging to the same radio source.
      * @param initialPosition            initial position to start the estimation of radio
      *                                   source position.
      * @param initialTransmittedPowerdBm initial transmitted power to start the
      *                                   estimation of radio source transmitted power
      *                                   (expressed in dBm's).
      * @param initialPathLossExponent    initial path loss exponent. A typical value is 2.0.
      * @param listener                   listener in charge of attending events raised by this instance.
      * @throws IllegalArgumentException if readings are not valid.
      */
     public LMedSRobustRssiRadioSourceEstimator3D(
             final List<? extends RssiReadingLocated<S, Point3D>> readings,
             final Point3D initialPosition, final Double initialTransmittedPowerdBm,
             final double initialPathLossExponent, final RobustRssiRadioSourceEstimatorListener<S, Point3D> listener) {
         super(readings, initialPosition, initialTransmittedPowerdBm, initialPathLossExponent, 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 to iterate
      * 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 to iterate
      * 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 this solver is locked.
      */
     public void setStopThreshold(final double stopThreshold) throws LockedException {
         if (isLocked()) {
             throw new LockedException();
         }
         if (stopThreshold <= MIN_STOP_THRESHOLD) {
             throw new IllegalArgumentException();
         }
 
         this.stopThreshold = stopThreshold;
     }
 
     /**
      * Robustly estimates position, transmitted power and path-loss exponent for a
      * radio source.
      *
      * @throws LockedException          if instance is busy during estimation.
      * @throws NotReadyException        if estimator is not ready.
      * @throws RobustEstimatorException if estimation fails for any reason
      *                                  (i.e. numerical instability, no solution available, etc).
      */
     @Override
     public void estimate() throws LockedException, NotReadyException, RobustEstimatorException {
         if (isLocked()) {
             throw new LockedException();
         }
         if (!isReady()) {
             throw new NotReadyException();
         }
 
         final var innerEstimator = new LMedSRobustEstimator<>(new LMedSRobustEstimatorListener<Solution<Point3D>>() {
             @Override
             public int getTotalSamples() {
                 return readings.size();
             }
 
             @Override
             public int getSubsetSize() {
                 return Math.max(preliminarySubsetSize, getMinReadings());
             }
 
             @Override
             public void estimatePreliminarSolutions(
                     final int[] samplesIndices, final List<Solution<Point3D>> solutions) {
                 solvePreliminarySolutions(samplesIndices, solutions);
             }
 
             @Override
             public double computeResidual(final Solution<Point3D> currentEstimation, final int i) {
                 return residual(currentEstimation, i);
             }
 
             @Override
             public boolean isReady() {
                 return LMedSRobustRssiRadioSourceEstimator3D.this.isReady();
             }
 
             @Override
             public void onEstimateStart(final RobustEstimator<Solution<Point3D>> estimator) {
                 // no action needed
             }
 
             @Override
             public void onEstimateEnd(final RobustEstimator<Solution<Point3D>> estimator) {
                 // no action needed
             }
 
             @Override
             public void onEstimateNextIteration(
                     final RobustEstimator<Solution<Point3D>> estimator, final int iteration) {
                 if (listener != null) {
                     listener.onEstimateNextIteration(LMedSRobustRssiRadioSourceEstimator3D.this, iteration);
                 }
             }
 
             @Override
             public void onEstimateProgressChange(
                     final RobustEstimator<Solution<Point3D>> estimator, final float progress) {
                 if (listener != null) {
                     listener.onEstimateProgressChange(LMedSRobustRssiRadioSourceEstimator3D.this, progress);
                 }
             }
         });
 
         try {
             locked = true;
 
             if (listener != null) {
                 listener.onEstimateStart(this);
             }
 
             inliersData = null;
             innerEstimator.setConfidence(confidence);
             innerEstimator.setMaxIterations(maxIterations);
             innerEstimator.setProgressDelta(progressDelta);
             final var result = innerEstimator.estimate();
             inliersData = innerEstimator.getInliersData();
             attemptRefine(result);
 
             if (listener != null) {
                 listener.onEstimateEnd(this);
             }
 
         } 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;
     }
 }