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Support and utility classes used by other JAI-tools components and available for general use.
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/*
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package jaitools.tilecache;

import java.awt.image.RenderedImage;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

/**
 * A basic visitor class for DiskMemTileCache that can be used
 * to examine cache contents.
 * 
 * Example of use:
 * 

 * // Query the cache for tiles that belong to a given image
 * // and that are currently resident in memory
 * DiskMemTileCache cache = ...
 * RenderedImage owner = ...
 *
 * Map filters = CollectionFactory.newMap();
 * filters.put(BasicCacheVisitor.Key.OWNER, owner);
 * filters.put(BasicCachevisitor.Key.RESIDENT, Boolean.TRUE);
 *
 * BasicCacheVisitor visitor = new BasicCacheVisitor();
 * visitor.setFilters(filters);
 * cache.accept(visitor);
 *
 * for (DiskCachedTile tile : visitor.getTiles()) {
 *     System.out.println(String.format("tile %d,%d", tile.getTileX(), tile.getTileY()));
 * }
 * 
 *
 * @author Michael Bedward
 * @since 1.0
 * @source $URL: https://jai-tools.googlecode.com/svn/tags/1.0.1/utils/src/main/java/jaitools/tilecache/BasicCacheVisitor.java $
 * @version $Id: BasicCacheVisitor.java 950 2009-09-28 02:27:03Z michael.bedward $
 */
public class BasicCacheVisitor implements DiskMemTileCacheVisitor {

    /**
     * Defines keys to filter the tles visited
     */
    public enum Key {
        /**
         * Filter on the image that owns the tile. The value
         * provided for this key must be a RenderedImage.
         */
        OWNER(RenderedImage.class),

        /**
         * Filter on whether the tile is currently resident
         * in memory. The value provided for this key must
         * be of type Boolean.
         */
        RESIDENT(Boolean.class);


        private Class clazz;

        private Key(Class clazz) {
            this.clazz = clazz;
        }

        public Class getValueClass() {
            return clazz;
        }
    }

    private List tiles = new ArrayList();
    private Map filters = new HashMap();


    /**
     * Set filter conditions. Any existing conditions are cleared.
     *
     * @param params a Map where each key is one of the constants
     * defined by BasicCacheVisitor.Key and each value is the
     * corresponding value to match tiles against
     */
    public void setFilters(Map params) {
        filters.clear();
        for (Entry e : params.entrySet()) {
            addFilter(e.getKey(), e.getValue());
        }
    }

    /**
     * Set a single filter condition. Any existing conditions
     * are cleared
     * 
     * @param key one of the constants defined by BasicCacheVisitor.Key
     * @param value corresponding value to match tiles against
     */
    public void setFilter(Key key, Object value) {
        filters.clear();
        addFilter(key, value);
    }

    /**
     * Clear all existing filter conditions
     */
    public void clearFilters() {
        filters.clear();
    }
    
    /**
     * Returns an unmodifiable collection of tiles retrieved from
     * the cache.
     * 
     * @return tiles retrieved from the cache
     */    
    public Collection getTiles() {
        return Collections.unmodifiableCollection(tiles);
    }


    /**
     * This method is called by the cache for each tile in turn. Tiles that
     * pass this visitor's filter conditions, if any, will be added to the
     * visitor's tile collection.
     *
     * @param tile the cached tile being visited
     * @param isResident set by the cache to indicate whether the tile is
     * currently resident in memory
     */
    public void visit(DiskCachedTile tile, boolean isResident) {
        if (filters.isEmpty()) {
            tiles.add(tile);

        } else {
            boolean pass = true;
            if (filters.containsKey(Key.OWNER)) {
                if ( !(tile.getOwner().equals(filters.get(Key.OWNER))) ) {
                    pass = false;
                }
            }

            if (pass && filters.containsKey(Key.RESIDENT)) {
                if ( ((Boolean)filters.get(Key.RESIDENT)).booleanValue() != isResident) {
                    pass = false;
                }
            }

            if (pass) {
                tiles.add(tile);
            }
        }
    }

    /**
     * Clear collected tile data. Useful if an instance of this
     * class makes multiple visits to a cache.
     */
    public void clear() {
        tiles.clear();
    }

    /**
     * Helper method for setFilters and setFilter
     * @param key
     * @param value
     */
    private void addFilter(Key key, Object value) {
        if (key.getValueClass().isAssignableFrom(value.getClass())) {
            filters.put(key, value);
        } else {
            throw new IllegalArgumentException(
                    String.format("Object of type %s cannot be used as value for %s",
                    value.getClass().getName(), key.toString()));
        }
    }

}