/*
 * Copyright 2002-2018 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.web.servlet.mvc.condition;

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

import javax.servlet.http.HttpServletRequest;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;

Implements the RequestCondition contract by delegating to multiple RequestCondition types and using a logical conjunction (' && ') to ensure all conditions match a given request. 
When CompositeRequestCondition instances are combined or compared they are expected to (a) contain the same number of conditions and (b) that conditions in the respective index are of the same type. It is acceptable to provide null conditions or no conditions at all to the constructor. 
Author:
Rossen Stoyanchev
Since:
3.2/**
 * Implements the {@link RequestCondition} contract by delegating to multiple
 * {@code RequestCondition} types and using a logical conjunction (' && ') to
 * ensure all conditions match a given request.
 *
 * <p>When {@code CompositeRequestCondition} instances are combined or compared
 * they are expected to (a) contain the same number of conditions and (b) that
 * conditions in the respective index are of the same type. It is acceptable to
 * provide {@code null} conditions or no conditions at all to the constructor.
 *
 * @author Rossen Stoyanchev
 * @since 3.2
 */
public class CompositeRequestCondition extends AbstractRequestCondition<CompositeRequestCondition> {

	private final RequestConditionHolder[] requestConditions;


	
Create an instance with 0 or more RequestCondition types. It is important to create CompositeRequestCondition instances with the same number of conditions so they may be compared and combined. It is acceptable to provide null conditions. /**
	 * Create an instance with 0 or more {@code RequestCondition} types. It is
	 * important to create {@code CompositeRequestCondition} instances with the
	 * same number of conditions so they may be compared and combined.
	 * It is acceptable to provide {@code null} conditions.
	 */
	public CompositeRequestCondition(RequestCondition<?>... requestConditions) {
		this.requestConditions = wrap(requestConditions);
	}

	private CompositeRequestCondition(RequestConditionHolder[] requestConditions) {
		this.requestConditions = requestConditions;
	}


	private RequestConditionHolder[] wrap(RequestCondition<?>... rawConditions) {
		RequestConditionHolder[] wrappedConditions = new RequestConditionHolder[rawConditions.length];
		for (int i = 0; i < rawConditions.length; i++) {
			wrappedConditions[i] = new RequestConditionHolder(rawConditions[i]);
		}
		return wrappedConditions;
	}

	
Whether this instance contains 0 conditions or not.
/**
	 * Whether this instance contains 0 conditions or not.
	 */
	@Override
	public boolean isEmpty() {
		return ObjectUtils.isEmpty(this.requestConditions);
	}

	
Return the underlying conditions (possibly empty but never null). /**
	 * Return the underlying conditions (possibly empty but never {@code null}).
	 */
	public List<RequestCondition<?>> getConditions() {
		return unwrap();
	}

	private List<RequestCondition<?>> unwrap() {
		List<RequestCondition<?>> result = new ArrayList<>();
		for (RequestConditionHolder holder : this.requestConditions) {
			result.add(holder.getCondition());
		}
		return result;
	}

	@Override
	protected Collection<?> getContent() {
		return (!isEmpty() ? getConditions() : Collections.emptyList());
	}

	@Override
	protected String getToStringInfix() {
		return " && ";
	}

	private int getLength() {
		return this.requestConditions.length;
	}

	
If one instance is empty, return the other.
If both instances have conditions, combine the individual conditions
after ensuring they are of the same type and number.
/**
	 * If one instance is empty, return the other.
	 * If both instances have conditions, combine the individual conditions
	 * after ensuring they are of the same type and number.
	 */
	@Override
	public CompositeRequestCondition combine(CompositeRequestCondition other) {
		if (isEmpty() && other.isEmpty()) {
			return this;
		}
		else if (other.isEmpty()) {
			return this;
		}
		else if (isEmpty()) {
			return other;
		}
		else {
			assertNumberOfConditions(other);
			RequestConditionHolder[] combinedConditions = new RequestConditionHolder[getLength()];
			for (int i = 0; i < getLength(); i++) {
				combinedConditions[i] = this.requestConditions[i].combine(other.requestConditions[i]);
			}
			return new CompositeRequestCondition(combinedConditions);
		}
	}

	private void assertNumberOfConditions(CompositeRequestCondition other) {
		Assert.isTrue(getLength() == other.getLength(),
				"Cannot combine CompositeRequestConditions with a different number of conditions. " +
				ObjectUtils.nullSafeToString(this.requestConditions) + " and  " +
				ObjectUtils.nullSafeToString(other.requestConditions));
	}

	
Delegate to all contained conditions to match the request and return the
resulting "matching" condition instances.
An empty CompositeRequestCondition matches to all requests. /**
	 * Delegate to <em>all</em> contained conditions to match the request and return the
	 * resulting "matching" condition instances.
	 * <p>An empty {@code CompositeRequestCondition} matches to all requests.
	 */
	@Override
	@Nullable
	public CompositeRequestCondition getMatchingCondition(HttpServletRequest request) {
		if (isEmpty()) {
			return this;
		}
		RequestConditionHolder[] matchingConditions = new RequestConditionHolder[getLength()];
		for (int i = 0; i < getLength(); i++) {
			matchingConditions[i] = this.requestConditions[i].getMatchingCondition(request);
			if (matchingConditions[i] == null) {
				return null;
			}
		}
		return new CompositeRequestCondition(matchingConditions);
	}

	
If one instance is empty, the other "wins". If both instances have
conditions, compare them in the order in which they were provided.
/**
	 * If one instance is empty, the other "wins". If both instances have
	 * conditions, compare them in the order in which they were provided.
	 */
	@Override
	public int compareTo(CompositeRequestCondition other, HttpServletRequest request) {
		if (isEmpty() && other.isEmpty()) {
			return 0;
		}
		else if (isEmpty()) {
			return 1;
		}
		else if (other.isEmpty()) {
			return -1;
		}
		else {
			assertNumberOfConditions(other);
			for (int i = 0; i < getLength(); i++) {
				int result = this.requestConditions[i].compareTo(other.requestConditions[i], request);
				if (result != 0) {
					return result;
				}
			}
			return 0;
		}
	}

}