source: trunk/quest-core-coverage/src/main/java/de/ugoe/cs/quest/coverage/SequenceTools.java @ 518

package de.ugoe.cs.quest.coverage;

import java.security.InvalidParameterException;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import de.ugoe.cs.quest.eventcore.Event;
import de.ugoe.cs.quest.usageprofiles.IStochasticProcess;

/**
 * <p>
 * This class gathers some helper functions to work with sequences.
 * </p>
 * 
 * @author Steffen Herbold
 * @version 1.0
 */
public class SequenceTools {
        
        /**
         * <p>
         * Private constructor to prevent initializing of the class.
         * </p>
         */
        private SequenceTools() {
                
        }

        /**
         * <p>
         * Calculates the weights for all sequences passed to this function as
         * defined by the stochastic process and stores them in a {@link Map}. The
         * weights are normalized, i.e., the sum of all weights contained in this
         * map is 1.
         * </p>
         * 
         * @param process
         *            process used for weight calculation
         * @param sequences
         *            sequences for which the weights are calculated
         * @return {@link Map} of weights
         */
        public static Map<List<? extends Event<?>>, Double> generateWeights(
                        IStochasticProcess process,
                        Collection<List<? extends Event<?>>> sequences) {
                Map<List<? extends Event<?>>, Double> subSeqWeights = new LinkedHashMap<List<? extends Event<?>>, Double>();
                if (sequences != null && !sequences.isEmpty()) {
                        if (process != null) {
                                double sum = 0.0;
                                for (List<? extends Event<?>> sequence : sequences) {
                                        double prob = process.getProbability(sequence);
                                        subSeqWeights.put(sequence, prob);
                                        sum += prob;
                                }
                                if (sum < 1.0) {
                                        for (Map.Entry<List<? extends Event<?>>, Double> entry : subSeqWeights
                                                        .entrySet()) {
                                                entry.setValue(entry.getValue() / sum);
                                        }
                                }
                        } else {
                                for( List<? extends Event<?>> sequence : sequences ) {
                                        subSeqWeights.put(sequence, 0.0d);
                                }
                        }
                }
                return subSeqWeights;
        }

        /**
         * <p>
         * Calculates the number of all existing sequences of a given length,
         * regardless whether they are possible or not.
         * </p>
         * 
         * @param process
         *            stochastic process whose symbols are the basis for this
         *            calculation
         * @param length
         *            lenght of the sequences
         * @return numStates^length
         * @throws InvalidParameterException
         *             thrown if length less or equal to 0
         */
        public static long numSequences(IStochasticProcess process, int length) {
                if (length <= 0) {
                        throw new InvalidParameterException(
                                        "length must be a positive integer");
                }
                long result = 0;
                if (process != null) {
                        result = (long) Math.pow(process.getNumSymbols(), length);
                }
                return result;
        }

        /**
         * <p>
         * Creates a {@link Set} of all subsequences of a given length that are
         * contained in a sequence collection.
         * </p>
         * 
         * @param sequences
         *            sequences from which the subsequences are extracted
         * @param length
         *            length of the subsequences
         * @return {@link Set} of all subsequences
         * @throws InvalidParameterException
         *             thrown if length less or equal to 0
         */
        public static Set<List<? extends Event<?>>> containedSubSequences(
                        Collection<List<? extends Event<?>>> sequences, int length) {
                if (length <= 0) {
                        throw new InvalidParameterException(
                                        "length must be a positive integer");
                }
                Set<List<? extends Event<?>>> containedSubSeqs = new LinkedHashSet<List<? extends Event<?>>>();
                if (sequences != null) {
                        for (List<? extends Event<?>> sequence : sequences) {
                                List<Event<?>> subSeq = new LinkedList<Event<?>>();
                                boolean minLengthReached = false;
                                for (Event<?> event : sequence) {
                                        subSeq.add(event);
                                        if (!minLengthReached) {
                                                if (subSeq.size() == length) {
                                                        minLengthReached = true;
                                                }
                                        } else {
                                                subSeq.remove(0);
                                        }
                                        if (minLengthReached) {
                                                if (!containedSubSeqs.contains(subSeq)) {
                                                        containedSubSeqs.add(new LinkedList<Event<?>>(
                                                                        subSeq));
                                                }
                                        }
                                }
                        }
                }
                return containedSubSeqs;
        }
}