package de.intevation.flys.collections;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.log4j.Logger;

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

import de.intevation.artifacts.ArtifactNamespaceContext;

import de.intevation.artifactdatabase.state.Facet;
import de.intevation.artifactdatabase.state.Output;

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

import de.intevation.flys.artifacts.model.ManagedFacet;

/**
 * Create attribute- element of describe document of an ArtifactCollection.
 * The attribute-element contains the merged output of all outputmodes and
 *  facets that are part of the collection.
 */
public class AttributeWriter {

    protected Map<String, Output> oldAttr;
    protected Map<String, Output> newAttr;

    private static Logger logger = Logger.getLogger(AttributeWriter.class);


    /**
     * Create a AttributeWriter.
     * Attributes not present in newAttr will not be included in the document.
     * @param oldAttr "Old" (possibly user-changed) outputs.
     * @param newAttr "New" (eventually re-read in its original, unchagnged
     *                form) outputs.
     */
    public AttributeWriter(
        Map<String, Output> oldAttr,
        Map<String, Output> newAttr)
    {
        this.oldAttr = oldAttr;
        this.newAttr = newAttr;
    }


    /**
     * Create document by merging outputs given in
     * constructor.
     * The "new" set rules about existance of attributes, so anything not
     * present in it will not be included in the resulting document.
     * The "old" set rules about the content of attributes (as user changes
     * are recorded here and not in the new set).
     * @return document with merged outputs as described.
     */
    protected Document write() {
        Document doc = XMLUtils.newDocument();

        ElementCreator cr = new ElementCreator(
            doc,
            ArtifactNamespaceContext.NAMESPACE_URI,
            ArtifactNamespaceContext.NAMESPACE_PREFIX);

        Element attribute = cr.create("attribute");
        Element outs      = cr.create("outputs");

        attribute.appendChild(outs);
        doc.appendChild(attribute);

        for (String outName: newAttr.keySet()) {

            Output a = newAttr.get(outName);
            Output b = oldAttr.get(outName);

            writeOutput(doc, outs, cr, a, b);
        }

        return doc;
    }


    /**
     * @param doc  Document to add output nodes to
     * @param outs Node in Document to add output nodes to
     * @param a    the new output
     * @param b    the old output
     */
    protected void writeOutput(
        Document       doc,
        Node           outs,
        ElementCreator cr,
        Output         a, /* new output */
        Output         b) /* old output */
    {
        Element output = cr.create("output");
        cr.addAttr(output, "name", a.getName());

        outs.appendChild(output);

        List<Facet> facetsA = a.getFacets();
        List<Facet> facetsB = null;

        if (b != null) {
            facetsB = b.getFacets();
        }

        writeFacets(doc, cr, output, facetsA, facetsB);
    }


    /**
     * @param doc    Document to add facet nodes to
     * @param output Node in Document to add facet nodes to
     * @param a      the new facets
     * @param b      the old facets
     */
    protected void writeFacets(
        Document       doc,
        ElementCreator cr,
        Element        output,
        List<Facet>    newFacets,
        List<Facet>    oldFacets)
    {
        int num = newFacets.size();

        // Add all new Facets either in their old state or (if really
        // new) as they are.
        List<ManagedFacet> currentFacets      = new ArrayList<ManagedFacet>();
        List<ManagedFacet> genuinelyNewFacets = new ArrayList<ManagedFacet>();
        for (int i = 0; i < num; i++) {
            ManagedFacet facet = (ManagedFacet) newFacets.get(i);

            ManagedFacet picked = pickFacet(facet, oldFacets);
            if (facet.equals(picked)) {
                genuinelyNewFacets.add(picked);
            }
            else {
                currentFacets.add(picked);
            }
        }

        // For each genuinely new Facet check positional conflicts.
        for (ManagedFacet newMF: genuinelyNewFacets) {
            boolean conflicts = true;
            // Loop until all conflicts resolved.
            while (conflicts) {
                conflicts = false;
                for (ManagedFacet oldMF: currentFacets) {
                    if (newMF.getPosition() == oldMF.getPosition()) {
                        conflicts = true;
                        logger.debug("Positional conflict while merging " +
                            "facets, pushing newest facet 1 up ("+newMF.getPosition()+")");
                        newMF.setPosition(newMF.getPosition() + 1);
                        break;
                    }
                }
            }
            currentFacets.add(newMF);
        }

        // Now add all facets.
        for (ManagedFacet oldMF: currentFacets) {
            Node node = oldMF.toXML(doc);
            if (node != null) {
                output.appendChild(node);
            }
        }
    }


    /**
     * Returns the facet to be added to Document.
     * Return the new facet only if the "same" facet was not present before.
     * Return the "old" facet otherwise (user-defined information sticks
     * to it).
     * @param facet     the new facet.
     * @param oldFacets the old facets, new facet is compared against each of
     *                  these.
     * @return facet if genuinely new, matching old facet otherwise.
     */
    protected ManagedFacet pickFacet(ManagedFacet facet,
         List<Facet> oldFacets) {
        if (oldFacets == null) {
            logger.debug("No old facets to compare a new to found.");
            return facet;
        }
       
        String hash = facet.getName() + facet.getIndex() + facet.getArtifact();

        // Compare "new" facet with all old facets.
        // Take oldFacet if that facet was already present (otherwise
        // information is lost, the new one otherwise.
        for (Facet oFacet: oldFacets) {
            ManagedFacet oldFacet = (ManagedFacet) oFacet;
            String oldHash = oldFacet.getName()
                           + oldFacet.getIndex()
                           + oldFacet.getArtifact();
            if (hash.equals(oldHash)) {
                return oldFacet;
            }
        }
        return facet;
    }
}
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