// Device detection provider which takes User-Agents and returns matches.
    protected final Provider provider;
    
    // User-Agent string of a iPhone mobile device.
    protected final String mobileUserAgent = "Mozilla/5.0 (iPhone; CPU iPhone "
            + "OS 7_1 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) "
            + "Version/7.0 Mobile/11D167 Safari/9537.53";
    
    // User-Agent string of Firefox Web browser of version 41 used on desktop.
    protected final String desktopUserAgent = "Mozilla/5.0 (Windows NT 6.3; " +
            "WOW64; rv:41.0) Gecko/20100101 Firefox/41.0";
    
    // User-Agent string of a MediaHub device.
    protected final String mediaHubUserAgent = "Mozilla/5.0 (Linux; Android 4.4"
            + ".2; X7 Quad Core Build/KOT49H) AppleWebKit/537.36 (KHTML, like "
            + "Gecko) Version/4.0 Chrome/30.0.0.0 Safari/537.36";

    /**
     * Initialises the device detection Provider with the included Lite data
     * file. For more data see: 
     * <a href="https://51degrees.com/compare-data-options">compare data options
     * </a>
     * 
     * @throws IOException can be thrown if there is a problem reading from the 
     * provided data file.
     */
    public MatchMetrics() throws IOException {
        provider = new Provider(StreamFactory.create(
                Shared.getLitePatternV32(), false));
    }
    
    /**
     * Extracts MatchMethods enumeration value from the {@link Match} object.
     * The extracted value represents the algorithm used to perform this
     * detection.
     * <p>
     * {@code Match} object must be created and populated by invoking the 
     * <code>provider.match(userAgentString)</code> before supplying to this 
     * method.
     * 
     * @param match Match object containing detection results, not null.
     * @return MatchMethods enumeration used for this detection.
     */
    public MatchMethods getMethod(Match match) {
        if (match == null) {
            throw new IllegalArgumentException();
        }
        return match.getMethod();
    }
    
    /**
     * Extract the difference value from the {@link Match} object provided.
     * Difference represents the level of confidence the detector has in the 
     * accuracy of the current detection. The higher the number the less 
     * confident the detector is.
     * <p>
     * Difference value is only relevant to Nearest, Closest and Numeric 
     * methods. Exact method will always have a value of zero. Difference is 
     * irrelevant to None as the User-Agent that yielded this result is almost 
     * certainly fake.
     * <p>
     * {@code Match} object must be created and populated by invoking the 
     * <code>provider.match(userAgentString)</code> before supplying to this 
     * method.
     * 
     * @param match Match object containing detection results, not null.
     * @return integer value of difference indicating the level of confidence 
     * the detector has in the current match results.
     */
    public int getDifference(Match match) {
        if (match == null) {
            throw new IllegalArgumentException();
        }
        return match.getDifference();
    }
    
    /**
     * Extracts the signature rank from the {@link Match} object provided.
     * Signature rank indicates the relative level of popularity of the given 
     * signature. The lower the value the more popular the requesting device is.
     * <p>
     * Popularity is determined by 51Degrees and is based on our statistics.
     * <p>
     * {@code Match} object must be created and populated by invoking the 
     * <code>provider.match(userAgentString)</code> before supplying to this 
     * method.
     * 
     * @param match Match object containing detection results, not null.
     * @return integer representing the popularity of the matched device. The 
     * lower the number the more popular device is.
     * @throws IOException if there is a problem accessing the data file.
     */
    public int getRank(Match match) throws IOException {
        if (match == null) {
            throw new IllegalArgumentException();
        }
        return match.getSignature().getRank();
    }
    
    /**
     * Device ID is a string of four numeric components separated by hyphen.
     * A relevant profile is picked by the detector for each of the following 
     * components: Hardware-Platform-Browser-IsCrawler.
     * 
     * @param match Match object containing detection results, not null.
     * @return String with device ID consisting of four profile IDs.
     * @throws IOException if there is a problem accessing the data file.
     */
    public String getDeviceId(Match match) throws IOException {
        if (match == null) {
            throw new IllegalArgumentException();
        }
        return match.getDeviceId();
    }
    
    /**
     * Main entry point for this example. For each of the User-Agents defined 
     * in this class: 
     * <ol>
     * <li>performs detection; 
     * <li>stores detection information in a {@link Match} object;
     * <li>Each {@code Match} object is then passed to one of the relevant 
     * methods to retrieve match metrics information, i.e.: 
     * {@link #getDeviceId} is invoked to return an Id string.
     * </ol>
     * 
     * @param args command line arguments, not used.
     * @throws IOException if there is a problem accessing the data file. 
     */
    public static void main(String[] args) throws IOException {
        MatchMetrics gs = new MatchMetrics();
        Match match;
        try {
            // Display metrics for mobile User-Agent.
            match = gs.provider.match(gs.mobileUserAgent);
            System.out.println("User-Agent: "+gs.mobileUserAgent);
            System.out.println("Id: "+gs.getDeviceId(match));
            System.out.println("Detection method: "+gs.getMethod(match));
            System.out.println("Difference: "+gs.getDifference(match));
            System.out.println("Rank: "+gs.getRank(match));
            // Display metrics for desktop User-Agent.
            match = gs.provider.match(gs.desktopUserAgent);
            System.out.println("User-Agent: "+gs.desktopUserAgent);
            System.out.println("Id: "+gs.getDeviceId(match));
            System.out.println("Detection method: "+gs.getMethod(match));
            System.out.println("Difference: "+gs.getDifference(match));
            System.out.println("Rank: "+gs.getRank(match));
            // Display metrics for mediahub User-Agent.
            match = gs.provider.match(gs.mediaHubUserAgent);
            System.out.println("User-Agent: "+gs.mediaHubUserAgent);
            System.out.println("Id: "+gs.getDeviceId(match));
            System.out.println("Detection method: "+gs.getMethod(match));
            System.out.println("Difference: "+gs.getDifference(match));
            System.out.println("Rank: "+gs.getRank(match));
        } finally {
            gs.close();
        }
    }
    
    /**
     * Closes the {@link fiftyone.mobile.detection.Dataset} by releasing data 
     * file readers and freeing the data file from locks. This method should 
     * only be used when the {@code Dataset} is no longer required, i.e. when 
     * device detection functionality is no longer required, or the data file 
     * needs to be freed.
     * 
     * @throws IOException if there is a problem accessing the data file.
     */
    @Override
    public void close() throws IOException {
        provider.dataSet.close();
    }