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/*
 * Copyright 2013 the original author or authors.
 *
 * 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 leap.lang;

import java.util.Collection;
import java.util.Enumeration;
import java.util.List;

import leap.lang.collection.ArrayIterable;
import leap.lang.collection.ArrayObjectIterable;
import leap.lang.collection.CollectionEnumerable;
import leap.lang.collection.EmptyIterable;
import leap.lang.collection.IterableEnumerable;
import leap.lang.collection.ListEnumerable;

/**
 * null safe utils for {@link Enumerable} objects.
 */
public class Enumerables {
	
	@SuppressWarnings("rawtypes")
    public static final Enumerable EMPTY = new EmptyIterable();

	@SuppressWarnings("unchecked")
    public static final  Enumerable empty(){
		return (Enumerable)EMPTY;
	}
	
	@SuppressWarnings("unchecked")
    public static final  Enumerable of(Object object) throws IllegalArgumentException {

        Enumerable e = tryOf(object);

        if(null == e) {
            throw new IllegalArgumentException("not a supported enumerable type '" + object.getClass().getName() + "'");
        }

        return e;
	}

    @SuppressWarnings("unchecked")
    public static final  Enumerable tryOf(Object object) throws IllegalArgumentException {
        if(null == object){
            return empty();
        }

        if(object instanceof Enumerable){
            return (Enumerable)object;
        }

        if(object instanceof List){
            return new ListEnumerable((List)object);
        }

        if(object instanceof Collection){
            return new CollectionEnumerable<>((Collection)object);
        }

        Class clazz = object.getClass();
        if(clazz.isArray()){
            if(clazz.getComponentType().isPrimitive()){
                return new ArrayObjectIterable(object);
            }else{
                return ofArray((E[])object);
            }
        }

        if(object instanceof Iterable){
            return new IterableEnumerable((Iterable)object);
        }

        return null;
    }
	
	@SuppressWarnings("unchecked")
    public static final  Enumerable ofArray(E... array){
		return null == array || array.length == 0 ? (Enumerable)EMPTY : new ArrayIterable(array);
	}
	
	protected Enumerables(){
		
	}
}