source: trunk/src_apollo/org/apollo/util/ODFrameHeirarchyFetcher.java@ 315

package org.apollo.util;

import java.util.LinkedList;
import java.util.Queue;

import javax.swing.SwingUtilities;

import org.apollo.audio.structure.OverdubbedFrame;
import org.apollo.audio.structure.TrackGraphLoopException;
import org.apollo.audio.structure.AudioStructureModel;
import org.expeditee.gui.FrameIO;

/**
 * Fetches overdubbed frame heirarchies on a dedicated thread.
 * 
 * @author Brook Novak
 *
 */
public class ODFrameHeirarchyFetcher {

        private FetchWorker fetcher = null;
        
        /** Using a FIFO queue implementation */
        private Queue<FetchRequest> fetchRequestQueue = new LinkedList<FetchRequest>(); // SHARED RESOURCE
        
        /** Singleton design pattern */
        private static ODFrameHeirarchyFetcher instance = new ODFrameHeirarchyFetcher();
        private ODFrameHeirarchyFetcher() { }
        public static ODFrameHeirarchyFetcher getInstance() {
                return instance;
        }
        
        /**
         * Asynchronously (non-blocking) performs a fetch for a given frame name. Once the fetch is
         * complete the odRec's {@link ODFrameReceiver#receiveResult(OverdubbedFrame, TrackGraphLoopException)}
         * is invoked.
         * 
         * If there is a request for the given ODFrameReceiver that is already pending, the old request is replaced
         * if the rootFrameName differs, otherwise the old fetch remains and the new fetch is ignored.
         * 
         * @see {@link ODFrameReceiver)}
         * 
         * @param rootFrameName
         *              The frame name to get the heirarchy for. Must be a valid framename
         * 
         * @param odRec
         *              The ODFrameReceiver to receive the result.
         * 
         * @throws NullPointerException
         *              If rootFrameName or odRec is null.
         * 
         * @throws IllegalArgumentException
         *              If rootFrameName is not a valid framename.
         */
        public void doFetch(String rootFrameName, ODFrameReceiver odRec) {
                if (rootFrameName == null) throw new NullPointerException("rootFrameName");
                if (!FrameIO.isValidFrameName(rootFrameName)) 
                        throw new IllegalArgumentException("rootFrameName is an invalid framename");
                
                if (odRec == null) throw new NullPointerException("odRec");

                
                FetchRequest newfr = new FetchRequest(rootFrameName, odRec);
                
                synchronized(fetchRequestQueue) {
                        
                        // See if a fetch for the receiver already exists
                        FetchRequest match = null;
                        for (FetchRequest existingfr : fetchRequestQueue) {
                                if (newfr.equals(existingfr)) {
                                        match = existingfr;
                                        break;
                                }
                        }
                        
                        // If a request already exists
                        if (match != null) {
                                // Check if the new fetch request is for a different odframe
                                if (!match.getRootFrameName().equals(rootFrameName)) {
                                        fetchRequestQueue.remove(match); // replace redundant request
                                        fetchRequestQueue.add(newfr);
                                }
                        } else {
                                fetchRequestQueue.add(newfr);
                        }
                        
                        // Ensure that the fetch thread is running
                        if (fetcher == null || !fetcher.isAlive()) {
                                fetcher = new FetchWorker();
                                fetcher.start();
                        }
                }

        }
        
        
        private class FetchWorker extends Thread {

                FetchWorker() {
                        super("FetchWorker");
                }
                
                public void run() {
                        
                        while (true) {

                                FetchRequest request = null;
                                
                                synchronized(fetchRequestQueue) {
        
                                        if (!fetchRequestQueue.isEmpty())
                                                request = fetchRequestQueue.remove();
                                        
                                        if (request == null) return;
                                }
        
                                boolean hasUpdated = false;
                                do {
                                        try {
                                                AudioStructureModel.getInstance().waitOnUpdates();
                                                hasUpdated = true;
                                        } catch (InterruptedException e) {
                                                e.printStackTrace();
                                                continue;
                                        }
                                } while (!hasUpdated);

                                while (true) {
                                        try {
                                                request.odFrameResult = AudioStructureModel.getInstance().fetchGraph(request.getRootFrameName());
                                                break;
                                        } catch (InterruptedException e) { // cancelled, retry
                                                /* Consume */
                                                
                                        } catch (TrackGraphLoopException e) { // contains loop
                                                request.loopExResult = e;
                                                break;
                                        }
                                } 
                                
                                // Run result notiofaction for this request on swing thread
                                SwingUtilities.invokeLater(request);
                                
                        }
                                
                                
                
                }
        }
        
        /**
         * Immutable two-tuple for storing fetch requests.
         * 
         * @author Brook Novak
         */
        private class FetchRequest implements Runnable {
                
                private String rootFrameName;
                private ODFrameReceiver receiver;
                
                OverdubbedFrame odFrameResult = null;
                TrackGraphLoopException loopExResult = null;
                
                /**
                 * 
                 * @param rootFrameName
                 *                      Must be a valid framename.
                 * 
                 * @param receiver
                 */
                public FetchRequest(String rootFrameName, ODFrameReceiver receiver) {
                        this.rootFrameName = rootFrameName;
                        this.receiver = receiver;
                        assert(rootFrameName != null);
                        assert(FrameIO.isValidFrameName(rootFrameName)) ;
                        assert(receiver != null);
                }

                @Override
                public boolean equals(Object obj) {
                        return receiver.equals(obj);
                }

                @Override
                public int hashCode() {
                        return receiver.hashCode();
                }

                public ODFrameReceiver getReceiver() {
                        return receiver;
                }

                public String getRootFrameName() {
                        return rootFrameName;
                }
                
                /**
                 * To be invoked on swing thread
                 */
                public void run() {
                        receiver.receiveResult(odFrameResult, loopExResult);
                }

        }
        
        /**
         * A frame receive can request for fetches and have their 
         * {@link #receiveResult(OverdubbedFrame, TrackGraphLoopException)}
         * method invoked once a result has occured.
         * 
         * @author Brook Novak
         */
        public interface ODFrameReceiver {
                
                /**
                 * Invoked once a request has been proccessed. <b>This is invoked on the swing thread.</b>
                 * 
                 * @see ODFrameHeirarchyFetcher#doFetch(String, org.apollo.util.ODFrameHeirarchyFetcher.ODFrameReceiver)
                 * 
                 * @param odFrame
                 *              The overdubbed frame. Null if the frame does not exist - or if it does exist but there are no track widgets on it.
                 *              Or Null if there was a loop.
                 *              
                 * @param loopEx
                 *              If there was a loop, then this will be set containing the loop info.
                 */
                public void receiveResult(OverdubbedFrame odFrame, TrackGraphLoopException loopEx);
        
        }

}