package hu.elte.txtuml.api.model;

import hu.elte.txtuml.api.model.ModelExecutor.Report;
import hu.elte.txtuml.utils.NotifierOfTermination.TerminationManager;

import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.LinkedBlockingQueue;

/*
 * Multiple classes and interfaces defined in this file.
 */

/**
 * The type of threads on which the model execution will run. By the current
 * implementation, this class might be considered singleton as it is
 * instantiated only once by the {@link ModelExecutor} class.
 * <p>
 * Unusable by the user.
 *
 * @author Gabor Ferenc Kovacs
 *
 */
class ModelExecutorThread extends Thread {

	/**
	 * The mailbox in which the to-be-sent signals are gathered and later
	 * processed (asynchronously).
	 */
	private final LinkedBlockingQueue<MailboxEntry> mailbox = new LinkedBlockingQueue<>();

	/**
	 * An object to manage termination notifications.
	 */
	private final TerminationManager terminationManager = new TerminationManager();

	/**
	 * A queue of checks which are to be performed at the beginning of the next
	 * <i>execution step</i>.
	 * <p>
	 * See the documentation of {@link Model} for information about execution
	 * steps.
	 */
	private final Queue<CheckQueueEntry> checkQueue = new ConcurrentLinkedQueue<>();

	private boolean shutdownWhenEmpty = false;
	private boolean shutdownImmediately = false;

	/**
	 * Sends the specified signal to the specified target object asynchronously.
	 * This method puts the signal into its global
	 * {@link ModelExecutorThread#mailbox mailbox} from where it will be taken
	 * and processed later.
	 * 
	 * @param target
	 *            the target of this send operation
	 * @param signal
	 *            the signal to send
	 */
	void send(Region target, Signal signal) {
		newMailboxEntry(() -> target.process(signal));
	}

	/**
	 * Puts the specified entry into the {@code mailbox}.
	 * 
	 * @param entry
	 *            the entry to put into the {@code mailbox}.
	 */
	private void newMailboxEntry(MailboxEntry entry) {
		try {
			mailbox.put(entry);
		} catch (InterruptedException e) {
		}
	}

	/**
	 * Sets the model executor to be shut down the moment when {@link #mailbox}
	 * becomes empty.
	 */
	void shutdown() {
		shutdownWhenEmpty = true;
		// wake up if waiting with an empty message
		mailbox.add(() -> {});
	}

	/**
	 * Sets the model executor to be shut down immediately. If the execution of
	 * a {@link #mailbox} item does not terminate it cannot guarantee the
	 * termination.
	 */
	void shutdownImmediately() {
		shutdownImmediately = true;
		// wake up if waiting with an empty message
		mailbox.add(() -> {});
	}

	/**
	 * Registers a check of the lower bound of the specified association end's
	 * multiplicity to be performed in the next <i>execution step</i>.
	 * <p>
	 * The lower bound of multiplicities might be offended temporarily but has
	 * to be restored before returning from the current <i>execution step</i>.
	 * <p>
	 * See the documentation of {@link Model} for information about execution
	 * steps.
	 * 
	 * @param obj
	 *            the object on the opposite end of the association
	 * @param assocEnd
	 *            the association end which's multiplicity is to be checked
	 */
	void checkLowerBoundOfMultiplicity(ModelClass obj,
			Class<? extends AssociationEnd<?>> assocEnd) {
		checkQueue.add(() -> obj.checkLowerBound(assocEnd));
	}

	/**
	 * This method starts an infinite loop which might only be exited if an
	 * exception is raised inside. In every iteration, it takes an entry from
	 * the {@link ModelExecutorThread#mailbox mailbox} and gives it to the
	 * target object to process. Blocks if the <code>mailbox</code> is empty.
	 */
	@Override
	public void run() {
		while (!shouldShutdown()) {
			CheckQueueEntry entry = checkQueue.poll();
			while (entry != null) {
				entry.performCheck();
				entry = checkQueue.poll();
			}

			try {
				mailbox.take().execute();
			} catch (InterruptedException e) {
				// user interruption by shutdownImmediately()
			}
		}
		Report.event.forEach(x -> x.executionTerminated());
		terminationManager.notifyAllOfTermination();
	}

	private boolean shouldShutdown() {
		return shutdownImmediately || (shutdownWhenEmpty && mailbox.isEmpty());
	}

	public void addToShutdownQueue(Runnable shutdownAction) {
		if (!terminationManager.addTerminationListener(shutdownAction)) {
			shutdownAction.run();
		}
	}

	public ModelExecutorThread autoStart() {
		start();
		return this;
	}
}

/**
 * The entry type of {@link ModelExecutorThread}<code>.mailbox</code>. Stores
 * and prepares an asynchronous operation to be executed in the future.
 * <p>
 * Unusable by the user.
 *
 * @author Gabor Ferenc Kovacs
 *
 */
@FunctionalInterface
interface MailboxEntry {

	/**
	 * Executes the asynchronous operation stored in this entry.
	 */
	void execute();
}

/**
 * The entry type of {@link ModelExecutorThread}<code>.checkList</code>. Stores
 * and prepares a check to be performed in the future.
 * <p>
 * Unusable by the user.
 * 
 * @author Gabor Ferenc Kovacs
 * 
 */
@FunctionalInterface
interface CheckQueueEntry {

	/**
	 * Performs the prepared check.
	 */
	void performCheck();

}

@@ -1354,32 +1354,41 @@
 ();%0D%0A%0D%0A%09private 
+volatile 
 boolean shutdown
@@ -1408,32 +1408,41 @@
 alse;%0D%0A%09private 
+volatile 
 boolean shutdown

set shutdown flags to volatile