/*
 * Copyright 2002-2019 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
 *
 *      https://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.security.oauth2.core.converter;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.util.ClassUtils;

/**
 * @author Joe Grandja
 * @since 5.2
 */
final class ObjectToListStringConverter implements ConditionalGenericConverter {

	@Override
	public Set<ConvertiblePair> getConvertibleTypes() {
		Set<ConvertiblePair> convertibleTypes = new LinkedHashSet<>();
		convertibleTypes.add(new ConvertiblePair(Object.class, List.class));
		convertibleTypes.add(new ConvertiblePair(Object.class, Collection.class));
		return convertibleTypes;
	}

	@Override
	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
		if (targetType.getElementTypeDescriptor() == null
				|| targetType.getElementTypeDescriptor().getType().equals(String.class) || sourceType == null
				|| ClassUtils.isAssignable(sourceType.getType(), targetType.getElementTypeDescriptor().getType())) {
			return true;
		}
		return false;
	}

	@Override
	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
		if (source == null) {
			return null;
		}
		if (source instanceof Collection) {
			Collection<String> results = new ArrayList<>();
			for (Object object : ((Collection<?>) source)) {
				if (object != null) {
					results.add(object.toString());
				}
			}
			return results;
		}
		return Collections.singletonList(source.toString());
	}

}
