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Java API for Natural Language Generation
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/*
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
 * License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is "Simplenlg".
 *
 * The Initial Developer of the Original Code is Ehud Reiter, Albert Gatt and Dave Westwater.
 * Portions created by Ehud Reiter, Albert Gatt and Dave Westwater are Copyright (C) 2010-11 The University of Aberdeen. All Rights Reserved.
 *
 * Contributor(s): Ehud Reiter, Albert Gatt, Dave Wewstwater, Roman Kutlak, Margaret Mitchell.
 */
package simplenlg.aggregation;

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

import simplenlg.features.DiscourseFunction;
import simplenlg.features.Feature;
import simplenlg.features.InternalFeature;
import simplenlg.framework.NLGElement;

/**
 * This class wraps an ordered list of phrases which are constituents of two or
 * more (different) clauses and have the same discourse function in their parent
 * clause. FunctionPairs are used by {@link AggregationRule}s to collect candidate
 * phrase for elision.
 * 
 * @author agatt
 * 
 */
public class PhraseSet {

	private DiscourseFunction function;
	private List phrases;

	/**
	 * Construct a set of compatible phrases and their function
	 * 
	 * @param function
	 *            their function
	 * @param phrases
	 *            the list of constituent phrases for the function.
	 */
	public PhraseSet(DiscourseFunction function, NLGElement... phrases) {
		this.function = function;
		this.phrases = new ArrayList(Arrays.asList(phrases));
	}

	/**
	 * Add a phrase
	 * 
	 * @param phrase
	 *            the phrase to add
	 */
	public void addPhrase(NLGElement phrase) {
		this.phrases.add(phrase);
	}

	/**
	 * Add a collection of phrases.
	 * 
	 * @param phrases
	 *            the phrases to add
	 */
	public void addPhrases(Collection phrases) {
		this.phrases.addAll(phrases);
	}

	/**
	 * 
	 * @return the function the pair of phrases have in their respective clauses
	 */
	public DiscourseFunction getFunction() {
		return this.function;
	}

	/**
	 * Elide the rightmost constituents in the phrase list, that is, all phrases
	 * except the first.
	 */
	public void elideRightmost() {
		for (int i = 1; i < this.phrases.size(); i++) {
			NLGElement phrase = this.phrases.get(i);

			if (phrase != null) {
				phrase.setFeature(Feature.ELIDED, true);
			}
		}
	}

	/**
	 * Elide the leftmost consitutents in the phrase list, that is, all phrases
	 * except the rightmost.
	 */
	public void elideLeftmost() {
		for (int i = this.phrases.size() - 2; i >= 0; i--) {
			NLGElement phrase = this.phrases.get(i);

			if (phrase != null) {
				phrase.setFeature(Feature.ELIDED, true);
			}
		}
	}

	/**
	 * Check whether the phrases are lemma identical. This method returns
	 * true in the following cases:
	 * 
	 * 
	 * All phrases are {@link simplenlg.framework.NLGElement}s and they
	 * have the same lexical head, irrespective of inflectional variations.
	 * 
	 * 
	 * @return true if the pair is lemma identical
	 */
	public boolean lemmaIdentical() {
		boolean ident = !this.phrases.isEmpty();

		for (int i = 1; i < this.phrases.size() && ident; i++) {
			NLGElement left = this.phrases.get(i - 1);
			NLGElement right = this.phrases.get(i);
			
			
			if (left != null && right != null) {				
				NLGElement leftHead = left.getFeatureAsElement(InternalFeature.HEAD);
				NLGElement rightHead = right.getFeatureAsElement(InternalFeature.HEAD);				
				ident = (leftHead == rightHead || leftHead.equals(rightHead));
			}
		}

		return ident;
	}

	/**
	 * Check whether the phrases in this set are identical in form. This method
	 * returns true if for every pair of phrases p1 and ,
	 * p1.equals(p2).
	 * 
	 * @return true if all phrases in the set are form-identical
	 */
	public boolean formIdentical() {
		boolean ident = !this.phrases.isEmpty();

		for (int i = 1; i < this.phrases.size() && ident; i++) {
			NLGElement left = this.phrases.get(i - 1);
			NLGElement right = this.phrases.get(i);

			if (left != null && right != null) {
				ident = left.equals(right);
			}
		}

		return ident;
	}
}