/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */
package org.eclipse.compare.rangedifferencer;

/**
 * For breaking an object to compare into a sequence of comparable entities.
 * <p>
 * It is used by <code>RangeDifferencer</code> to find longest sequences of
 * matching and non-matching ranges.
 * <p>
 * For example, to compare two text documents and find longest common sequences
 * of matching and non-matching lines, the implementation must break the document
 * into lines. <code>getRangeCount</code> would return the number of lines in the 
 * document, and <code>rangesEqual</code> would compare a specified line given 
 * with one in another <code>IRangeComparator</code>.
 * </p>
 * <p>
 * Clients should implement this interface; there is no standard implementation.
 * </p>
 */
public interface IRangeComparator {

	/**
	 * Returns the number of comparable entities.
	 *
	 * @return the number of comparable entities 
	 */
	int getRangeCount();

	/**
	 * Returns whether the comparable entity given by the first index
	 * matches an entity specified by the other <code>IRangeComparator</code> and index.
	 *
	 * @param thisIndex the index of the comparable entity within this <code>IRangeComparator</code>
	 * @param other the IRangeComparator to compare this with
	 * @param otherIndex the index of the comparable entity within the other <code>IRangeComparator</code>
	 * @return <code>true</code> if the comparable entities are equal
	 */
	boolean rangesEqual(int thisIndex, IRangeComparator other, int otherIndex);

	/**
	 * Returns whether a comparison should be skipped because it would be too costly (or lengthy).
	 * 
	 * @param length a number on which to base the decision whether to return
	 * 	<code>true</code> or <code>false</code>
	 * @param maxLength another number on which to base the decision whether to return
	 *	<code>true</code> or <code>false</code>
	 * @param other the other <code>IRangeComparator</code> to compare with
	 * @return <code>true</code> to avoid a too lengthy range comparison
	 */
	boolean skipRangeComparison(int length, int maxLength, IRangeComparator other);
}