/*
    * 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.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.HomogeneousLinearLeastSquaresLaterationSolver;
  import com.irurueta.navigation.lateration.InhomogeneousLinearLeastSquaresLaterationSolver;
  import com.irurueta.navigation.lateration.LaterationException;
  import com.irurueta.navigation.lateration.LaterationSolver;
  import com.irurueta.navigation.lateration.LaterationSolverListener;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Linearly estimates position 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 LinearRssiPositionEstimator<P extends Point<P>> extends RssiPositionEstimator<P> {
  
      /**
       * Indicates that by default an homogeneous linear solver is used to estimate
       * position.
       */
      public static final boolean DEFAULT_USE_HOMOGENEOUS_LINEAR_SOLVER = true;
  
      /**
       * An homogeneous linear lateration solver to solve position.
       */
      protected HomogeneousLinearLeastSquaresLaterationSolver<P> homogeneousTrilaterationSolver;
  
      /**
       * An inhomogeneous linear lateration solver to solve position.
       */
      protected InhomogeneousLinearLeastSquaresLaterationSolver<P> inhomogeneousTrilaterationSolver;
  
      /**
       * Listener for the lateration solver.
       */
      protected LaterationSolverListener<P> laterationSolverListener;
  
      /**
       * Indicates whether an homogeneous linear solver is used to estimate position.
       */
      protected boolean useHomogeneousLinearSolver = DEFAULT_USE_HOMOGENEOUS_LINEAR_SOLVER;
  
      /**
       * Constructor.
       */
      protected LinearRssiPositionEstimator() {
          super();
          init();
      }
  
      /**
       * Constructor.
       *
       * @param listener listener in charge of handling events.
       */
      protected LinearRssiPositionEstimator(final RssiPositionEstimatorListener<P> listener) {
          super(listener);
          init();
      }
  
      /**
       * Indicates whether an homogeneous linear solver is used to estimate position.
       *
       * @return true if homogeneous linear solver is used, false if an inhomogeneous
       * linear one is used instead.
       */
      public boolean isHomogeneousLinearSolverUsed() {
          return useHomogeneousLinearSolver;
      }
  
      /**
      * Specifies whether an homogeneous linear solver is used to estimate position.
      *
      * @param useHomogeneousLinearSolver true if homogeneous linear solver is used, false
      *                                   if an inhomogeneous linear one is used instead.
      * @throws LockedException if estimator is locked.
      */
     public void setHomogeneousLinearSolverUsed(final boolean useHomogeneousLinearSolver) throws LockedException {
         if (isLocked()) {
             throw new LockedException();
         }
 
         this.useHomogeneousLinearSolver = useHomogeneousLinearSolver;
     }
 
     /**
      * 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 useHomogeneousLinearSolver ? homogeneousTrilaterationSolver.getMinRequiredPositionsAndDistances()
                 : inhomogeneousTrilaterationSolver.getMinRequiredPositionsAndDistances();
     }
 
     /**
      * Indicates whether estimator is ready to find a solution.
      *
      * @return true if estimator is ready, false otherwise.
      */
     @Override
     public boolean isReady() {
         return (!useHomogeneousLinearSolver && inhomogeneousTrilaterationSolver.isReady())
                 || (useHomogeneousLinearSolver && homogeneousTrilaterationSolver.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 inhomogeneousTrilaterationSolver.isLocked() || homogeneousTrilaterationSolver.isLocked();
     }
 
     /**
      * Estimates position based on provided located radio sources and RSSI 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.
      */
     @SuppressWarnings("Duplicates")
     @Override
     public void estimate() throws LockedException, NotReadyException, PositionEstimationException {
         try {
             if (useHomogeneousLinearSolver) {
                 homogeneousTrilaterationSolver.solve();
                 estimatedPositionCoordinates = homogeneousTrilaterationSolver.getEstimatedPositionCoordinates();
             } else {
                 inhomogeneousTrilaterationSolver.solve();
                 estimatedPositionCoordinates = inhomogeneousTrilaterationSolver.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 useHomogeneousLinearSolver ? homogeneousTrilaterationSolver.getPositions()
                 : inhomogeneousTrilaterationSolver.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 useHomogeneousLinearSolver ? homogeneousTrilaterationSolver.getDistances()
                 : inhomogeneousTrilaterationSolver.getDistances();
     }
 
     /**
      * 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);
         buildPositionsAndDistances();
     }
 
     /**
      * 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);
         buildPositionsAndDistances();
     }
 
     /**
      * Sets positions and distances on internal lateration solver.
      *
      * @param positions positions to be set.
      * @param distances distances to be set.
      */
     protected abstract void setPositionsAndDistances(final List<P> positions, final List<Double> distances);
 
     /**
      * 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(LinearRssiPositionEstimator.this);
                 }
             }
 
             @Override
             public void onSolveEnd(final LaterationSolver<P> solver) {
                 if (listener != null) {
                     listener.onEstimateEnd(LinearRssiPositionEstimator.this);
                 }
             }
         };
     }
 
     /**
      * Builds positions and distances for the internal lateration solver.
      */
     @SuppressWarnings("Duplicates")
     private void buildPositionsAndDistances() {
         if ((useHomogeneousLinearSolver && homogeneousTrilaterationSolver == null)
                 || (!useHomogeneousLinearSolver && inhomogeneousTrilaterationSolver == 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>();
         PositionEstimatorHelper.buildPositionsAndDistances(sources, fingerprint, positions, distances);
 
         setPositionsAndDistances(positions, distances);
     }
 }