Copyright (c) 2000, 2008 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
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2008 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
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.expressions;

import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

import org.w3c.dom.Element;

import org.eclipse.core.expressions.EvaluationResult;
import org.eclipse.core.expressions.Expression;
import org.eclipse.core.expressions.ExpressionInfo;
import org.eclipse.core.expressions.IEvaluationContext;
import org.eclipse.core.expressions.IIterable;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;

public class IterateExpression extends CompositeExpression {

	private static class IteratePool implements IEvaluationContext {

		private Iterator<?> fIterator;
		private Object fDefaultVariable;
		private IEvaluationContext fParent;

		public IteratePool(IEvaluationContext parent, Iterator<?> iterator) {
			Assert.isNotNull(parent);
			Assert.isNotNull(iterator);
			fParent= parent;
			fIterator= iterator;
		}
		@Override
		public IEvaluationContext getParent() {
			return fParent;
		}
		@Override
		public IEvaluationContext getRoot() {
			return fParent.getRoot();
		}
		@Override
		public Object getDefaultVariable() {
			return fDefaultVariable;
		}
		@Override
		public boolean getAllowPluginActivation() {
			return fParent.getAllowPluginActivation();
		}
		@Override
		public void setAllowPluginActivation(boolean value) {
			fParent.setAllowPluginActivation(value);
		}
		@Override
		public void addVariable(String name, Object value) {
			fParent.addVariable(name, value);
		}
		@Override
		public Object removeVariable(String name) {
			return fParent.removeVariable(name);
		}
		@Override
		public Object getVariable(String name) {
			return fParent.getVariable(name);
		}
		@Override
		public Object resolveVariable(String name, Object[] args) throws CoreException {
			return fParent.resolveVariable(name, args);
		}
		public Object next() {
			fDefaultVariable= fIterator.next();
			return fDefaultVariable;
		}
		public boolean hasNext() {
			return fIterator.hasNext();
		}
	}

	private static final String ATT_OPERATOR= "operator"; //$NON-NLS-1$
	private static final String ATT_IF_EMPTY= "ifEmpty"; //$NON-NLS-1$
	private static final int OR= 1;
	private static final int AND= 2;

	
The seed for the hash code for all iterate expressions.
/**
	 * The seed for the hash code for all iterate expressions.
	 */
	private static final int HASH_INITIAL= IterateExpression.class.getName().hashCode();

	private int fOperator;
	private Boolean fEmptyResult;

	public IterateExpression(IConfigurationElement configElement) throws CoreException {
		String opValue= configElement.getAttribute(ATT_OPERATOR);
		initializeOperatorValue(opValue);
		initializeEmptyResultValue(configElement.getAttribute(ATT_IF_EMPTY));
	}

	public IterateExpression(Element element) throws CoreException {
		String opValue= element.getAttribute(ATT_OPERATOR);
		initializeOperatorValue(opValue.isEmpty() ? null : opValue);
		String ifEmpty= element.getAttribute(ATT_IF_EMPTY);
		initializeEmptyResultValue(ifEmpty.isEmpty() ? null : ifEmpty);
	}

	public IterateExpression(String opValue) throws CoreException {
		initializeOperatorValue(opValue);
	}

	public IterateExpression(String opValue, String ifEmpty) throws CoreException {
		initializeOperatorValue(opValue);
		initializeEmptyResultValue(ifEmpty);
	}

	private void initializeOperatorValue(String opValue) throws CoreException {
		if (opValue == null) {
			fOperator= AND;
		} else {
			Expressions.checkAttribute(ATT_OPERATOR, opValue, new String[] {"and", "or"});  //$NON-NLS-1$//$NON-NLS-2$
			if ("and".equals(opValue)) { //$NON-NLS-1$
				fOperator= AND;
			} else {
				fOperator= OR;
			}
		}
	}

	private void initializeEmptyResultValue(String value) {
		if (value == null) {
			fEmptyResult= null;
		} else {
			fEmptyResult= Boolean.valueOf(value);
		}
	}

	/* (non-Javadoc)
	 * @see Expression#evaluate(IVariablePool)
	 */
	@Override
	public EvaluationResult evaluate(IEvaluationContext context) throws CoreException {
		Object var= context.getDefaultVariable();
		if (var instanceof Collection) {
			Collection<?> col= (Collection<?>)var;
			switch (col.size()) {
				case 0:
					if (fEmptyResult == null) {
						return fOperator == AND ? EvaluationResult.TRUE : EvaluationResult.FALSE;
					} else {
						return fEmptyResult.booleanValue() ? EvaluationResult.TRUE : EvaluationResult.FALSE;
					}
				case 1:
					if (col instanceof List)
						return evaluateAnd(new DefaultVariable(context, ((List<?>)col).get(0)));
					//$FALL-THROUGH$
				default:
					IteratePool iter= new IteratePool(context, col.iterator());
					EvaluationResult result= fOperator == AND ? EvaluationResult.TRUE : EvaluationResult.FALSE;
					while (iter.hasNext()) {
						iter.next();
						switch(fOperator) {
							case OR:
								result= result.or(evaluateAnd(iter));
								if (result == EvaluationResult.TRUE)
									return result;
								break;
							case AND:
								result= result.and(evaluateAnd(iter));
								if (result != EvaluationResult.TRUE)
									return result;
								break;
						}
					}
					return result;
			}
		} else {
			IIterable<?> iterable= Expressions.getAsIIterable(var, this);
			if (iterable == null)
				return EvaluationResult.NOT_LOADED;
			int count= 0;
			IteratePool iter= new IteratePool(context, iterable.iterator());
			EvaluationResult result= fOperator == AND ? EvaluationResult.TRUE : EvaluationResult.FALSE;
			while (iter.hasNext()) {
				iter.next();
				count++;
				switch(fOperator) {
					case OR:
						result= result.or(evaluateAnd(iter));
						if (result == EvaluationResult.TRUE)
							return result;
						break;
					case AND:
						result= result.and(evaluateAnd(iter));
						if (result != EvaluationResult.TRUE)
							return result;
						break;
				}
			}
			if (count > 0) {
				return result;
			} else {
				if (fEmptyResult == null) {
					return fOperator == AND ? EvaluationResult.TRUE : EvaluationResult.FALSE;
				} else {
					return fEmptyResult.booleanValue() ? EvaluationResult.TRUE : EvaluationResult.FALSE;
				}
			}
		}
	}

	@Override
	public void collectExpressionInfo(ExpressionInfo info) {
		// Although we access every single variable we only mark the default
		// variable as accessed since we don't have single variables for the
		// elements.
		info.markDefaultVariableAccessed();
		super.collectExpressionInfo(info);
	}

	@Override
	public boolean equals(final Object object) {
		if (!(object instanceof IterateExpression))
			return false;

		final IterateExpression that= (IterateExpression)object;
		return (this.fOperator == that.fOperator) && equals(this.fExpressions, that.fExpressions);
	}

	@Override
	protected int computeHashCode() {
		return HASH_INITIAL * HASH_FACTOR + hashCode(fExpressions)
			* HASH_FACTOR + fOperator;
	}

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder(getClass().getSimpleName());
		builder.append(" [type=").append(fOperator == AND ? "AND" : "OR"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
		Expression[] children = getChildren();
		if (children.length > 0) {
			builder.append(", children="); //$NON-NLS-1$
			builder.append(Arrays.toString(children));
		}
		builder.append("]"); //$NON-NLS-1$
		return builder.toString();
	}
}