LastFmSignature.java

/*
 * Copyright 2011 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.social.lastfm.connect;

import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * @author Michael Lavelle
 */
public class LastFmSignature {

	private String secret;
	private SortedMap<String, List<String>> sortedMap = new TreeMap<String, List<String>>();

	private void addParameter(String name, String value) {
		List<String> values = sortedMap.get(name);
		if (values == null) {
			values = new ArrayList<String>();
			sortedMap.put(name, values);
		}
		values.add(value);
	}

	public LastFmSignature(String apiKey, String method, String token,
			String secret, String sessionKey, Map<String, String> params) {

		this.secret = secret;

		addParameter("api_key", apiKey);
		addParameter("method", method);
		addParameter("sk", sessionKey);
		addParameter("token", token);

		for (Map.Entry<String, String> entry : params.entrySet()) {
			addParameter(entry.getKey(), entry.getValue());
		}

	}

	public LastFmSignature(String apiKey, String method, String token,
			String secret, Map<String, String> params) {

		this.secret = secret;

		addParameter("api_key", apiKey);
		addParameter("method", method);
		addParameter("token", token);

		for (Map.Entry<String, String> entry : params.entrySet()) {
			addParameter(entry.getKey(), entry.getValue());
		}

	}

	public String toString() {

		String s = "";
		for (Map.Entry<String, List<String>> entry : sortedMap.entrySet()) {
			for (String value : entry.getValue()) {
				s = s + entry.getKey() + value;
			}
		}
		s = s + secret;

		byte[] defaultBytes = s.getBytes();
		try {
			MessageDigest m = MessageDigest.getInstance("MD5");
			m.reset();
			m.update(s.getBytes());
			byte[] digest = m.digest();
			BigInteger bigInt = new BigInteger(1, digest);
			String hashtext = bigInt.toString(16);
			// Now we need to zero pad it if you actually want the full 32
			// chars.
			while (hashtext.length() < 32) {
				hashtext = "0" + hashtext;
			}

			return hashtext;

		} catch (NoSuchAlgorithmException nsae) {
			throw new RuntimeException(nsae);
		}

	}

}