/*
 * Copyright 2002-2014 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 org.springframework.core.convert.support;

import java.lang.reflect.Array;
import java.util.Collection;
import java.util.Collections;
import java.util.Set;

import org.springframework.core.CollectionFactory;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.lang.Nullable;

Converts an array to a Collection.
First, creates a new Collection of the requested target type.
Then adds each array element to the target collection.
Will perform an element conversion from the source component type
to the collection's parameterized type if necessary.
Author:
Keith Donald, Juergen Hoeller
Since:
3.0/**
 * Converts an array to a Collection.
 *
 * <p>First, creates a new Collection of the requested target type.
 * Then adds each array element to the target collection.
 * Will perform an element conversion from the source component type
 * to the collection's parameterized type if necessary.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 3.0
 */
final class ArrayToCollectionConverter implements ConditionalGenericConverter {

	private final ConversionService conversionService;


	public ArrayToCollectionConverter(ConversionService conversionService) {
		this.conversionService = conversionService;
	}


	@Override
	public Set<ConvertiblePair> getConvertibleTypes() {
		return Collections.singleton(new ConvertiblePair(Object[].class, Collection.class));
	}

	@Override
	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
		return ConversionUtils.canConvertElements(
				sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), this.conversionService);
	}

	@Override
	@Nullable
	public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
		if (source == null) {
			return null;
		}

		int length = Array.getLength(source);
		TypeDescriptor elementDesc = targetType.getElementTypeDescriptor();
		Collection<Object> target = CollectionFactory.createCollection(targetType.getType(),
				(elementDesc != null ? elementDesc.getType() : null), length);

		if (elementDesc == null) {
			for (int i = 0; i < length; i++) {
				Object sourceElement = Array.get(source, i);
				target.add(sourceElement);
			}
		}
		else {
			for (int i = 0; i < length; i++) {
				Object sourceElement = Array.get(source, i);
				Object targetElement = this.conversionService.convert(sourceElement,
						sourceType.elementTypeDescriptor(sourceElement), elementDesc);
				target.add(targetElement);
			}
		}
		return target;
	}

}