URIExtractor.java

/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package com.apigee.sdk.apm.http.impl.client.cache;

import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.apache.http.Header;
import org.apache.http.HeaderElement;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.protocol.HTTP;

import com.apigee.sdk.apm.http.annotation.Immutable;
import com.apigee.sdk.apm.http.client.cache.HeaderConstants;
import com.apigee.sdk.apm.http.client.cache.HttpCacheEntry;

/**
 * @since 4.1
 */
@Immutable
class URIExtractor {

	/**
	 * For a given {@link HttpHost} and {@link HttpRequest} get a URI from the
	 * pair that I can use as an identifier KEY into my HttpCache
	 * 
	 * @param host
	 *            The host for this request
	 * @param req
	 *            the {@link HttpRequest}
	 * @return String the extracted URI
	 */
	public String getURI(HttpHost host, HttpRequest req) {
		if (isRelativeRequest(req)) {
			return canonicalizeUri(String.format("%s%s", host.toString(), req
					.getRequestLine().getUri()));
		}
		return canonicalizeUri(req.getRequestLine().getUri());
	}

	public String canonicalizeUri(String uri) {
		try {
			URL u = new URL(uri);
			String protocol = u.getProtocol().toLowerCase();
			String hostname = u.getHost().toLowerCase();
			int port = canonicalizePort(u.getPort(), protocol);
			String path = canonicalizePath(u.getPath());
			if ("".equals(path))
				path = "/";
			String query = u.getQuery();
			String file = (query != null) ? (path + "?" + query) : path;
			URL out = new URL(protocol, hostname, port, file);
			return out.toString();
		} catch (MalformedURLException e) {
			return uri;
		}
	}

	private String canonicalizePath(String path) {
		try {
			String decoded = URLDecoder.decode(path, "UTF-8");
			return (new URI(decoded)).getPath();
		} catch (UnsupportedEncodingException e) {
		} catch (URISyntaxException e) {
		}
		return path;
	}

	private int canonicalizePort(int port, String protocol) {
		if (port == -1 && "http".equalsIgnoreCase(protocol)) {
			return 80;
		} else if (port == -1 && "https".equalsIgnoreCase(protocol)) {
			return 443;
		}
		return port;
	}

	private boolean isRelativeRequest(HttpRequest req) {
		String requestUri = req.getRequestLine().getUri();
		return ("*".equals(requestUri) || requestUri.startsWith("/"));
	}

	protected String getFullHeaderValue(Header[] headers) {
		if (headers == null)
			return "";

		StringBuilder buf = new StringBuilder("");
		boolean first = true;
		for (Header hdr : headers) {
			if (!first) {
				buf.append(", ");
			}
			buf.append(hdr.getValue().trim());
			first = false;

		}
		return buf.toString();
	}

	/**
	 * For a given {@link HttpHost} and {@link HttpRequest} if the request has a
	 * VARY header - I need to get an additional URI from the pair of host and
	 * request so that I can also store the variant into my HttpCache.
	 * 
	 * @param host
	 *            The host for this request
	 * @param req
	 *            the {@link HttpRequest}
	 * @param entry
	 *            the parent entry used to track the varients
	 * @return String the extracted variant URI
	 */
	public String getVariantURI(HttpHost host, HttpRequest req,
			HttpCacheEntry entry) {
		Header[] varyHdrs = entry.getHeaders(HeaderConstants.VARY);
		if (varyHdrs == null || varyHdrs.length == 0) {
			return getURI(host, req);
		}

		List<String> variantHeaderNames = new ArrayList<String>();
		for (Header varyHdr : varyHdrs) {
			for (HeaderElement elt : varyHdr.getElements()) {
				variantHeaderNames.add(elt.getName());
			}
		}
		Collections.sort(variantHeaderNames);

		try {
			StringBuilder buf = new StringBuilder("{");
			boolean first = true;
			for (String headerName : variantHeaderNames) {
				if (!first) {
					buf.append("&");
				}
				buf.append(URLEncoder.encode(headerName, HTTP.UTF_8));
				buf.append("=");
				buf.append(URLEncoder.encode(
						getFullHeaderValue(req.getHeaders(headerName)),
						HTTP.UTF_8));
				first = false;
			}
			buf.append("}");
			buf.append(getURI(host, req));
			return buf.toString();
		} catch (UnsupportedEncodingException uee) {
			throw new RuntimeException("couldn't encode to UTF-8", uee);
		}
	}

}