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package javax.swing.plaf.nimbus;

import java.awt.GraphicsConfiguration;
import java.awt.Image;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

ImageCache - A fixed pixel count sized cache of Images keyed by arbitrary set of arguments. All images are held with
SoftReferences so they will be dropped by the GC if heap memory gets tight. When our size hits max pixel count least
recently requested images are removed first.
Author:
Created by Jasper Potts (Aug 7, 2007)/**
 * ImageCache - A fixed pixel count sized cache of Images keyed by arbitrary set of arguments. All images are held with
 * SoftReferences so they will be dropped by the GC if heap memory gets tight. When our size hits max pixel count least
 * recently requested images are removed first.
 *
 * @author Created by Jasper Potts (Aug 7, 2007)
 */
class ImageCache {
    // Ordered Map keyed by args hash, ordered by most recent accessed entry.
    private final LinkedHashMap<Integer, PixelCountSoftReference> map =
            new LinkedHashMap<Integer, PixelCountSoftReference>(16, 0.75f, true);
    // Maximum number of pixels to cache, this is used if maxCount
    private final int maxPixelCount;
    // Maximum cached image size in pxiels
    private final int maxSingleImagePixelSize;
    // The current number of pixels stored in the cache
    private int currentPixelCount = 0;
    // Lock for concurrent access to map
    private ReadWriteLock lock = new ReentrantReadWriteLock();
    // Reference queue for tracking lost softreferences to images in the cache
    private ReferenceQueue<Image> referenceQueue = new ReferenceQueue<Image>();
    // Singleton Instance
    private static final ImageCache instance = new ImageCache();


    
Get static singleton instance /** Get static singleton instance */
    static ImageCache getInstance() {
        return instance;
    }

    public ImageCache() {
        this.maxPixelCount = (8 * 1024 * 1024) / 4; // 8Mb of pixels
        this.maxSingleImagePixelSize = 300 * 300;
    }

    public ImageCache(int maxPixelCount, int maxSingleImagePixelSize) {
        this.maxPixelCount = maxPixelCount;
        this.maxSingleImagePixelSize = maxSingleImagePixelSize;
    }

    
Clear the cache /** Clear the cache */
    public void flush() {
        lock.readLock().lock();
        try {
            map.clear();
        } finally {
            lock.readLock().unlock();
        }
    }

    
Check if the image size is to big to be stored in the cache
Params:
w – The image width
h – The image height
Returns:
True if the image size is less than max/**
     * Check if the image size is to big to be stored in the cache
     *
     * @param w The image width
     * @param h The image height
     * @return True if the image size is less than max
     */
    public boolean isImageCachable(int w, int h) {
        return (w * h) < maxSingleImagePixelSize;
    }

    
Get the cached image for given keys
Params:
config – The graphics configuration, needed if cached image is a Volatile Image. Used as part of cache key
w –      The image width, used as part of cache key
h –      The image height, used as part of cache key
args –   Other arguments to use as part of the cache key
Returns:
Returns the cached Image, or null there is no cached image for key/**
     * Get the cached image for given keys
     *
     * @param config The graphics configuration, needed if cached image is a Volatile Image. Used as part of cache key
     * @param w      The image width, used as part of cache key
     * @param h      The image height, used as part of cache key
     * @param args   Other arguments to use as part of the cache key
     * @return Returns the cached Image, or null there is no cached image for key
     */
    public Image getImage(GraphicsConfiguration config, int w, int h, Object... args) {
        lock.readLock().lock();
        try {
            PixelCountSoftReference ref = map.get(hash(config, w, h, args));
            // check reference has not been lost and the key truly matches, in case of false positive hash match
            if (ref != null && ref.equals(config,w, h, args)) {
                return ref.get();
            } else {
                return null;
            }
        } finally {
            lock.readLock().unlock();
        }
    }

    
Sets the cached image for the specified constraints.
Params:
image –  The image to store in cache
config – The graphics configuration, needed if cached image is a Volatile Image. Used as part of cache key
w –      The image width, used as part of cache key
h –      The image height, used as part of cache key
args –   Other arguments to use as part of the cache key
Returns:
true if the image could be cached or false if the image is too big/**
     * Sets the cached image for the specified constraints.
     *
     * @param image  The image to store in cache
     * @param config The graphics configuration, needed if cached image is a Volatile Image. Used as part of cache key
     * @param w      The image width, used as part of cache key
     * @param h      The image height, used as part of cache key
     * @param args   Other arguments to use as part of the cache key
     * @return true if the image could be cached or false if the image is too big
     */
    public boolean setImage(Image image, GraphicsConfiguration config, int w, int h, Object... args) {
        if (!isImageCachable(w, h)) return false;
        int hash = hash(config, w, h, args);
        lock.writeLock().lock();
        try {
            PixelCountSoftReference ref = map.get(hash);
            // check if currently in map
            if (ref != null && ref.get() == image) {
                return true;
            }
            // clear out old
            if (ref != null) {
                currentPixelCount -= ref.pixelCount;
                map.remove(hash);
            }
            // add new image to pixel count
            int newPixelCount = image.getWidth(null) * image.getHeight(null);
            currentPixelCount += newPixelCount;
            // clean out lost references if not enough space
            if (currentPixelCount > maxPixelCount) {
                while ((ref = (PixelCountSoftReference)referenceQueue.poll()) != null){
                    //reference lost
                    map.remove(ref.hash);
                    currentPixelCount -= ref.pixelCount;
                }
            }
            // remove old items till there is enough free space
            if (currentPixelCount > maxPixelCount) {
                Iterator<Map.Entry<Integer, PixelCountSoftReference>> mapIter = map.entrySet().iterator();
                while ((currentPixelCount > maxPixelCount) && mapIter.hasNext()) {
                    Map.Entry<Integer, PixelCountSoftReference> entry = mapIter.next();
                    mapIter.remove();
                    Image img = entry.getValue().get();
                    if (img != null) img.flush();
                    currentPixelCount -= entry.getValue().pixelCount;
                }
            }
            // finaly put new in map
            map.put(hash, new PixelCountSoftReference(image, referenceQueue, newPixelCount,hash, config, w, h, args));
            return true;
        } finally {
            lock.writeLock().unlock();
        }
    }

    
Create a unique hash from all the input /** Create a unique hash from all the input */
    private int hash(GraphicsConfiguration config, int w, int h, Object ... args) {
        int hash;
        hash = (config != null ? config.hashCode() : 0);
        hash = 31 * hash + w;
        hash = 31 * hash + h;
        hash = 31 * hash + Arrays.deepHashCode(args);
        return hash;
    }


    
Extended SoftReference that stores the pixel count even after the image is lost /** Extended SoftReference that stores the pixel count even after the image is lost */
    private static class PixelCountSoftReference extends SoftReference<Image> {
        private final int pixelCount;
        private final int hash;
        // key parts
        private final GraphicsConfiguration config;
        private final int w;
        private final int h;
        private final Object[] args;

        public PixelCountSoftReference(Image referent, ReferenceQueue<? super Image> q, int pixelCount, int hash,
                                       GraphicsConfiguration config, int w, int h, Object[] args) {
            super(referent, q);
            this.pixelCount = pixelCount;
            this.hash = hash;
            this.config = config;
            this.w = w;
            this.h = h;
            this.args = args;
        }

        public boolean equals (GraphicsConfiguration config, int w, int h, Object[] args){
            return config == this.config &&
                            w == this.w &&
                            h == this.h &&
                            Arrays.equals(args, this.args);
        }
    }
}