import javax.swing.filechooser.FileFilter;
import java.io.File;
import java.util.Enumeration;
import java.util.Hashtable;

/**
 * A convenience implementation of FileFilter that filters out
 * all files except for those type extensions that it knows about.
 * <p/>
 * Extensions are of the type ".foo", which is typically found on
 * Windows and Unix boxes, but not on Macinthosh. Case is ignored.
 * <p/>
 * Example - create a new filter that filerts out all files
 * but gif and jpg image files:
 * <p/>
 * JFileChooser chooser = new JFileChooser();
 * ExampleFileFilter filter = new ExampleFileFilter(
 * new String{"gif", "jpg"}, "JPEG & GIF Images")
 * chooser.addChoosableFileFilter(filter);
 * chooser.showOpenDialog(this);
 *
 * @author Jeff Dinkins
 * @version 1.3 04/14/98
 */
public class ExtensionFileFilter extends FileFilter {

	private static String TYPE_UNKNOWN = "Type Unknown";
	private static String HIDDEN_FILE = "Hidden File";

	private Hashtable filters = null;
	private String description = null;
	private String fullDescription = null;
	private boolean useExtensionsInDescription = true;

	/**
	 * Creates a file filter. If no filters are added, then all
	 * files are accepted.
	 */
	public ExtensionFileFilter() {
		this((String) null, (String) null);
	}

	/**
	 * Creates a file filter that accepts files with the given extension.
	 * Example: new ExampleFileFilter("jpg");
	 */
	public ExtensionFileFilter(String extension) {
		this(extension, null);
	}

	/**
	 * Creates a file filter that accepts the given file type.
	 * Example: new ExampleFileFilter("jpg", "JPEG Image Images");
	 * <p/>
	 * Note that the "." before the extension is not needed. If
	 * provided, it will be ignored.
	 */
	public ExtensionFileFilter(String extension, String description) {
		this(new String[]{extension}, description);
	}

	/**
	 * Creates a file filter from the given string array.
	 * Example: new ExampleFileFilter(String {"gif", "jpg"});
	 * <p/>
	 * Note that the "." before the extension is not needed adn
	 * will be ignored.
	 */
	public ExtensionFileFilter(String[] filters) {
		this(filters, null);
	}

	/**
	 * Creates a file filter from the given string array and description.
	 * Example: new ExampleFileFilter(String {"gif", "jpg"}, "Gif and JPG Images");
	 * <p/>
	 * Note that the "." before the extension is not needed and will be ignored.
	 */
	public ExtensionFileFilter(String[] filters, String description) {
		this.filters = new Hashtable(filters.length);
		for (int i = 0; i < filters.length; i++) {
			// add filters one by one
			addExtension(filters[i]);
		}
		setDescription(description);
	}

	/**
	 * Return true if this file should be shown in the directory pane,
	 * false if it shouldn't.
	 * <p/>
	 * Files that begin with "." are ignored.
	 */
	public boolean accept(File f) {
		if (f != null) {
			if (f.isDirectory()) {
				return true;
			}
			String extension = getExtension(f);
			if (extension != null && filters.get(getExtension(f)) != null) {
				return true;
			}
			;
		}
		return false;
	}

	/**
	 * Return the extension portion of the file's name .
	 */
	public String getExtension(File f) {
		if (f != null) {
			String filename = f.getName();
			int i = filename.lastIndexOf('.');
			if (i > 0 && i < filename.length() - 1) {
				return filename.substring(i + 1).toLowerCase();
			}
			;
		}
		return null;
	}

	/**
	 * Adds a filetype "dot" extension to filter against.
	 * <p/>
	 * For example: the following code will create a filter that filters
	 * out all files except those that end in ".jpg" and ".tif":
	 * <p/>
	 * ExampleFileFilter filter = new ExampleFileFilter();
	 * filter.addExtension("jpg");
	 * filter.addExtension("tif");
	 * <p/>
	 * Note that the "." before the extension is not needed and will be ignored.
	 */
	public void addExtension(String extension) {
		if (filters == null) {
			filters = new Hashtable(5);
		}
		filters.put(extension.toLowerCase(), this);
		fullDescription = null;
	}


	/**
	 * Returns the human readable description of this filter. For
	 * example: "JPEG and GIF Image Files (*.jpg, *.gif)"
	 */
	public String getDescription() {
		if (fullDescription == null) {
			if (description == null || isExtensionListInDescription()) {
				if (description != null) {
					fullDescription = description;
				}
				fullDescription += " (";
				// build the description from the extension list
				Enumeration extensions = filters.keys();
				if (extensions != null) {
					fullDescription += "." + (String) extensions.nextElement();
					while (extensions.hasMoreElements()) {
						fullDescription += ", " + (String) extensions.nextElement();
					}
				}
				fullDescription += ")";
			} else {
				fullDescription = description;
			}
		}
		return fullDescription;
	}

	/**
	 * Sets the human readable description of this filter. For
	 * example: filter.setDescription("Gif and JPG Images");
	 */
	public void setDescription(String description) {
		this.description = description;
		fullDescription = null;
	}

	/**
	 * Determines whether the extension list (.jpg, .gif, etc) should
	 * show up in the human readable description.
	 * <p/>
	 * Only relevent if a description was provided in the constructor
	 * or using setDescription();
	 */
	public void setExtensionListInDescription(boolean b) {
		useExtensionsInDescription = b;
		fullDescription = null;
	}

	/**
	 * Returns whether the extension list (.jpg, .gif, etc) should
	 * show up in the human readable description.
	 * <p/>
	 * Only relevent if a description was provided in the constructor
	 * or using setDescription();
	 */
	public boolean isExtensionListInDescription() {
		return useExtensionsInDescription;
	}
}