BFDictionaryDirective.java

package co.insecurity.policy.directive;

import orestes.bloomfilter.BloomFilter;
import orestes.bloomfilter.FilterBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.BufferedReader;
import java.io.IOException;
import java.util.ConcurrentModificationException;

public class BFDictionaryDirective implements Directive<String> {

    private static final Logger LOG = LoggerFactory.getLogger(BFDictionaryDirective.class);
    private static final String DEFAULT_DICTIONARY = "passwords.dat";

    private final BloomFilter<String> filter;

    public BFDictionaryDirective() throws IOException {
        this(Dictionary.fromResource(DEFAULT_DICTIONARY));
    }

    public BFDictionaryDirective(Dictionary dictionary) throws IOException {
        filter = new FilterBuilder(dictionary.getNumWords(), 0.001)
                .buildBloomFilter();
        loadDictionary(dictionary);
        LOG.debug("Instantiated new directive: {}", this.toString());
    }

    public BFDictionaryDirective(BloomFilter<String> filter) {
        this.filter = filter;
        LOG.debug("Instantiated new directive: {}", this.toString());
    }

    public void loadDictionary(Dictionary dictionary) throws IOException {
        LOG.debug("Loading {} into filter", dictionary);
        int numExpected = filter.getExpectedElements();
        int numAdded = 0;
        try (BufferedReader reader = dictionary.getReader()) {
            String word = null;
            while ((word = reader.readLine()) != null) {
                if (filter.add(word))
                    numAdded++;
                else
                    LOG.debug("Not loaded into filter (may be duplicate): {}", word);
                if (numAdded > numExpected) {
                    String msg = String.format("Added %d words but expected %d. Did the data file change?",
                            numAdded, numExpected);
                    LOG.error(msg);
                    throw new ConcurrentModificationException(msg);
                }
            }
        }
        LOG.debug("Successfully loaded {} words into filter", numAdded);
    }

    @Override
    public boolean isMet(String s) {
        return !filter.contains(s);
    }

    @Override
    public String toString() {
        return String.format("[BFDictionaryDirective[%s]", filter.asString());
    }
}