package de.intevation.flys.client.server;

import java.io.InputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import javax.xml.xpath.XPathConstants;

import com.google.gwt.user.server.rpc.RemoteServiceServlet;

import org.w3c.dom.Document;

import org.apache.log4j.Logger;

import de.intevation.artifacts.common.utils.XMLUtils;

import de.intevation.flys.client.shared.exceptions.ServerException;
import de.intevation.flys.client.shared.model.Capabilities;
import de.intevation.flys.client.client.services.GCService;


/**
 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
 */
public class GCServiceImpl
extends      RemoteServiceServlet
implements   GCService
{
    public static final String ERR_GC_REQUEST_FAILED =
        "error_gc_req_failed";

    public static final String ERR_GC_DOC_NOT_VALID =
        "error_gc_doc_not_valid";

    public static final String ERR_MALFORMED_URL =
        "error_malformed_url";

    public static final String XPATH_FEES =
        "/WMS_Capabilities/Service/Fees/text()";

    public static final String XPATH_ACCESS_CONSTRAINTS =
        "/WMS_Capabilities/Service/AccessConstraints/text()";


    private Logger logger = Logger.getLogger(GCServiceImpl.class);


    public Capabilities query(String path)
    throws ServerException
    {
        logger.info("GCServiceImpl.query");

        try {
            URL url = new URL(path);

            logger.debug("Open connection to url: " + path);

            URLConnection conn = url.openConnection();
            conn.connect();

            InputStream is = conn.getInputStream();

            return parseCapabilitiesResponse(is);
        }
        catch (MalformedURLException mue) {
            logger.warn(mue, mue);
            throw new ServerException(ERR_MALFORMED_URL);
        }
        catch (IOException ioe) {
            logger.warn(ioe, ioe);
        }

        throw new ServerException(ERR_GC_REQUEST_FAILED);
    }


    protected Capabilities parseCapabilitiesResponse(InputStream is)
    throws ServerException
    {
        logger.debug("GCServiceImpl.parseCapabilitiesResponse");

        Document doc = XMLUtils.parseDocument(is, false);

        if (doc == null) {
            throw new ServerException(ERR_GC_DOC_NOT_VALID);
        }

        String fees = (String) XMLUtils.xpath(
            doc,
            XPATH_FEES,
            XPathConstants.STRING);

        String accessConstraints = (String) XMLUtils.xpath(
            doc,
            XPATH_ACCESS_CONSTRAINTS,
            XPathConstants.STRING);

        logger.debug("Found fees: " + fees);
        logger.debug("Found access constraints: " + accessConstraints);

        // TODO PARSE LAYERS

        return new Capabilities(fees, accessConstraints, null);
    }
}
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