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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 io.milton.http;

import io.milton.resource.GetableResource;
import io.milton.resource.Resource;
import io.milton.http.entity.CompressedResourceEntity;
import io.milton.http.entity.InputStreamEntity;
import io.milton.http.exceptions.NotFoundException;
import io.milton.http.http11.DefaultHttp11ResponseHandler;
import io.milton.http.exceptions.BadRequestException;
import java.io.OutputStream;
import java.util.Map;
import java.util.zip.GZIPOutputStream;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import io.milton.http.exceptions.NotAuthorizedException;
import io.milton.http.http11.CacheControlHelper;
import io.milton.http.http11.DefaultCacheControlHelper;
import io.milton.http.webdav.WebDavResponseHandler;
import io.milton.common.BufferingOutputStream;
import io.milton.common.FileUtils;
import java.io.IOException;
import java.util.Date;

/**
 * Response Handler which wraps another, and compresses content if appropriate
 *
 * Usually, this will wrap a DefaultResponseHandler, but custom implementations
 * can be wrapped as well.
 *
 * @author brad
 */
public class CompressingResponseHandler extends AbstractWrappingResponseHandler {

	private static final Logger log = LoggerFactory.getLogger(CompressingResponseHandler.class);
	/**
	 * The size to buffer in memory before switching to disk cache.
	 */
	private int maxMemorySize = 100000;
	private CacheControlHelper cacheControlHelper = new DefaultCacheControlHelper();

	public CompressingResponseHandler() {
	}

	public CompressingResponseHandler(WebDavResponseHandler wrapped) {
		super(wrapped);
	}

	/**
	 * Defaults to io.milton.http.http11.DefaultCacheControlHelper
	 *
	 * @return
	 */
	public CacheControlHelper getCacheControlHelper() {
		return cacheControlHelper;
	}

	public void setCacheControlHelper(CacheControlHelper cacheControlHelper) {
		this.cacheControlHelper = cacheControlHelper;
	}

	@Override
	public void respondContent(Resource resource, Response response, Request request, Map params) throws NotAuthorizedException, BadRequestException, NotFoundException {
		if (resource instanceof GetableResource) {
			GetableResource r = (GetableResource) resource;

			String acceptableContentTypes = request.getAcceptHeader();
			String contentType = r.getContentType(acceptableContentTypes);

			// Experimental support for already compressed content...
			String acceptableEncodings = request.getAcceptEncodingHeader();
			if (r instanceof CompressedResource) {
				CompressedResource compressedResource = (CompressedResource) r;
				String acceptableEncoding = compressedResource.getSupportedEncoding(acceptableEncodings);
				if (acceptableEncoding != null) {
					response.setContentTypeHeader(contentType);
					cacheControlHelper.setCacheControl(r, response, request.getAuthorization());
					Long contentLength = compressedResource.getCompressedContentLength(acceptableEncoding);
					response.setContentLengthHeader(contentLength);
					response.setContentEncodingHeader(Response.ContentEncoding.GZIP);
					response.setVaryHeader("Accept-Encoding");
					response.setEntity(new CompressedResourceEntity(
							compressedResource, params, contentType, acceptableEncoding
					));
					return;
				}
			}

			if (canCompress(r, contentType, acceptableEncodings)) {
				log.trace("respondContent: compressable");

				// get the zipped content before sending so we can determine its
				// compressed size
				BufferingOutputStream tempOut = new BufferingOutputStream(maxMemorySize);
				try {
					OutputStream gzipOut = new GZIPOutputStream(tempOut);
					r.sendContent(gzipOut, null, params, contentType);
					gzipOut.flush();
					gzipOut.close();
					tempOut.flush();
				} catch (NotFoundException e) {
					tempOut.deleteTempFileIfExists();
					throw e;
				} catch (IOException ex) {
					tempOut.deleteTempFileIfExists();
					throw new RuntimeException(ex);
				} finally {
					FileUtils.close(tempOut);
				}

				log.trace("respondContent-compressed: " + resource.getClass());
				setRespondContentCommonHeaders(response, resource, Response.Status.SC_OK, request.getAuthorization());
				response.setContentEncodingHeader(Response.ContentEncoding.GZIP);
				response.setVaryHeader("Accept-Encoding");
				long contentLength = tempOut.getSize();
				response.setContentLengthHeader(contentLength);
				response.setContentTypeHeader(contentType);
				cacheControlHelper.setCacheControl(r, response, request.getAuthorization());
				response.setEntity(new InputStreamEntity(tempOut.getInputStream()));
			} else {
				log.trace("respondContent: not compressable");
				// We really should set this header, but it causes IE to not cache files (eg images)
				//response.setVaryHeader( "Accept-Encoding" );
				wrapped.respondContent(resource, response, request, params);
			}
		} else {
			throw new RuntimeException("Cant generate content for non-Getable resource: " + resource.getClass());
		}
	}

	protected void setRespondContentCommonHeaders(Response response, Resource resource, Response.Status status, Auth auth) {
		response.setDateHeader(new Date());
		if (response.getStatus() == null || response.getStatus().code == 200) { // if status is not set (normal case) or is defaulted to 200 (often the case) set it
			response.setStatus(status);
			String etag = wrapped.generateEtag(resource);
			if (etag != null) {
				response.setEtag(etag);
			}
			DefaultHttp11ResponseHandler.setModifiedDate(response, resource, auth);
		}
	}

	private boolean canCompress(GetableResource r, String contentType, String acceptableEncodings) {
		log.trace("canCompress: contentType: " + contentType + " acceptable-encodings: " + acceptableEncodings);
		if (contentType != null) {
			contentType = contentType.toLowerCase();
			// We don't want to compress things like jpg's, mp3's, video files, etc, since they're already compressed
			// and attempting to compress compressed data is just dumb
			// This list really should be from a parameter - TODO
			boolean contentIsCompressable = contentType.contains("text") || contentType.contains("css") || contentType.contains("js") || contentType.contains("javascript");
			if (contentIsCompressable) {
				boolean supportsGzip = (acceptableEncodings != null && acceptableEncodings.toLowerCase().contains("gzip"));
				log.trace("supports gzip: " + supportsGzip);
				return supportsGzip;
			}
		}
		return false;
	}

	public void setMaxMemorySize(int maxMemorySize) {
		this.maxMemorySize = maxMemorySize;
	}

	public int getMaxMemorySize() {
		return maxMemorySize;
	}
}