/*******************************************************************************
 * Copyright 2012 The MITRE Corporation
 * 
 * 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.mitre.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.net.URL;
import java.security.Key;
import java.security.KeyFactory;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.spec.RSAPublicKeySpec;
import java.security.PublicKey;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.codec.binary.Base64;
import org.mitre.jwk.model.AbstractJwk;
import org.mitre.jwk.model.EC;
import org.mitre.jwk.model.Jwk;
import org.mitre.jwk.model.Rsa;

import com.google.gson.JsonArray;
import com.google.gson.JsonIOException;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonSyntaxException;

/**
 * A collection of utility methods.
 * 
 */
public class Utility {

	/**
	 * Returns the base URL from a HttpServletRequest
	 * 
	 * @param request
	 * @return
	 */
	public static String findBaseUrl(HttpServletRequest request) {
		String issuer = String.format("%s://%s%s", request.getScheme(),
				request.getServerName(), request.getContextPath());

		if ((request.getScheme().equals("http") && request.getServerPort() != 80)
				|| (request.getScheme().equals("https") && request
						.getServerPort() != 443)) {
			// nonstandard port, need to include it
			issuer = String.format("%s://%s:%d%s", request.getScheme(),
					request.getServerName(), request.getServerPort(),
					request.getContextPath());
		}
		return issuer;
	}
	
	public static List<Jwk> retrieveJwk(URL path) throws Exception {
		List<Jwk> keys = new ArrayList<Jwk>();
		
		JsonParser parser = new JsonParser();
		JsonObject json = parser.parse(new BufferedReader(new InputStreamReader(path.openStream()))).getAsJsonObject();
		JsonArray getArray = json.getAsJsonArray("jwk");
		
		for(int i = 0; i < getArray.size(); i++){
			
			JsonObject object = getArray.get(i).getAsJsonObject();
			String algorithm = object.get("alg").getAsString();
			
			if(algorithm.equals("RSA")){
				Rsa rsa = new Rsa(object);
				keys.add(rsa);
			}

			else{
				EC ec = new EC(object);
				keys.add(ec);
			}
		}	
		return keys;
	}
	
	public static Key retrieveX509Key(URL url) throws Exception {
		
		CertificateFactory factory = CertificateFactory.getInstance("X.509");
		X509Certificate cert = (X509Certificate) factory.generateCertificate(url.openStream());
		Key key = cert.getPublicKey();

		return key;
	}
	
	public static Key retrieveJwkKey(URL url) throws Exception {
		
		JsonParser parser = new JsonParser();
		JsonObject json = parser.parse(new BufferedReader(new InputStreamReader(url.openStream()))).getAsJsonObject();
		JsonArray getArray = json.getAsJsonArray("jwk");
		JsonObject object = getArray.get(0).getAsJsonObject();
			
		byte[] modulusByte = Base64.decodeBase64(object.get("mod").getAsString());
		BigInteger modulus = new BigInteger(modulusByte);
		byte[] exponentByte = Base64.decodeBase64(object.get("exp").getAsString());
		BigInteger exponent = new BigInteger(exponentByte);
				
		RSAPublicKeySpec spec = new RSAPublicKeySpec(modulus, exponent);
		KeyFactory factory = KeyFactory.getInstance("RSA");
		PublicKey pub = factory.generatePublic(spec);

		return pub;
	}
}