plugins/org.eclipse.ease/src/org/eclipse/ease/AbstractScriptEngine.java - ease/org.eclipse.ease.core - Git at Google

 /*******************************************************************************
  * Copyright (c) 2013 Christian Pontesegger and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
  * https://www.eclipse.org/legal/epl-2.0/
  *
  * SPDX-License_Identifier: EPL-2.0
  *
  * Contributors:
  *     Christian Pontesegger - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ease;

 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.PrintStream;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.ExecutionException;

 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.core.runtime.IProgressMonitorWithBlocking;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.jobs.Job;
 import org.eclipse.debug.core.ILaunch;
 import org.eclipse.ease.ISecurityCheck.ActionType;
 import org.eclipse.ease.debugging.EaseDebugFrame;
 import org.eclipse.ease.debugging.IScriptDebugFrame;
 import org.eclipse.ease.debugging.ScriptStackTrace;
 import org.eclipse.ease.security.ScriptUIAccess;
 import org.eclipse.ease.service.EngineDescription;
 import org.eclipse.ease.tools.ListenerList;
 import org.eclipse.ease.tools.ResourceTools;
 import org.eclipse.ui.internal.progress.ProgressManager.JobMonitor;
 import org.osgi.framework.Version;

 /**
  * Base implementation for a script engine. Handles Job implementation of script engine, adding script code for execution, module loading support and a basic
  * online help system.
  */
 public abstract class AbstractScriptEngine extends Job implements IScriptEngine {

 	/**
 	 * Get the current script engine. Works only if executed from the script engine thread.
 	 *
 	 * @return script engine or <code>null</code>
 	 */
 	public static IScriptEngine getCurrentScriptEngine() {
 		if (Job.getJobManager().currentJob() instanceof IScriptEngine)
 			return (IScriptEngine) Job.getJobManager().currentJob();

 		return null;
 	}

 	/**
 	 * Get the beautified name of a file to be set as part of the job title.
 	 *
 	 * @param file
 	 *            executed file
 	 * @return beautified name or <code>null</code>
 	 */
 	private static String getFilename(Object file) {
 		if (file instanceof IFile) {
 			return ResourceTools.toAbsoluteLocation(file, null);
 		} else if (file instanceof File) {
 			return ResourceTools.toAbsoluteLocation(file, null);
 		} else {
 			return null;
 		}
 	}

 	/** List of code parts to be executed. */
 	private final List<Script> fScheduledScripts = new ArrayList<>();

 	private final ListenerList<IExecutionListener> fExecutionListeners = new ListenerList<>();

 	private PrintStream fOutputStream = null;

 	private PrintStream fErrorStream = null;

 	private InputStream fInputStream = null;

 	private final ScriptStackTrace fStackTrace = new ScriptStackTrace();

 	private EngineDescription fDescription;

 	private boolean fSetupDone = false;

 	/** Variables tried to set before engine was started. */
 	private final Map<String, Object> fBufferedVariables = new HashMap<>();

 	private boolean fCloseStreamsOnTerminate;

 	/** Registered security checks for engine actions. */
 	private final Map<ActionType, List<ISecurityCheck>> fSecurityChecks = new HashMap<>();

 	private Object fExecutionRootFile;;

 	/** Launch associated with this engine. */
 	private ILaunch fLaunch = null;

 	private IProgressMonitor fMonitor;

 	/**
 	 * Constructor. Sets the name for the underlying job.
 	 *
 	 * @param name
 	 *            name of script engine job
 	 */
 	public AbstractScriptEngine(final String name) {
 		super(String.format("[EASE %s Engine]", name));

 		setSystem(false);
 	}

 	@Override
 	public EngineDescription getDescription() {
 		return fDescription;
 	}

 	@Override
 	public final ScriptResult execute(final Object content) {
 		final Script script = (content instanceof Script) ? (Script) content : new Script(content);

 		synchronized (fScheduledScripts) {
 			fScheduledScripts.add(script);
 			fScheduledScripts.notifyAll();
 		}

 		return script.getResult();
 	}

 	@Override
 	public Object inject(Object content, boolean uiThread) throws ExecutionException {
 		final Script script = (content instanceof Script) ? (Script) content : new Script(content);

 		// injected code shall not trigger a new event, therefore notifyListerners needs to be false
 		return inject(script, false, uiThread).get();
 	}

 	/**
 	 * Inject script code to the script engine. Injected code is processed synchronous by the current thread unless <i>uiThread</i> is set to <code>true</code>.
 	 * Nevertheless this is a blocking call.
 	 *
 	 * @param script
 	 *            script to be executed
 	 * @param notifyListeners
 	 *            <code>true</code> when listeners should be informed of code fragment
 	 * @param uiThread
 	 *            when set to <code>true</code> run injected code in UI thread
 	 * @return script execution result
 	 */
 	private ScriptResult inject(final Script script, final boolean notifyListeners, final boolean uiThread) {

 		try {
 			Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Executing script (" + script.getTitle() + "):", script.getCode());
 			final String filename = getFilename(script.getFile());
 			fStackTrace.add(0, new EaseDebugFrame(script, 0, IScriptDebugFrame.TYPE_FILE, filename));
 			updateJobName(filename);

 			// apply security checks
 			final List<ISecurityCheck> securityChecks = fSecurityChecks.get(ActionType.INJECT_CODE);
 			if (securityChecks != null) {
 				for (final ISecurityCheck check : securityChecks) {
 					if (!check.doIt(ActionType.INJECT_CODE, script, uiThread))
 						throw new ScriptEngineException("Security check failed: " + check.toString());
 				}
 			}

 			// execution
 			if (notifyListeners)
 				notifyExecutionListeners(script, IExecutionListener.SCRIPT_START);
 			else
 				notifyExecutionListeners(script, IExecutionListener.SCRIPT_INJECTION_START);

 			script.setResult(execute(script, fStackTrace.get(0).getName(), uiThread));

 		} catch (final BreakException e) {
 			script.setResult(e.getCondition());

 		} catch (final Throwable e) {
 			// only do the printing if this is the last script on the stack
 			// otherwise we will print multiple times for each rethrow
 			if (fStackTrace.size() <= 1)
 				e.printStackTrace(getErrorStream());

 			if (e instanceof ScriptExecutionException)
 				script.setException((ScriptExecutionException) e);
 			else
 				script.setException(new ScriptExecutionException(e));

 		} finally {
 			if (notifyListeners)
 				notifyExecutionListeners(script, IExecutionListener.SCRIPT_END);
 			else
 				notifyExecutionListeners(script, IExecutionListener.SCRIPT_INJECTION_END);

 			if (!fStackTrace.isEmpty())
 				fStackTrace.remove(0);
 		}

 		return script.getResult();
 	}

 	private void updateJobName(String filename) {
 		if (filename != null) {
 			String baseName = getName();
 			if (baseName.contains("]"))
 				baseName = baseName.substring(0, baseName.indexOf(']') + 1);

 			setName(baseName + " " + filename);
 		}
 	}

 	@Override
 	protected IStatus run(final IProgressMonitor monitor) {
 		fMonitor = monitor;

 		addStopButtonMonitor();

 		IStatus returnStatus = setupRun();
 		if (Status.OK_STATUS.equals(returnStatus)) {
 			// main loop
 			while (!shallTerminate()) {

 				try {
 					synchronized (fScheduledScripts) {
 						waitForNextScript();

 						if (!fScheduledScripts.isEmpty()) {
 							final Script piece = fScheduledScripts.remove(0);
 							inject(piece, true, false);
 						}
 					}
 				} catch (final InterruptedException e) {
 					// waiting got interrupted, quite likely a shutdown
 				}
 			}
 		}

 		if (getMonitor().isCanceled())
 			returnStatus = Status.CANCEL_STATUS;

 		return cleanupRun(returnStatus);
 	}

 	private void waitForNextScript() throws InterruptedException {
 		synchronized (fScheduledScripts) {
 			while ((fScheduledScripts.isEmpty()) && (!shallTerminate())) {
 				Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Engine idle: " + getName());
 				fScheduledScripts.wait();
 			}
 		}
 	}

 	private IStatus setupRun() {
 		Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Engine started: " + getName());

 		addSecurityCheck(ActionType.INJECT_CODE, ScriptUIAccess.getInstance());

 		try {
 			setupEngine();
 			fSetupDone = true;

 			// engine is initialized, set buffered variables
 			for (final Entry<String, Object> entry : fBufferedVariables.entrySet()) {
 				setVariable(entry.getKey(), entry.getValue());
 			}

 			fBufferedVariables.clear();

 			// setup new trace
 			fStackTrace.clear();

 			notifyExecutionListeners(null, IExecutionListener.ENGINE_START);

 		} catch (final ScriptEngineException e) {
 			return new Status(IStatus.ERROR, Activator.PLUGIN_ID, "Could not setup script engine", e);
 		}

 		return Status.OK_STATUS;
 	}

 	private IStatus cleanupRun(IStatus returnStatus) {

 		// discard pending code pieces
 		synchronized (fScheduledScripts) {
 			for (final Script script : fScheduledScripts)
 				script.setException(new ScriptExecutionException("Engine got terminated"));

 			fScheduledScripts.clear();
 		}

 		notifyExecutionListeners(null, IExecutionListener.ENGINE_END);

 		try {
 			teardownEngine();
 		} catch (final ScriptEngineException e) {
 			if (returnStatus.getSeverity() < IStatus.ERROR) {
 				// We were almost all OK (or just warnings/infos) but then we failed at shutdown
 				// Note we don't override a CANCEL
 				returnStatus = new Status(IStatus.ERROR, Activator.PLUGIN_ID, "Could not teardown script engine", e);
 			}
 		} finally {
 			synchronized (fScheduledScripts) {
 				fScheduledScripts.notifyAll();
 			}

 			closeStreams();

 			Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Engine terminated: " + getName());

 			fMonitor.done();
 			fMonitor = null;
 		}

 		return returnStatus;
 	}

 	/**
 	 * Add monitor to detect clicks on the stop button in the Progress view. This functionality improves usability, but is not essential to scripting.
 	 */
 	private void addStopButtonMonitor() {
 		if (fMonitor instanceof JobMonitor) {
 			final Version workbenchBundleVersion = Platform.getBundle("org.eclipse.ui.workbench").getVersion();
 			if (workbenchBundleVersion.compareTo(Version.valueOf("3.120.0")) >= 0) {
 				addStopButtonMonitorForEclipse2020v09();

 			} else if (workbenchBundleVersion.compareTo(Version.valueOf("3.110.1")) >= 0) {
 				addStopButtonMonitorForEclipseOxygenTo2020v06();
 			} else {
 				// JobMonitor is a private class up to 3.110.1 (Eclipse Oxygen)
 			}
 		}
 	}

 	private void addStopButtonMonitorForEclipseOxygenTo2020v06() {
 		// JobMonitor changed its API from
 		// addProgressListener(IProgressMonitor)
 		// to
 		// addProgressListener(IProgressMonitorWithBlocking)
 		// in 2020.09
 		try {
 			final Method addProgressListener = JobMonitor.class.getDeclaredMethod("addProgressListener", new Class[] { IProgressMonitorWithBlocking.class });
 			addProgressListener.invoke(fMonitor, new ScriptEngineMonitor());
 		} catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
 			// silently ignore
 		}
 	}

 	private void addStopButtonMonitorForEclipse2020v09() {
 		((JobMonitor) fMonitor).addProgressListener(new ScriptEngineMonitor());
 	}

 	/**
 	 * Evaluate if the engine shall terminate.
 	 *
 	 * @return <code>true</code> when termination is requested or there is no more work to be done
 	 */
 	protected boolean shallTerminate() {
 		synchronized (fScheduledScripts) {
 			return getMonitor().isCanceled() || fScheduledScripts.isEmpty();
 		}
 	}

 	@Override
 	public void terminate() {
 		final IProgressMonitor monitor = getMonitor();
 		if ((monitor != null) && (!monitor.isCanceled()))
 			monitor.setCanceled(true);

 		terminateCurrent();

 		synchronized (fScheduledScripts) {
 			fScheduledScripts.notifyAll();
 		}
 	}

 	@Override
 	public boolean isFinished() {
 		// setup was done, hence we were started
 		return (Job.NONE == getState()) && fSetupDone;
 	}

 	@Override
 	public void joinEngine() throws InterruptedException {
 		if (!Thread.currentThread().equals(getThread())) {
 			// we cannot join our own thread

 			synchronized (fScheduledScripts) {
 				while (!isFinished())
 					fScheduledScripts.wait(1000);
 			}
 		}
 	}

 	@Override
 	public void joinEngine(final long timeout) throws InterruptedException {
 		if (!Thread.currentThread().equals(getThread())) {
 			// we cannot join our own thread

 			synchronized (fScheduledScripts) {
 				if (!isFinished())
 					fScheduledScripts.wait(timeout);
 			}
 		}
 	}

 	@Override
 	public IProgressMonitor getMonitor() {
 		return fMonitor;
 	}

 	private void closeStreams() {
 		if (fCloseStreamsOnTerminate) {
 			// gracefully close I/O streams
 			try {
 				if ((getInputStream() != null) && (!System.in.equals(getInputStream())))
 					getInputStream().close();
 			} catch (final IOException e) {
 			}
 			try {
 				if ((getOutputStream() != null) && (!System.out.equals(getOutputStream())))
 					getOutputStream().close();
 			} catch (final Exception e) {
 			}
 			try {
 				if ((getErrorStream() != null) && (!System.err.equals(getErrorStream())))
 					getErrorStream().close();
 			} catch (final Exception e) {
 			}
 		}

 		fOutputStream = null;
 		fErrorStream = null;
 		fInputStream = null;
 	}

 	@Override
 	public void setCloseStreamsOnTerminate(final boolean closeStreams) {
 		fCloseStreamsOnTerminate = closeStreams;
 	}

 	@Override
 	public PrintStream getOutputStream() {
 		return (fOutputStream != null) ? fOutputStream : System.out;
 	}

 	@Override
 	public void setOutputStream(final OutputStream outputStream) {
 		if (outputStream instanceof PrintStream)
 			fOutputStream = (PrintStream) outputStream;

 		else if (outputStream != null)
 			fOutputStream = new PrintStream(outputStream);
 		else
 			fOutputStream = null;
 	}

 	@Override
 	public InputStream getInputStream() {
 		return (fInputStream != null) ? fInputStream : System.in;
 	}

 	@Override
 	public void setInputStream(final InputStream inputStream) {
 		fInputStream = inputStream;
 	}

 	@Override
 	public PrintStream getErrorStream() {
 		return (fErrorStream != null) ? fErrorStream : System.err;
 	}

 	@Override
 	public void setErrorStream(final OutputStream errorStream) {
 		if (errorStream instanceof PrintStream)
 			fErrorStream = (PrintStream) errorStream;

 		else if (errorStream != null)
 			fErrorStream = new PrintStream(errorStream);
 		else
 			fErrorStream = null;
 	}

 	@Override
 	public void addExecutionListener(final IExecutionListener listener) {
 		fExecutionListeners.add(listener);
 	}

 	@Override
 	public void removeExecutionListener(final IExecutionListener listener) {
 		fExecutionListeners.remove(listener);
 	}

 	protected void notifyExecutionListeners(final Script script, final int status) {
 		for (final Object listener : fExecutionListeners.getListeners()) {
 			try {
 				((IExecutionListener) listener).notify(this, script, status);
 			} catch (final Throwable e) {
 				Logger.warning(Activator.PLUGIN_ID, "Execution listener did throw an exception", e);
 			}
 		}
 	}

 	public ScriptStackTrace getStackTrace() {
 		return fStackTrace;
 	}

 	@Override
 	public Object getExecutedFile() {
 		for (final IScriptDebugFrame trace : getStackTrace()) {
 			if (trace.getType() == IScriptDebugFrame.TYPE_FILE) {
 				if (trace.getScript() != null) {
 					final Object file = trace.getScript().getFile();
 					if (file != null)
 						return file;
 				}
 			}
 		}

 		return fExecutionRootFile;
 	}

 	public void setExecutionRootFile(Object executionRootFile) {
 		fExecutionRootFile = executionRootFile;
 	}

 	public void setEngineDescription(final EngineDescription description) {
 		fDescription = description;
 	}

 	@Override
 	public void setVariable(final String name, final Object content) {
 		if (fSetupDone)
 			internalSetVariable(name, content);

 		else
 			fBufferedVariables.put(name, content);
 	}

 	@Override
 	public Object getVariable(final String name) {
 		if (fSetupDone)
 			return internalGetVariable(name);

 		return fBufferedVariables.get(name);
 	}

 	@Override
 	public boolean hasVariable(final String name) {
 		if (fSetupDone)
 			return internalHasVariable(name);

 		return fBufferedVariables.containsKey(name);
 	}

 	@Override
 	public Map<String, Object> getVariables() {
 		if (fSetupDone)
 			return internalGetVariables();

 		return Collections.unmodifiableMap(fBufferedVariables);
 	}

 	@Override
 	public void addSecurityCheck(ActionType type, ISecurityCheck check) {
 		if (!fSecurityChecks.containsKey(type))
 			fSecurityChecks.put(type, new ArrayList<ISecurityCheck>());

 		if (!fSecurityChecks.get(type).contains(check))
 			fSecurityChecks.get(type).add(check);
 	}

 	protected List<Script> getScheduledScripts() {
 		return fScheduledScripts;
 	}

 	public void setLaunch(ILaunch launch) {
 		fLaunch = launch;
 	}

 	@Override
 	public ILaunch getLaunch() {
 		return fLaunch;
 	}

 	/**
 	 * Internal version of {@link #getVariable(String)}. Only called after script engine was initialized successfully.
 	 *
 	 * @param name
 	 *            variable to retrieve
 	 * @return variable content
 	 */
 	protected abstract Object internalGetVariable(String name);

 	/**
 	 * Internal version of {@link #getVariables()}. Only called after script engine was initialized successfully.
 	 *
 	 * @return map of engine variables: name -> value
 	 */
 	protected abstract Map<String, Object> internalGetVariables();

 	/**
 	 * Internal version of {@link #hasVariable(String)}. Only called after script engine was initialized successfully.
 	 *
 	 * @param name
 	 *            variable to verify
 	 * @return <code>true</code> when variable exists
 	 */
 	protected abstract boolean internalHasVariable(String name);

 	/**
 	 * Internal version of {@link #setVariable(String, Object)}. Only called after script engine was initialized successfully.
 	 *
 	 * @param name
 	 *            variable to set
 	 * @param content
 	 *            value to set variable to
 	 */
 	protected abstract void internalSetVariable(String name, Object content);

 	/**
 	 * Setup method for script engine. Run directly after the engine is activated.
 	 *
 	 * Unresolvable errors should be indicated by throwing a ScriptEngineException with details as to what went wrong.
 	 */
 	protected abstract void setupEngine() throws ScriptEngineException;

 	/**
 	 * Teardown engine. Called immediately before the engine terminates. This method is called even when {@link #setupEngine()} fails.
 	 */
 	protected abstract void teardownEngine() throws ScriptEngineException;

 	/**
 	 * Execute script code.
 	 *
 	 * @param script
 	 *            script to be executed
 	 * @param fileName
 	 *            name of file executed
 	 * @param uiThread
 	 *            when set to <code>true</code> run code in UI thread
 	 * @return execution result
 	 * @throws Throwable
 	 *             any exception thrown during script execution
 	 */
 	protected abstract Object execute(Script script, String fileName, boolean uiThread) throws Throwable;

 	/**
 	 * Simple monitor to forward cancellation requests to the script engine.
 	 */
 	private class ScriptEngineMonitor extends NullProgressMonitor implements IProgressMonitorWithBlocking {

 		@Override
 		public void setCanceled(boolean cancelled) {
 			super.setCanceled(cancelled);

 			if (isCanceled())
 				terminate();
 		}

 		@Override
 		public void setBlocked(IStatus reason) {
 			// nothing to do
 		}

 		@Override
 		public void clearBlocked() {
 			// nothing to do
 		}
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2013 Christian Pontesegger and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v2.0
	* which accompanies this distribution, and is available at
	* https://www.eclipse.org/legal/epl-2.0/
	*
	* SPDX-License_Identifier: EPL-2.0
	*
	* Contributors:
	* Christian Pontesegger - initial API and implementation
	*******************************************************************************/
	package org.eclipse.ease;

	import java.io.File;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.io.PrintStream;
	import java.lang.reflect.InvocationTargetException;
	import java.lang.reflect.Method;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.Map.Entry;
	import java.util.concurrent.ExecutionException;

	import org.eclipse.core.resources.IFile;
	import org.eclipse.core.runtime.IProgressMonitor;
	import org.eclipse.core.runtime.IProgressMonitorWithBlocking;
	import org.eclipse.core.runtime.IStatus;
	import org.eclipse.core.runtime.NullProgressMonitor;
	import org.eclipse.core.runtime.Platform;
	import org.eclipse.core.runtime.Status;
	import org.eclipse.core.runtime.jobs.Job;
	import org.eclipse.debug.core.ILaunch;
	import org.eclipse.ease.ISecurityCheck.ActionType;
	import org.eclipse.ease.debugging.EaseDebugFrame;
	import org.eclipse.ease.debugging.IScriptDebugFrame;
	import org.eclipse.ease.debugging.ScriptStackTrace;
	import org.eclipse.ease.security.ScriptUIAccess;
	import org.eclipse.ease.service.EngineDescription;
	import org.eclipse.ease.tools.ListenerList;
	import org.eclipse.ease.tools.ResourceTools;
	import org.eclipse.ui.internal.progress.ProgressManager.JobMonitor;
	import org.osgi.framework.Version;

	/**
	* Base implementation for a script engine. Handles Job implementation of script engine, adding script code for execution, module loading support and a basic
	* online help system.
	*/
	public abstract class AbstractScriptEngine extends Job implements IScriptEngine {

	/**
	* Get the current script engine. Works only if executed from the script engine thread.
	*
	* @return script engine or <code>null</code>
	*/
	public static IScriptEngine getCurrentScriptEngine() {
	if (Job.getJobManager().currentJob() instanceof IScriptEngine)
	return (IScriptEngine) Job.getJobManager().currentJob();

	return null;
	}

	/**
	* Get the beautified name of a file to be set as part of the job title.
	*
	* @param file
	* executed file
	* @return beautified name or <code>null</code>
	*/
	private static String getFilename(Object file) {
	if (file instanceof IFile) {
	return ResourceTools.toAbsoluteLocation(file, null);
	} else if (file instanceof File) {
	return ResourceTools.toAbsoluteLocation(file, null);
	} else {
	return null;
	}
	}

	/** List of code parts to be executed. */
	private final List<Script> fScheduledScripts = new ArrayList<>();

	private final ListenerList<IExecutionListener> fExecutionListeners = new ListenerList<>();

	private PrintStream fOutputStream = null;

	private PrintStream fErrorStream = null;

	private InputStream fInputStream = null;

	private final ScriptStackTrace fStackTrace = new ScriptStackTrace();

	private EngineDescription fDescription;

	private boolean fSetupDone = false;

	/** Variables tried to set before engine was started. */
	private final Map<String, Object> fBufferedVariables = new HashMap<>();

	private boolean fCloseStreamsOnTerminate;

	/** Registered security checks for engine actions. */
	private final Map<ActionType, List<ISecurityCheck>> fSecurityChecks = new HashMap<>();

	private Object fExecutionRootFile;;

	/** Launch associated with this engine. */
	private ILaunch fLaunch = null;

	private IProgressMonitor fMonitor;

	/**
	* Constructor. Sets the name for the underlying job.
	*
	* @param name
	* name of script engine job
	*/
	public AbstractScriptEngine(final String name) {
	super(String.format("[EASE %s Engine]", name));

	setSystem(false);
	}

	@Override
	public EngineDescription getDescription() {
	return fDescription;
	}

	@Override
	public final ScriptResult execute(final Object content) {
	final Script script = (content instanceof Script) ? (Script) content : new Script(content);

	synchronized (fScheduledScripts) {
	fScheduledScripts.add(script);
	fScheduledScripts.notifyAll();
	}

	return script.getResult();
	}

	@Override
	public Object inject(Object content, boolean uiThread) throws ExecutionException {
	final Script script = (content instanceof Script) ? (Script) content : new Script(content);

	// injected code shall not trigger a new event, therefore notifyListerners needs to be false
	return inject(script, false, uiThread).get();
	}

	/**
	* Inject script code to the script engine. Injected code is processed synchronous by the current thread unless <i>uiThread</i> is set to <code>true</code>.
	* Nevertheless this is a blocking call.
	*
	* @param script
	* script to be executed
	* @param notifyListeners
	* <code>true</code> when listeners should be informed of code fragment
	* @param uiThread
	* when set to <code>true</code> run injected code in UI thread
	* @return script execution result
	*/
	private ScriptResult inject(final Script script, final boolean notifyListeners, final boolean uiThread) {

	try {
	Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Executing script (" + script.getTitle() + "):", script.getCode());
	final String filename = getFilename(script.getFile());
	fStackTrace.add(0, new EaseDebugFrame(script, 0, IScriptDebugFrame.TYPE_FILE, filename));
	updateJobName(filename);

	// apply security checks
	final List<ISecurityCheck> securityChecks = fSecurityChecks.get(ActionType.INJECT_CODE);
	if (securityChecks != null) {
	for (final ISecurityCheck check : securityChecks) {
	if (!check.doIt(ActionType.INJECT_CODE, script, uiThread))
	throw new ScriptEngineException("Security check failed: " + check.toString());
	}
	}

	// execution
	if (notifyListeners)
	notifyExecutionListeners(script, IExecutionListener.SCRIPT_START);
	else
	notifyExecutionListeners(script, IExecutionListener.SCRIPT_INJECTION_START);

	script.setResult(execute(script, fStackTrace.get(0).getName(), uiThread));

	} catch (final BreakException e) {
	script.setResult(e.getCondition());

	} catch (final Throwable e) {
	// only do the printing if this is the last script on the stack
	// otherwise we will print multiple times for each rethrow
	if (fStackTrace.size() <= 1)
	e.printStackTrace(getErrorStream());

	if (e instanceof ScriptExecutionException)
	script.setException((ScriptExecutionException) e);
	else
	script.setException(new ScriptExecutionException(e));

	} finally {
	if (notifyListeners)
	notifyExecutionListeners(script, IExecutionListener.SCRIPT_END);
	else
	notifyExecutionListeners(script, IExecutionListener.SCRIPT_INJECTION_END);

	if (!fStackTrace.isEmpty())
	fStackTrace.remove(0);
	}

	return script.getResult();
	}

	private void updateJobName(String filename) {
	if (filename != null) {
	String baseName = getName();
	if (baseName.contains("]"))
	baseName = baseName.substring(0, baseName.indexOf(']') + 1);

	setName(baseName + " " + filename);
	}
	}

	@Override
	protected IStatus run(final IProgressMonitor monitor) {
	fMonitor = monitor;

	addStopButtonMonitor();

	IStatus returnStatus = setupRun();
	if (Status.OK_STATUS.equals(returnStatus)) {
	// main loop
	while (!shallTerminate()) {

	try {
	synchronized (fScheduledScripts) {
	waitForNextScript();

	if (!fScheduledScripts.isEmpty()) {
	final Script piece = fScheduledScripts.remove(0);
	inject(piece, true, false);
	}
	}
	} catch (final InterruptedException e) {
	// waiting got interrupted, quite likely a shutdown
	}
	}
	}

	if (getMonitor().isCanceled())
	returnStatus = Status.CANCEL_STATUS;

	return cleanupRun(returnStatus);
	}

	private void waitForNextScript() throws InterruptedException {
	synchronized (fScheduledScripts) {
	while ((fScheduledScripts.isEmpty()) && (!shallTerminate())) {
	Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Engine idle: " + getName());
	fScheduledScripts.wait();
	}
	}
	}

	private IStatus setupRun() {
	Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Engine started: " + getName());

	addSecurityCheck(ActionType.INJECT_CODE, ScriptUIAccess.getInstance());

	try {
	setupEngine();
	fSetupDone = true;

	// engine is initialized, set buffered variables
	for (final Entry<String, Object> entry : fBufferedVariables.entrySet()) {
	setVariable(entry.getKey(), entry.getValue());
	}

	fBufferedVariables.clear();

	// setup new trace
	fStackTrace.clear();

	notifyExecutionListeners(null, IExecutionListener.ENGINE_START);

	} catch (final ScriptEngineException e) {
	return new Status(IStatus.ERROR, Activator.PLUGIN_ID, "Could not setup script engine", e);
	}

	return Status.OK_STATUS;
	}

	private IStatus cleanupRun(IStatus returnStatus) {

	// discard pending code pieces
	synchronized (fScheduledScripts) {
	for (final Script script : fScheduledScripts)
	script.setException(new ScriptExecutionException("Engine got terminated"));

	fScheduledScripts.clear();
	}

	notifyExecutionListeners(null, IExecutionListener.ENGINE_END);

	try {
	teardownEngine();
	} catch (final ScriptEngineException e) {
	if (returnStatus.getSeverity() < IStatus.ERROR) {
	// We were almost all OK (or just warnings/infos) but then we failed at shutdown
	// Note we don't override a CANCEL
	returnStatus = new Status(IStatus.ERROR, Activator.PLUGIN_ID, "Could not teardown script engine", e);
	}
	} finally {
	synchronized (fScheduledScripts) {
	fScheduledScripts.notifyAll();
	}

	closeStreams();

	Logger.trace(Activator.PLUGIN_ID, TRACE_SCRIPT_ENGINE, "Engine terminated: " + getName());

	fMonitor.done();
	fMonitor = null;
	}

	return returnStatus;
	}

	/**
	* Add monitor to detect clicks on the stop button in the Progress view. This functionality improves usability, but is not essential to scripting.
	*/
	private void addStopButtonMonitor() {
	if (fMonitor instanceof JobMonitor) {
	final Version workbenchBundleVersion = Platform.getBundle("org.eclipse.ui.workbench").getVersion();
	if (workbenchBundleVersion.compareTo(Version.valueOf("3.120.0")) >= 0) {
	addStopButtonMonitorForEclipse2020v09();

	} else if (workbenchBundleVersion.compareTo(Version.valueOf("3.110.1")) >= 0) {
	addStopButtonMonitorForEclipseOxygenTo2020v06();
	} else {
	// JobMonitor is a private class up to 3.110.1 (Eclipse Oxygen)
	}
	}
	}

	private void addStopButtonMonitorForEclipseOxygenTo2020v06() {
	// JobMonitor changed its API from
	// addProgressListener(IProgressMonitor)
	// to
	// addProgressListener(IProgressMonitorWithBlocking)
	// in 2020.09
	try {
	final Method addProgressListener = JobMonitor.class.getDeclaredMethod("addProgressListener", new Class[] { IProgressMonitorWithBlocking.class });
	addProgressListener.invoke(fMonitor, new ScriptEngineMonitor());
	} catch (NoSuchMethodException \| SecurityException \| IllegalAccessException \| IllegalArgumentException \| InvocationTargetException e) {
	// silently ignore
	}
	}

	private void addStopButtonMonitorForEclipse2020v09() {
	((JobMonitor) fMonitor).addProgressListener(new ScriptEngineMonitor());
	}

	/**
	* Evaluate if the engine shall terminate.
	*
	* @return <code>true</code> when termination is requested or there is no more work to be done
	*/
	protected boolean shallTerminate() {
	synchronized (fScheduledScripts) {
	return getMonitor().isCanceled() \|\| fScheduledScripts.isEmpty();
	}
	}

	@Override
	public void terminate() {
	final IProgressMonitor monitor = getMonitor();
	if ((monitor != null) && (!monitor.isCanceled()))
	monitor.setCanceled(true);

	terminateCurrent();

	synchronized (fScheduledScripts) {
	fScheduledScripts.notifyAll();
	}
	}

	@Override
	public boolean isFinished() {
	// setup was done, hence we were started
	return (Job.NONE == getState()) && fSetupDone;
	}

	@Override
	public void joinEngine() throws InterruptedException {
	if (!Thread.currentThread().equals(getThread())) {
	// we cannot join our own thread

	synchronized (fScheduledScripts) {
	while (!isFinished())
	fScheduledScripts.wait(1000);
	}
	}
	}

	@Override
	public void joinEngine(final long timeout) throws InterruptedException {
	if (!Thread.currentThread().equals(getThread())) {
	// we cannot join our own thread

	synchronized (fScheduledScripts) {
	if (!isFinished())
	fScheduledScripts.wait(timeout);
	}
	}
	}

	@Override
	public IProgressMonitor getMonitor() {
	return fMonitor;
	}

	private void closeStreams() {
	if (fCloseStreamsOnTerminate) {
	// gracefully close I/O streams
	try {
	if ((getInputStream() != null) && (!System.in.equals(getInputStream())))
	getInputStream().close();
	} catch (final IOException e) {
	}
	try {
	if ((getOutputStream() != null) && (!System.out.equals(getOutputStream())))
	getOutputStream().close();
	} catch (final Exception e) {
	}
	try {
	if ((getErrorStream() != null) && (!System.err.equals(getErrorStream())))
	getErrorStream().close();
	} catch (final Exception e) {
	}
	}

	fOutputStream = null;
	fErrorStream = null;
	fInputStream = null;
	}

	@Override
	public void setCloseStreamsOnTerminate(final boolean closeStreams) {
	fCloseStreamsOnTerminate = closeStreams;
	}

	@Override
	public PrintStream getOutputStream() {
	return (fOutputStream != null) ? fOutputStream : System.out;
	}

	@Override
	public void setOutputStream(final OutputStream outputStream) {
	if (outputStream instanceof PrintStream)
	fOutputStream = (PrintStream) outputStream;

	else if (outputStream != null)
	fOutputStream = new PrintStream(outputStream);
	else
	fOutputStream = null;
	}

	@Override
	public InputStream getInputStream() {
	return (fInputStream != null) ? fInputStream : System.in;
	}

	@Override
	public void setInputStream(final InputStream inputStream) {
	fInputStream = inputStream;
	}

	@Override
	public PrintStream getErrorStream() {
	return (fErrorStream != null) ? fErrorStream : System.err;
	}

	@Override
	public void setErrorStream(final OutputStream errorStream) {
	if (errorStream instanceof PrintStream)
	fErrorStream = (PrintStream) errorStream;

	else if (errorStream != null)
	fErrorStream = new PrintStream(errorStream);
	else
	fErrorStream = null;
	}

	@Override
	public void addExecutionListener(final IExecutionListener listener) {
	fExecutionListeners.add(listener);
	}

	@Override
	public void removeExecutionListener(final IExecutionListener listener) {
	fExecutionListeners.remove(listener);
	}

	protected void notifyExecutionListeners(final Script script, final int status) {
	for (final Object listener : fExecutionListeners.getListeners()) {
	try {
	((IExecutionListener) listener).notify(this, script, status);
	} catch (final Throwable e) {
	Logger.warning(Activator.PLUGIN_ID, "Execution listener did throw an exception", e);
	}
	}
	}

	public ScriptStackTrace getStackTrace() {
	return fStackTrace;
	}

	@Override
	public Object getExecutedFile() {
	for (final IScriptDebugFrame trace : getStackTrace()) {
	if (trace.getType() == IScriptDebugFrame.TYPE_FILE) {
	if (trace.getScript() != null) {
	final Object file = trace.getScript().getFile();
	if (file != null)
	return file;
	}
	}
	}

	return fExecutionRootFile;
	}

	public void setExecutionRootFile(Object executionRootFile) {
	fExecutionRootFile = executionRootFile;
	}

	public void setEngineDescription(final EngineDescription description) {
	fDescription = description;
	}

	@Override
	public void setVariable(final String name, final Object content) {
	if (fSetupDone)
	internalSetVariable(name, content);

	else
	fBufferedVariables.put(name, content);
	}

	@Override
	public Object getVariable(final String name) {
	if (fSetupDone)
	return internalGetVariable(name);

	return fBufferedVariables.get(name);
	}

	@Override
	public boolean hasVariable(final String name) {
	if (fSetupDone)
	return internalHasVariable(name);

	return fBufferedVariables.containsKey(name);
	}

	@Override
	public Map<String, Object> getVariables() {
	if (fSetupDone)
	return internalGetVariables();

	return Collections.unmodifiableMap(fBufferedVariables);
	}

	@Override
	public void addSecurityCheck(ActionType type, ISecurityCheck check) {
	if (!fSecurityChecks.containsKey(type))
	fSecurityChecks.put(type, new ArrayList<ISecurityCheck>());

	if (!fSecurityChecks.get(type).contains(check))
	fSecurityChecks.get(type).add(check);
	}

	protected List<Script> getScheduledScripts() {
	return fScheduledScripts;
	}

	public void setLaunch(ILaunch launch) {
	fLaunch = launch;
	}

	@Override
	public ILaunch getLaunch() {
	return fLaunch;
	}

	/**
	* Internal version of {@link #getVariable(String)}. Only called after script engine was initialized successfully.
	*
	* @param name
	* variable to retrieve
	* @return variable content
	*/
	protected abstract Object internalGetVariable(String name);

	/**
	* Internal version of {@link #getVariables()}. Only called after script engine was initialized successfully.
	*
	* @return map of engine variables: name -> value
	*/
	protected abstract Map<String, Object> internalGetVariables();

	/**
	* Internal version of {@link #hasVariable(String)}. Only called after script engine was initialized successfully.
	*
	* @param name
	* variable to verify
	* @return <code>true</code> when variable exists
	*/
	protected abstract boolean internalHasVariable(String name);

	/**
	* Internal version of {@link #setVariable(String, Object)}. Only called after script engine was initialized successfully.
	*
	* @param name
	* variable to set
	* @param content
	* value to set variable to
	*/
	protected abstract void internalSetVariable(String name, Object content);

	/**
	* Setup method for script engine. Run directly after the engine is activated.
	*
	* Unresolvable errors should be indicated by throwing a ScriptEngineException with details as to what went wrong.
	*/
	protected abstract void setupEngine() throws ScriptEngineException;

	/**
	* Teardown engine. Called immediately before the engine terminates. This method is called even when {@link #setupEngine()} fails.
	*/
	protected abstract void teardownEngine() throws ScriptEngineException;

	/**
	* Execute script code.
	*
	* @param script
	* script to be executed
	* @param fileName
	* name of file executed
	* @param uiThread
	* when set to <code>true</code> run code in UI thread
	* @return execution result
	* @throws Throwable
	* any exception thrown during script execution
	*/
	protected abstract Object execute(Script script, String fileName, boolean uiThread) throws Throwable;

	/**
	* Simple monitor to forward cancellation requests to the script engine.
	*/
	private class ScriptEngineMonitor extends NullProgressMonitor implements IProgressMonitorWithBlocking {

	@Override
	public void setCanceled(boolean cancelled) {
	super.setCanceled(cancelled);

	if (isCanceled())
	terminate();
	}

	@Override
	public void setBlocked(IStatus reason) {
	// nothing to do
	}

	@Override
	public void clearBlocked() {
	// nothing to do
	}
	}
	}