/*
 * Copyright (c) 2010 by Intevation GmbH
 *
 * This program is free software under the LGPL (>=v2.1)
 * Read the file LGPL.txt coming with the software for details
 * or visit http://www.gnu.org/licenses/ if it does not exist.
 */

package de.intevation.artifactdatabase;

import de.intevation.artifacts.ArtifactContextFactory;
import de.intevation.artifacts.ArtifactFactory;
import de.intevation.artifacts.ServiceFactory;

import java.util.ArrayList;

import org.apache.log4j.Logger;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

/**
 * Bootstrap facility for the global context and the artifact factories.
 *
 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
 */
public class FactoryBootstrap
{
    private static Logger logger = Logger.getLogger(FactoryBootstrap.class);

    /**
     * XPath to figure out the class name of the context factory from
     * the global configuration.
     */
    public static final String CONTEXT_FACTORY =
        "/artifact-database/factories/context-factory/text()";

    /**
     * The name of the default context factory.
     */
    public static final String DEFAULT_CONTEXT_FACTORY =
        "de.intevation.artifactdatabase.DefaultArtifactContextFactory";

    /**
     * XPath to figure out the names of the artifact factories from
     * the global configuration to be exposed by the artifact database.
     */
    public static final String ARTIFACT_FACTORIES =
        "/artifact-database/factories/artifact-factories/artifact-factory";

    /**
     * XPath to figure out the names of the service factories from
     * the global configuration to build the services offered by the
     * artifact database.
     */
    public static final String SERVICE_FACTORIES =
        "/artifact-database/factories/service-factories/service-factory";

    /**
     * XPath to figure out the secret used to sign the artifact exports
     * made by the artfifact database server.
     */
    public static final String EXPORT_SECRET =
        "/artifact-database/export-secret/text()";

    /**
     * Default export signing secret.
     * <strong>PLEASE CHANGE THE SECRET VIA THE XPATH EXPORT_SECRET
     * IN THE CONFIGURATION.</strong>.
     */
    public static final String DEFAULT_EXPORT_SECRET =
        "!!!CHANGE ME! I'M NO SECRET!!!";

    /**
     * Reference to the global context build by the global context factory.
     */
    protected Object context;

    /**
     * List of the artifact factories to be exposed by the
     * artifact database.
     */
    protected ArtifactFactory [] artifactFactories;

    /**
     * List of service factories which creates services that are
     * exposed by the artifact database.
     */
    protected ServiceFactory [] serviceFactories;

    /**
     * byte array holding the export signing secret.
     */
    protected byte [] exportSecret;


    /**
     * Default constructor
     */
    public FactoryBootstrap() {
    }

    void buildContext() {
        String className = Config.getStringXPath(
            CONTEXT_FACTORY, DEFAULT_CONTEXT_FACTORY);

        ArtifactContextFactory factory = null;

        try {
            Class clazz = Class.forName(className);
            factory = (ArtifactContextFactory)clazz.newInstance();
        }
        catch (ClassNotFoundException cnfe) {
            logger.error(cnfe.getLocalizedMessage(), cnfe);
        }
        catch (InstantiationException ie) {
            logger.error(ie.getLocalizedMessage(), ie);
        }
        catch (ClassCastException cce) {
            logger.error(cce.getLocalizedMessage(), cce);
        }
        catch (IllegalAccessException iae) {
            logger.error(iae.getLocalizedMessage(), iae);
        }

        if (factory == null) {
            factory = new DefaultArtifactContextFactory();
        }

        logger.info("Using class '" + factory.getClass().getName()
            + "' for context creation.");

        context = factory.createArtifactContext(Config.getConfig());
    }

    /**
     * Scans the global configuration to load the configured
     * artifact factories and sets them up.
     */
    protected void loadArtifactFactories() {

        logger.info("loading artifact factories");

        ArrayList loadedFactories = new ArrayList();

        NodeList nodes = Config.getNodeSetXPath(ARTIFACT_FACTORIES);

        if (nodes == null) {
            logger.warn("No factories found");
        }

        Document config = Config.getConfig();

        for (int i = 0, N = nodes != null ? nodes.getLength() : 0; i < N; ++i) {
            String className = nodes.item(i).getTextContent().trim();

            ArtifactFactory factory = null;

            try {
                Class clazz = Class.forName(className);
                factory = (ArtifactFactory)clazz.newInstance();
            }
            catch (ClassNotFoundException cnfe) {
                logger.error(cnfe.getLocalizedMessage(), cnfe);
            }
            catch (InstantiationException ie) {
                logger.error(ie.getLocalizedMessage(), ie);
            }
            catch (ClassCastException cce) {
                logger.error(cce.getLocalizedMessage(), cce);
            }
            catch (IllegalAccessException iae) {
                logger.error(iae.getLocalizedMessage(), iae);
            }

            if (factory != null) {
                factory.setup(config, nodes.item(i));
                loadedFactories.add(factory);
                logger.info("Registering '"
                    + factory.getName() + "' as artifact factory.");
            }
        }

        artifactFactories = (ArtifactFactory [])loadedFactories.toArray(
            new ArtifactFactory[loadedFactories.size()]);
    }

    /**
     * Scans the global configuration for the configured service factories
     * and sets them up.
     */
    protected void loadServiceFactories() {

        logger.info("loading service factories");

        ArrayList loadedFactories = new ArrayList();

        NodeList nodes = Config.getNodeSetXPath(SERVICE_FACTORIES);

        if (nodes == null) {
            logger.warn("No factories found");
        }

        Document config = Config.getConfig();

        for (int i = 0, N = nodes != null ? nodes.getLength() : 0; i < N; ++i) {
            String className = nodes.item(i).getTextContent().trim();

            ServiceFactory factory = null;

            try {
                Class clazz = Class.forName(className);
                factory = (ServiceFactory)clazz.newInstance();
            }
            catch (ClassNotFoundException cnfe) {
                logger.error(cnfe.getLocalizedMessage(), cnfe);
            }
            catch (InstantiationException ie) {
                logger.error(ie.getLocalizedMessage(), ie);
            }
            catch (ClassCastException cce) {
                logger.error(cce.getLocalizedMessage(), cce);
            }
            catch (IllegalAccessException iae) {
                logger.error(iae.getLocalizedMessage(), iae);
            }

            if (factory != null) {
                factory.setup(config, nodes.item(i));
                loadedFactories.add(factory);
                logger.info( "Registering '" + factory.getName()
                    + "' as service factory.");
            }
        }

        serviceFactories = (ServiceFactory [])loadedFactories.toArray(
            new ServiceFactory[loadedFactories.size()]);
    }

    /**
     * Fetches the export signing secret from the global configuration.
     * If none is found if defaults to the DEFAULT_EXORT_SECRET which
     * is insecure.
     */
    protected void setupExportSecret() {
        String secret = Config.getStringXPath(EXPORT_SECRET);

        if (secret == null) {
            logger.warn("NO EXPORT SECRET SET! USING INSECURE DEFAULT!");
            secret = DEFAULT_EXPORT_SECRET;
        }

        exportSecret = StringUtils.getUTF8Bytes(secret);
    }

    /**
     * Loads all the dynamic classes configured by the global configuration.
     */
    public void boot() {
        setupExportSecret();
        buildContext();
        loadArtifactFactories();
        loadServiceFactories();
    }

    /**
     * Returns the list of ready to use artifact factories.
     * @return The list of artifact factories.
     */
    public ArtifactFactory [] getArtifactFactories() {
        return artifactFactories;
    }

    /**
     * Returns the ready to use service factories.
     * @return The list of service factories.
     */
    public ServiceFactory [] getServiceFactories() {
        return serviceFactories;
    }

    /**
     * Returns the global context created by the global context factory.
     * @return The global context.
     */
    public Object getContext() {
        return context;
    }

    /**
     * Returns the signing secret to be used when ex- and importing
     * artifacts from and into the artifact database.
     * @return the byte array containg the signing secret.
     */
    public byte [] getExportSecret() {
        return exportSecret;
    }
}
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