/*
 * Copyright 2002-2014 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.io.IOException;
import java.io.InputStream;
import java.util.Locale;
import java.util.Map;
import javax.activation.FileTypeMap;
import javax.activation.MimetypesFileTypeMap;
import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.HttpMediaTypeNotAcceptableException;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.util.UrlPathHelper;
import org.springframework.web.util.WebUtils;

/**
 * A ContentNegotiationStrategy that uses the path extension of the URL to
 * determine what media types are requested. The path extension is first looked
 * up in the map of media types provided to the constructor. If that fails, the
 * Java Activation framework is used as a fallback mechanism.
 *
 * <p>
 * The presence of the Java Activation framework is detected and enabled
 * automatically but the {@link #setUseJaf(boolean)} property may be used to
 * override that setting.
 *
 * @author Rossen Stoyanchev
 * @since 3.2
 */
public class PathExtensionContentNegotiationStrategy extends AbstractMappingContentNegotiationStrategy {

	private static final boolean JAF_PRESENT = ClassUtils.isPresent("javax.activation.FileTypeMap",
					PathExtensionContentNegotiationStrategy.class.getClassLoader());

	private static final Log logger = LogFactory.getLog(PathExtensionContentNegotiationStrategy.class);

	private static final UrlPathHelper urlPathHelper = new UrlPathHelper();

	static {
		urlPathHelper.setUrlDecode(false);
	}

	private boolean useJaf = JAF_PRESENT;

	private boolean ignoreUnknownExtensions = true;


	/**
	 * Create an instance with the given extension-to-MediaType lookup.
	 * @throws IllegalArgumentException if a media type string cannot be parsed
	 */
	public PathExtensionContentNegotiationStrategy(Map<String, MediaType> mediaTypes) {
		super(mediaTypes);
	}

	/**
	 * Create an instance without any mappings to start with. Mappings may be added
	 * later on if any extensions are resolved through the Java Activation framework.
	 */
	public PathExtensionContentNegotiationStrategy() {
		super(null);
	}


	/**
	 * Indicate whether to use the Java Activation Framework to map from file
	 * extensions to media types.
	 *
	 * <p>Default is {@code true}, i.e. the Java Activation Framework is used
	 * (if available).
	 */
	public void setUseJaf(boolean useJaf) {
		this.useJaf = useJaf;
	}

	/**
	 * 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}.
	 *
	 * <p>By default this is set to {@code true}.
	 */
	public void setIgnoreUnknownExtensions(boolean ignoreUnknownExtensions) {
		this.ignoreUnknownExtensions = ignoreUnknownExtensions;
	}


	@Override
	protected String getMediaTypeKey(NativeWebRequest webRequest) {
		HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class);
		if (servletRequest == null) {
			logger.warn("An HttpServletRequest is required to determine the media type key");
			return null;
		}
		String path = urlPathHelper.getLookupPathForRequest(servletRequest);
		String filename = WebUtils.extractFullFilenameFromUrlPath(path);
		String extension = StringUtils.getFilenameExtension(filename);
		return (StringUtils.hasText(extension)) ? extension.toLowerCase(Locale.ENGLISH) : null;
	}

	@Override
	protected void handleMatch(String extension, MediaType mediaType) {
	}

	@Override
	protected MediaType handleNoMatch(NativeWebRequest webRequest, String extension)
			throws HttpMediaTypeNotAcceptableException {

		if (this.useJaf) {
			MediaType jafMediaType = JafMediaTypeFactory.getMediaType("file." + extension);
			if (jafMediaType != null && !MediaType.APPLICATION_OCTET_STREAM.equals(jafMediaType)) {
				return jafMediaType;
			}
		}
		if (!this.ignoreUnknownExtensions) {
			throw new HttpMediaTypeNotAcceptableException(getAllMediaTypes());
		}
		return null;
	}


	/**
	 * Inner class to avoid hard-coded dependency on JAF.
	 */
	private static class JafMediaTypeFactory {

		private static final FileTypeMap fileTypeMap;

		static {
			fileTypeMap = initFileTypeMap();
		}

		/**
		 * Find extended mime.types from the spring-context-support module.
		 */
		private static FileTypeMap initFileTypeMap() {
			Resource resource = new ClassPathResource("org/springframework/mail/javamail/mime.types");
			if (resource.exists()) {
				if (logger.isTraceEnabled()) {
					logger.trace("Loading Java Activation Framework FileTypeMap from " + resource);
				}
				InputStream inputStream = null;
				try {
					inputStream = resource.getInputStream();
					return new MimetypesFileTypeMap(inputStream);
				}
				catch (IOException ex) {
					// ignore
				}
				finally {
					if (inputStream != null) {
						try {
							inputStream.close();
						}
						catch (IOException ex) {
							// ignore
						}
					}
				}
			}
			if (logger.isTraceEnabled()) {
				logger.trace("Loading default Java Activation Framework FileTypeMap");
			}
			return FileTypeMap.getDefaultFileTypeMap();
		}

		public static MediaType getMediaType(String filename) {
			String mediaType = fileTypeMap.getContentType(filename);
			return (StringUtils.hasText(mediaType) ? MediaType.parseMediaType(mediaType) : null);
		}
	}

}
