/*
 * Copyright 2002-2015 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.accept;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;
import javax.servlet.ServletContext;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.http.MediaType;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.web.context.ServletContextAware;

/**
 * A factory providing convenient access to a {@code ContentNegotiationManager}
 * configured with one or more {@link ContentNegotiationStrategy} instances.
 *
 * <p>By default strategies for checking the extension of the request path and
 * the {@code Accept} header are registered. The path extension check will perform
 * lookups through the {@link ServletContext} and the Java Activation Framework
 * (if present) unless {@linkplain #setMediaTypes media types} are configured.
 *
 * @author Rossen Stoyanchev
 * @since 3.2
 */
public class ContentNegotiationManagerFactoryBean
		implements FactoryBean<ContentNegotiationManager>, ServletContextAware, InitializingBean {

	private boolean favorPathExtension = true;

	private boolean favorParameter = false;

	private boolean ignoreAcceptHeader = false;

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

	private boolean ignoreUnknownPathExtensions = true;

	private Boolean useJaf;

	private String parameterName = "format";

	private ContentNegotiationStrategy defaultNegotiationStrategy;

	private ContentNegotiationManager contentNegotiationManager;

	private ServletContext servletContext;


	/**
	 * Indicate whether the extension of the request path should be used to determine
	 * the requested media type with the <em>highest priority</em>.
	 * <p>By default this value 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 {@code Accept} header.
	 */
	public void setFavorPathExtension(boolean favorPathExtension) {
		this.favorPathExtension = favorPathExtension;
	}

	/**
	 * 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 JAF (if present) to resolve path
	 * extensions. To change this behavior see the {@link #useJaf} property.
	 * @param mediaTypes media type mappings
	 * @see #addMediaType(String, MediaType)
	 * @see #addMediaTypes(Map)
	 */
	public void setMediaTypes(Properties mediaTypes) {
		if (!CollectionUtils.isEmpty(mediaTypes)) {
			for (Entry<Object, Object> entry : mediaTypes.entrySet()) {
				String extension = ((String)entry.getKey()).toLowerCase(Locale.ENGLISH);
				this.mediaTypes.put(extension, MediaType.valueOf((String) entry.getValue()));
			}
		}
	}

	/**
	 * Add a mapping from a file extension to a media type.
	 * <p>If no mapping is added or when an extension is not found, the Java
	 * Action Framework, if available, may be used if enabled via
	 * {@link #setFavorPathExtension(boolean)}.
	 */
	public void addMediaType(String fileExtension, MediaType mediaType) {
		this.mediaTypes.put(fileExtension, mediaType);
	}

	/**
	 * Add mappings from file extensions to media types.
	 * <p>If no mappings are added or when an extension is not found, the Java
	 * Action Framework, if available, may be used if enabled via
	 * {@link #setFavorPathExtension(boolean)}.
	 */
	public void addMediaTypes(Map<String, MediaType> mediaTypes) {
		if (mediaTypes != null) {
			this.mediaTypes.putAll(mediaTypes);
		}
	}

	/**
	 * Whether to ignore requests that have a file extension that does not match
	 * any mapped media types. Setting this to {@code false} will result in a
	 * {@code HttpMediaTypeNotAcceptableException} when there is no match.
	 *
	 * <p>By default this is set to {@code true}.
	 */
	public void setIgnoreUnknownPathExtensions(boolean ignoreUnknownPathExtensions) {
		this.ignoreUnknownPathExtensions = ignoreUnknownPathExtensions;
	}

	/**
	 * Indicate whether to use the Java Activation Framework as a fallback option
	 * to map from file extensions to media types. This is used only when
	 * {@link #setFavorPathExtension(boolean)} is set to {@code true}.
	 * <p>The default value is {@code true}.
	 * @see #setParameterName
	 * @see #setMediaTypes
	 */
	public void setUseJaf(boolean useJaf) {
		this.useJaf = useJaf;
	}

	private boolean isUseJafTurnedOff() {
		return (this.useJaf != null && !this.useJaf);
	}

	/**
	 * Indicate whether a request parameter should be used to determine the
	 * requested media type with the <em>2nd highest priority</em>, i.e.
	 * after path extensions but before the {@code Accept} header.
	 * <p>The default value is {@code false}. If set to to {@code true}, a request
	 * for {@code /hotels?format=pdf} will be interpreted as a request for
	 * {@code "application/pdf"} regardless of the {@code Accept} header.
	 * <p>To use this option effectively you must also configure the MediaType
	 * type mappings via {@link #setMediaTypes(Properties)}.
	 * @see #setParameterName
	 */
	public void setFavorParameter(boolean favorParameter) {
		this.favorParameter = favorParameter;
	}

	/**
	 * Set the parameter name that can be used to determine the requested media type
	 * if the {@link #setFavorParameter} property is {@code true}.
	 * <p>The default parameter name is {@code "format"}.
	 */
	public void setParameterName(String parameterName) {
		Assert.notNull(parameterName, "parameterName is required");
		this.parameterName = parameterName;
	}

	/**
	 * Indicate whether the HTTP {@code Accept} header should be ignored altogether.
	 * If set the {@code Accept} header is checked at the
	 * <em>3rd highest priority</em>, i.e. after the request path extension and
	 * possibly a request parameter if configured.
	 * <p>By default this value is set to {@code false}.
	 */
	public void setIgnoreAcceptHeader(boolean ignoreAcceptHeader) {
		this.ignoreAcceptHeader = ignoreAcceptHeader;
	}

	/**
	 * Set the default content type to use when no content type was requested.
	 * <p>Note that internally this method creates and adds a
	 * {@link org.springframework.web.accept.FixedContentNegotiationStrategy
	 * FixedContentNegotiationStrategy}. Alternatively you can also provide a
	 * custom strategy via {@link #setDefaultContentTypeStrategy}.
	 */
	public void setDefaultContentType(MediaType defaultContentType) {
		this.defaultNegotiationStrategy = new FixedContentNegotiationStrategy(defaultContentType);
	}

	/**
	 * Configure a custom {@link ContentNegotiationStrategy} to use to determine
	 * the default content type to use when no content type was requested.
	 * <p>However also consider using {@link #setDefaultContentType} which
	 * provides a simpler alternative to doing the same.
	 * @since 4.1.2
	 */
	public void setDefaultContentTypeStrategy(ContentNegotiationStrategy defaultStrategy) {
		this.defaultNegotiationStrategy = defaultStrategy;
	}

	@Override
	public void setServletContext(ServletContext servletContext) {
		this.servletContext = servletContext;
	}


	@Override
	public void afterPropertiesSet() {
		List<ContentNegotiationStrategy> strategies = new ArrayList<ContentNegotiationStrategy>();

		if (this.favorPathExtension) {
			PathExtensionContentNegotiationStrategy strategy;
			if (this.servletContext != null && !isUseJafTurnedOff()) {
				strategy = new ServletPathExtensionContentNegotiationStrategy(this.servletContext, this.mediaTypes);
			}
			else {
				strategy = new PathExtensionContentNegotiationStrategy(this.mediaTypes);
			}
			strategy.setIgnoreUnknownExtensions(this.ignoreUnknownPathExtensions);
			if (this.useJaf != null) {
				strategy.setUseJaf(this.useJaf);
			}
			strategies.add(strategy);
		}

		if (this.favorParameter) {
			ParameterContentNegotiationStrategy strategy = new ParameterContentNegotiationStrategy(this.mediaTypes);
			strategy.setParameterName(this.parameterName);
			strategies.add(strategy);
		}

		if (!this.ignoreAcceptHeader) {
			strategies.add(new HeaderContentNegotiationStrategy());
		}

		if (this.defaultNegotiationStrategy != null) {
			strategies.add(defaultNegotiationStrategy);
		}

		this.contentNegotiationManager = new ContentNegotiationManager(strategies);
	}


	@Override
	public ContentNegotiationManager getObject() {
		return this.contentNegotiationManager;
	}

	@Override
	public Class<?> getObjectType() {
		return ContentNegotiationManager.class;
	}

	@Override
	public boolean isSingleton() {
		return true;
	}

}
