/*=============================================================================#
 # Copyright (c) 2008, 2020 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.ltk.model.core.impl;

import java.util.HashMap;
import java.util.LinkedList;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.ISafeRunnable;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.SafeRunner;
import org.eclipse.core.runtime.Status;
import org.eclipse.core.runtime.jobs.Job;

import org.eclipse.statet.jcommons.collections.ImIdentityList;
import org.eclipse.statet.jcommons.lang.NonNullByDefault;
import org.eclipse.statet.jcommons.lang.Nullable;

import org.eclipse.statet.internal.ltk.core.LtkCorePlugin;
import org.eclipse.statet.ltk.core.Ltk;
import org.eclipse.statet.ltk.core.WorkingContext;
import org.eclipse.statet.ltk.model.core.ElementChangedEvent;
import org.eclipse.statet.ltk.model.core.ElementChangedListener;
import org.eclipse.statet.ltk.model.core.LtkModelUtils;
import org.eclipse.statet.ltk.model.core.element.LtkModelElement;
import org.eclipse.statet.ltk.model.core.element.LtkModelElementDelta;
import org.eclipse.statet.ltk.model.core.element.SourceUnit;
import org.eclipse.statet.ltk.model.core.element.SourceUnitModelInfo;


/**
 * Abstract model update event job
 */
@NonNullByDefault
public abstract class AbstractModelEventJob<TModelElement extends LtkModelElement<?>, InfoType extends SourceUnitModelInfo> extends Job {
	
	
	private static class SafeRunnable implements ISafeRunnable {
		
		final ElementChangedEvent event;
		ElementChangedListener listener;
		
		public SafeRunnable(final ElementChangedEvent event) {
			this.event= event;
		}
		
		@Override
		public void run() {
			this.listener.elementChanged(this.event);
		}
		
		@Override
		public void handleException(final Throwable e) {
			LtkCorePlugin.log(new Status(IStatus.ERROR, Ltk.BUNDLE_ID, -1,
					"An error occured while notifying an ElementChangedListener.", e )); //$NON-NLS-1$
		}
		
	}
	
	protected class Task {
		
		private final TModelElement element;
		private InfoType oldInfo;
		private InfoType newInfo;
		
		
		public Task(final TModelElement element) {
			this.element= element;
		}
		
		
		public TModelElement getElement() {
			return this.element;
		}
		
		public InfoType getOldInfo() {
			return this.oldInfo;
		}
		
		public InfoType getNewInfo() {
			return this.newInfo;
		}
		
		
		void run() {
			final LtkModelElementDelta delta= createDelta(this);
			fireDelta(delta);
		}
	}
	
	
	private final AbstractModelManager modelManager;
	
	private final Object tasksLock= new Object();
	private final LinkedList<TModelElement> taskQueue= new LinkedList<>();
	private final HashMap<TModelElement, Task> taskDetail= new HashMap<>();
	
	private boolean working= false;
	private boolean stop= false;
	
	
	public AbstractModelEventJob(final AbstractModelManager manager) {
		super("Model Events for " + manager.getModelTypeId()); //$NON-NLS-1$
		setPriority(BUILD);
		setSystem(true);
		setUser(false);
		
		this.modelManager= manager;
	}
	
	
	public void addUpdate(final TModelElement element,
			final InfoType oldModel, final InfoType newModel) {
		synchronized (this.tasksLock) {
			Task task= this.taskDetail.get(element);
			if (task == null) {
				task= new Task(element);
				task.oldInfo= oldModel;
				this.taskDetail.put(element, task);
			}
			else {
				this.taskQueue.remove(element);
			}
			task.newInfo= newModel;
			this.taskQueue.add(element);
			
			if (!this.working) {
				schedule();
			}
		}
	}
	
	protected abstract LtkModelElementDelta createDelta(Task task);
	
	
	@Override
	protected IStatus run(final IProgressMonitor monitor) {
		while (true) {
			Task task;
			synchronized (this.tasksLock) {
				final @Nullable TModelElement element= (!this.taskQueue.isEmpty()) ? this.taskQueue.removeFirst() : null;
				if (element == null || this.stop) {
					this.working= false;
					return Status.OK_STATUS;
				}
				this.working= true;
				task= this.taskDetail.remove(element);
			}
			try {
				task.run();
			}
			catch (final Throwable e) {
				LtkCorePlugin.log(new Status(IStatus.ERROR, Ltk.BUNDLE_ID, -1,
						"An error occurred when firing model event for " + this.modelManager.getModelTypeId() + ".", //$NON-NLS-1$
						e ));
			}
		}
	}
	
	protected void dispose() {
		synchronized (this.tasksLock) {
			this.stop= true;
			this.taskQueue.clear();
			this.taskDetail.clear();
		}
	}
	
	private void fireDelta(final LtkModelElementDelta delta) {
		final SourceUnit su= LtkModelUtils.getSourceUnit(delta.getModelElement());
		if (su == null) {
			return;
		}
		final WorkingContext context= su.getWorkingContext();
		final ElementChangedEvent event= new ElementChangedEvent(delta, context);
		final SafeRunnable runnable= new SafeRunnable(event);
		final ImIdentityList<ElementChangedListener> listeners= this.modelManager.getElementChangedListeners(context);
		for (final ElementChangedListener listener : listeners) {
			runnable.listener= listener;
			SafeRunner.run(runnable);
		}
	}
	
}