/*******************************************************************************
 * Copyright (c) 2000, 2019 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * This is an implementation of an early-draft specification developed under the Java
 * Community Process (JCP) and is made available for testing and evaluation purposes
 * only. The code is not compatible with any specification of the JCP.
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Jesper Steen Moller - Bugs 341232, 427089
 *     Chris West (Faux) - Bug 45507
 *******************************************************************************/
package org.eclipse.jdt.internal.debug.eval.ast.engine;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Date;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.debug.core.DebugEvent;
import org.eclipse.debug.core.DebugException;
import org.eclipse.debug.core.DebugPlugin;
import org.eclipse.debug.core.IDebugEventFilter;
import org.eclipse.debug.core.model.ITerminate;
import org.eclipse.debug.core.model.IThread;
import org.eclipse.debug.core.model.IVariable;
import org.eclipse.jdt.core.IJavaProject;
import org.eclipse.jdt.core.Signature;
import org.eclipse.jdt.core.compiler.IProblem;
import org.eclipse.jdt.core.dom.AST;
import org.eclipse.jdt.core.dom.ASTParser;
import org.eclipse.jdt.core.dom.CompilationUnit;
import org.eclipse.jdt.debug.core.IEvaluationRunnable;
import org.eclipse.jdt.debug.core.IJavaArray;
import org.eclipse.jdt.debug.core.IJavaArrayType;
import org.eclipse.jdt.debug.core.IJavaDebugTarget;
import org.eclipse.jdt.debug.core.IJavaObject;
import org.eclipse.jdt.debug.core.IJavaReferenceType;
import org.eclipse.jdt.debug.core.IJavaStackFrame;
import org.eclipse.jdt.debug.core.IJavaThread;
import org.eclipse.jdt.debug.core.IJavaType;
import org.eclipse.jdt.debug.core.IJavaValue;
import org.eclipse.jdt.debug.core.IJavaVariable;
import org.eclipse.jdt.debug.eval.IAstEvaluationEngine;
import org.eclipse.jdt.debug.eval.ICompiledExpression;
import org.eclipse.jdt.debug.eval.IEvaluationListener;
import org.eclipse.jdt.debug.eval.IEvaluationResult;
import org.eclipse.jdt.internal.debug.core.JDIDebugOptions;
import org.eclipse.jdt.internal.debug.core.JDIDebugPlugin;
import org.eclipse.jdt.internal.debug.core.logicalstructures.JDILambdaVariable;
import org.eclipse.jdt.internal.debug.core.logicalstructures.JDIReturnValueVariable;
import org.eclipse.jdt.internal.debug.core.model.JDIDebugTarget;
import org.eclipse.jdt.internal.debug.core.model.JDIThisVariable;
import org.eclipse.jdt.internal.debug.core.model.JDIThread;
import org.eclipse.jdt.internal.debug.core.model.JDIValue;
import org.eclipse.jdt.internal.debug.core.model.LambdaUtils;
import org.eclipse.jdt.internal.debug.eval.EvaluationResult;
import org.eclipse.jdt.internal.debug.eval.ast.instructions.InstructionSequence;

import com.sun.jdi.InvocationException;
import com.sun.jdi.ObjectReference;

public class ASTEvaluationEngine implements IAstEvaluationEngine {
	public static final String ANONYMOUS_VAR_PREFIX = "val$"; //$NON-NLS-1$
	private IJavaProject fProject;

	private IJavaDebugTarget fDebugTarget;

	/**
	 * Regex to find occurrences of 'this' in a code snippet
	 */
	private static Pattern fgThisPattern = Pattern
			.compile("(.*[^a-zA-Z0-9]+|^)(this)([^a-zA-Z0-9]+|$).*"); //$NON-NLS-1$

	/**
	 * Filters variable change events during an evaluation to avoid refreshing
	 * the variables view until done.
	 */
	class EventFilter implements IDebugEventFilter {

		/*
		 * (non-Javadoc)
		 *
		 * @see
		 * org.eclipse.debug.core.IDebugEventFilter#filterDebugEvents(org.eclipse
		 * .debug.core.DebugEvent[])
		 */
		@Override
		public DebugEvent[] filterDebugEvents(DebugEvent[] events) {
			if (events.length == 1) {
				DebugEvent event = events[0];
				if (event.getSource() instanceof IJavaVariable
						&& event.getKind() == DebugEvent.CHANGE) {
					if (((IJavaVariable) event.getSource()).getDebugTarget()
							.equals(getDebugTarget())) {
						return null;
					}
				}
			}
			return events;
		}

	}

	public ASTEvaluationEngine(IJavaProject project,
			IJavaDebugTarget debugTarget) {
		setJavaProject(project);
		setDebugTarget(debugTarget);
	}

	public void setJavaProject(IJavaProject project) {
		fProject = project;
	}

	public void setDebugTarget(IJavaDebugTarget debugTarget) {
		fDebugTarget = debugTarget;
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.jdt.debug.eval.IEvaluationEngine#evaluate(java.lang.String,
	 * org.eclipse.jdt.debug.core.IJavaStackFrame,
	 * org.eclipse.jdt.debug.eval.IEvaluationListener, int, boolean)
	 */
	@Override
	public void evaluate(String snippet, IJavaStackFrame frame,
			IEvaluationListener listener, int evaluationDetail,
			boolean hitBreakpoints) throws DebugException {
		traceCaller(snippet, frame.getThread());
		ICompiledExpression expression = getCompiledExpression(snippet, frame);
		evaluateExpression(expression, frame, listener, evaluationDetail,
				hitBreakpoints);
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.jdt.debug.eval.IEvaluationEngine#evaluate(java.lang.String,
	 * org.eclipse.jdt.debug.core.IJavaObject,
	 * org.eclipse.jdt.debug.core.IJavaThread,
	 * org.eclipse.jdt.debug.eval.IEvaluationListener, int, boolean)
	 */
	@Override
	public void evaluate(String snippet, IJavaObject thisContext,
			IJavaThread thread, IEvaluationListener listener,
			int evaluationDetail, boolean hitBreakpoints) throws DebugException {
		traceCaller(snippet, thread);
		ICompiledExpression expression = getCompiledExpression(snippet,
				thisContext);
		evaluateExpression(expression, thisContext, thread, listener,
				evaluationDetail, hitBreakpoints);
	}

	/**
	 * Writes a stack dump to trace the calling thread.
	 *
	 * @param snippet
	 *            expression to evaluate
	 * @param thread
	 *            thread to evaluate in
	 */
	private void traceCaller(String snippet, IThread thread) {
		if (JDIDebugOptions.DEBUG_AST_EVAL_THREAD_TRACE) {
			StringBuilder buf = new StringBuilder();
			buf.append(JDIDebugOptions.FORMAT.format(new Date()));
			buf.append(" : Evaluation Request Trace - Expression: "); //$NON-NLS-1$
			buf.append(snippet);
			buf.append("\n\tThread: "); //$NON-NLS-1$
			try {
				String name = thread.getName();
				buf.append('[');
				buf.append(name);
				buf.append("] "); //$NON-NLS-1$
			} catch (DebugException e) {
				buf.append(thread.toString());
			}
			JDIDebugOptions.trace(buf.toString());
		}
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.jdt.debug.eval.IAstEvaluationEngine#evaluateExpression(org
	 * .eclipse.jdt.debug.eval.ICompiledExpression,
	 * org.eclipse.jdt.debug.core.IJavaStackFrame,
	 * org.eclipse.jdt.debug.eval.IEvaluationListener, int, boolean)
	 */
	@Override
	public void evaluateExpression(ICompiledExpression expression,
			IJavaStackFrame frame, IEvaluationListener listener,
			int evaluationDetail, boolean hitBreakpoints) throws DebugException {
		traceCaller(expression.getSnippet(), frame.getThread());
		RuntimeContext context = new RuntimeContext(getJavaProject(), frame);
		doEvaluation(expression, context, (IJavaThread) frame.getThread(),
				listener, evaluationDetail, hitBreakpoints);
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.jdt.debug.eval.IAstEvaluationEngine#evaluateExpression(org
	 * .eclipse.jdt.debug.eval.ICompiledExpression,
	 * org.eclipse.jdt.debug.core.IJavaObject,
	 * org.eclipse.jdt.debug.core.IJavaThread,
	 * org.eclipse.jdt.debug.eval.IEvaluationListener, int, boolean)
	 */
	@Override
	public void evaluateExpression(ICompiledExpression expression,
			IJavaObject thisContext, IJavaThread thread,
			IEvaluationListener listener, int evaluationDetail,
			boolean hitBreakpoints) throws DebugException {
		traceCaller(expression.getSnippet(), thread);
		IRuntimeContext context = null;
		if (thisContext instanceof IJavaArray) {
			context = new ArrayRuntimeContext((IJavaArray) thisContext, thread,
					getJavaProject());
		} else {
			context = new JavaObjectRuntimeContext(thisContext,
					getJavaProject(), thread);
		}
		doEvaluation(expression, context, thread, listener, evaluationDetail,
				hitBreakpoints);
	}

	/**
	 * Evaluates the given expression in the given thread and the given runtime
	 * context.
	 */
	private void doEvaluation(ICompiledExpression expression,
			IRuntimeContext context, IJavaThread thread,
			IEvaluationListener listener, int evaluationDetail,
			boolean hitBreakpoints) throws DebugException {
		if (expression instanceof InstructionSequence) {
			// don't queue explicit evaluation if the thread is all ready
			// performing an evaluation.
			if (thread.isSuspended() && ((JDIThread) thread).isInvokingMethod()
					|| thread.isPerformingEvaluation()
					&& evaluationDetail == DebugEvent.EVALUATION) {
				EvaluationResult result = new EvaluationResult(this,
						expression.getSnippet(), thread);
				result.addError(EvaluationEngineMessages.ASTEvaluationEngine_Cannot_perform_nested_evaluations);
				listener.evaluationComplete(result);
				return;
			}
			thread.queueRunnable(new EvalRunnable(
					(InstructionSequence) expression, thread, context,
					listener, evaluationDetail, hitBreakpoints));
		} else {
			throw new DebugException(
					new Status(
							IStatus.ERROR,
							JDIDebugPlugin.getUniqueIdentifier(),
							IStatus.OK,
							EvaluationEngineMessages.ASTEvaluationEngine_AST_evaluation_engine_cannot_evaluate_expression,
							null));
		}
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.jdt.debug.eval.IAstEvaluationEngine#getCompiledExpression
	 * (java.lang.String, org.eclipse.jdt.debug.core.IJavaStackFrame)
	 */
	@Override
	public ICompiledExpression getCompiledExpression(String snippet,
			IJavaStackFrame frame) {
		IJavaProject javaProject = getJavaProject();
		RuntimeContext context = new RuntimeContext(javaProject, frame);

		EvaluationSourceGenerator mapper = null;
		CompilationUnit unit = null;
		try {
			List<IJavaVariable> localsVar = new ArrayList<>();
			localsVar.addAll(Arrays.asList(context.getLocals()));
			IJavaObject thisClass = context.getThis();
			IVariable[] innerClassFields; // For anonymous classes, getting variables from outer class
			if (null != thisClass) {
				innerClassFields = thisClass.getVariables();
			} else {
				innerClassFields = new IVariable[0];
			}
			List<IVariable> lambdaFrameVariables = LambdaUtils.getLambdaFrameVariables(frame);
			int numLocalsVar = localsVar.size();
			Set<String> names = new HashSet<>();
			// ******
			// to hide problems with local variable declare as instance of Local
			// Types
			// and to remove locals with duplicate names
			// IJavaVariable[] locals = new IJavaVariable[numLocalsVar];
			IJavaVariable[] locals = new IJavaVariable[numLocalsVar + innerClassFields.length + lambdaFrameVariables.size()];
			String[] localVariablesWithNull = new String[numLocalsVar + innerClassFields.length + lambdaFrameVariables.size()];
			int numLocals = 0;
			for (int i = 0; i < numLocalsVar; i++) {
				IJavaVariable variable = localsVar.get(i);
				if (!isLocalType(variable.getSignature()) && !names.contains(variable.getName())) {
					locals[numLocals] = variable;
					names.add(variable.getName());
					localVariablesWithNull[numLocals++] = variable.getName();
				}
			}
			/*
			 * If we are in a lambda frame, the variable context is not complete; names of outer-scope variables are mangled by the compiler. So we
			 * check variables one stack frame above the lambda frames, in order to also include outer-scope variables. This is necessary to use local
			 * variables defined in a method, within a breakpoint condition inside a lambda also defined in that method.
			 */
			for (IVariable variable : lambdaFrameVariables) {
				if (variable instanceof IJavaVariable && !isLambdaOrImplicitVariable(variable)) {
					IJavaVariable javaVariable = (IJavaVariable) variable;
					String variableName = variable.getName();
					if (variableName != null && !variableName.contains("$")) { //$NON-NLS-1$
						if (!isLocalType(javaVariable.getSignature()) && !names.contains(variableName)) {
							locals[numLocals] = javaVariable;
							names.add(variable.getName());
							localVariablesWithNull[numLocals++] = variable.getName();
						}
					}
				}
			}
			// Adding outer class variables to inner class scope
			for (IVariable var : innerClassFields) {
				if (var instanceof IJavaVariable && var.getName().startsWith(ANONYMOUS_VAR_PREFIX)) {
					String name = var.getName().substring(ANONYMOUS_VAR_PREFIX.length());
					if (!names.contains(name)) {
						locals[numLocals] = (IJavaVariable) var;
						names.add(name);
						localVariablesWithNull[numLocals++] = name;
					}
				}
			}
			// to solve and remove
			// ******
			String[] localTypesNames = new String[numLocals];
			for (int i = 0; i < numLocals; i++) {
				localTypesNames[i] = Signature.toString(
						locals[i].getGenericSignature()).replace('/', '.');
			}
			// Copying local variables removing the nulls in the last
			// String[] localVariables = Arrays.clonesub(localVariablesWithNull, names.size());
			String[] localVariables = new String[names.size()];
			System.arraycopy(localVariablesWithNull, 0, localVariables, 0, localVariables.length);
			mapper = new EvaluationSourceGenerator(localTypesNames,
					localVariables, snippet, getJavaProject());
			// Compile in context of declaring type to get proper visibility of
			// locals and members.
			// Compiling in context of receiving type potentially provides
			// access to more members,
			// but does not allow access to privates members in declaring type
			IJavaReferenceType receivingType = frame.getReferenceType();

			// currently disabled - see bugs 99416 and 106492
			// if (frame.isStatic()) {
			// receivingType= frame.getReferenceType();
			// } else {
			// receivingType= (IJavaReferenceType)
			// frame.getThis().getJavaType();
			// }

			unit = parseCompilationUnit(
					mapper.getSource(receivingType, frame.getLineNumber(), javaProject,
							frame.isStatic()).toCharArray(),
					mapper.getCompilationUnitName(), javaProject);
		} catch (CoreException e) {
			InstructionSequence expression = new InstructionSequence(snippet);
			expression.addError(e.getStatus().getMessage());
			return expression;
		}

		return createExpressionFromAST(snippet, mapper, unit);
	}

	private CompilationUnit parseCompilationUnit(char[] source,
			String unitName, IJavaProject project) {
		return parseCompilationUnit(source, unitName, project, Collections.EMPTY_MAP);
	}

	private CompilationUnit parseCompilationUnit(char[] source,
			String unitName, IJavaProject project, Map<String, String> extraCompileOptions) {
		ASTParser parser = ASTParser.newParser(AST.JLS14);
		parser.setSource(source);
		parser.setUnitName(unitName);
		parser.setProject(project);
		parser.setResolveBindings(true);
		Map<String, String> options = EvaluationSourceGenerator
				.getCompilerOptions(project);
		options = new LinkedHashMap<>(options);
		for (Entry<String, String> extraCompileOption : extraCompileOptions.entrySet()) {
			options.put(extraCompileOption.getKey(), extraCompileOption.getValue());
		}
		parser.setCompilerOptions(options);
		return (CompilationUnit) parser.createAST(null);
	}

	// ******
	// to hide problems with local variable declare as instance of Local Types
	private boolean isLocalType(String typeName) {
		StringTokenizer strTok = new StringTokenizer(typeName, "$"); //$NON-NLS-1$
		strTok.nextToken();
		while (strTok.hasMoreTokens()) {
			char char0 = strTok.nextToken().charAt(0);
			if ('0' <= char0 && char0 <= '9') {
				return true;
			}
		}
		return false;
	}

	// ******

	/**
	 * Returns a compiled expression for an evaluation in the context of an
	 * array as a receiver.
	 */
	private ICompiledExpression getCompiledExpression(String snippet,
			IJavaArrayType arrayType) {
		EvaluationSourceGenerator mapper = null;
		CompilationUnit unit = null;
		try {
			IJavaProject javaProject = getJavaProject();
			// replace all occurrences of 'this' with '_a_t'
			String newSnippet = replaceThisReferences(snippet);

			int dimension = 1;
			IJavaType componentType = arrayType.getComponentType();
			while (componentType instanceof IJavaArrayType) {
				componentType = ((IJavaArrayType) componentType)
						.getComponentType();
				dimension++;
			}

			// Primitive arrays are evaluated in the context of Object.
			// Arrays with a base component type of a class or interface are
			// treated
			// as Object arrays and evaluated in Object.
			String recTypeName = "java.lang.Object"; //$NON-NLS-1$
			String typeName = arrayType.getName();
			if (componentType instanceof IJavaReferenceType) {
				StringBuilder buf = new StringBuilder();
				buf.append("java.lang.Object"); //$NON-NLS-1$
				for (int i = 0; i < dimension; i++) {
					buf.append("[]"); //$NON-NLS-1$
				}
				typeName = buf.toString();
			}

			String[] localTypesNames = new String[] { typeName };
			String[] localVariables = new String[] { ArrayRuntimeContext.ARRAY_THIS_VARIABLE };
			mapper = new EvaluationSourceGenerator(localTypesNames,
					localVariables, newSnippet, getJavaProject());

			int index = typeName.indexOf('$');
			// if the argument is an inner type, compile in context of outer
			// type so type is visible
			if (index >= 0) {
				recTypeName = typeName.substring(0, index);
			}
			IJavaType[] javaTypes = getDebugTarget().getJavaTypes(recTypeName);
			if (javaTypes.length > 0) {
				IJavaReferenceType recType = (IJavaReferenceType) javaTypes[0];
				unit = parseCompilationUnit(
						mapper.getSource(recType, -1, getJavaProject(), false)
								.toCharArray(),
						mapper.getCompilationUnitName(), javaProject);
			} else {
				IStatus status = new Status(IStatus.ERROR,
						JDIDebugPlugin.getUniqueIdentifier(),
						JDIDebugPlugin.ERROR,
						EvaluationEngineMessages.ASTEvaluationEngine_1, null);
				throw new CoreException(status);
			}
		} catch (CoreException e) {
			InstructionSequence expression = new InstructionSequence(snippet);
			expression.addError(e.getStatus().getMessage());
			return expression;
		}

		return createExpressionFromAST(snippet, mapper, unit);
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.jdt.debug.eval.IAstEvaluationEngine#getCompiledExpression
	 * (java.lang.String, org.eclipse.jdt.debug.core.IJavaObject)
	 */
	@Override
	public ICompiledExpression getCompiledExpression(String snippet,
			IJavaObject thisContext) {
		try {
			if (thisContext instanceof IJavaArray) {
				return getCompiledExpression(snippet,
						(IJavaArrayType) thisContext.getJavaType());
			}
			return getCompiledExpression(snippet,
					(IJavaReferenceType) thisContext.getJavaType());
		} catch (DebugException e) {
			InstructionSequence expression = new InstructionSequence(snippet);
			expression.addError(e.getStatus().getMessage());
			return expression;
		}

	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.jdt.debug.eval.IAstEvaluationEngine#getCompiledExpression
	 * (java.lang.String, org.eclipse.jdt.debug.core.IJavaType)
	 */
	@Override
	public ICompiledExpression getCompiledExpression(String snippet,
			IJavaReferenceType type) {
		return getCompiledExpression(snippet, type, Collections.EMPTY_MAP);
	}

	@Override
	public ICompiledExpression getCompiledExpression(String snippet,
			IJavaReferenceType type, Map<String, String> compileOptions) {
		if (type instanceof IJavaArrayType) {
			return getCompiledExpression(snippet, (IJavaArrayType) type);
		}
		IJavaProject javaProject = getJavaProject();

		EvaluationSourceGenerator mapper = null;
		CompilationUnit unit = null;

		mapper = new EvaluationSourceGenerator(new String[0], new String[0],
				snippet, getJavaProject());

		try {
			unit = parseCompilationUnit(
					mapper.getSource(type, -1, javaProject, false).toCharArray(),
					mapper.getCompilationUnitName(), javaProject, compileOptions);
		} catch (CoreException e) {
			InstructionSequence expression = new InstructionSequence(snippet);
			expression.addError(e.getStatus().getMessage());
			return expression;
		}
		return createExpressionFromAST(snippet, mapper, unit);
	}

	/**
	 * Creates a compiled expression for the given snippet using the given
	 * mapper and compilation unit (AST).
	 *
	 * @param snippet
	 *            the code snippet to be compiled
	 * @param mapper
	 *            the object which will be used to create the expression
	 * @param unit
	 *            the compilation unit (AST) generated for the snippet
	 */
	private ICompiledExpression createExpressionFromAST(String snippet,
			EvaluationSourceGenerator mapper, CompilationUnit unit) {
		IProblem[] problems = unit.getProblems();
		if (problems.length != 0) {
			boolean snippetError = false;
			boolean runMethodError = false;
			InstructionSequence errorSequence = new InstructionSequence(snippet);
			int codeSnippetStart = mapper.getSnippetStart();
			int codeSnippetEnd = codeSnippetStart
					+ mapper.getSnippet().length();
			int runMethodStart = mapper.getRunMethodStart();
			int runMethodEnd = runMethodStart + mapper.getRunMethodLength();
			for (IProblem problem : problems) {
				int errorOffset = problem.getSourceStart();
				int problemId = problem.getID();
				if (problemId == IProblem.IsClassPathCorrect) {
					errorSequence.addError(problem.getMessage());
					snippetError = true;
				}
				if (problemId == IProblem.VoidMethodReturnsValue
						|| problemId == IProblem.NotVisibleMethod
						|| problemId == IProblem.NotVisibleConstructor
						|| problemId == IProblem.NotVisibleField
						|| problemId == IProblem.NotVisibleType) {
					continue;
				}
				if (problem.isError()) {
					if (codeSnippetStart <= errorOffset
							&& errorOffset <= codeSnippetEnd) {
						errorSequence.addError(problem.getMessage());
						snippetError = true;
					} else if (runMethodStart <= errorOffset
							&& errorOffset <= runMethodEnd) {
						runMethodError = true;
						DebugPlugin.log(new Status(IStatus.WARNING, DebugPlugin.getUniqueIdentifier(), "Compile error during code evaluation: " //$NON-NLS-1$
								+ problem.getMessage()));
					}
				}
			}
			if (snippetError || runMethodError) {
				if (runMethodError) {
					errorSequence
							.addError(EvaluationEngineMessages.ASTEvaluationEngine_Evaluations_must_contain_either_an_expression_or_a_block_of_well_formed_statements_1);
				}
				return errorSequence;
			}
		}

		ASTInstructionCompiler visitor = new ASTInstructionCompiler(
				mapper.getSnippetStart(), snippet, getJavaProject());
		unit.accept(visitor);

		return visitor.getInstructions();
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see org.eclipse.jdt.debug.eval.IEvaluationEngine#getJavaProject()
	 */
	@Override
	public IJavaProject getJavaProject() {
		return fProject;
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see org.eclipse.jdt.debug.eval.IEvaluationEngine#getDebugTarget()
	 */
	@Override
	public IJavaDebugTarget getDebugTarget() {
		return fDebugTarget;
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see org.eclipse.jdt.debug.eval.IEvaluationEngine#dispose()
	 */
	@Override
	public void dispose() {
	}

	class EvalRunnable implements Runnable {

		private InstructionSequence fExpression;

		private IJavaThread fThread;

		private int fEvaluationDetail;

		private boolean fHitBreakpoints;

		private IRuntimeContext fContext;

		private IEvaluationListener fListener;

		public EvalRunnable(InstructionSequence expression, IJavaThread thread,
				IRuntimeContext context, IEvaluationListener listener,
				int evaluationDetail, boolean hitBreakpoints) {
			fExpression = expression;
			fThread = thread;
			fContext = context;
			fListener = listener;
			fEvaluationDetail = evaluationDetail;
			fHitBreakpoints = hitBreakpoints;
		}

		@Override
		public void run() {
			if (JDIDebugOptions.DEBUG_AST_EVAL) {
				StringBuilder buf = new StringBuilder();
				buf.append(JDIDebugOptions.FORMAT.format(new Date()));
				buf.append(" : AST Evaluation"); //$NON-NLS-1$
				buf.append("\n\tExpression: "); //$NON-NLS-1$
				buf.append(fExpression.getSnippet());
				buf.append("\n\tThread: "); //$NON-NLS-1$
				try {
					String name = fThread.getName();
					buf.append('[');
					buf.append(name);
					buf.append("] "); //$NON-NLS-1$
				} catch (DebugException e) {
				}
				buf.append(fThread.toString());
				buf.append("\n\tDetail: "); //$NON-NLS-1$
				if (fEvaluationDetail == DebugEvent.EVALUATION) {
					buf.append("EVALUATION"); //$NON-NLS-1$
				} else if (fEvaluationDetail == DebugEvent.EVALUATION_IMPLICIT) {
					buf.append("EVALUATION_IMPLICIT"); //$NON-NLS-1$
				} else {
					buf.append(fEvaluationDetail);
				}
				buf.append(" Hit Breakpoints: "); //$NON-NLS-1$
				buf.append(fHitBreakpoints);
				JDIDebugOptions.trace(buf.toString());
			}
			EvaluationResult result = new EvaluationResult(
					ASTEvaluationEngine.this, fExpression.getSnippet(), fThread);
			if (fExpression.hasErrors()) {
				String[] errors = fExpression.getErrorMessages();
				for (String error : errors) {
					result.addError(error);
				}
				evaluationFinished(result);
				if (JDIDebugOptions.DEBUG_AST_EVAL) {
					StringBuilder buf = new StringBuilder();
					buf.append("\tErrors: "); //$NON-NLS-1$
					for (int i = 0; i < errors.length; i++) {
						if (i > 0) {
							buf.append('\n');
						}
						buf.append("\t\t"); //$NON-NLS-1$
						buf.append(errors[i]);
					}
					JDIDebugOptions.trace(buf.toString());
				}
				return;
			}
			final Interpreter interpreter = new Interpreter(fExpression,
					fContext);

			class EvaluationRunnable implements IEvaluationRunnable, ITerminate {

				CoreException fException;
				boolean fTerminated = false;

				@Override
				public void run(IJavaThread jt, IProgressMonitor pm) {
					EventFilter filter = new EventFilter();
					try {
						DebugPlugin.getDefault().addDebugEventFilter(filter);
						interpreter.execute();
					} catch (CoreException exception) {
						fException = exception;
						if (fEvaluationDetail == DebugEvent.EVALUATION
								&& exception.getStatus().getException() instanceof InvocationException) {
							// print the stack trace for the exception if an
							// *explicit* evaluation
							InvocationException invocationException = (InvocationException) exception
									.getStatus().getException();
							ObjectReference exObject = invocationException
									.exception();
							IJavaObject modelObject = (IJavaObject) JDIValue
									.createValue(
											(JDIDebugTarget) getDebugTarget(),
											exObject);
							try {
								modelObject
										.sendMessage(
												"printStackTrace", "()V", null, jt, false); //$NON-NLS-1$ //$NON-NLS-2$
							} catch (DebugException e) {
								// unable to print stack trace
							}
						}
					} finally {
						DebugPlugin.getDefault().removeDebugEventFilter(filter);
					}
				}

				@Override
				public void terminate() {
					fTerminated = true;
					interpreter.stop();
				}

				@Override
				public boolean canTerminate() {
					return true;
				}

				@Override
				public boolean isTerminated() {
					return false;
				}

				public CoreException getException() {
					return fException;
				}
			}

			EvaluationRunnable er = new EvaluationRunnable();
			CoreException exception = null;
			long start = System.currentTimeMillis();
			try {
				fThread.runEvaluation(er, null, fEvaluationDetail,
						fHitBreakpoints);
			} catch (DebugException e) {
				exception = e;
			}
			long end = System.currentTimeMillis();

			IJavaValue value = interpreter.getResult();

			if (exception == null) {
				exception = er.getException();
			}

			result.setTerminated(er.fTerminated);
			if (exception != null) {
				if (JDIDebugOptions.DEBUG_AST_EVAL) {
					StringBuilder buf = new StringBuilder();
					buf.append("\tException: "); //$NON-NLS-1$
					buf.append(exception.toString());
					JDIDebugOptions.trace(buf.toString());
				}
				if (exception instanceof DebugException) {
					result.setException((DebugException) exception);
				} else {
					result.setException(new DebugException(exception
							.getStatus()));
				}
			} else {
				if (value != null) {
					result.setValue(value);
					if (JDIDebugOptions.DEBUG_AST_EVAL) {
						StringBuilder buf = new StringBuilder();
						buf.append("\tResult: "); //$NON-NLS-1$
						buf.append(value);
						JDIDebugOptions.trace(buf.toString());
					}
				} else {
					result.addError(EvaluationEngineMessages.ASTEvaluationEngine_An_unknown_error_occurred_during_evaluation);
				}
			}

			if (JDIDebugOptions.DEBUG_AST_EVAL) {
				StringBuilder buf = new StringBuilder();
				buf.append("\tDuration: "); //$NON-NLS-1$
				buf.append(end - start);
				buf.append("ms"); //$NON-NLS-1$
				JDIDebugOptions.trace(buf.toString());
			}

			evaluationFinished(result);
		}

		private void evaluationFinished(IEvaluationResult result) {
			// only notify if plug-in not yet shutdown - bug# 8693
			if (JDIDebugPlugin.getDefault() != null) {
				fListener.evaluationComplete(result);
			}
		}

	}

	/**
	 * Replaces references to 'this' with the 'array_this' variable.
	 *
	 * @param snippet
	 *            code snippet
	 * @return snippet with 'this' references replaced
	 */
	public static String replaceThisReferences(String snippet) {
		// replace all occurrences of 'this' with 'array_this'
		StringBuilder updatedSnippet = new StringBuilder();
		Matcher matcher = fgThisPattern.matcher(snippet);
		int start = 0;
		while (matcher.find()) {
			int end = matcher.start(2);
			updatedSnippet.append(snippet.substring(start, end));
			updatedSnippet.append(ArrayRuntimeContext.ARRAY_THIS_VARIABLE);
			start = end + 4;
		}
		if (start < snippet.length()) {
			updatedSnippet.append(snippet.substring(start, snippet.length()));
		}
		return updatedSnippet.toString();
	}

	private static boolean isLambdaOrImplicitVariable(IVariable variable) {
		boolean isLambdaOrImplicitVariable = variable instanceof JDILambdaVariable || variable instanceof JDIReturnValueVariable
				|| variable instanceof JDIThisVariable;
		return isLambdaOrImplicitVariable;
	}
}