/*
 * 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
 *
 *      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.web.servlet.mvc.condition;

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 javax.servlet.http.HttpServletRequest;

import org.springframework.http.InvalidMediaTypeException;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.cors.CorsUtils;
import org.springframework.web.servlet.mvc.condition.HeadersRequestCondition.HeaderExpression;

A logical disjunction (' || ') request condition to match a request's 'Content-Type' header to a list of media type expressions. Two kinds of media type expressions are supported, which are described in RequestMapping.consumes() and RequestMapping.headers() where the header name is 'Content-Type'. Regardless of which syntax is used, the semantics are the same. 
Author:
Arjen Poutsma, Rossen Stoyanchev
Since:
3.1/**
 * A logical disjunction (' || ') request condition to match a request's
 * 'Content-Type' header to a list of media type expressions. Two kinds of
 * media type expressions are supported, which are described in
 * {@link RequestMapping#consumes()} and {@link RequestMapping#headers()}
 * where the header name is 'Content-Type'. Regardless of which syntax is
 * used, the semantics are the same.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public final class ConsumesRequestCondition extends AbstractRequestCondition<ConsumesRequestCondition> {

	private static final ConsumesRequestCondition PRE_FLIGHT_MATCH = new ConsumesRequestCondition();

	private final List<ConsumeMediaTypeExpression> expressions;


	
Creates a new instance from 0 or more "consumes" expressions.
Params:
consumes – expressions with the syntax described in RequestMapping.consumes(); if 0 expressions are provided, the condition will match to every request/**
	 * Creates a new instance from 0 or more "consumes" expressions.
	 * @param consumes expressions with the syntax described in
	 * {@link RequestMapping#consumes()}; if 0 expressions are provided,
	 * the condition will match to every request
	 */
	public ConsumesRequestCondition(String... consumes) {
		this(consumes, null);
	}

	
Creates a new instance with "consumes" and "header" expressions.
"Header" expressions where the header name is not 'Content-Type' or have
no header value defined are ignored. If 0 expressions are provided in
total, the condition will match to every request
Params:
consumes – as described in RequestMapping.consumes()
headers – as described in RequestMapping.headers()/**
	 * Creates a new instance with "consumes" and "header" expressions.
	 * "Header" expressions where the header name is not 'Content-Type' or have
	 * no header value defined are ignored. If 0 expressions are provided in
	 * total, the condition will match to every request
	 * @param consumes as described in {@link RequestMapping#consumes()}
	 * @param headers as described in {@link RequestMapping#headers()}
	 */
	public ConsumesRequestCondition(String[] consumes, @Nullable String[] headers) {
		this(parseExpressions(consumes, headers));
	}

	
Private constructor accepting parsed media type expressions.
/**
	 * Private constructor accepting parsed media type expressions.
	 */
	private ConsumesRequestCondition(Collection<ConsumeMediaTypeExpression> expressions) {
		this.expressions = new ArrayList<>(expressions);
		Collections.sort(this.expressions);
	}


	private static Set<ConsumeMediaTypeExpression> parseExpressions(String[] consumes, @Nullable String[] headers) {
		Set<ConsumeMediaTypeExpression> result = new LinkedHashSet<>();
		if (headers != null) {
			for (String header : headers) {
				HeaderExpression expr = new HeaderExpression(header);
				if ("Content-Type".equalsIgnoreCase(expr.name) && expr.value != null) {
					for (MediaType mediaType : MediaType.parseMediaTypes(expr.value)) {
						result.add(new ConsumeMediaTypeExpression(mediaType, expr.isNegated));
					}
				}
			}
		}
		for (String consume : consumes) {
			result.add(new ConsumeMediaTypeExpression(consume));
		}
		return result;
	}


	
Return the contained MediaType expressions.
/**
	 * Return the contained MediaType expressions.
	 */
	public Set<MediaTypeExpression> getExpressions() {
		return new LinkedHashSet<>(this.expressions);
	}

	
Returns the media types for this condition excluding negated expressions.
/**
	 * Returns the media types for this condition excluding negated expressions.
	 */
	public Set<MediaType> getConsumableMediaTypes() {
		Set<MediaType> result = new LinkedHashSet<>();
		for (ConsumeMediaTypeExpression expression : this.expressions) {
			if (!expression.isNegated()) {
				result.add(expression.getMediaType());
			}
		}
		return result;
	}

	
Whether the condition has any media type expressions.
/**
	 * Whether the condition has any media type expressions.
	 */
	@Override
	public boolean isEmpty() {
		return this.expressions.isEmpty();
	}

	@Override
	protected Collection<ConsumeMediaTypeExpression> getContent() {
		return this.expressions;
	}

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

	
Returns the "other" instance if it has any expressions; returns "this"
instance otherwise. Practically that means a method-level "consumes"
overrides a type-level "consumes" condition.
/**
	 * Returns the "other" instance if it has any expressions; returns "this"
	 * instance otherwise. Practically that means a method-level "consumes"
	 * overrides a type-level "consumes" condition.
	 */
	@Override
	public ConsumesRequestCondition combine(ConsumesRequestCondition other) {
		return (!other.expressions.isEmpty() ? other : this);
	}

	
Checks if any of the contained media type expressions match the given request 'Content-Type' header and returns an instance that is guaranteed to contain matching expressions only. The match is performed via MediaType.includes(MediaType). 
Params:
request – the current request
Returns:
the same instance if the condition contains no expressions; or a new condition with matching expressions only; or null if no expressions match/**
	 * Checks if any of the contained media type expressions match the given
	 * request 'Content-Type' header and returns an instance that is guaranteed
	 * to contain matching expressions only. The match is performed via
	 * {@link MediaType#includes(MediaType)}.
	 * @param request the current request
	 * @return the same instance if the condition contains no expressions;
	 * or a new condition with matching expressions only;
	 * or {@code null} if no expressions match
	 */
	@Override
	@Nullable
	public ConsumesRequestCondition getMatchingCondition(HttpServletRequest request) {
		if (CorsUtils.isPreFlightRequest(request)) {
			return PRE_FLIGHT_MATCH;
		}
		if (isEmpty()) {
			return this;
		}

		MediaType contentType;
		try {
			contentType = (StringUtils.hasLength(request.getContentType()) ?
					MediaType.parseMediaType(request.getContentType()) :
					MediaType.APPLICATION_OCTET_STREAM);
		}
		catch (InvalidMediaTypeException ex) {
			return null;
		}

		Set<ConsumeMediaTypeExpression> result = new LinkedHashSet<>(this.expressions);
		result.removeIf(expression -> !expression.match(contentType));
		return (!result.isEmpty() ? new ConsumesRequestCondition(result) : null);
	}

	
Returns:

0 if the two conditions have the same number of expressions
Less than 0 if "this" has more or more specific media type expressions
Greater than 0 if "other" has more or more specific media type expressions

It is assumed that both instances have been obtained via getMatchingCondition(HttpServletRequest) and each instance contains the matching consumable media type expression only or is otherwise empty. /**
	 * Returns:
	 * <ul>
	 * <li>0 if the two conditions have the same number of expressions
	 * <li>Less than 0 if "this" has more or more specific media type expressions
	 * <li>Greater than 0 if "other" has more or more specific media type expressions
	 * </ul>
	 * <p>It is assumed that both instances have been obtained via
	 * {@link #getMatchingCondition(HttpServletRequest)} and each instance contains
	 * the matching consumable media type expression only or is otherwise empty.
	 */
	@Override
	public int compareTo(ConsumesRequestCondition other, HttpServletRequest request) {
		if (this.expressions.isEmpty() && other.expressions.isEmpty()) {
			return 0;
		}
		else if (this.expressions.isEmpty()) {
			return 1;
		}
		else if (other.expressions.isEmpty()) {
			return -1;
		}
		else {
			return this.expressions.get(0).compareTo(other.expressions.get(0));
		}
	}


	
Parses and matches a single media type expression to a request's 'Content-Type' header.
/**
	 * Parses and matches a single media type expression to a request's 'Content-Type' header.
	 */
	static class ConsumeMediaTypeExpression extends AbstractMediaTypeExpression {

		ConsumeMediaTypeExpression(String expression) {
			super(expression);
		}

		ConsumeMediaTypeExpression(MediaType mediaType, boolean negated) {
			super(mediaType, negated);
		}

		public final boolean match(MediaType contentType) {
			boolean match = getMediaType().includes(contentType);
			return (!isNegated() ? match : !match);
		}
	}

}