FileAppenderPriorityComparator.java

package io.konik.csv.pdf;

import com.google.common.base.Function;
import io.konik.harness.FileAppender;

import javax.annotation.Nullable;
import java.util.Comparator;

/**
 * {@link FileAppender} {@link Comparator} that uses {@code FileAppender.getPriority()} method
 * to define correct order.
 *
 * Objects with higher priority come first.
 */
public class FileAppenderPriorityComparator implements Comparator<FileAppender> {

	public enum Order {
		DESC(new Function<Integer, Integer>() {
			public Integer apply(Integer input) {
				return input * -1;
			}
		}),
		ASC(new Function<Integer, Integer>() {
			public Integer apply(@Nullable Integer input) {
				return input;
			}
		});

		private Function<Integer,Integer> transform;

		Order(Function<Integer,Integer> transform) {
			this.transform = transform;
		}

		public Integer apply(Integer value) {
			return this.transform.apply(value);
		}
	}

	private final Order order;

	public FileAppenderPriorityComparator(Order order) {
		this.order = order;
	}

	@Override
	public int compare(FileAppender fa1, FileAppender fa2) {
		if (fa1 != null && fa2 != null) {
			return order.apply(fa1.getPriority() - fa2.getPriority());
		}

		if (fa1 != null) {
			return order.apply(1);
		}

		return 0;
	}
}