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Provides common utility functions
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/*
 * Copyright (c) CQSE GmbH
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.conqat.lib.commons.enums;

import java.util.Arrays;
import java.util.Collection;
import java.util.EnumSet;
import java.util.Set;

import org.conqat.lib.commons.assertion.CCSMAssert;
import org.conqat.lib.commons.collections.CollectionUtils;

/**
 * Utility class for enumerations.
 */
public class EnumUtils {

	/**
	 * This works like {@link Enum#valueOf(java.lang.Class, java.lang.String)} but returns
	 * null if constant wasn't found instead of throwing an
	 * IllegalArgumentException.
	 *
	 * @param enumType
	 *            Enumeration class
	 * @param constantName
	 *            name of the constant
	 * @return the matching constant or null if not found
	 */
	public static > T valueOf(Class enumType, String constantName) {
		try {
			T constant = Enum.valueOf(enumType, constantName);
			return constant;
		} catch (IllegalArgumentException ex) {
			return null;
		}
	}

	/**
	 * Returns an {@link EnumSet} by converting the given constants given as Strings to enums of the
	 * specified type.
	 */
	public static > EnumSet valuesOf(Class enumType, Collection constantNames) {
		EnumSet result = EnumSet.noneOf(enumType);
		for (String constant : constantNames) {
			result.add(Enum.valueOf(enumType, constant));
		}
		return result;
	}

	/**
	 * Works like {@link #valueOf(Class, String)} but ignores case.
	 *
	 * Worst case runtime is O('number of constants in enum').
	 */
	public static > T valueOfIgnoreCase(Class enumType, String constantName) {
		T[] constants = enumType.getEnumConstants();
		CCSMAssert.isNotNull(constants);
		for (T constant : constants) {
			if (constant.name().equalsIgnoreCase(constantName)) {
				return constant;
			}
		}
		return null;
	}

	/**
	 * Returns an array containing the names of the enum element. Ordering is same as element ordering
	 * in enum.
	 */
	public static > String[] names(Class enumType) {
		T[] constants = enumType.getEnumConstants();
		CCSMAssert.isNotNull(constants);
		String[] result = new String[constants.length];
		for (int i = 0; i < constants.length; i++) {
			result[i] = constants[i].name();
		}
		return result;
	}

	/**
	 * Merges an EnumSet and a list of enum values into one EnumSet.
	 */
	@SafeVarargs
	public static > EnumSet mergeSets(Set set, T... values) {
		EnumSet newSet = EnumSet.copyOf(set);
		newSet.addAll(Arrays.asList(values));
		return newSet;
	}

	/**
	 * Returns a new EnumSet that excludes the given enum values.
	 */
	@SafeVarargs
	public static > EnumSet copyOfExcept(Set set, T... values) {
		EnumSet newSet = EnumSet.copyOf(set);
		CollectionUtils.removeAll(newSet, Arrays.asList(values));
		return newSet;
	}
}