/*
    * Copyright (C) 2019 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.position;
  
  import com.irurueta.algebra.Matrix;
  import com.irurueta.geometry.Point;
  import com.irurueta.navigation.LockedException;
  import com.irurueta.navigation.NotReadyException;
  import com.irurueta.navigation.indoor.Fingerprint;
  import com.irurueta.navigation.indoor.RadioSource;
  import com.irurueta.navigation.indoor.RadioSourceLocated;
  import com.irurueta.navigation.indoor.RssiReading;
  import com.irurueta.navigation.lateration.LaterationException;
  import com.irurueta.navigation.lateration.LaterationSolver;
  import com.irurueta.navigation.lateration.LaterationSolverListener;
  import com.irurueta.navigation.lateration.NonLinearLeastSquaresLaterationSolver;
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Estimates position non-linearly using located radio sources and their RSSI readings at
   * unknown locations.
   * These kind of estimators can be used to determine the position of a given device by
   * getting RSSI readings at an unknown location of different radio sources whose locations
   * are known.
   *
   * @param <P> a {@link Point} type.
   */
  public abstract class NonLinearRssiPositionEstimator<P extends Point<?>> extends RssiPositionEstimator<P> {
  
      /**
       * Distance standard deviation assumed for provided distances as a fallback when
       * none can be determined.
       */
      public static final double FALLBACK_DISTANCE_STANDARD_DEVIATION =
              NonLinearLeastSquaresLaterationSolver.DEFAULT_DISTANCE_STANDARD_DEVIATION;
  
      /**
       * A non-linear lateration solver to solve position.
       */
      protected NonLinearLeastSquaresLaterationSolver<P> trilaterationSolver;
  
      /**
       * Listener for the lateration solver.
       */
      protected LaterationSolverListener<P> laterationSolverListener;
  
      /**
       * Initial position to start position estimation.
       * If not defined, centroid of provided located sources will be used.
       */
      private P initialPosition;
  
      /**
       * Indicates whether located radio source position covariance must be taken
       * into account (if available) to determine distance standard deviation.
       */
      private boolean useRadioSourcePositionCovariance;
  
      /**
       * Distance standard deviation fallback value to use when none can be
       * determined from provided radio sources and fingerprint readings.
       */
      private double fallbackDistanceStandardDeviation = FALLBACK_DISTANCE_STANDARD_DEVIATION;
  
      /**
       * Constructor.
       */
      protected NonLinearRssiPositionEstimator() {
          super();
          init();
      }
  
      /**
       * Constructor.
       *
       * @param listener listener in charge of handling events.
       */
      protected NonLinearRssiPositionEstimator(final RssiPositionEstimatorListener<P> listener) {
          super(listener);
          init();
      }
  
      /**
       * Constructor.
       *
      * @param initialPosition initial position to start position estimation.
      */
     protected NonLinearRssiPositionEstimator(final P initialPosition) {
         this();
         this.initialPosition = initialPosition;
     }
 
     /**
      * Constructor.
      *
      * @param initialPosition initial position to start position estimation.
      * @param listener        listener in charge of handling events.
      */
     protected NonLinearRssiPositionEstimator(
             final P initialPosition, final RssiPositionEstimatorListener<P> listener) {
         this(listener);
         this.initialPosition = initialPosition;
     }
 
     /**
      * Gets initial position to start position estimation.
      * If not defined, centroid of located sources position will be used to start
      * the estimation.
      *
      * @return initial position to start position estimation.
      */
     public P getInitialPosition() {
         return initialPosition;
     }
 
     /**
      * Sets initial position to start position estimation.
      * If not defined, centroid of located sources position will be used to start
      * the estimation.
      *
      * @param initialPosition initial position to start position estimation.
      * @throws LockedException if estimator is locked.
      */
     public void setInitialPosition(final P initialPosition) throws LockedException {
         if (isLocked()) {
             throw new LockedException();
         }
         this.initialPosition = initialPosition;
     }
 
     /**
      * Indicates whether located radio source position covariance must be taken into
      * account (if available) to determine distance standard deviation.
      *
      * @return true to take radio source position covariance into account, false
      * otherwise.
      */
     public boolean isRadioSourcePositionCovarianceUsed() {
         return useRadioSourcePositionCovariance;
     }
 
     /**
      * Specifies whether located radio source position covariance must be taken into
      * account (if available) to determine distance standard deviation.
      *
      * @param useRadioSourcePositionCovariance true to take radio source position
      *                                         covariance into account, false otherwise.
      * @throws LockedException if estimator is locked.
      */
     public void setRadioSourcePositionCovarianceUsed(final boolean useRadioSourcePositionCovariance)
             throws LockedException {
         if (isLocked()) {
             throw new LockedException();
         }
         this.useRadioSourcePositionCovariance = useRadioSourcePositionCovariance;
     }
 
     /**
      * Gets distance standard deviation fallback value to use when none can be
      * determined from provided radio sources and fingerprint readings.
      *
      * @return distance standard deviation to use as fallback.
      */
     public double getFallbackDistanceStandardDeviation() {
         return fallbackDistanceStandardDeviation;
     }
 
     /**
      * Sets distance standard deviation fallback value to use when none can be
      * determined from provided radio sources and fingerprint readings.
      *
      * @param fallbackDistanceStandardDeviation distance standard deviation to use
      *                                          as fallback.
      * @throws LockedException if estimator is locked.
      */
     public void setFallbackDistanceStandardDeviation(final double fallbackDistanceStandardDeviation)
             throws LockedException {
         if (isLocked()) {
             throw new LockedException();
         }
         this.fallbackDistanceStandardDeviation = fallbackDistanceStandardDeviation;
     }
 
     /**
      * Gets minimum required number of located radio sources to perform lateration.
      *
      * @return minimum required number of located radio sources to perform lateration.
      */
     @Override
     public int getMinRequiredSources() {
         return trilaterationSolver.getMinRequiredPositionsAndDistances();
     }
 
     /**
      * Indicates whether estimator is ready to find a solution.
      *
      * @return true if estimator is ready, false otherwise.
      */
     @Override
     public boolean isReady() {
         return trilaterationSolver.isReady();
     }
 
     /**
      * Returns boolean indicating whether this estimator is locked because an estimation
      * is already in progress.
      *
      * @return true if estimator is locked, false otherwise.
      */
     @Override
     public boolean isLocked() {
         return trilaterationSolver.isLocked();
     }
 
     /**
      * Gets standard deviations of distances from known located radio sources to the
      * location of provided readings in a fingerprint.
      * Distance standard deviations are used internally to solve lateration.
      *
      * @return standard deviations used internally.
      */
     public double[] getDistanceStandardDeviations() {
         return trilaterationSolver.getDistanceStandardDeviations();
     }
 
     /**
      * Estimates position based on provided located radio sources and readings of such
      * radio sources at an unknown location.
      *
      * @throws LockedException             if estimator is locked.
      * @throws NotReadyException           if estimator is not ready.
      * @throws PositionEstimationException if estimation fails for some other reason.
      */
     @Override
     public void estimate() throws LockedException, NotReadyException, PositionEstimationException {
         try {
             trilaterationSolver.setInitialPosition(initialPosition);
 
             trilaterationSolver.solve();
             estimatedPositionCoordinates = trilaterationSolver.getEstimatedPositionCoordinates();
         } catch (final LaterationException e) {
             throw new PositionEstimationException(e);
         }
     }
 
     /**
      * Gets known positions of radio sources used internally to solve lateration.
      *
      * @return known positions used internally.
      */
     @Override
     public P[] getPositions() {
         return trilaterationSolver.getPositions();
     }
 
     /**
      * Gets Euclidean distances from known located radio sources to the location of
      * provided readings in a fingerprint.
      * Distance values are used internally to solve lateration.
      *
      * @return Euclidean distances used internally.
      */
     @Override
     public double[] getDistances() {
         return trilaterationSolver.getDistances();
     }
 
     /**
      * Gets estimated covariance matrix for estimated position.
      *
      * @return estimated covariance matrix for estimated position.
      */
     public Matrix getCovariance() {
         return trilaterationSolver.getCovariance();
     }
 
     /**
      * Internally sets located radio sources used for lateration.
      *
      * @param sources located radio sources used for lateration.
      * @throws IllegalArgumentException if provided value is null or the number of
      *                                  provided sources is less than the required minimum.
      */
     @Override
     protected void internalSetSources(final List<? extends RadioSourceLocated<P>> sources) {
         super.internalSetSources(sources);
         buildPositionsDistancesAndDistanceStandardDeviations();
     }
 
     /**
      * Internally sets fingerprint containing readings at an unknown location for provided
      * located radio sources.
      *
      * @param fingerprint fingerprint containing readings at an unknown location for
      *                    provided located radio sources.
      * @throws IllegalArgumentException if provided value is null.
      */
     @Override
     protected void internalSetFingerprint(
             final Fingerprint<? extends RadioSource, ? extends RssiReading<? extends RadioSource>> fingerprint) {
         super.internalSetFingerprint(fingerprint);
         buildPositionsDistancesAndDistanceStandardDeviations();
     }
 
     /**
      * Sets positions, distances and standard deviations of distances on internal
      * lateration solver.
      *
      * @param positions                  positions to be set.
      * @param distances                  distances to be set.
      * @param distanceStandardDeviations standard deviations of distances to be set.
      */
     protected abstract void setPositionsDistancesAndDistanceStandardDeviations(
             final List<P> positions, final List<Double> distances, final List<Double> distanceStandardDeviations);
 
     /**
      * Initializes lateration solver listener.
      */
     @SuppressWarnings("Duplicates")
     private void init() {
         laterationSolverListener = new LaterationSolverListener<>() {
             @Override
             public void onSolveStart(final LaterationSolver<P> solver) {
                 if (listener != null) {
                     listener.onEstimateStart(NonLinearRssiPositionEstimator.this);
                 }
             }
 
             @Override
             public void onSolveEnd(final LaterationSolver<P> solver) {
                 if (listener != null) {
                     listener.onEstimateEnd(NonLinearRssiPositionEstimator.this);
                 }
             }
         };
     }
 
     /**
      * Builds positions, distances and standard deviation of distances for the internal
      * lateration solver.
      */
     @SuppressWarnings("Duplicates")
     private void buildPositionsDistancesAndDistanceStandardDeviations() {
         if (trilaterationSolver == null) {
             return;
         }
 
         final var min = getMinRequiredSources();
         if (sources == null || fingerprint == null || sources.size() < min || fingerprint.getReadings() == null
                 || fingerprint.getReadings().size() < min) {
             return;
         }
 
         final var positions = new ArrayList<P>();
         final var distances = new ArrayList<Double>();
         final var distanceStandardDeviations = new ArrayList<Double>();
         PositionEstimatorHelper.buildPositionsDistancesAndDistanceStandardDeviations(sources, fingerprint,
                 useRadioSourcePositionCovariance, fallbackDistanceStandardDeviation, positions, distances,
                 distanceStandardDeviations);
 
         setPositionsDistancesAndDistanceStandardDeviations(positions, distances, distanceStandardDeviations);
     }
 }