/*
    * Copyright (c) 2005, The K-Wf Grid Consortium
    * Fraunhofer Institute for Computer Architecture and Software Technology
    * See http://www.kwfgrid.eu and http://www.first.fraunhofer.de for more details.
    */
   package net.kwfgrid.gwes.uiproxy;
   
   import java.util.*;
   
  import org.apache.log4j.Logger;
  
  /**
   * The UIProxy. Facade for buffers, subscription handler and leasing system.
   * The current implementation has no sophisticating synchronization management. This may lead to performance issues with
   * multiple clients and buffers and should be fixed in the future.
   */
  public class UIProxyImpl implements UIProxy {
      protected class Lease extends Thread {
          protected String _clientid;
          protected boolean _valid;
  
          public Lease(String clientid) {
              super("UIProxy.Lease [" + clientid + "]");
              _clientid = clientid;
              _valid = true;
              start();
          }
  
          public synchronized void renew() {
              _valid = true;
              notifyAll();
          }
  
          public synchronized void cancel() {
              _valid = false;
              notifyAll();
          }
  
          public synchronized void run() {
              if (Thread.currentThread() == this) {
                  try {
                      while (_valid) {
                          _valid = false;
                          wait(UIProxyImpl.this.getLeaseTime());
                      }
                  } catch (InterruptedException x) {
                      // LOG
                  }
                  UIProxyImpl.this.timeout(_clientid);
              }
          }
      }
  
      public static final int DEFAULT_LEASE_TIME = 60000;//ms
  
      /**
       * clientid -> bufferids -> buffer.
       */
      protected HashMapOfMaps _clients;
      /**
       * clientid -> bufferids -> subscription
       */
      protected HashMapOfMaps _subscriptions;
      /**
       * clientid -> lease
       */
      protected HashMap _leases;
  
      protected BufferFactory _bfact;
      protected SubscriptionHandler _shandler;
      protected MessageCodec _codec;
      protected int _leasetime;
  
      public UIProxyImpl(BufferFactory bfact, MessageCodec codec, SubscriptionHandler shandler) {
          _bfact = bfact;
          _shandler = shandler;
          _codec = codec;
  
          _clients = new HashMapOfMaps();
          _subscriptions = new HashMapOfMaps();
          _leases = new HashMap();
          _leasetime = DEFAULT_LEASE_TIME;
      }
  
      public void setLeaseTime(int time) {
          _leasetime = time;
      }
  
      public int getLeaseTime() {
          return _leasetime;
      }
  
      protected Buffer getBuffer(String clientid, String bufferid) {
          return (Buffer) _clients.get(clientid, bufferid);
      }
  
      /**
       * Subscribe for messages at a publisher. This will instantiate a buffer which stores the notification provided by the publisher.
       * The specification of the subuscription must conform to the format which is defined by the SubscriptionHandler of the UIProxy.
      *
      * @param clientid     The UUID of the client.
      * @param subscription Specification of the subscription.
      * @param buffertype   The type of the buffer to be created.
      * @param propkeys     The keys of the properties of the buffer, same index as <code>propvalues</code>.
      * @param propvalues   The values of the properties of the buffer, same index as <code>propkeys</code>.
      * @return The UUID of the newly created buffer. Needed to poll notifications from that buffer.
      * @throws SubscriptionFailed If the subscription failed.
      */
     public synchronized String subscribe(String clientid, String subscription, String buffertype, String[] propkeys, String[] propvalues) throws SubscriptionFailed {
         Logger.getLogger(UIProxyImpl.class).debug("Subscribing buffer " + buffertype + " for client " + clientid + ".");
 
         Map client = _clients.getMap(clientid);
         if (client == null) {
             Logger.getLogger(UIProxyImpl.class).debug("New client: " + clientid + ", creating lease.");
 
             client = _clients.createKey(clientid);
             _leases.put(clientid, new Lease(clientid));
         } else {
             renewLease(clientid);
         }
 
         if (propkeys.length != propvalues.length)
             throw new SubscriptionFailed("Subscription failed. Different number of keys and values in properties.");
 
         Buffer buffer = null;
 
         Properties bufferprops = new Properties();
         for (int i = 0; i < propkeys.length; i++) {
             bufferprops.setProperty(propkeys[i], propvalues[i]);
         }
 
         try {
             buffer = _bfact.createBuffer(buffertype, bufferprops);
         } catch (InstantiationException x) {
             Logger.getLogger(UIProxyImpl.class).warn("Could not create buffer " + buffertype + ": " + x + " " + x.getMessage());
             throw new SubscriptionFailed("Could not create buffer " + buffertype + ": " + x + " " + x.getMessage());
         }
 
         client.put(buffer.getID(), buffer);
 
         boolean exception = true;
         try {
             String sid = _shandler.subscribe(buffer, subscription);
             _subscriptions.put(clientid, buffer.getID(), sid);
             String bufid = buffer.getID();
             exception = false;
             return bufid;
         } finally {
             if (exception) {
                 Logger.getLogger(UIProxyImpl.class).warn("Subscription failed for client " + clientid + ".");
                 disposeBuffer(clientid, buffer.getID());
             }
         }
     }
 
     /**
      * Renew the lease for the specified client.
      * If the client is unknown the request is silently discarded.
      *
      * @param clientid The UUID of the client.
      */
     public synchronized void renewLease(String clientid) {
         Logger.getLogger(UIProxyImpl.class).debug("Renewing lease for client " + clientid + ".");
 
         Lease lease = (Lease) _leases.get(clientid);
         if (lease != null) lease.renew();
     }
 
     /**
      * Set a property of a buffer.
      * Calling this method will also renew the lease for the specified client.
      * If the client is not the creator of the buffer, this method will silently discard the request.
      *
      * @param clientid The UUID of the client.
      * @param bufferid The UUID of the buffer.
      * @param key      The name of the property.
      * @param value    The value of the property
      * @throws BufferException If an exception occured when setting the property.
      */
     public synchronized void setBufferProperty(String clientid, String bufferid, String key, String value) throws BufferException {
         Logger.getLogger(UIProxyImpl.class).debug("Setting buffer property " + key + " to " + value + " for client " + clientid + ", buffer " + bufferid + ".");
 
         Buffer buffer = (Buffer) _clients.get(clientid, bufferid);
         if (buffer != null) buffer.setProperty(key, value);
         renewLease(clientid);
     }
 
     /**
      * Dispose a buffer.
      * Calling this method will also renew the lease for the specified client.
      * If the client is not the creator of the buffer, this method will silently discard the request.
      *
      * @param clientid The UUID of the client.
      * @param bufferid The UUID of the buffer.
      */
     public synchronized void disposeBuffer(String clientid, String bufferid) {
         Logger.getLogger(UIProxyImpl.class).debug("Disposing buffer " + bufferid + " for client " + clientid + ".");
 
         Buffer buffer = (Buffer) _clients.remove(clientid, bufferid);
         String subscription = (String) _subscriptions.remove(clientid, bufferid);
         if (subscription != null) _shandler.cancel(subscription);
         renewLease(clientid);
     }
 
     /**
      * Dispose a whole client. This will free all resources associated with the client.
      * If the client is unknown the request will be silently discarded.
      *
      * @param clientid The UUID of the client.
      */
     public synchronized void disposeClient(String clientid) {
         Logger.getLogger(UIProxyImpl.class).debug("Disposing client " + clientid + ".");
 
         Lease lease = (Lease) _leases.remove(clientid);
 
 	if (lease==null) 
 	    Logger.getLogger(UIProxyImpl.class).info("Client "+clientid+" has no lease.");
 	else
 	    lease.cancel();
 
         _clients.remove(clientid);
 
         Map subscriptions = ((Map) _subscriptions.remove(clientid));
 	if (subscriptions==null) {
 	    Logger.getLogger(UIProxyImpl.class).info("Client "+clientid+" has no subscriptions.");
 	} else {
 	    Iterator i = subscriptions.values().iterator();
 	    while (i.hasNext()) {
 		_shandler.cancel(i.next().toString());
 	    }
 	}
     }
 
     /**
      * Called if a lease has timed out. Disposes the client.
      */
     protected synchronized void timeout(String clientid) {
         Logger.getLogger(UIProxyImpl.class).warn("Lease timed out for client " + clientid + ".");
 
         _clients.remove(clientid);
         _leases.remove(clientid);
         Map subscriptions = ((Map) _subscriptions.remove(clientid));
 	if (subscriptions!=null) {
 	    Iterator i = subscriptions.values().iterator();
 	    while (i.hasNext()) {
 		_shandler.cancel(i.next().toString());
 	    }
 	}
     }
 
     /**
      * Poll all buffered notifications for the specified client and buffer.
      * Calling this method will also renew the lease for the specified client.
      * If the client is not the creator of the buffer, this method will silently discard the request and return an empty collection.
      *
      * @return A collection of all buffered notifications from the specified buffer.
      * @throws BufferException        If a exception occured at the buffer when handling a message. In that case the client will have to create a new
      *                                Buffer.
      * @throws UnknownClientException If the specified client is unknown to the UIProxy. This may also happen if the lease has timed out for the
      *                                specified client.
      * @throws UnknownBufferException If the specified buffer is unknown to the UIProxy. This may also happen if the buffer previously encountered
      *                                a <code>BufferException</code>.
      *                                specified client.
      */
     public synchronized String[] poll(String clientid, String bufferid) throws CodecException, BufferException, UnknownClientException, UnknownBufferException {
         Logger.getLogger(UIProxyImpl.class).debug("Client " + clientid + " polls buffer " + bufferid + ".");
 
         Map client = _clients.getMap(clientid);
         if (client == null) {
             Logger.getLogger(UIProxyImpl.class).warn("Client " + clientid + " unknown.");
             throw new UnknownClientException("unknown client: " + clientid);
         }
         renewLease(clientid);
         Buffer buffer = (Buffer) client.get(bufferid);
         if (buffer == null) {
             Logger.getLogger(UIProxyImpl.class).warn("Buffer " + bufferid + " unknown.");
             throw new UnknownBufferException("unknwon buffer: " + clientid + "/" + bufferid);
         }
         boolean exception = true;
         try {
             Object[] messages = buffer.read();
             String[] spec = new String[messages.length];
             for (int i = 0; i < messages.length; i++) {
                 spec[i] = _codec.marshal(messages[i]);
             }
             exception = false;
             return spec;
         } finally {
             if (exception) {
                 Logger.getLogger(UIProxyImpl.class).warn("Reading buffer caused exception.");
                 disposeBuffer(clientid, bufferid);
             }
         }
     }
 }