package de.lmu.ifi.dbs.elki.algorithm.outlier.lof;

/*
 This file is part of ELKI:
 Environment for Developing KDD-Applications Supported by Index-Structures

 Copyright (C) 2015
 Ludwig-Maximilians-Universität München
 Lehr- und Forschungseinheit für Datenbanksysteme
 ELKI Development Team

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU Affero General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.util.Arrays;

import de.lmu.ifi.dbs.elki.algorithm.AbstractDistanceBasedAlgorithm;
import de.lmu.ifi.dbs.elki.algorithm.outlier.OutlierAlgorithm;
import de.lmu.ifi.dbs.elki.data.type.TypeInformation;
import de.lmu.ifi.dbs.elki.data.type.TypeUtil;
import de.lmu.ifi.dbs.elki.database.Database;
import de.lmu.ifi.dbs.elki.database.datastore.DataStoreFactory;
import de.lmu.ifi.dbs.elki.database.datastore.DataStoreUtil;
import de.lmu.ifi.dbs.elki.database.datastore.WritableDataStore;
import de.lmu.ifi.dbs.elki.database.datastore.WritableDoubleDataStore;
import de.lmu.ifi.dbs.elki.database.ids.DBIDIter;
import de.lmu.ifi.dbs.elki.database.ids.DBIDs;
import de.lmu.ifi.dbs.elki.database.ids.DoubleDBIDList;
import de.lmu.ifi.dbs.elki.database.ids.DoubleDBIDListIter;
import de.lmu.ifi.dbs.elki.database.query.distance.DistanceQuery;
import de.lmu.ifi.dbs.elki.database.query.range.RangeQuery;
import de.lmu.ifi.dbs.elki.database.relation.DoubleRelation;
import de.lmu.ifi.dbs.elki.database.relation.MaterializedDoubleRelation;
import de.lmu.ifi.dbs.elki.database.relation.Relation;
import de.lmu.ifi.dbs.elki.distance.distancefunction.DistanceFunction;
import de.lmu.ifi.dbs.elki.logging.Logging;
import de.lmu.ifi.dbs.elki.logging.progress.FiniteProgress;
import de.lmu.ifi.dbs.elki.math.DoubleMinMax;
import de.lmu.ifi.dbs.elki.math.MeanVariance;
import de.lmu.ifi.dbs.elki.result.outlier.OutlierResult;
import de.lmu.ifi.dbs.elki.result.outlier.OutlierScoreMeta;
import de.lmu.ifi.dbs.elki.result.outlier.QuotientOutlierScoreMeta;
import de.lmu.ifi.dbs.elki.utilities.Alias;
import de.lmu.ifi.dbs.elki.utilities.datastructures.arrays.DoubleIntegerArrayQuickSort;
import de.lmu.ifi.dbs.elki.utilities.documentation.Description;
import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
import de.lmu.ifi.dbs.elki.utilities.documentation.Title;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.OptionID;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameterization.Parameterization;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.DoubleParameter;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.IntParameter;

/**
 * Fast Outlier Detection Using the "Local Correlation Integral".
 * 
 * Exact implementation only, not aLOCI. See {@link ALOCI}.
 * 
 * Outlier detection using multiple epsilon neighborhoods.
 * 
 * This implementation has O(n<sup>3</sup> log n) runtime complexity!
 * 
 * Based on: S. Papadimitriou, H. Kitagawa, P. B. Gibbons and C. Faloutsos:
 * LOCI: Fast Outlier Detection Using the Local Correlation Integral. In: Proc.
 * 19th IEEE Int. Conf. on Data Engineering (ICDE '03), Bangalore, India, 2003.
 * 
 * @author Erich Schubert
 * 
 * @apiviz.has RangeQuery
 * 
 * @param <O> Object type
 */
@Title("LOCI: Fast Outlier Detection Using the Local Correlation Integral")
@Description("Algorithm to compute outliers based on the Local Correlation Integral")
@Reference(authors = "S. Papadimitriou, H. Kitagawa, P. B. Gibbons, C. Faloutsos", title = "LOCI: Fast Outlier Detection Using the Local Correlation Integral", booktitle = "Proc. 19th IEEE Int. Conf. on Data Engineering (ICDE '03), Bangalore, India, 2003", url = "http://dx.doi.org/10.1109/ICDE.2003.1260802")
@Alias({ "de.lmu.ifi.dbs.elki.algorithm.outlier.LOCI" })
public class LOCI<O> extends AbstractDistanceBasedAlgorithm<O, OutlierResult> implements OutlierAlgorithm {
  /**
   * The logger for this class.
   */
  private static final Logging LOG = Logging.getLogger(LOCI.class);

  /**
   * Parameter to specify the maximum radius of the neighborhood to be
   * considered, must be suitable to the distance function specified.
   */
  public static final OptionID RMAX_ID = new OptionID("loci.rmax", "The maximum radius of the neighborhood to be considered.");

  /**
   * Parameter to specify the minimum neighborhood size
   */
  public static final OptionID NMIN_ID = new OptionID("loci.nmin", "Minimum neighborhood size to be considered.");

  /**
   * Parameter to specify the averaging neighborhood scaling.
   */
  public static final OptionID ALPHA_ID = new OptionID("loci.alpha", "Scaling factor for averaging neighborhood");

  /**
   * Holds the value of {@link #RMAX_ID}.
   */
  private double rmax;

  /**
   * Holds the value of {@link #NMIN_ID}.
   */
  private int nmin;

  /**
   * Holds the value of {@link #ALPHA_ID}.
   */
  private double alpha;

  /**
   * Constructor.
   * 
   * @param distanceFunction Distance function
   * @param rmax Maximum radius
   * @param nmin Minimum neighborhood size
   * @param alpha Alpha value
   */
  public LOCI(DistanceFunction<? super O> distanceFunction, double rmax, int nmin, double alpha) {
    super(distanceFunction);
    this.rmax = rmax;
    this.nmin = nmin;
    this.alpha = alpha;
  }

  /**
   * Run the algorithm
   * 
   * @param database Database to process
   * @param relation Relation to process
   * @return Outlier result
   */
  public OutlierResult run(Database database, Relation<O> relation) {
    DistanceQuery<O> distFunc = database.getDistanceQuery(relation, getDistanceFunction());
    RangeQuery<O> rangeQuery = database.getRangeQuery(distFunc);
    DBIDs ids = relation.getDBIDs();

    // LOCI preprocessing step
    WritableDataStore<DoubleIntArrayList> interestingDistances = DataStoreUtil.makeStorage(relation.getDBIDs(), DataStoreFactory.HINT_TEMP | DataStoreFactory.HINT_SORTED, DoubleIntArrayList.class);
    precomputeInterestingRadii(ids, rangeQuery, interestingDistances);
    // LOCI main step
    FiniteProgress progressLOCI = LOG.isVerbose() ? new FiniteProgress("LOCI scores", relation.size(), LOG) : null;
    WritableDoubleDataStore mdef_norm = DataStoreUtil.makeDoubleStorage(relation.getDBIDs(), DataStoreFactory.HINT_STATIC);
    WritableDoubleDataStore mdef_radius = DataStoreUtil.makeDoubleStorage(relation.getDBIDs(), DataStoreFactory.HINT_STATIC);
    DoubleMinMax minmax = new DoubleMinMax();

    // Shared instance, to save allocations.
    MeanVariance mv_n_r_alpha = new MeanVariance();

    for(DBIDIter iditer = ids.iter(); iditer.valid(); iditer.advance()) {
      final DoubleIntArrayList cdist = interestingDistances.get(iditer);
      final double maxdist = cdist.getDouble(cdist.size() - 1);
      final int maxneig = cdist.getInt(cdist.size() - 1);

      double maxmdefnorm = 0.0;
      double maxnormr = 0;
      if(maxneig >= nmin) {
        // Compute the largest neighborhood we will need.
        DoubleDBIDList maxneighbors = rangeQuery.getRangeForDBID(iditer, maxdist);
        // TODO: Ensure the result is sorted. This is currently implied.

        // For any critical distance, compute the normalized MDEF score.
        for(int i = 0, size = cdist.size(); i < size; i++) {
          // Only start when minimum size is fulfilled
          if(cdist.getInt(i) < nmin) {
            continue;
          }
          final double r = cdist.getDouble(i);
          final double alpha_r = alpha * r;
          // compute n(p_i, \alpha * r) from list (note: alpha_r is not cdist!)
          final int n_alphar = cdist.getInt(cdist.find(alpha_r));
          // compute \hat{n}(p_i, r, \alpha) and the corresponding \simga_{MDEF}
          mv_n_r_alpha.reset();
          for(DoubleDBIDListIter neighbor = maxneighbors.iter(); neighbor.valid(); neighbor.advance()) {
            // Stop at radius r
            if(neighbor.doubleValue() > r) {
              break;
            }
            DoubleIntArrayList cdist2 = interestingDistances.get(neighbor);
            int rn_alphar = cdist2.getInt(cdist2.find(alpha_r));
            mv_n_r_alpha.put(rn_alphar);
          }
          // We only use the average and standard deviation
          final double nhat_r_alpha = mv_n_r_alpha.getMean();
          final double sigma_nhat_r_alpha = mv_n_r_alpha.getNaiveStddev();

          // Redundant divisions by nhat_r_alpha removed.
          final double mdef = nhat_r_alpha - n_alphar;
          final double sigmamdef = sigma_nhat_r_alpha;
          final double mdefnorm = mdef / sigmamdef;

          if(mdefnorm > maxmdefnorm) {
            maxmdefnorm = mdefnorm;
            maxnormr = r;
          }
        }
      }
      else {
        // FIXME: when nmin was not fulfilled - what is the proper value then?
        maxmdefnorm = Double.POSITIVE_INFINITY;
        maxnormr = maxdist;
      }
      mdef_norm.putDouble(iditer, maxmdefnorm);
      mdef_radius.putDouble(iditer, maxnormr);
      minmax.put(maxmdefnorm);
      LOG.incrementProcessed(progressLOCI);
    }
    LOG.ensureCompleted(progressLOCI);
    DoubleRelation scoreResult = new MaterializedDoubleRelation("LOCI normalized MDEF", "loci-mdef-outlier", mdef_norm, relation.getDBIDs());
    OutlierScoreMeta scoreMeta = new QuotientOutlierScoreMeta(minmax.getMin(), minmax.getMax(), 0.0, Double.POSITIVE_INFINITY, 0.0);
    OutlierResult result = new OutlierResult(scoreMeta, scoreResult);
    result.addChildResult(new MaterializedDoubleRelation("LOCI MDEF Radius", "loci-critical-radius", mdef_radius, relation.getDBIDs()));
    return result;
  }

  /**
   * Preprocessing step: determine the radii of interest for each point.
   * 
   * @param ids IDs to process
   * @param rangeQuery Range query
   * @param interestingDistances Distances of interest
   */
  protected void precomputeInterestingRadii(DBIDs ids, RangeQuery<O> rangeQuery, WritableDataStore<DoubleIntArrayList> interestingDistances) {
    FiniteProgress progressPreproc = LOG.isVerbose() ? new FiniteProgress("LOCI preprocessing", ids.size(), LOG) : null;
    for(DBIDIter iditer = ids.iter(); iditer.valid(); iditer.advance()) {
      DoubleDBIDList neighbors = rangeQuery.getRangeForDBID(iditer, rmax);
      // build list of critical distances
      DoubleIntArrayList cdist = new DoubleIntArrayList(neighbors.size() << 1);
      {
        int i = 0;
        DoubleDBIDListIter ni = neighbors.iter();
        while(ni.valid()) {
          final double curdist = ni.doubleValue();
          ++i;
          ni.advance();
          // Skip, if tied to the next object:
          if(ni.valid() && curdist == ni.doubleValue()) {
            continue;
          }
          cdist.append(curdist, i);
          // Scale radius, and reinsert
          if(alpha != 1.) {
            final double ri = curdist / alpha;
            if(ri <= rmax) {
              cdist.append(ri, Integer.MIN_VALUE);
            }
          }
        }
      }
      cdist.sort();

      // fill the gaps to have fast lookups of number of neighbors at a given
      // distance.
      int lastk = 0;
      for(int i = 0, size = cdist.size(); i < size; i++) {
        final int k = cdist.getInt(i);
        if(k == Integer.MIN_VALUE) {
          cdist.setValue(i, lastk);
        }
        else {
          lastk = k;
        }
      }
      // TODO: shrink the list, removing duplicate radii?

      interestingDistances.put(iditer, cdist);
      LOG.incrementProcessed(progressPreproc);
    }
    LOG.ensureCompleted(progressPreproc);
  }

  /**
   * Array of double-int values.
   * 
   * @author Erich Schubert
   *
   * @apiviz.exclude
   */
  protected static class DoubleIntArrayList {
    /**
     * Double keys
     */
    double[] keys;

    /**
     * Integer values
     */
    int[] vals;

    /**
     * Used size
     */
    int size = 0;

    /**
     * Constructor.
     * 
     * @param alloc Initial allocation.
     */
    public DoubleIntArrayList(int alloc) {
      keys = new double[alloc];
      vals = new int[alloc];
      size = 0;
    }

    /**
     * Collection size.
     * 
     * @return Size
     */
    public int size() {
      return size;
    }

    /**
     * Get the key at the given position.
     * 
     * @param i Position
     * @return Key
     */
    public double getDouble(int i) {
      return keys[i];
    }

    /**
     * Get the value at the given position.
     * 
     * @param i Position
     * @return Value
     */
    public int getInt(int i) {
      return vals[i];
    }

    /**
     * Get the value at the given position.
     * 
     * @param i Position
     * @param val New value
     */
    public void setValue(int i, int val) {
      vals[i] = val;
    }

    /**
     * Append a key-value pair.
     * 
     * @param key Key to append
     * @param val Value to append.
     */
    public void append(double key, int val) {
      if(size == keys.length) {
        keys = Arrays.copyOf(keys, size << 1);
        vals = Arrays.copyOf(vals, size << 1);
      }
      keys[size] = key;
      vals[size] = val;
      ++size;
    }

    /**
     * Find the last position with a smaller or equal key.
     * 
     * @param search Key
     * @return Position
     */
    public int find(final double search) {
      int a = 0, b = size - 1;
      while(a <= b) {
        final int mid = (a + b) >>> 1;
        final double cur = keys[mid];
        if(cur > search) {
          b = mid - 1;
        }
        else { // less or equal!
          a = mid + 1;
        }
      }
      return b;
    }

    /**
     * Sort the array list.
     */
    public void sort() {
      DoubleIntegerArrayQuickSort.sort(keys, vals, size);
    }
  }

  @Override
  public TypeInformation[] getInputTypeRestriction() {
    return TypeUtil.array(getDistanceFunction().getInputTypeRestriction());
  }

  @Override
  protected Logging getLogger() {
    return LOG;
  }

  /**
   * Parameterization class.
   * 
   * @author Erich Schubert
   * 
   * @apiviz.exclude
   * 
   * @param <O> Object type
   */
  public static class Parameterizer<O> extends AbstractDistanceBasedAlgorithm.Parameterizer<O> {
    protected double rmax;

    protected int nmin = 0;

    protected double alpha = 0.5;

    @Override
    protected void makeOptions(Parameterization config) {
      super.makeOptions(config);
      final DoubleParameter rmaxP = new DoubleParameter(RMAX_ID);
      if(config.grab(rmaxP)) {
        rmax = rmaxP.doubleValue();
      }

      final IntParameter nminP = new IntParameter(NMIN_ID, 20);
      if(config.grab(nminP)) {
        nmin = nminP.intValue();
      }

      final DoubleParameter alphaP = new DoubleParameter(ALPHA_ID, 0.5);
      if(config.grab(alphaP)) {
        alpha = alphaP.getValue();
      }
    }

    @Override
    protected LOCI<O> makeInstance() {
      return new LOCI<>(distanceFunction, rmax, nmin, alpha);
    }
  }
}