/**
 * AmbientTalk/2 Project
 * NATActorMirror.java created on Oct 16, 2006 at 1:55:05 PM
 * (c) Programming Technology Lab, 2006 - 2007
 * Authors: Tom Van Cutsem & Stijn Mostinckx
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
package edu.vub.at.actors.natives;

import edu.vub.at.actors.ATActorMirror;
import edu.vub.at.actors.ATAsyncMessage;
import edu.vub.at.actors.ATLetter;
import edu.vub.at.actors.natives.DiscoveryManager.Publication;
import edu.vub.at.actors.natives.DiscoveryManager.Subscription;
import edu.vub.at.eval.Evaluator;
import edu.vub.at.exceptions.InterpreterException;
import edu.vub.at.exceptions.XArityMismatch;
import edu.vub.at.exceptions.XIllegalOperation;
import edu.vub.at.exceptions.XTypeMismatch;
import edu.vub.at.objects.ATBoolean;
import edu.vub.at.objects.ATClosure;
import edu.vub.at.objects.ATContext;
import edu.vub.at.objects.ATNil;
import edu.vub.at.objects.ATObject;
import edu.vub.at.objects.ATTable;
import edu.vub.at.objects.ATTypeTag;
import edu.vub.at.objects.coercion.NativeTypeTags;
import edu.vub.at.objects.grammar.ATSymbol;
import edu.vub.at.objects.mirrors.NATIntrospectiveMirror;
import edu.vub.at.objects.mirrors.NativeClosure;
import edu.vub.at.objects.mirrors.PrimitiveMethod;
import edu.vub.at.objects.natives.NATByRef;
import edu.vub.at.objects.natives.NATMethodInvocation;
import edu.vub.at.objects.natives.NATNumber;
import edu.vub.at.objects.natives.NATObject;
import edu.vub.at.objects.natives.NATTable;
import edu.vub.at.objects.natives.NATText;
import edu.vub.at.objects.natives.OBJLexicalRoot;
import edu.vub.at.objects.natives.grammar.AGSymbol;

import java.util.LinkedList;

/**
 * The NATActorMirror class implements the concurrency model of ambienttalk. It continually
 * consumes meta-events which are written to a synchronized queue. This way the actor
 * is notified of incoming messages, discovered and lost services, etc. When no meta-
 * messages are available, the actor consumes base-level messages as they are stored
 * in its inbox. These messages have a receiver object internal to the actor and they 
 * will be invoked on this receiver by the actor's thread.
 *
 * @author smostinc
 */
public class NATActorMirror extends NATByRef implements ATActorMirror {
	
	// INSTANCE VARIABLES
	
	// the actor mirror refers directly to its ELActor because
	// using ELActor.currentActor is slower
	private ELActor myActor_;
	private final ELDiscoveryActor discoveryActor_;
	
	/**
	 * When initializing a new actor, do not forget that this constructor is still executed by the
	 * creating actor, not by the created actor. To make the created actor perform something, it is
	 * necessary to use meta_receive to send itself messages for later execution.
	 */
	public NATActorMirror(ELVirtualMachine host) {
		discoveryActor_ = host.discoveryActor_;
	}
	
	/** set the mirror's base actor instance */
	protected void setActor(ELActor myActor) {
		myActor_ = myActor;
	}
	
    /* ------------------------------------------
     * -- Language Construct to Actor Protocol --
     * ------------------------------------------ */

	public ATAsyncMessage base_createMessage(ATSymbol selector, ATTable arguments, ATTable types) throws InterpreterException {
		ATAsyncMessage msg = new NATAsyncMessage(selector, arguments, types);
		// types.inject: msg into: { |constructingMsg, type| type.annotate(constructingMsg) }
		ATAsyncMessage returnMsg = types.base_inject_into_(msg, new NativeClosure(this) {
			public ATObject base_apply(ATTable args) throws InterpreterException {
				checkArity(args, 2);
				ATObject newMessage = get(args, 1);
				ATObject type = get(args, 2);
				return type.asTypeTag().base_annotateMessage(newMessage);
			}
		}).asAsyncMessage();
		// if the message was indeed annotated, set the correct location informal on the original message.
		if (! returnMsg.equals(msg)){
			msg.impl_setLocation(types.impl_getLocation());
		}
		return returnMsg;
	}
	
	public ATObject base_createMirror(ATObject reflectee) throws InterpreterException {
		return NATIntrospectiveMirror.atValue(reflectee);
	}
	
	/**
	 * A publication object is defined as:
	 * object: {
	 *   def topic := //topic under which service is published;
	 *   def service := //the exported service object;
	 *   def cancel() { //unexport the service object }
	 * }
	 */
	public static class NATPublication extends NATObject {
		private static final AGSymbol _TOPIC_ = AGSymbol.jAlloc("topic");
		private static final AGSymbol _SERVICE_ = AGSymbol.jAlloc("service");
		private static final AGSymbol _CANCEL_ = AGSymbol.jAlloc("cancel");
		public NATPublication(final ELDiscoveryActor discoveryActor,
				              ATTypeTag topic, ATObject service,
				              final Publication pub) throws InterpreterException {
			meta_defineField(_TOPIC_, topic);
			meta_defineField(_SERVICE_, service);
			meta_addMethod(new PrimitiveMethod(_CANCEL_, NATTable.EMPTY) {
			      public ATObject base_apply(ATTable arguments, ATContext ctx) throws InterpreterException {
						int arity = arguments.base_length().asNativeNumber().javaValue;
						if (arity != 0) {
							throw new XArityMismatch("cancel", 0, arity);
						}
						discoveryActor.event_cancelPublication(pub);
						return Evaluator.getNil();
			      }
			});
		}
		public NATText meta_print() throws InterpreterException {
			return NATText.atValue("<publication:"+impl_invokeAccessor(this, _TOPIC_, NATTable.EMPTY)+">");
		}
	}
	
	/**
	 * A subscription object is defined as:
	 * object: {
	 *   def topic := //topic subscribed to;
	 *   def handler := //the closure to be triggered;
	 *   def cancel() { //unsubscribe the handler }
	 * }
	 */
	public static class NATSubscription extends NATObject {
		private static final AGSymbol _TOPIC_ = AGSymbol.jAlloc("topic");
		private static final AGSymbol _HANDLER_ = AGSymbol.jAlloc("handler");
		private static final AGSymbol _CANCEL_ = AGSymbol.jAlloc("cancel");
		public NATSubscription(final ELDiscoveryActor discoveryActor,
				               ATTypeTag topic, ATClosure handler,
				               final Subscription sub) throws InterpreterException {
			meta_defineField(_TOPIC_, topic);
			meta_defineField(_HANDLER_, handler);
			meta_addMethod(new PrimitiveMethod(_CANCEL_, NATTable.EMPTY) {
			      public ATObject base_apply(ATTable arguments, ATContext ctx) throws InterpreterException {
						int arity = arguments.base_length().asNativeNumber().javaValue;
						if (arity != 0) {
							throw new XArityMismatch("cancel", 0, arity);
						}
						discoveryActor.event_cancelSubscription(sub);
						return Evaluator.getNil();
			      }
			});
		}
		public NATText meta_print() throws InterpreterException {
			return NATText.atValue("<subscription:"+impl_invokeAccessor(this, _TOPIC_, NATTable.EMPTY)+">");
		}
	}
	
	public ATObject base_provide(final ATTypeTag topic, final ATObject service) throws InterpreterException {
		Publication pub = new Publication(myActor_,
				new Packet(topic),
				new Packet(service),
				service);
		discoveryActor_.event_servicePublished(pub);
		return new NATPublication(discoveryActor_, topic, service, pub);
	}
	
	public ATObject base_require(final ATTypeTag topic, final ATClosure handler, ATBoolean isPermanent) throws InterpreterException {
		Subscription sub = new Subscription(myActor_,
				                            new Packet(topic),
				                            new Packet(handler),
				                            isPermanent.asNativeBoolean().javaValue);
		discoveryActor_.event_clientSubscribed(sub);
		return new NATSubscription(discoveryActor_, topic, handler, sub);
	}

	public ATTable base_listPublications() throws InterpreterException {
		Publication[] pubs = discoveryActor_.sync_event_listPublications(myActor_);
        NATPublication[] natpubs = new NATPublication[pubs.length];
        for(int i = 0; i < pubs.length; i++) {
        	Publication pub = pubs[i];
        	natpubs[i] = new NATPublication(
        			discoveryActor_,
        			pub.providedTypeTag_.unpack().asTypeTag(),
        			pub.exportedService_.unpack(),
        			pub);
        }
        return NATTable.atValue(natpubs);
	}

	public ATTable base_listSubscriptions() throws InterpreterException {
		Subscription[] subs = discoveryActor_.sync_event_listSubscriptions(myActor_);
		NATSubscription[] natsubs = new NATSubscription[subs.length];
        for(int i = 0; i < subs.length; i++) {
        	Subscription sub = subs[i];
        	natsubs[i] = new NATSubscription(
        			discoveryActor_,
        			sub.requiredTypeTag_.unpack().asTypeTag(),
        			sub.registeredHandler_.unpack().asClosure(),
        			sub);
        }
        return NATTable.atValue(natsubs);
	}
	
    /* --------------------------
     * -- VM to Actor Protocol --
     * -------------------------- */

    public ATObject meta_clone() throws InterpreterException {
        throw new XIllegalOperation("Cannot clone actor " + toString());
    }

    /**
     * actor.new(closure)
     *  => same effect as evaluating 'actor: closure'
     */
	public ATObject meta_newInstance(ATTable initargs) throws InterpreterException {
		int length = initargs.base_length().asNativeNumber().javaValue;
		if(length != 1)
			throw new XArityMismatch("newInstance", 1, length);
		
		ATClosure closure = initargs.base_at(NATNumber.ONE).asClosure();
		return OBJLexicalRoot._INSTANCE_.base_actor_(closure);
	}
	
	public NATText meta_print() throws InterpreterException {
		return NATText.atValue("<actormirror:" + this.hashCode() + ">");
	}

    public ATTable meta_typeTags() throws InterpreterException {
    	return NATTable.of(NativeTypeTags._ACTORMIRROR_);
    }
	
	/* -----------------------------
	 * -- Object Passing Protocol --
	 * ----------------------------- */
	
	/**
	 * When default base-level objects send an asynchronous message, they delegate
	 * this responsibility to their actor by means of this base-level method.
	 * 
	 * The actor's default implementation is to invoke the receiver mirror's <tt>receive</tt> method
	 * which defines the default asynchronous message reception semantics.
	 * 
	 * Note: in pre-2.9 versions of AmbientTalk, this method did not immediately pass
	 * control to the receiver via the <tt>receive</tt> method. By delegating to the receiver
	 * in the same execution turn as the message send, we allow possible proxies (custom eventual
	 * references) to intervene in the message sending process.
	 */
	public ATObject base_send(ATObject receiver, ATAsyncMessage message) throws InterpreterException {
		return receiver.meta_receive(message);
	}
	
	/**
	 * def becomeMirroredBy: protocol
	 *  => returns the old installed protocol
	 * 
	 * @see ATActorMirror#base_becomeMirroredBy_(ATClosure)
	 */
	public ATObject base_becomeMirroredBy_(ATActorMirror newActorMirror) throws InterpreterException {
		ATActorMirror oldMirror = myActor_.getImplicitActorMirror();
		myActor_.setActorMirror(newActorMirror);
		return oldMirror;
	}
	
	/**
	 * def getExplicitActorMirror()
	 *  => return an explicit actor mirror for the current actor.
	 * 
	 * The default implementation uses the actor's implicit mirror as the
	 * default explicit mirror.
	 * 
	 * @see ATActorMirror#base_getExplicitActorMirror()
	 */
	public ATActorMirror base_getExplicitActorMirror() throws InterpreterException {
		return myActor_.getImplicitActorMirror();
	}
	
	/**
	 * This operation is
	 * introduced as a mechanism to alter the semantics of message reception for all objects
	 * owned by an actor. It can be used e.g. to keep track of all successfully processed messages. 
	 * 
	 * Note that this operation is *only* invoked for messages received from *other*
	 * actors (i.e. local or remote actors), it is *not* invoked for recursive asynchronous self-sends
	 * (intra-actor message sends)! This is an important change w.r.t pre-2.9 versions of AmbientTalk.
	 */
	public ATObject base_receive(ATObject receiver, ATAsyncMessage message) throws InterpreterException {
		// this additional dispatch to receive will schedule an async self-send when performed
		// on near references, which then invokes message.base_process in a later execution turn
		// We do not short-circuit this behaviour for consistency purposes: receive is invoked
		// on all receiver objects consistently, whether they are near refs, far refs, custom eventual
		// refs or any other kind of mirage.
		return receiver.meta_receive(message);
	}
	
	/**
	 * Export the given local object such that it is now remotely accessible via the
	 * returned object id.
	 * @param object a **near** reference to the object to export
	 * @return a local far reference to the object being exported
	 * @throws XIllegalOperation if the passed object is a far reference, i.e. non-local
	 */
	public ATObject base_createReference(ATObject object) throws InterpreterException {
		// receptionist set will check whether ATObject is really local to me
		return myActor_.receptionists_.exportObject(object);
	}
	
	/**
	 * Provides access to this actor's "behaviour" object. This is the first
	 * object created within an actor.
	 * 
	 * Note: if the behaviour is accessed when evaluating the "init.at" initialization
	 * file of an actor, the behaviour will <em>not have been initialized</em> yet.
	 * It will appear as an empty object.
	 */
	public ATObject base_behaviour() throws InterpreterException {
		return myActor_.behaviour_;
	}
	
    public ATActorMirror asActorMirror() throws XTypeMismatch {
    	return this;
    }
    
    public NATActorMirror asNativeActorMirror() throws XTypeMismatch {
    	return this;
    }
    
    /* -------------------------
	 * -- Scheduling Protocol --
	 * ------------------------- */
    
    /**
     * The inbox of this actor. It contains objects that implement the {@link ATLetter} interface
     */
    private LinkedList inbox_ = new LinkedList();
	
	/**
	 * A letter object is defined as:
	 * object: {
	 *   def receiver := //receiver of the letter;
	 *   def message := //the message that is being sent;
	 *   def cancel() { //cancel the delivery of the letter }
	 * }
	 */
	public static class NATLetter extends NATObject implements ATLetter {
		private static final AGSymbol _RCVR_ = AGSymbol.jAlloc("receiver");
		private static final AGSymbol _MSG_ = AGSymbol.jAlloc("message");
		private static final AGSymbol _CANCEL_ = AGSymbol.jAlloc("cancel");
		public NATLetter(final LinkedList mailbox, ATObject receiver, ATObject message) throws InterpreterException {
			super(new ATTypeTag[] { NativeTypeTags._LETTER_ });
			meta_defineField(_RCVR_, receiver);
			meta_defineField(_MSG_, message);
			final NATLetter thisLetter = this;
			meta_addMethod(new PrimitiveMethod(_CANCEL_, NATTable.EMPTY) {
			      public ATObject base_apply(ATTable arguments, ATContext ctx) throws InterpreterException {
						int arity = arguments.base_length().asNativeNumber().javaValue;
						if (arity != 0) {
							throw new XArityMismatch("cancel", 0, arity);
						}
						// Note: if the receiver and message fields are changed by an AmbientTalk program
						// canceling the letter will still remove the original letter, not a letter that corresponds
						// to the new receiver and message.
						mailbox.remove(thisLetter);
						return Evaluator.getNil();
			      }
			});
		}
		public NATText meta_print() throws InterpreterException {
			return NATText.atValue("<letter:"+impl_invokeAccessor(this, _MSG_, NATTable.EMPTY)+">");
		}

		public ATLetter asLetter() { return this; }
		public ATObject base_cancel() throws InterpreterException {
			return this.meta_invoke(this, new NATMethodInvocation(_CANCEL_, NATTable.EMPTY, NATTable.EMPTY));
		}
		public ATAsyncMessage base_message() throws InterpreterException {
			return this.meta_invokeField(this, _MSG_).asAsyncMessage();
		}
		public ATObject base_receiver() throws InterpreterException {
			return this.meta_invokeField(this, _RCVR_);
		}
	}

	/**
	 * Returns a table with all letters currently in the inbox
	 */
	public ATTable base_listIncomingLetters() throws InterpreterException {
		ATObject[] incoming = (ATObject[]) inbox_.toArray(new ATObject[inbox_.size()]);
		return NATTable.atValue(incoming);
	}

	/**
	 * Creates a letter object and adds it to the actor's inbox
	 */
	public ATObject base_schedule(ATObject receiver, ATAsyncMessage message) throws InterpreterException {
		NATLetter letter = new NATLetter(inbox_, receiver, message);
		inbox_.addFirst(letter);
    	// signal a serve event for every message that is scheduled
    	myActor_.event_serve();
		return letter;
	}

	/**
	 * Fetches the next letter from the actor's inbox, if any, and processes it.
	 */
	public ATObject base_serve() throws InterpreterException {
		if (inbox_.size() > 0) {
			ATObject next = (ATObject) inbox_.removeLast();
			ATLetter letter = next.asLetter();
			// receive has already been invoked prior to scheduling
			// the receive is known to be a local object, therefore we
			// can immediately process the message
			return letter.base_message().base_process(letter.base_receiver());
		} else {
			return Evaluator.getNil();
		}
	}
}