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package org.openjdk.jmc.flightrecorder.rules.jdk.combine;

/**
 * Utility class for combining {@link Combinable} objects.
 */
public class Combiner {

	/**
	 * Combine an array of {@link Combinable} objects.
	 *
	 * @param objects
	 *            The objects to combine. This array will contain the combined objects on return.
	 * @param <T>
	 *            common combinable type of objects
	 * @return the number of objects in the input array {@code objects} that are valid after return
	 */
	public static <T extends Combinable<T>> int combine(T[] objects) {
		int lastIndex = objects.length - 1;
		while (lastIndex > 0) {
			int lastKeepIndex = 0;
			for (int i = 0; i < lastIndex; i++) {
				int secondIndex = i + 1;
				if (secondIndex == lastIndex) {
					objects[lastKeepIndex] = objects[i];
				} else {
					T combined = objects[i].combineWith(objects[secondIndex]);
					if (combined != null) {
						objects[lastKeepIndex] = combined;
						i++;
					} else {
						objects[lastKeepIndex] = objects[i];
					}
				}
				lastKeepIndex++;
			}
			if (lastKeepIndex == lastIndex) {
				break;
			}
			lastIndex = lastKeepIndex;
		}
		return lastIndex + 1;
	}

}
