core/plugins/org.eclipse.dltk.launching/src/org/eclipse/dltk/internal/launching/InterpreterDefinitionsContainer.java

/*******************************************************************************
 * Copyright (c) 2000, 2007 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 
 *******************************************************************************/
package org.eclipse.dltk.internal.launching;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.TransformerException;

import org.eclipse.core.runtime.Path;
import org.eclipse.dltk.launching.EnvironmentVariable;
import org.eclipse.dltk.launching.IInterpreterInstall;
import org.eclipse.dltk.launching.IInterpreterInstallType;
import org.eclipse.dltk.launching.InterpreterStandin;
import org.eclipse.dltk.launching.LaunchingMessages;
import org.eclipse.dltk.launching.LibraryLocation;
import org.eclipse.dltk.launching.ScriptRuntime;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * This is a container for interpreter definitions such as the interpreter
 * definitions that are stored in the workbench preferences.
 * <p>
 * An instance of this class may be obtained from an XML document by calling
 * <code>parseXMLIntoContainer</code>.
 * </p>
 * <p>
 * An instance of this class may be translated into an XML document by calling
 * <code>getAsXML</code>.
 * </p>
 * <p>
 * Clients may instantiate this class; it is not intended to be subclassed.
 * </p>
 */
public class InterpreterDefinitionsContainer {

	private static final String PATH_ATTR = "path";
	private static final String INTERPRETER_NAME_ATTR = "name";
	private static final String INTERPRETER_TAG = "interpreter";
	private static final String INTERPRETER_TYPE_TAG = "interpreterType";
	private static final String ID_ATTR = "id";
	private static final String NATURE_ATTR = "nature";
	private static final String DEFAULT_INTERPRETER_TAG = "defaultInterpreter";
	private static final String INTERPRETER_SETTINGS_TAG = "interpreterSettings";
	private static final String VARIABLE_VALUE_ATTR = "variableValue";
	private static final String VARIABLE_NAME_ATTR = "variableName";
	private static final String LIBRARY_PATH_ATTR = "libraryPath";
	private static final String IARGS_ATTR = "iargs";
	private static final String ENVIRONMENT_VARIABLES_TAG = "environmentVariables";
	private static final String ENVIRONMENT_VARIABLE_TAG = "environmentVariable";
	private static final String LIBRARY_LOCATIONS_TAG = "libraryLocations";
	private static final String LIBRARY_LOCATION_TAG = "libraryLocation";

	/**
	 * Map of InterpreterInstallTypes to Lists of corresponding
	 * InterpreterInstalls.
	 */
	private Map fInterTypeToInterMap;

	/**
	 * Cached list of Interpreters in this container
	 */
	private List fInterpreterList;

	/**
	 * Interpreters managed by this container whose install locations don't
	 * actually exist.
	 */
	private List fInvalidInterpreterList;

	/**
	 * The composite identifier of the default Interpreter. This consists of the
	 * install type ID plus an ID for the Interpreter.
	 */
	// map bind default interpreter to each nature
	private Map fDefaultInterpreterInstallCompositeID;

	/**
	 * The identifier of the connector to use for the default Interpreter.
	 */
	// map bind default connector to each nature
	private Map fDefaultInterpreterInstallConnectorTypeID;

	/**
	 * Constructs an empty Interpreter container
	 */
	public InterpreterDefinitionsContainer() {
		fInterTypeToInterMap = new HashMap(10);
		fInvalidInterpreterList = new ArrayList(10);
		fInterpreterList = new ArrayList(10);
		fDefaultInterpreterInstallCompositeID = new HashMap();
		fDefaultInterpreterInstallConnectorTypeID = new HashMap();
	}

	/**
	 * Returns list of default interpreters natures TODO: rename
	 * 
	 * @return
	 */
	public String[] getInterpreterNatures() {
		Set s = fDefaultInterpreterInstallCompositeID.keySet();
		return (String[]) s.toArray(new String[s.size()]);
	}

	/**
	 * Add the specified Interpreter to the Interpreter definitions managed by
	 * this container.
	 * <p>
	 * If distinguishing valid from invalid Interpreters is important, the
	 * specified Interpreter must have already had its install location set. An
	 * invalid Interpreter is one whose install location doesn't exist.
	 * </p>
	 * 
	 * @param Interpreter
	 *            the Interpreter to be added to this container
	 */
	public void addInterpreter(IInterpreterInstall Interpreter) {
		if (!fInterpreterList.contains(Interpreter)) {
			IInterpreterInstallType InterpreterInstallType = Interpreter
					.getInterpreterInstallType();
			List InterpreterList = (List) fInterTypeToInterMap
					.get(InterpreterInstallType);
			if (InterpreterList == null) {
				InterpreterList = new ArrayList(3);
				fInterTypeToInterMap.put(InterpreterInstallType,
						InterpreterList);
			}
			InterpreterList.add(Interpreter);
			File installLocation = Interpreter.getInstallLocation();
			if (installLocation == null
					|| !InterpreterInstallType.validateInstallLocation(
							installLocation).isOK()) {
				fInvalidInterpreterList.add(Interpreter);
			}
			fInterpreterList.add(Interpreter);
		}
	}

	/**
	 * Add all Interpreter's in the specified list to the Interpreter
	 * definitions managed by this container.
	 * <p>
	 * If distinguishing valid from invalid Interpreters is important, the
	 * specified Interpreters must have already had their install locations set.
	 * An invalid Interpreter is one whose install location doesn't exist.
	 * </p>
	 * 
	 * @param InterpreterList
	 *            a list of Interpreters to be added to this container
	 */
	public void addInterpreterList(List InterpreterList) {
		Iterator iterator = InterpreterList.iterator();
		while (iterator.hasNext()) {
			IInterpreterInstall Interpreter = (IInterpreterInstall) iterator
					.next();
			addInterpreter(Interpreter);
		}
	}

	/**
	 * Return a mapping of Interpreter install types to lists of Interpreters.
	 * The keys of this map are instances of
	 * <code>IInterpreterInstallType</code>. The values are instances of
	 * <code>java.util.List</code> which contain instances of
	 * <code>IInterpreterInstall</code>.
	 * 
	 * @return Map the mapping of Interpreter install types to lists of
	 *         Interpreters
	 */
	public Map getInterpreterTypeToInterpreterMap() {
		return fInterTypeToInterMap;
	}

	/**
	 * Return a list of all Interpreters in this container, including any
	 * invalid Interpreters. An invalid Interpreter is one whose install
	 * location does not exist on the file system. The order of the list is not
	 * specified.
	 * 
	 * @return List the data structure containing all Interpreters managed by
	 *         this container
	 */
	public List getInterpreterList() {
		return fInterpreterList;
	}

	/**
	 * Return filtered list of all Interpreters in this container, including any
	 * invalid Interpreters. An invalid Interpreter is one whose install
	 * location does not exist on the file system. The order of the list is not
	 * specified.
	 * 
	 * @return List the data structure containing all Interpreters managed by
	 *         this container
	 */
	public List getInterpreterList(String nature) {
		List res = new ArrayList(fInterpreterList.size());
		for (Iterator iter = fInterpreterList.iterator(); iter.hasNext();) {
			IInterpreterInstall Interpreter = (IInterpreterInstall) iter.next();
			if (Interpreter.getInterpreterInstallType().getNatureId().equals(
					nature))
				res.add(Interpreter);
		}
		return res;
	}

	/**
	 * Return a list of all valid Interpreters in this container. A valid
	 * Interpreter is one whose install location exists on the file system. The
	 * order of the list is not specified.
	 * 
	 * @return List
	 */
	public List getValidInterpreterList() {
		List Interpreters = getInterpreterList();
		List resultList = new ArrayList(Interpreters.size());
		resultList.addAll(Interpreters);
		resultList.removeAll(fInvalidInterpreterList);
		return resultList;
	}

	/**
	 * Return filtered list of valid Interpreters in this container. A valid
	 * Interpreter is one whose install location exists on the file system. The
	 * order of the list is not specified.
	 * 
	 * @return List
	 */
	public List getValidInterpreterList(String nature) {
		List Interpreters = getInterpreterList(nature);
		List resultList = new ArrayList(Interpreters.size());
		resultList.addAll(Interpreters);
		resultList.removeAll(fInvalidInterpreterList);
		return resultList;
	}

	/**
	 * Returns the composite ID for the default Interpreter. The composite ID
	 * consists of an ID for the Interpreter install type together with an ID
	 * for Interpreter. This is necessary because Interpreter ids by themselves
	 * are not necessarily unique across Interpreter install types.
	 * 
	 * @return String returns the composite ID of the current default
	 *         Interpreter
	 */
	public String getDefaultInterpreterInstallCompositeID(String nature) {
		return (String) fDefaultInterpreterInstallCompositeID.get(nature);
	}

	public String[] getDefaultInterpreterInstallCompositeID() {
		Collection ids = fDefaultInterpreterInstallCompositeID.values();
		return (String[]) ids.toArray(new String[ids.size()]);
	}

	/**
	 * Sets the composite ID for the default Interpreter. The composite ID
	 * consists of an ID for the Interpreter install type together with an ID
	 * for Interpreter. This is necessary because Interpreter ids by themselves
	 * are not necessarily unique across Interpreter install types.
	 * 
	 * @param id
	 *            identifies the new default Interpreter using a composite ID
	 */
	public void setDefaultInterpreterInstallCompositeID(String nature, String id) {
		if (id != null)
			fDefaultInterpreterInstallCompositeID.put(nature, id);
		else
			fDefaultInterpreterInstallCompositeID.remove(nature);
	}

	/**
	 * Return the default Interpreter's connector type ID.
	 * 
	 * @return String the current value of the default Interpreter's connector
	 *         type ID
	 */
	public String getDefaultInterpreterInstallConnectorTypeID(String nature) {
		return (String) fDefaultInterpreterInstallConnectorTypeID.get(nature);
	}

	/**
	 * Set the default Interpreter's connector type ID.
	 * 
	 * @param id
	 *            the new value of the default Interpreter's connector type ID
	 */
	public void setDefaultInterpreterInstallConnectorTypeID(String nature,
			String id) {
		fDefaultInterpreterInstallConnectorTypeID.put(nature, id);
	}

	/**
	 * Return the Interpreter definitions contained in this object as a String
	 * of XML. The String is suitable for storing in the workbench preferences.
	 * <p>
	 * The resulting XML is compatible with the static method
	 * <code>parseXMLIntoContainer</code>.
	 * </p>
	 * 
	 * @return String the results of flattening this object into XML
	 * @throws IOException
	 *             if this method fails. Reasons include:
	 *             <ul>
	 *             <li>serialization of the XML document failed</li>
	 *             </ul>
	 * @throws ParserConfigurationException
	 *             if creation of the XML document failed
	 * @throws TransformerException
	 *             if serialization of the XML document failed
	 */
	public String getAsXML() throws ParserConfigurationException, IOException,
			TransformerException {

		// Create the Document and the top-level node
		Document doc = DLTKLaunchingPlugin.getDocument();
		Element config = doc.createElement(INTERPRETER_SETTINGS_TAG); //$NON-NLS-1$
		doc.appendChild(config);

		// Set the defaultInterpreter attribute on the top-level node
		for (Iterator iter = fDefaultInterpreterInstallCompositeID.keySet()
				.iterator(); iter.hasNext();) {
			String nature = (String) iter.next();
			Element defaulte = doc.createElement(DEFAULT_INTERPRETER_TAG);
			config.appendChild(defaulte);
			defaulte.setAttribute(NATURE_ATTR, nature);
			defaulte.setAttribute(ID_ATTR,
					(String) fDefaultInterpreterInstallCompositeID.get(nature));
		}

		// Set the defaultInterpreterConnector attribute on the top-level node
		for (Iterator iter = fDefaultInterpreterInstallConnectorTypeID.keySet()
				.iterator(); iter.hasNext();) {
			String nature = (String) iter.next();
			Element defaulte = doc.createElement("defaultInterpreterConnector");
			config.appendChild(defaulte);
			defaulte.setAttribute(NATURE_ATTR, nature);
			defaulte.setAttribute(ID_ATTR,
					(String) fDefaultInterpreterInstallConnectorTypeID
							.get(nature));
		}

		// Create a node for each install type represented in this container
		Set InterpreterInstallTypeSet = getInterpreterTypeToInterpreterMap()
				.keySet();
		Iterator keyIterator = InterpreterInstallTypeSet.iterator();
		while (keyIterator.hasNext()) {
			IInterpreterInstallType InterpreterInstallType = (IInterpreterInstallType) keyIterator
					.next();
			Element InterpreterTypeElement = interpreterTypeAsElement(doc,
					InterpreterInstallType);
			config.appendChild(InterpreterTypeElement);
		}

		// Serialize the Document and return the resulting String
		return DLTKLaunchingPlugin.serializeDocument(doc);
	}

	/**
	 * Create and return a node for the specified Interpreter install type in
	 * the specified Document.
	 */
	private Element interpreterTypeAsElement(Document doc,
			IInterpreterInstallType InterpreterType) {

		// Create a node for the Interpreter type and set its 'id' attribute
		Element element = doc.createElement(INTERPRETER_TYPE_TAG); //$NON-NLS-1$
		element.setAttribute(ID_ATTR, InterpreterType.getId()); //$NON-NLS-1$

		// For each Interpreter of the specified type, create a subordinate node
		// for it
		List InterpreterList = (List) getInterpreterTypeToInterpreterMap().get(
				InterpreterType);
		Iterator InterpreterIterator = InterpreterList.iterator();
		while (InterpreterIterator.hasNext()) {
			IInterpreterInstall Interpreter = (IInterpreterInstall) InterpreterIterator
					.next();
			Element InterpreterElement = interpreterAsElement(doc, Interpreter);
			element.appendChild(InterpreterElement);
		}

		return element;
	}

	/**
	 * Create and return a node for the specified Interpreter in the specified
	 * Document.
	 */
	private Element interpreterAsElement(Document doc,
			IInterpreterInstall Interpreter) {

		// Create the node for the Interpreter and set its 'id' & 'name'
		// attributes
		Element element = doc.createElement(INTERPRETER_TAG); //$NON-NLS-1$
		element.setAttribute(ID_ATTR, Interpreter.getId()); //$NON-NLS-1$
		element.setAttribute(INTERPRETER_NAME_ATTR, Interpreter.getName()); //$NON-NLS-1$

		// Determine and set the 'path' attribute for the Interpreter
		String installPath = ""; //$NON-NLS-1$
		File installLocation = Interpreter.getRawInstallLocation();
		if (installLocation != null) {
			installPath = installLocation.toString();
		}
		element.setAttribute(PATH_ATTR, installPath); //$NON-NLS-1$

		// If the 'libraryLocations' attribute is specified, create a node for
		// it
		LibraryLocation[] libraryLocations = Interpreter.getLibraryLocations();
		if (libraryLocations != null) {
			Element libLocationElement = libraryLocationsAsElement(doc,
					libraryLocations);
			element.appendChild(libLocationElement);
		}

		EnvironmentVariable[] environmentVariables = Interpreter
				.getEnvironmentVariables();
		if (environmentVariables != null) {
			Element environmentVariableElement = environmentVariablesAsElement(
					doc, environmentVariables);
			element.appendChild(environmentVariableElement);
		}

		String[] InterpreterArgs = Interpreter.getInterpreterArguments();
		if (InterpreterArgs != null && InterpreterArgs.length > 0) {
			StringBuffer buffer = new StringBuffer();
			for (int i = 0; i < InterpreterArgs.length; i++) {
				buffer.append(InterpreterArgs[i] + " "); //$NON-NLS-1$
			}
			element.setAttribute(IARGS_ATTR, buffer.toString()); //$NON-NLS-1$
		}

		return element;
	}

	/**
	 * Create and return a 'libraryLocations' node. This node owns subordinate
	 * nodes that list individual library locations.
	 */
	private static Element libraryLocationsAsElement(Document doc,
			LibraryLocation[] locations) {
		Element root = doc.createElement(LIBRARY_LOCATIONS_TAG); //$NON-NLS-1$
		for (int i = 0; i < locations.length; i++) {
			Element element = doc.createElement(LIBRARY_LOCATION_TAG); //$NON-NLS-1$
			element.setAttribute(LIBRARY_PATH_ATTR, locations[i]
					.getLibraryPath().toString()); //$NON-NLS-1$
			root.appendChild(element);
		}
		return root;
	}

	private static Element environmentVariablesAsElement(Document doc,
			EnvironmentVariable[] variables) {
		Element root = doc.createElement(ENVIRONMENT_VARIABLES_TAG); //$NON-NLS-1$
		for (int i = 0; i < variables.length; i++) {
			Element element = doc.createElement(ENVIRONMENT_VARIABLE_TAG); //$NON-NLS-1$
			element.setAttribute(VARIABLE_NAME_ATTR, variables[i].getName()); //$NON-NLS-1$
			element.setAttribute(VARIABLE_VALUE_ATTR, variables[i].getValue()); //$NON-NLS-1$
			root.appendChild(element);
		}
		return root;
	}

	public static InterpreterDefinitionsContainer parseXMLIntoContainer(
			InputStream inputStream) throws IOException {
		InterpreterDefinitionsContainer container = new InterpreterDefinitionsContainer();
		parseXMLIntoContainer(inputStream, container);
		return container;
	}

	/**
	 * Parse the Interpreter definitions contained in the specified InputStream
	 * into the specified container.
	 * <p>
	 * The Interpreters in the returned container are instances of
	 * <code>InterpreterStandin</code>.
	 * </p>
	 * <p>
	 * This method has no side-effects. That is, no notifications are sent for
	 * Interpreter adds, changes, deletes, and the workbench preferences are not
	 * affected.
	 * </p>
	 * <p>
	 * If the <code>getAsXML</code> method is called on the returned container
	 * object, the resulting XML will be sematically equivalent (though not
	 * necessarily syntactically equivalent) as the XML contained in
	 * <code>inputStream</code>.
	 * </p>
	 * 
	 * @param inputStream
	 *            the <code>InputStream</code> containing XML that declares a
	 *            set of Interpreters and a default Interpreter
	 * @param container
	 *            the container to add the Interpreter defs to
	 * @return InterpreterDefinitionsContainer a container for the Interpreter
	 *         objects declared in <code>inputStream</code>
	 * @throws IOException
	 *             if this method fails. Reasons include:
	 *             <ul>
	 *             <li>the XML in <code>inputStream</code> was badly
	 *             formatted</li>
	 *             <li>the top-level node was not 'InterpreterSettings'</li>
	 *             </ul>
	 * 
	 */
	public static void parseXMLIntoContainer(InputStream inputStream,
			InterpreterDefinitionsContainer container) throws IOException {

		// Wrapper the stream for efficient parsing
		InputStream stream = new BufferedInputStream(inputStream);

		// Do the parsing and obtain the top-level node
		Element config = null;
		try {
			DocumentBuilder parser = DocumentBuilderFactory.newInstance()
					.newDocumentBuilder();
			parser.setErrorHandler(new DefaultHandler());
			config = parser.parse(new InputSource(stream)).getDocumentElement();
		} catch (SAXException e) {
			throw new IOException(LaunchingMessages.ScriptRuntime_badFormat);
		} catch (ParserConfigurationException e) {
			stream.close();
			throw new IOException(LaunchingMessages.ScriptRuntime_badFormat);
		} finally {
			stream.close();
		}

		// If the top-level node wasn't what we expected, bail out
		if (!config.getNodeName().equalsIgnoreCase(INTERPRETER_SETTINGS_TAG)) { //$NON-NLS-1$
			throw new IOException(LaunchingMessages.ScriptRuntime_badFormat);
		}

		// Traverse the parsed structure and populate the InterpreterType to
		// Interpreter Map
		NodeList list = config.getChildNodes();
		int length = list.getLength();
		for (int i = 0; i < length; ++i) {
			Node node = list.item(i);
			short type = node.getNodeType();
			if (type == Node.ELEMENT_NODE) {
				Element InterpreterTypeElement = (Element) node;
				if (InterpreterTypeElement.getNodeName().equalsIgnoreCase(
						INTERPRETER_TYPE_TAG)) { //$NON-NLS-1$
					populateInterpreterTypes(InterpreterTypeElement, container);
				}
				if (InterpreterTypeElement.getNodeName().equalsIgnoreCase(
						DEFAULT_INTERPRETER_TAG)) { //$NON-NLS-1$
					String nature = InterpreterTypeElement
							.getAttribute(NATURE_ATTR);
					String id = InterpreterTypeElement.getAttribute(ID_ATTR);
					container.setDefaultInterpreterInstallCompositeID(nature,
							id);
				}
				if (InterpreterTypeElement.getNodeName().equalsIgnoreCase(
						"defaultInterpreterConnector")) { //$NON-NLS-1$
					String nature = InterpreterTypeElement
							.getAttribute(NATURE_ATTR);
					String id = InterpreterTypeElement.getAttribute(ID_ATTR);
					container.setDefaultInterpreterInstallConnectorTypeID(
							nature, id);
				}
			}
		}
	}

	/**
	 * For the specified Interpreter type node, parse all subordinate
	 * Interpreter definitions and add them to the specified container.
	 */
	private static void populateInterpreterTypes(
			Element InterpreterTypeElement,
			InterpreterDefinitionsContainer container) {

		// Retrieve the 'id' attribute and the corresponding Interpreter type
		// object
		String id = InterpreterTypeElement.getAttribute(ID_ATTR); //$NON-NLS-1$
		IInterpreterInstallType InterpreterType = ScriptRuntime
				.getInterpreterInstallType(id);
		if (InterpreterType != null) {

			// For each Interpreter child node, populate the container with a
			// subordinate node
			NodeList InterpreterNodeList = InterpreterTypeElement
					.getChildNodes();
			for (int i = 0; i < InterpreterNodeList.getLength(); ++i) {
				Node InterpreterNode = InterpreterNodeList.item(i);
				short type = InterpreterNode.getNodeType();
				if (type == Node.ELEMENT_NODE) {
					Element InterpreterElement = (Element) InterpreterNode;
					if (InterpreterElement.getNodeName().equalsIgnoreCase(
							INTERPRETER_TAG)) { //$NON-NLS-1$
						populateInterpreterForType(InterpreterType,
								InterpreterElement, container);
					}
				}
			}
		} else {
			DLTKLaunchingPlugin
					.log("Interpreter type element with unknown id."); //$NON-NLS-1$
		}
	}

	/**
	 * Parse the specified Interpreter node, create a InterpreterStandin for it,
	 * and add this to the specified container.
	 */
	private static void populateInterpreterForType(
			IInterpreterInstallType installType, Element element,
			InterpreterDefinitionsContainer container) {
		String id = element.getAttribute(ID_ATTR); //$NON-NLS-1$
		if (id != null) {

			// Retrieve the 'path' attribute. If none, skip this node.
			String installPath = element.getAttribute(PATH_ATTR); //$NON-NLS-1$
			if (installPath == null) {
				return;
			}

			// Create a InterpreterStandin for the node and set its 'name' &
			// 'installLocation' attributes
			InterpreterStandin standin = new InterpreterStandin(installType, id);
			standin.setName(element.getAttribute(INTERPRETER_NAME_ATTR)); //$NON-NLS-1$
			File installLocation = new File(installPath);
			standin.setInstallLocation(installLocation);
			container.addInterpreter(standin);

			// Look for subordinate nodes. These may be 'libraryLocation',
			// 'libraryLocations' or 'versionInfo'.
			NodeList list = element.getChildNodes();
			int length = list.getLength();
			for (int i = 0; i < length; ++i) {
				Node node = list.item(i);
				short type = node.getNodeType();
				if (type == Node.ELEMENT_NODE) {
					Element subElement = (Element) node;
					String subElementName = subElement.getNodeName();
					if (subElementName.equals(LIBRARY_LOCATION_TAG)) { //$NON-NLS-1$
						LibraryLocation loc = getLibraryLocation(subElement);
						standin
								.setLibraryLocations(new LibraryLocation[] { loc });
					} else if (subElementName.equals(LIBRARY_LOCATIONS_TAG)) { //$NON-NLS-1$
						setLibraryLocations(standin, subElement);
					} else if (subElementName.equals(ENVIRONMENT_VARIABLE_TAG)) {
						EnvironmentVariable var = getEnvironmentVariable(subElement);
						standin
								.setEnvironmentVariables(new EnvironmentVariable[] { var });
					} else if (subElementName.equals(ENVIRONMENT_VARIABLES_TAG)) {
						setEnvironmentVariables(standin, subElement);
					}
				}
			}

			// Interpreter Arguments
			String args = element.getAttribute(IARGS_ATTR); //$NON-NLS-1$
			if (args != null && args.length() > 0) {
				standin.setInterpreterArgs(args);
			}
		} else {
			DLTKLaunchingPlugin
					.log("id attribute missing from Interpreter element specification."); //$NON-NLS-1$
		}
	}

	/**
	 * Create & return a LibraryLocation object populated from the attribute
	 * values in the specified node.
	 */
	private static LibraryLocation getLibraryLocation(Element libLocationElement) {
		String interpreterEnvironmentArchive = libLocationElement
				.getAttribute(LIBRARY_PATH_ATTR); //$NON-NLS-1$		
		if (interpreterEnvironmentArchive != null) {
			return new LibraryLocation(new Path(interpreterEnvironmentArchive));
		}
		DLTKLaunchingPlugin
				.log("Library location element is specified incorrectly."); //$NON-NLS-1$
		return null;
	}

	private static EnvironmentVariable getEnvironmentVariable(
			Element libLocationElement) {
		String name = libLocationElement.getAttribute(VARIABLE_NAME_ATTR); //$NON-NLS-1$
		String value = libLocationElement.getAttribute(VARIABLE_VALUE_ATTR); //$NON-NLS-1$
		if (name != null && value != null) {
			return new EnvironmentVariable(name, value);
		}
		DLTKLaunchingPlugin
				.log("Environment variable element is specified incorrectly."); //$NON-NLS-1$
		return null;
	}

	/**
	 * Set the LibraryLocations on the specified Interpreter, by extracting the
	 * subordinate nodes from the specified 'lirbaryLocations' node.
	 */
	private static void setLibraryLocations(IInterpreterInstall Interpreter,
			Element libLocationsElement) {
		NodeList list = libLocationsElement.getChildNodes();
		int length = list.getLength();
		List locations = new ArrayList(length);
		for (int i = 0; i < length; ++i) {
			Node node = list.item(i);
			short type = node.getNodeType();
			if (type == Node.ELEMENT_NODE) {
				Element libraryLocationElement = (Element) node;
				if (libraryLocationElement.getNodeName().equals(
						LIBRARY_LOCATION_TAG)) { //$NON-NLS-1$
					locations.add(getLibraryLocation(libraryLocationElement));
				}
			}
		}
		Interpreter.setLibraryLocations((LibraryLocation[]) locations
				.toArray(new LibraryLocation[locations.size()]));
	}

	private static void setEnvironmentVariables(
			IInterpreterInstall Interpreter, Element environmentVariablesElement) {
		NodeList list = environmentVariablesElement.getChildNodes();
		int length = list.getLength();
		List variables = new ArrayList(length);
		for (int i = 0; i < length; ++i) {
			Node node = list.item(i);
			short type = node.getNodeType();
			if (type == Node.ELEMENT_NODE) {
				Element envVarElement = (Element) node;
				if (envVarElement.getNodeName().equals(
						ENVIRONMENT_VARIABLE_TAG)) { //$NON-NLS-1$
					variables.add(getEnvironmentVariable(envVarElement));
				}
			}
		}
		Interpreter.setEnvironmentVariables((EnvironmentVariable[]) variables
				.toArray(new EnvironmentVariable[variables.size()]));
	}

	/**
	 * Removes the Interpreter from this container.
	 * 
	 * @param Interpreter
	 *            Interpreter intall
	 */
	public void removeInterpreter(IInterpreterInstall Interpreter) {
		fInterpreterList.remove(Interpreter);
		fInvalidInterpreterList.remove(Interpreter);
		List list = (List) fInterTypeToInterMap.get(Interpreter
				.getInterpreterInstallType());
		if (list != null) {
			list.remove(Interpreter);
		}
	}

}