package de.intevation.flys.artifacts.context;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import javax.xml.xpath.XPathConstants;

import org.apache.log4j.Logger;

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

import de.intevation.artifacts.ArtifactContextFactory;

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

import de.intevation.artifactdatabase.Config;

import de.intevation.flys.artifacts.transitions.Transition;
import de.intevation.flys.artifacts.transitions.TransitionEngine;
import de.intevation.flys.artifacts.transitions.TransitionFactory;


/**
 * The ArtifactContextFactory is used to initialize basic components and put
 * them into the global context of the application.
 *
 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
 */
public class FLYSContextFactory implements ArtifactContextFactory {

    /** The logger that is used in this class */
    private static Logger logger = Logger.getLogger(FLYSContextFactory.class);

    /** The XPath to the artifacts configured in the configuration. */
    public static final String XPATH_ARTIFACTS =
        "/artifact-database/artifacts/artifact";

    /** The XPath to the name of the artifact. */
    public static final String XPATH_ARTIFACT_NAME = "@name";

    /** The XPath to the xlink ref in an artifact configuration. */
    public static final String XPATH_XLINK = "xlink:href";

    /** The XPath to the transitions configured in the artifact config. */
    public static final String XPATH_TRANSITIONS =
        "/artifact/states/transition";

    /**
     * Creates a new FLYSArtifactContext object and initialize all
     * components required by the application.
     *
     * @param config The artifact server configuration.
     * @return a FLYSArtifactContext.
     */
    public Object createArtifactContext(Document config) {
        FLYSContext context = new FLYSContext(config);

        configureTransitions(config, context);

        return context;
    }


    /**
     * This method initializes the transition configuration.
     *
     * @param config the config document.
     * @param context the FLYSContext.
     */
    protected void configureTransitions(Document config, FLYSContext context) {
        TransitionEngine engine = new TransitionEngine();

        Document[] artifacts = getArtifactConfigurations(config);
        logger.info("Found " + artifacts.length + " artifacts in the config.");

        for (Document doc: artifacts) {
            List<Transition> transitions = new ArrayList<Transition>();

            String artName = (String) XMLUtils.xpath(
                doc, XPATH_ARTIFACT_NAME, XPathConstants.STRING);

            NodeList transitionList = (NodeList) XMLUtils.xpath(
                doc, XPATH_TRANSITIONS, XPathConstants.NODESET);

            if (transitionList == null) {
                logger.warn("The artifact has no transitions configured.");
                return;
            }

            int trans = transitionList.getLength();

            logger.info(
                "Artifact '" + artName + "' has " + trans + " transitions.");

            for (int i = 0; i < trans; i++) {
                transitions.add(TransitionFactory.createTransition(
                    transitionList.item(i)));
            }

            engine.addTransition(artName, transitions);
        }

        context.put(FLYSContext.TRANSITION_ENGINE_KEY, engine);
    }


    /**
     * This method returns all artifact documents defined in
     * <code>config</code>. <br>NOTE: The artifact configurations need to be
     * stored in own files referenced by an xlink.
     *
     * @param config The global configuration.
     *
     * @return an array of Artifact configurations.
     */
    protected Document[] getArtifactConfigurations(Document config) {
        NodeList artifacts = (NodeList) XMLUtils.xpath(
            config, XPATH_ARTIFACTS, XPathConstants.NODESET);

        int count = artifacts.getLength();

        Document[] artifactDocs = new Document[count];

        for (int i = 0; i < count; i++) {
            Element tmp = (Element) artifacts.item(i);

            String xlink = tmp.getAttribute(XPATH_XLINK);
            xlink        = Config.replaceConfigDir(xlink);

            File artifactFile = new File(xlink);
            artifactDocs[i]   = XMLUtils.parseDocument(artifactFile);
        }

        return artifactDocs;
    }
}
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