bundles/org.eclipse.capra.ui.sunburst/src/org/eclipse/capra/ui/sunburst/view/SunburstView.java - capra/org.eclipse.capra - Git at Google

 /*******************************************************************************
  * Copyright (c) 2016, 2020 Chalmers | University of Gothenburg, rt-labs 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
  * http://www.eclipse.org/legal/epl-v20.html
  *
  * SPDX-License-Identifier: EPL-2.0
  *
  * Contributors:
  *     Chalmers | University of Gothenburg and rt-labs - initial API and implementation and/or initial documentation
  *     Chalmers | University of Gothenburg - additional features, updated API
  *     Fredrik Johansson and Themistoklis Ntoukolis - initial implementation of the Sunburst View
  *******************************************************************************/
 package org.eclipse.capra.ui.sunburst.view;

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.List;

 import org.eclipse.capra.core.adapters.Connection;
 import org.eclipse.capra.core.adapters.TraceMetaModelAdapter;
 import org.eclipse.capra.core.adapters.TracePersistenceAdapter;
 import org.eclipse.capra.core.handlers.IArtifactHandler;
 import org.eclipse.capra.core.handlers.IArtifactUnpacker;
 import org.eclipse.capra.core.helpers.ArtifactHelper;
 import org.eclipse.capra.core.helpers.EMFHelper;
 import org.eclipse.capra.core.helpers.ExtensionPointHelper;
 import org.eclipse.capra.core.helpers.TraceHelper;
 import org.eclipse.capra.ui.helpers.SelectionSupportHelper;
 import org.eclipse.capra.ui.sunburst.SunburstPreferences;
 import org.eclipse.core.runtime.preferences.IEclipsePreferences;
 import org.eclipse.emf.ecore.EObject;
 import org.eclipse.emf.ecore.resource.ResourceSet;
 import org.eclipse.emf.ecore.resource.impl.ResourceSetImpl;
 import org.eclipse.jface.action.Action;
 import org.eclipse.jface.action.IMenuManager;
 import org.eclipse.jface.dialogs.Dialog;
 import org.eclipse.jface.dialogs.IInputValidator;
 import org.eclipse.jface.dialogs.InputDialog;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.browser.Browser;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.ui.IActionBars;
 import org.eclipse.ui.ISelectionListener;
 import org.eclipse.ui.IWorkbenchPart;
 import org.eclipse.ui.part.ViewPart;
 import org.osgi.service.prefs.BackingStoreException;

 /**
  * Provides a view of the trace model using a navigable sunburst view.
  * <p>
  * The sunburst view visualises the traced artifacts as circle segments centred
  * around a circle that represents the currently selected artifact. Each circle
  * segment is in turn surrounded by circle fragments that represent the
  * artifacts that are traced from it. This way, it is possible to visualise even
  * complex trace models in a compact way.
  * <p>
  * The view is navigable. When clicking on one of the circle segments, the view
  * centres on the artifact represented by the circle segment. Clicking on the
  * centre zooms out again.
  * <p>
  * The sunburst view is based on <a href="https://d3js.org/d3.js</a> and
  * <a href="https://github.com/vasturiano/sunburst-chart">sunburst-chart</a>.
  * The library d3.js is licensed under BSD-3-Clause and sunburst-chart is
  * licensed under MIT.
  *
  *
  * @author Fredrik Johansson
  * @author Themistoklis Ntoukolis
  *
  */
 public class SunburstView extends ViewPart {

 	/**
 	 * The location of the HTML file the JSON code of the sunburst data will be
 	 * injected in.
 	 */
 	private static final String HTML_SOURCE_LOCATION = "platform:/plugin/org.eclipse.capra.ui.sunburst/src/html/index.html";

 	private int maxRecursionLevel;
 	IEclipsePreferences preferences = SunburstPreferences.getPreferences();

 	private Browser browser;
 	private Action selectDepthAction;

 	final TraceMetaModelAdapter traceAdapter = ExtensionPointHelper.getTraceMetamodelAdapter().get();
 	TraceMetaModelAdapter metamodelAdapter = ExtensionPointHelper.getTraceMetamodelAdapter().get();
 	TracePersistenceAdapter persistenceAdapter = ExtensionPointHelper.getTracePersistenceAdapter().get();

 	private ResourceSet resourceSet = new ResourceSetImpl();
 	private EObject traceModel = persistenceAdapter.getTraceModel(resourceSet);
 	private EObject artifactModel = persistenceAdapter.getArtifactWrappers(resourceSet);

 	private ArtifactHelper artifactHelper = new ArtifactHelper(artifactModel);
 	private TraceHelper traceHelper = new TraceHelper(traceModel);

 	private List<Object> selectedModels = new ArrayList<>();

 	private ISelectionListener listener = new ISelectionListener() {
 		@Override
 		public void selectionChanged(IWorkbenchPart part, ISelection selection) {
 			getSelected(part, selection);
 			browser.setText(createHTML());
 		}
 	};

 	/**
 	 * Retrieves the selected elements from {@code selection} and stores them in
 	 * {@link #selectedModels}.
 	 *
 	 * @param part      the workbench part
 	 * @param selection the selection
 	 */
 	private void getSelected(IWorkbenchPart part, ISelection selection) {
 		selectedModels.clear();
 		if (part.getSite().getSelectionProvider() != null) {
 			selectedModels.addAll(SelectionSupportHelper
 					.extractSelectedElements(part.getSite().getSelectionProvider().getSelection(), part));
 		}
 	}

 	@Override
 	public void createPartControl(Composite parent) {
 		this.maxRecursionLevel = preferences.getInt(SunburstPreferences.MAX_RECURSION_LEVEL,
 				SunburstPreferences.MAX_RECURSION_LEVEL_DEFAULT);
 		browser = new Browser(parent, SWT.NONE);
 		browser.setText(createHTML());
 		makeActions();
 		contributeToActionBars();
 		getViewSite().getPage().addSelectionListener(listener);
 	}

 	/**
 	 * Disposes the internal browser widget.
 	 */
 	@Override
 	public void dispose() {
 		getViewSite().getPage().removeSelectionListener(listener);
 		browser.dispose();
 		browser = null;
 		super.dispose();
 	}

 	@Override
 	public void setFocus() {
 		// Deliberately do nothing.
 	}

 	/**
 	 * Creates the actions for the toolbar and the menu.
 	 */
 	private void makeActions() {
 		selectDepthAction = new SelectDepthAction();
 		selectDepthAction.setText("Set recursion depth...");
 		selectDepthAction.setToolTipText("Select the maximum depth until which traceability links will be traversed.");
 	}

 	/**
 	 * Adds the relevant actions to the pull down menu.
 	 *
 	 * @param manager the menu manager for the pull down menu
 	 */
 	private void fillLocalPullDown(IMenuManager manager) {
 		manager.removeAll();
 		manager.add(selectDepthAction);
 	}

 	/**
 	 * Adds relevant entries to the tool bar and pull down menu.
 	 */
 	private void contributeToActionBars() {
 		IActionBars bars = getViewSite().getActionBars();
 		fillLocalPullDown(bars.getMenuManager());
 	}

 	/**
 	 * Retrieves the code of the HTML container for the sunburst view from the
 	 * filesystem.
 	 *
 	 * @return the HMTL code stored in {@link SunburstView#HTML_SOURCE_LOCATION}
 	 */
 	private String getHTML() {
 		URL url;
 		StringBuilder html = new StringBuilder();
 		try {
 			url = new URL(HTML_SOURCE_LOCATION);
 			InputStream inputStream = url.openConnection().getInputStream();
 			BufferedReader in = new BufferedReader(new InputStreamReader(inputStream));
 			String inputLine;

 			while ((inputLine = in.readLine()) != null) {
 				html.append(inputLine);
 				html.append(System.lineSeparator());
 			}

 			in.close();

 		} catch (IOException e) {
 			e.printStackTrace();
 		}
 		return html.toString();
 	}

 	/**
 	 * Injects the generated JSON code into the HTML page and returns the full page
 	 * to be displayed in the browser.
 	 *
 	 * @return the HTML code to display in the browser
 	 */
 	private String createHTML() {
 		String json = convertToJSON();
 		String html = getHTML();
 		return html.replace("const nodeData;", "const nodeData = " + json + ";");
 	}

 	/**
 	 * Converts the trace model into a JSON format that serves as input for the
 	 * sunburst visualisation.
 	 *
 	 * @return the trace model in JSON format
 	 */
 	@SuppressWarnings("unchecked")
 	private String convertToJSON() {
 		List<EObject> secondLevelNodes = new ArrayList<>();
 		String start = "";
 		String end = "]}";
 		StringBuilder inner = new StringBuilder();

 		EObject selectedObject;
 		List<EObject> alreadySeen = new ArrayList<>();

 		if (!selectedModels.isEmpty()) {
 			ArtifactHelper artifactHelper = new ArtifactHelper(artifactModel);
 			for (Object selection : selectedModels) {

 				IArtifactHandler<Object> handler = (IArtifactHandler<Object>) artifactHelper.getHandler(selection)
 						.orElse(null);
 				if (handler != null) {
 					Object unpackedElement = null;
 					if (handler instanceof IArtifactUnpacker) {
 						unpackedElement = IArtifactUnpacker.class.cast(handler).unpack(selection);
 					} else {
 						unpackedElement = selection;
 					}
 					EObject wrappedElement = handler.createWrapper(unpackedElement, artifactModel);
 					if (traceHelper.isArtifactInTraceModel(wrappedElement)) {
 						selectedObject = wrappedElement;
 						if (selectedModels.size() == 1) {
 							secondLevelNodes = getUniqueChildren(null, selectedObject);
 							start = "{\"name\": \"" + artifactHelper.getArtifactLabel(selectedObject)
 									+ "\",\"children\":[";
 							alreadySeen.add(selectedObject);
 						} else {
 							// if more than one artifact is selected, we introduce a "virtual" node and add
 							// them both to the second level
 							start = "{\"name\":\"\",\"children\":[";
 							secondLevelNodes.add(selectedObject);
 						}
 					}
 				}
 			}
 		}
 		for (int secondLevelIndex = 0; secondLevelIndex < secondLevelNodes.size(); secondLevelIndex++) {
 			processHierarchyLevel(inner, secondLevelNodes.get(secondLevelIndex), alreadySeen, 1);
 			if (secondLevelIndex < secondLevelNodes.size() - 1) {
 				inner.append(",");
 			}
 		}

 		String json = start + inner.toString() + end;
 		return json;
 	}

 	/**
 	 * Recursive method that traverses the trace model starting from {@code parent}.
 	 * It adds the JSON code for the parent and all children to the given
 	 * {@link StringBuilder} as long as the maximum recursion depth has not been
 	 * reached.
 	 *
 	 * @param builder      the {@code StringBuilder} to which the JSON code should
 	 *                     be added
 	 * @param parent       the node that should be traversed in this iteration of
 	 *                     the recursion
 	 * @param alreadySeen  a list of nodes that have already been treated
 	 * @param currentLevel the current recursion level
 	 */
 	private void processHierarchyLevel(StringBuilder builder, EObject parent, List<EObject> alreadySeen,
 			int currentLevel) {
 		if (alreadySeen == null)
 			alreadySeen = new ArrayList<>();

 		// Add the current parent to the view
 		String text = artifactHelper.getArtifactLabel(parent);
 		getEntryJSON(builder, text);
 		alreadySeen.add(parent);

 		// Stop the recursion if we have reached the maximum depth
 		if (currentLevel < this.maxRecursionLevel) {
 			List<EObject> children = getUniqueChildren(alreadySeen, parent);
 			if (!children.isEmpty()) {
 				builder.append("\"children\":[");
 				// Go through the children and recurse
 				for (int childLevelIndex = 0; childLevelIndex < children.size(); childLevelIndex++) {
 					processHierarchyLevel(builder, children.get(childLevelIndex), alreadySeen, currentLevel + 1);
 					alreadySeen.remove(children.get(childLevelIndex));

 					if (childLevelIndex < children.size() - 1) {
 						builder.append(",");
 					}
 				}
 				builder.append("]}");
 			} else {
 				builder.append("\"size\": 1}");
 			}
 		} else {
 			builder.append("\"size\": 1}");
 		}
 	}

 	/**
 	 * Adds the JSON code for the entry with the provided {@code name} to the
 	 * provided {@code builder}.
 	 *
 	 * @param builder   the {@link StringBuilder} to add the code to
 	 * @param entryName the name of the entry to add
 	 */
 	private void getEntryJSON(StringBuilder builder, String entryName) {
 		builder.append("{\"name\":\"").append(entryName).append("\",");
 	}

 	/**
 	 * Retrieves a unique list of {@link EObject} instances that are connected to
 	 * the provided {@code artifact}. The elements in the result are unique in the
 	 * sense that they will not contain {@code artifact}, will be free of
 	 * duplicates, and will not contain any elements contained in {@code prev}.
 	 * <p>
 	 * The method will always return a valid list which can be empty.
 	 *
 	 * @param prev     a list of elements that should be excluded from the result
 	 * @param artifact the artifact whose children are requested
 	 * @return a list of unique elements connected to {@code artifact}
 	 */
 	public List<EObject> getUniqueChildren(List<EObject> prev, EObject artifact) {
 		List<Connection> conNow = traceAdapter.getConnectedElements(artifact, traceModel);
 		List<EObject> allConnected = new ArrayList<>(TraceHelper.getTracedElements(conNow));
 		if (EMFHelper.isElementInList(allConnected, artifact)) {
 			allConnected.remove(artifact);
 		}
 		if (prev != null) {
 			for (EObject x : prev) {
 				if (EMFHelper.isElementInList(allConnected, x)) {
 					allConnected.remove(x);
 				}
 			}
 		}
 		return allConnected;
 	}

 	/**
 	 * Class to allow selecting the maximum traversal depth of trace model. Stores
 	 * the selection in the Eclipse Capra preferences.
 	 */
 	private class SelectDepthAction extends Action {
 		@Override
 		public void run() {
 			IInputValidator numberValidator = new IInputValidator() {

 				@Override
 				public String isValid(String newText) {
 					boolean validationError = false;
 					try {
 						int i = Integer.parseInt(newText);
 						if (i < 1) {
 							validationError = true;
 						}
 					} catch (NumberFormatException ex) {
 						validationError = true;
 					}
 					if (validationError) {
 						return "Please enter a valid number larger than 0.";
 					}
 					return null;
 				}
 			};
 			InputDialog dialog = new InputDialog(getViewSite().getShell(), "Trace link depth",
 					"Please select the maximum depth until which traceability links will be traversed for the Sunburst view.",
 					String.valueOf(maxRecursionLevel), numberValidator);
 			dialog.setBlockOnOpen(true);
 			dialog.open();
 			if (dialog.getReturnCode() == Dialog.OK) {
 				maxRecursionLevel = Integer.parseInt(dialog.getValue());
 				preferences.putInt(SunburstPreferences.MAX_RECURSION_LEVEL, maxRecursionLevel);
 				try {
 					// forces the application to save the preferences
 					preferences.flush();
 				} catch (BackingStoreException e) {
 					e.printStackTrace();
 				}
 				browser.setText(createHTML());
 			}
 		}
 	};

 }
	/*******************************************************************************
	* Copyright (c) 2016, 2020 Chalmers \| University of Gothenburg, rt-labs 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
	* http://www.eclipse.org/legal/epl-v20.html
	*
	* SPDX-License-Identifier: EPL-2.0
	*
	* Contributors:
	* Chalmers \| University of Gothenburg and rt-labs - initial API and implementation and/or initial documentation
	* Chalmers \| University of Gothenburg - additional features, updated API
	* Fredrik Johansson and Themistoklis Ntoukolis - initial implementation of the Sunburst View
	*******************************************************************************/
	package org.eclipse.capra.ui.sunburst.view;

	import java.io.BufferedReader;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.InputStreamReader;
	import java.net.URL;
	import java.util.ArrayList;
	import java.util.List;

	import org.eclipse.capra.core.adapters.Connection;
	import org.eclipse.capra.core.adapters.TraceMetaModelAdapter;
	import org.eclipse.capra.core.adapters.TracePersistenceAdapter;
	import org.eclipse.capra.core.handlers.IArtifactHandler;
	import org.eclipse.capra.core.handlers.IArtifactUnpacker;
	import org.eclipse.capra.core.helpers.ArtifactHelper;
	import org.eclipse.capra.core.helpers.EMFHelper;
	import org.eclipse.capra.core.helpers.ExtensionPointHelper;
	import org.eclipse.capra.core.helpers.TraceHelper;
	import org.eclipse.capra.ui.helpers.SelectionSupportHelper;
	import org.eclipse.capra.ui.sunburst.SunburstPreferences;
	import org.eclipse.core.runtime.preferences.IEclipsePreferences;
	import org.eclipse.emf.ecore.EObject;
	import org.eclipse.emf.ecore.resource.ResourceSet;
	import org.eclipse.emf.ecore.resource.impl.ResourceSetImpl;
	import org.eclipse.jface.action.Action;
	import org.eclipse.jface.action.IMenuManager;
	import org.eclipse.jface.dialogs.Dialog;
	import org.eclipse.jface.dialogs.IInputValidator;
	import org.eclipse.jface.dialogs.InputDialog;
	import org.eclipse.jface.viewers.ISelection;
	import org.eclipse.swt.SWT;
	import org.eclipse.swt.browser.Browser;
	import org.eclipse.swt.widgets.Composite;
	import org.eclipse.ui.IActionBars;
	import org.eclipse.ui.ISelectionListener;
	import org.eclipse.ui.IWorkbenchPart;
	import org.eclipse.ui.part.ViewPart;
	import org.osgi.service.prefs.BackingStoreException;

	/**
	* Provides a view of the trace model using a navigable sunburst view.
	* <p>
	* The sunburst view visualises the traced artifacts as circle segments centred
	* around a circle that represents the currently selected artifact. Each circle
	* segment is in turn surrounded by circle fragments that represent the
	* artifacts that are traced from it. This way, it is possible to visualise even
	* complex trace models in a compact way.
	* <p>
	* The view is navigable. When clicking on one of the circle segments, the view
	* centres on the artifact represented by the circle segment. Clicking on the
	* centre zooms out again.
	* <p>
	* The sunburst view is based on <a href="https://d3js.org/d3.js</a> and
	* <a href="https://github.com/vasturiano/sunburst-chart">sunburst-chart</a>.
	* The library d3.js is licensed under BSD-3-Clause and sunburst-chart is
	* licensed under MIT.
	*
	*
	* @author Fredrik Johansson
	* @author Themistoklis Ntoukolis
	*
	*/
	public class SunburstView extends ViewPart {

	/**
	* The location of the HTML file the JSON code of the sunburst data will be
	* injected in.
	*/
	private static final String HTML_SOURCE_LOCATION = "platform:/plugin/org.eclipse.capra.ui.sunburst/src/html/index.html";

	private int maxRecursionLevel;
	IEclipsePreferences preferences = SunburstPreferences.getPreferences();

	private Browser browser;
	private Action selectDepthAction;

	final TraceMetaModelAdapter traceAdapter = ExtensionPointHelper.getTraceMetamodelAdapter().get();
	TraceMetaModelAdapter metamodelAdapter = ExtensionPointHelper.getTraceMetamodelAdapter().get();
	TracePersistenceAdapter persistenceAdapter = ExtensionPointHelper.getTracePersistenceAdapter().get();

	private ResourceSet resourceSet = new ResourceSetImpl();
	private EObject traceModel = persistenceAdapter.getTraceModel(resourceSet);
	private EObject artifactModel = persistenceAdapter.getArtifactWrappers(resourceSet);

	private ArtifactHelper artifactHelper = new ArtifactHelper(artifactModel);
	private TraceHelper traceHelper = new TraceHelper(traceModel);

	private List<Object> selectedModels = new ArrayList<>();

	private ISelectionListener listener = new ISelectionListener() {
	@Override
	public void selectionChanged(IWorkbenchPart part, ISelection selection) {
	getSelected(part, selection);
	browser.setText(createHTML());
	}
	};

	/**
	* Retrieves the selected elements from {@code selection} and stores them in
	* {@link #selectedModels}.
	*
	* @param part the workbench part
	* @param selection the selection
	*/
	private void getSelected(IWorkbenchPart part, ISelection selection) {
	selectedModels.clear();
	if (part.getSite().getSelectionProvider() != null) {
	selectedModels.addAll(SelectionSupportHelper
	.extractSelectedElements(part.getSite().getSelectionProvider().getSelection(), part));
	}
	}

	@Override
	public void createPartControl(Composite parent) {
	this.maxRecursionLevel = preferences.getInt(SunburstPreferences.MAX_RECURSION_LEVEL,
	SunburstPreferences.MAX_RECURSION_LEVEL_DEFAULT);
	browser = new Browser(parent, SWT.NONE);
	browser.setText(createHTML());
	makeActions();
	contributeToActionBars();
	getViewSite().getPage().addSelectionListener(listener);
	}

	/**
	* Disposes the internal browser widget.
	*/
	@Override
	public void dispose() {
	getViewSite().getPage().removeSelectionListener(listener);
	browser.dispose();
	browser = null;
	super.dispose();
	}

	@Override
	public void setFocus() {
	// Deliberately do nothing.
	}

	/**
	* Creates the actions for the toolbar and the menu.
	*/
	private void makeActions() {
	selectDepthAction = new SelectDepthAction();
	selectDepthAction.setText("Set recursion depth...");
	selectDepthAction.setToolTipText("Select the maximum depth until which traceability links will be traversed.");
	}

	/**
	* Adds the relevant actions to the pull down menu.
	*
	* @param manager the menu manager for the pull down menu
	*/
	private void fillLocalPullDown(IMenuManager manager) {
	manager.removeAll();
	manager.add(selectDepthAction);
	}

	/**
	* Adds relevant entries to the tool bar and pull down menu.
	*/
	private void contributeToActionBars() {
	IActionBars bars = getViewSite().getActionBars();
	fillLocalPullDown(bars.getMenuManager());
	}

	/**
	* Retrieves the code of the HTML container for the sunburst view from the
	* filesystem.
	*
	* @return the HMTL code stored in {@link SunburstView#HTML_SOURCE_LOCATION}
	*/
	private String getHTML() {
	URL url;
	StringBuilder html = new StringBuilder();
	try {
	url = new URL(HTML_SOURCE_LOCATION);
	InputStream inputStream = url.openConnection().getInputStream();
	BufferedReader in = new BufferedReader(new InputStreamReader(inputStream));
	String inputLine;

	while ((inputLine = in.readLine()) != null) {
	html.append(inputLine);
	html.append(System.lineSeparator());
	}

	in.close();

	} catch (IOException e) {
	e.printStackTrace();
	}
	return html.toString();
	}

	/**
	* Injects the generated JSON code into the HTML page and returns the full page
	* to be displayed in the browser.
	*
	* @return the HTML code to display in the browser
	*/
	private String createHTML() {
	String json = convertToJSON();
	String html = getHTML();
	return html.replace("const nodeData;", "const nodeData = " + json + ";");
	}

	/**
	* Converts the trace model into a JSON format that serves as input for the
	* sunburst visualisation.
	*
	* @return the trace model in JSON format
	*/
	@SuppressWarnings("unchecked")
	private String convertToJSON() {
	List<EObject> secondLevelNodes = new ArrayList<>();
	String start = "";
	String end = "]}";
	StringBuilder inner = new StringBuilder();

	EObject selectedObject;
	List<EObject> alreadySeen = new ArrayList<>();

	if (!selectedModels.isEmpty()) {
	ArtifactHelper artifactHelper = new ArtifactHelper(artifactModel);
	for (Object selection : selectedModels) {

	IArtifactHandler<Object> handler = (IArtifactHandler<Object>) artifactHelper.getHandler(selection)
	.orElse(null);
	if (handler != null) {
	Object unpackedElement = null;
	if (handler instanceof IArtifactUnpacker) {
	unpackedElement = IArtifactUnpacker.class.cast(handler).unpack(selection);
	} else {
	unpackedElement = selection;
	}
	EObject wrappedElement = handler.createWrapper(unpackedElement, artifactModel);
	if (traceHelper.isArtifactInTraceModel(wrappedElement)) {
	selectedObject = wrappedElement;
	if (selectedModels.size() == 1) {
	secondLevelNodes = getUniqueChildren(null, selectedObject);
	start = "{\"name\": \"" + artifactHelper.getArtifactLabel(selectedObject)
	+ "\",\"children\":[";
	alreadySeen.add(selectedObject);
	} else {
	// if more than one artifact is selected, we introduce a "virtual" node and add
	// them both to the second level
	start = "{\"name\":\"\",\"children\":[";
	secondLevelNodes.add(selectedObject);
	}
	}
	}
	}
	}
	for (int secondLevelIndex = 0; secondLevelIndex < secondLevelNodes.size(); secondLevelIndex++) {
	processHierarchyLevel(inner, secondLevelNodes.get(secondLevelIndex), alreadySeen, 1);
	if (secondLevelIndex < secondLevelNodes.size() - 1) {
	inner.append(",");
	}
	}

	String json = start + inner.toString() + end;
	return json;
	}

	/**
	* Recursive method that traverses the trace model starting from {@code parent}.
	* It adds the JSON code for the parent and all children to the given
	* {@link StringBuilder} as long as the maximum recursion depth has not been
	* reached.
	*
	* @param builder the {@code StringBuilder} to which the JSON code should
	* be added
	* @param parent the node that should be traversed in this iteration of
	* the recursion
	* @param alreadySeen a list of nodes that have already been treated
	* @param currentLevel the current recursion level
	*/
	private void processHierarchyLevel(StringBuilder builder, EObject parent, List<EObject> alreadySeen,
	int currentLevel) {
	if (alreadySeen == null)
	alreadySeen = new ArrayList<>();

	// Add the current parent to the view
	String text = artifactHelper.getArtifactLabel(parent);
	getEntryJSON(builder, text);
	alreadySeen.add(parent);

	// Stop the recursion if we have reached the maximum depth
	if (currentLevel < this.maxRecursionLevel) {
	List<EObject> children = getUniqueChildren(alreadySeen, parent);
	if (!children.isEmpty()) {
	builder.append("\"children\":[");
	// Go through the children and recurse
	for (int childLevelIndex = 0; childLevelIndex < children.size(); childLevelIndex++) {
	processHierarchyLevel(builder, children.get(childLevelIndex), alreadySeen, currentLevel + 1);
	alreadySeen.remove(children.get(childLevelIndex));

	if (childLevelIndex < children.size() - 1) {
	builder.append(",");
	}
	}
	builder.append("]}");
	} else {
	builder.append("\"size\": 1}");
	}
	} else {
	builder.append("\"size\": 1}");
	}
	}

	/**
	* Adds the JSON code for the entry with the provided {@code name} to the
	* provided {@code builder}.
	*
	* @param builder the {@link StringBuilder} to add the code to
	* @param entryName the name of the entry to add
	*/
	private void getEntryJSON(StringBuilder builder, String entryName) {
	builder.append("{\"name\":\"").append(entryName).append("\",");
	}

	/**
	* Retrieves a unique list of {@link EObject} instances that are connected to
	* the provided {@code artifact}. The elements in the result are unique in the
	* sense that they will not contain {@code artifact}, will be free of
	* duplicates, and will not contain any elements contained in {@code prev}.
	* <p>
	* The method will always return a valid list which can be empty.
	*
	* @param prev a list of elements that should be excluded from the result
	* @param artifact the artifact whose children are requested
	* @return a list of unique elements connected to {@code artifact}
	*/
	public List<EObject> getUniqueChildren(List<EObject> prev, EObject artifact) {
	List<Connection> conNow = traceAdapter.getConnectedElements(artifact, traceModel);
	List<EObject> allConnected = new ArrayList<>(TraceHelper.getTracedElements(conNow));
	if (EMFHelper.isElementInList(allConnected, artifact)) {
	allConnected.remove(artifact);
	}
	if (prev != null) {
	for (EObject x : prev) {
	if (EMFHelper.isElementInList(allConnected, x)) {
	allConnected.remove(x);
	}
	}
	}
	return allConnected;
	}

	/**
	* Class to allow selecting the maximum traversal depth of trace model. Stores
	* the selection in the Eclipse Capra preferences.
	*/
	private class SelectDepthAction extends Action {
	@Override
	public void run() {
	IInputValidator numberValidator = new IInputValidator() {

	@Override
	public String isValid(String newText) {
	boolean validationError = false;
	try {
	int i = Integer.parseInt(newText);
	if (i < 1) {
	validationError = true;
	}
	} catch (NumberFormatException ex) {
	validationError = true;
	}
	if (validationError) {
	return "Please enter a valid number larger than 0.";
	}
	return null;
	}
	};
	InputDialog dialog = new InputDialog(getViewSite().getShell(), "Trace link depth",
	"Please select the maximum depth until which traceability links will be traversed for the Sunburst view.",
	String.valueOf(maxRecursionLevel), numberValidator);
	dialog.setBlockOnOpen(true);
	dialog.open();
	if (dialog.getReturnCode() == Dialog.OK) {
	maxRecursionLevel = Integer.parseInt(dialog.getValue());
	preferences.putInt(SunburstPreferences.MAX_RECURSION_LEVEL, maxRecursionLevel);
	try {
	// forces the application to save the preferences
	preferences.flush();
	} catch (BackingStoreException e) {
	e.printStackTrace();
	}
	browser.setText(createHTML());
	}
	}
	};

	}