/**
 * Copyright 2005-2013 Restlet S.A.S.
 * 
 * The contents of this file are subject to the terms of one of the following
 * open source licenses: Apache 2.0 or LGPL 3.0 or LGPL 2.1 or CDDL 1.0 or EPL
 * 1.0 (the "Licenses"). You can select the license that you prefer but you may
 * not use this file except in compliance with one of these Licenses.
 * 
 * You can obtain a copy of the Apache 2.0 license at
 * http://www.opensource.org/licenses/apache-2.0
 * 
 * You can obtain a copy of the LGPL 3.0 license at
 * http://www.opensource.org/licenses/lgpl-3.0
 * 
 * You can obtain a copy of the LGPL 2.1 license at
 * http://www.opensource.org/licenses/lgpl-2.1
 * 
 * You can obtain a copy of the CDDL 1.0 license at
 * http://www.opensource.org/licenses/cddl1
 * 
 * You can obtain a copy of the EPL 1.0 license at
 * http://www.opensource.org/licenses/eclipse-1.0
 * 
 * See the Licenses for the specific language governing permissions and
 * limitations under the Licenses.
 * 
 * Alternatively, you can obtain a royalty free commercial license with less
 * limitations, transferable or non-transferable, directly at
 * http://www.restlet.com/products/restlet-framework
 * 
 * Restlet is a registered trademark of Restlet S.A.S.
 */

package org.restlet.ext.crypto.internal;

import java.util.Date;

import org.restlet.Request;
import org.restlet.data.ChallengeResponse;
import org.restlet.data.ChallengeScheme;
import org.restlet.data.Form;
import org.restlet.data.Parameter;
import org.restlet.data.Reference;
import org.restlet.engine.header.ChallengeWriter;
import org.restlet.engine.header.Header;
import org.restlet.engine.header.HeaderConstants;
import org.restlet.engine.security.AuthenticatorHelper;
import org.restlet.engine.util.Base64;
import org.restlet.engine.util.DateUtils;
import org.restlet.ext.crypto.DigestUtils;
import org.restlet.util.Series;

/**
 * Implements the Shared Key Lite authentication for Azure services. This
 * concerns Table storage on Azure Storage.<br>
 * <br>
 * More documentation is available <a
 * href="http://msdn.microsoft.com/en-us/library/dd179428.aspx">here</a>
 * 
 * @author Thierry Boileau
 */
public class HttpAzureSharedKeyLiteHelper extends AuthenticatorHelper {

    /**
     * Returns the canonicalized resource name.
     * 
     * @param resourceRef
     *            The resource reference.
     * @return The canonicalized resource name.
     */
    private static String getCanonicalizedResourceName(Reference resourceRef) {
        Form form = resourceRef.getQueryAsForm();
        Parameter param = form.getFirst("comp", true);

        if (param != null) {
            StringBuilder sb = new StringBuilder(resourceRef.getPath());
            return sb.append("?").append("comp=").append(param.getValue())
                    .toString();
        }

        return resourceRef.getPath();
    }

    /**
     * Constructor.
     */
    public HttpAzureSharedKeyLiteHelper() {
        super(ChallengeScheme.HTTP_AZURE_SHAREDKEY_LITE, true, false);
    }

    @Override
    public void formatResponse(ChallengeWriter cw,
            ChallengeResponse challenge, Request request,
            Series<Header> httpHeaders) {

        // Setup the Date header
        String date = "";

        if (httpHeaders.getFirstValue("x-ms-date", true) == null) {
            // X-ms-Date header didn't override the standard Date header
            date = httpHeaders.getFirstValue(HeaderConstants.HEADER_DATE, true);

            if (date == null) {
                // Add a fresh Date header
                date = DateUtils.format(new Date(),
                        DateUtils.FORMAT_RFC_1123.get(0));
                httpHeaders.add(HeaderConstants.HEADER_DATE, date);
            }
        } else {
            date = httpHeaders.getFirstValue("x-ms-date", true);
        }

        // Setup the canonicalized path
        String canonicalizedResource = getCanonicalizedResourceName(request
                .getResourceRef());

        // Setup the message part
        StringBuilder rest = new StringBuilder();
        rest.append(date).append('\n').append('/')
                .append(challenge.getIdentifier())
                .append(canonicalizedResource);

        // Append the SharedKey credentials
        cw.append(challenge.getIdentifier())
                .append(':')
                .append(Base64.encode(
                        DigestUtils.toHMacSha256(rest.toString(),
                                Base64.decode(challenge.getSecret())), true));
    }
}