/*
 * 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.config.annotation;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletContext;

import org.springframework.http.MediaType;
import org.springframework.http.MediaTypeFactory;
import org.springframework.lang.Nullable;
import org.springframework.web.accept.ContentNegotiationManager;
import org.springframework.web.accept.ContentNegotiationManagerFactoryBean;
import org.springframework.web.accept.ContentNegotiationStrategy;
import org.springframework.web.accept.FixedContentNegotiationStrategy;
import org.springframework.web.accept.HeaderContentNegotiationStrategy;
import org.springframework.web.accept.ParameterContentNegotiationStrategy;
import org.springframework.web.accept.PathExtensionContentNegotiationStrategy;

/**
 * Creates a {@code ContentNegotiationManager} and configures it with
 * one or more {@link ContentNegotiationStrategy} instances.
 *
 * <p>As of 5.0 you can set the exact strategies to use via
 * {@link #strategies(List)}.
 *
 * <p>As an alternative you can also rely on the set of defaults described below
 * which can be turned on or off or customized through the methods of this
 * builder:
 *
 * <table>
 * <tr>
 * <th>Configurer Property</th>
 * <th>Underlying Strategy</th>
 * <th>Default Setting</th>
 * </tr>
 * <tr>
 * <td>{@link #favorPathExtension}</td>
 * <td>{@link PathExtensionContentNegotiationStrategy Path Extension strategy}</td>
 * <td>On</td>
 * </tr>
 * <tr>
 * <td>{@link #favorParameter}</td>
 * <td>{@link ParameterContentNegotiationStrategy Parameter strategy}</td>
 * <td>Off</td>
 * </tr>
 * <tr>
 * <td>{@link #ignoreAcceptHeader}</td>
 * <td>{@link HeaderContentNegotiationStrategy Header strategy}</td>
 * <td>On</td>
 * </tr>
 * <tr>
 * <td>{@link #defaultContentType}</td>
 * <td>{@link FixedContentNegotiationStrategy Fixed content strategy}</td>
 * <td>Not set</td>
 * </tr>
 * <tr>
 * <td>{@link #defaultContentTypeStrategy}</td>
 * <td>{@link ContentNegotiationStrategy}</td>
 * <td>Not set</td>
 * </tr>
 * </table>
 *
 * <p>The order in which strategies are configured is fixed. You can only turn
 * them on or off.
 *
 * <strong>Note:</strong> if you must use URL-based content type resolution,
 * the use of a query parameter is simpler and preferable to the use of a path
 * extension since the latter can cause issues with URI variables, path
 * parameters, and URI decoding. Consider setting {@link #favorPathExtension}
 * to {@literal false} or otherwise set the strategies to use explicitly via
 * {@link #strategies(List)}.
 *
 * @author Rossen Stoyanchev
 * @since 3.2
 */
public class ContentNegotiationConfigurer {

	private final ContentNegotiationManagerFactoryBean factory = new ContentNegotiationManagerFactoryBean();

	private final Map<String, MediaType> mediaTypes = new HashMap<>();


	/**
	 * Class constructor with {@link javax.servlet.ServletContext}.
	 */
	public ContentNegotiationConfigurer(@Nullable ServletContext servletContext) {
		if (servletContext != null) {
			this.factory.setServletContext(servletContext);
		}
	}


	/**
	 * Set the exact list of strategies to use.
	 * <p><strong>Note:</strong> use of this method is mutually exclusive with
	 * use of all other setters in this class which customize a default, fixed
	 * set of strategies. See class level doc for more details.
	 * @param strategies the strategies to use
	 * @since 5.0
	 */
	public void strategies(@Nullable List<ContentNegotiationStrategy> strategies) {
		this.factory.setStrategies(strategies);
	}

	/**
	 * Whether the path extension in the URL path should be used to determine
	 * the requested media type.
	 * <p>By default this is set to {@code true} in which case a request
	 * for {@code /hotels.pdf} will be interpreted as a request for
	 * {@code "application/pdf"} regardless of the 'Accept' header.
	 */
	public ContentNegotiationConfigurer favorPathExtension(boolean favorPathExtension) {
		this.factory.setFavorPathExtension(favorPathExtension);
		return this;
	}

	/**
	 * Add a mapping from a key, extracted from a path extension or a query
	 * parameter, to a MediaType. This is required in order for the parameter
	 * strategy to work. Any extensions explicitly registered here are also
	 * whitelisted for the purpose of Reflected File Download attack detection
	 * (see Spring Framework reference documentation for more details on RFD
	 * attack protection).
	 * <p>The path extension strategy will also try to use
	 * {@link ServletContext#getMimeType} and {@link MediaTypeFactory} to resolve path
	 * extensions. To change this behavior see the {@link #useRegisteredExtensionsOnly} property.
	 * @param extension the key to look up
	 * @param mediaType the media type
	 * @see #mediaTypes(Map)
	 * @see #replaceMediaTypes(Map)
	 */
	public ContentNegotiationConfigurer mediaType(String extension, MediaType mediaType) {
		this.mediaTypes.put(extension, mediaType);
		return this;
	}

	/**
	 * An alternative to {@link #mediaType}.
	 * @see #mediaType(String, MediaType)
	 * @see #replaceMediaTypes(Map)
	 */
	public ContentNegotiationConfigurer mediaTypes(@Nullable Map<String, MediaType> mediaTypes) {
		if (mediaTypes != null) {
			this.mediaTypes.putAll(mediaTypes);
		}
		return this;
	}

	/**
	 * Similar to {@link #mediaType} but for replacing existing mappings.
	 * @see #mediaType(String, MediaType)
	 * @see #mediaTypes(Map)
	 */
	public ContentNegotiationConfigurer replaceMediaTypes(Map<String, MediaType> mediaTypes) {
		this.mediaTypes.clear();
		mediaTypes(mediaTypes);
		return this;
	}

	/**
	 * Whether to ignore requests with path extension that cannot be resolved
	 * to any media type. Setting this to {@code false} will result in an
	 * {@code HttpMediaTypeNotAcceptableException} if there is no match.
	 * <p>By default this is set to {@code true}.
	 */
	public ContentNegotiationConfigurer ignoreUnknownPathExtensions(boolean ignore) {
		this.factory.setIgnoreUnknownPathExtensions(ignore);
		return this;
	}

	/**
	 * When {@link #favorPathExtension} is set, this property determines whether
	 * to allow use of JAF (Java Activation Framework) to resolve a path
	 * extension to a specific MediaType.
	 * @deprecated as of 5.0, in favor of {@link #useRegisteredExtensionsOnly(boolean)}
	 * which has reverse behavior
	 */
	@Deprecated
	public ContentNegotiationConfigurer useJaf(boolean useJaf) {
		return this.useRegisteredExtensionsOnly(!useJaf);
	}

	/**
	 * When {@link #favorPathExtension favorPathExtension} is set, this
	 * property determines whether to use only registered {@code MediaType} mappings
	 * to resolve a path extension to a specific MediaType.
	 * <p>By default this is not set in which case
	 * {@code PathExtensionContentNegotiationStrategy} will use defaults if available.
	 */
	public ContentNegotiationConfigurer useRegisteredExtensionsOnly(boolean useRegisteredExtensionsOnly) {
		this.factory.setUseRegisteredExtensionsOnly(useRegisteredExtensionsOnly);
		return this;
	}

	/**
	 * Whether a request parameter ("format" by default) should be used to
	 * determine the requested media type. For this option to work you must
	 * register {@link #mediaType(String, MediaType) media type mappings}.
	 * <p>By default this is set to {@code false}.
	 * @see #parameterName(String)
	 */
	public ContentNegotiationConfigurer favorParameter(boolean favorParameter) {
		this.factory.setFavorParameter(favorParameter);
		return this;
	}

	/**
	 * Set the query parameter name to use when {@link #favorParameter} is on.
	 * <p>The default parameter name is {@code "format"}.
	 */
	public ContentNegotiationConfigurer parameterName(String parameterName) {
		this.factory.setParameterName(parameterName);
		return this;
	}

	/**
	 * Whether to disable checking the 'Accept' request header.
	 * <p>By default this value is set to {@code false}.
	 */
	public ContentNegotiationConfigurer ignoreAcceptHeader(boolean ignoreAcceptHeader) {
		this.factory.setIgnoreAcceptHeader(ignoreAcceptHeader);
		return this;
	}

	/**
	 * Set the default content type(s) to use when no content type is requested
	 * in order of priority.
	 * <p>If destinations are present that do not support any of the given media
	 * types, consider appending {@link MediaType#ALL} at the end.
	 * <p>By default this is not set.
	 * @see #defaultContentTypeStrategy
	 */
	public ContentNegotiationConfigurer defaultContentType(MediaType... defaultContentTypes) {
		this.factory.setDefaultContentTypes(Arrays.asList(defaultContentTypes));
		return this;
	}

	/**
	 * Set a custom {@link ContentNegotiationStrategy} to use to determine
	 * the content type to use when no content type is requested.
	 * <p>By default this is not set.
	 * @since 4.1.2
	 * @see #defaultContentType
	 */
	public ContentNegotiationConfigurer defaultContentTypeStrategy(ContentNegotiationStrategy defaultStrategy) {
		this.factory.setDefaultContentTypeStrategy(defaultStrategy);
		return this;
	}


	/**
	 * Build a {@link ContentNegotiationManager} based on this configurer's settings.
	 * @since 4.3.12
	 * @see ContentNegotiationManagerFactoryBean#getObject()
	 */
	protected ContentNegotiationManager buildContentNegotiationManager() {
		this.factory.addMediaTypes(this.mediaTypes);
		return this.factory.build();
	}

}
