/**
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */
package org.dspace.discovery;

import org.apache.log4j.Logger;
import org.dspace.content.Bundle;
import org.dspace.content.DSpaceObject;
import org.dspace.core.Constants;
import org.dspace.core.Context;
import org.dspace.event.Consumer;
import org.dspace.event.Event;
import org.dspace.services.factory.DSpaceServicesFactory;

import java.util.HashSet;
import java.util.Set;

/**
 * Class for updating search indices in discovery from content events.
 *
 * @author Kevin Van de Velde (kevin at atmire dot com)
 * @author Mark Diggory (markd at atmire dot com)
 * @author Ben Bosman (ben at atmire dot com)
 */
public class IndexEventConsumer implements Consumer {
    /**
     * log4j logger
     */
    private static Logger log = Logger.getLogger(IndexEventConsumer.class);

    // collect Items, Collections, Communities that need indexing
    private Set<DSpaceObject> objectsToUpdate = null;

    // handles to delete since IDs are not useful by now.
    private Set<String> handlesToDelete = null;

    IndexingService indexer = DSpaceServicesFactory.getInstance().getServiceManager().getServiceByName(IndexingService.class.getName(),IndexingService.class);

    @Override
    public void initialize() throws Exception {

    }

    /**
     * Consume a content event -- just build the sets of objects to add (new) to
     * the index, update, and delete.
     *
     * @param ctx   DSpace context
     * @param event Content event
     */
    @Override
    public void consume(Context ctx, Event event) throws Exception {

        if (objectsToUpdate == null) {
            objectsToUpdate = new HashSet<DSpaceObject>();
            handlesToDelete = new HashSet<String>();
        }

        int st = event.getSubjectType();
        if (!(st == Constants.ITEM || st == Constants.BUNDLE
                || st == Constants.COLLECTION || st == Constants.COMMUNITY)) {
            log
                    .warn("IndexConsumer should not have been given this kind of Subject in an event, skipping: "
                            + event.toString());
            return;
        }

        DSpaceObject subject = event.getSubject(ctx);

        DSpaceObject object = event.getObject(ctx);


        // If event subject is a Bundle and event was Add or Remove,
        // transform the event to be a Modify on the owning Item.
        // It could be a new bitstream in the TEXT bundle which
        // would change the index.
        int et = event.getEventType();
        if (st == Constants.BUNDLE) {
            if ((et == Event.ADD || et == Event.REMOVE) && subject != null
                    && ((Bundle) subject).getName().equals("TEXT")) {
                st = Constants.ITEM;
                et = Event.MODIFY;
                subject = ((Bundle) subject).getItems().get(0);
                if (log.isDebugEnabled())
                {
                    log.debug("Transforming Bundle event into MODIFY of Item "
                            + subject.getHandle());
                }
            } else
            {
                return;
            }
        }

        switch (et) {
            case Event.CREATE:
            case Event.MODIFY:
            case Event.MODIFY_METADATA:
                if (subject == null)
                {
                    log.warn(event.getEventTypeAsString() + " event, could not get object for "
                            + event.getSubjectTypeAsString() + " id="
                            + String.valueOf(event.getSubjectID())
                            + ", perhaps it has been deleted.");
                }
                else {
                    log.debug("consume() adding event to update queue: " + event.toString());
                    objectsToUpdate.add(subject);
                }
                break;

            case Event.REMOVE:
            case Event.ADD:
                if (object == null)
                {
                    log.warn(event.getEventTypeAsString() + " event, could not get object for "
                            + event.getObjectTypeAsString() + " id="
                            + String.valueOf(event.getObjectID())
                            + ", perhaps it has been deleted.");
                }
                else {
                    log.debug("consume() adding event to update queue: " + event.toString());
                    objectsToUpdate.add(object);
                }
                break;

            case Event.DELETE:
                String detail = event.getDetail();
                if (detail == null)
                {
                    log.warn("got null detail on DELETE event, skipping it.");
                }
                else {
                    log.debug("consume() adding event to delete queue: " + event.toString());
                    handlesToDelete.add(detail);
                }
                break;
            default:
                log
                        .warn("IndexConsumer should not have been given a event of type="
                                + event.getEventTypeAsString()
                                + " on subject="
                                + event.getSubjectTypeAsString());
                break;
        }
    }

    /**
     * Process sets of objects to add, update, and delete in index. Correct for
     * interactions between the sets -- e.g. objects which were deleted do not
     * need to be added or updated, new objects don't also need an update, etc.
     */
    @Override
    public void end(Context ctx) throws Exception {

        if (objectsToUpdate != null && handlesToDelete != null) {

            // update the changed Items not deleted because they were on create list
            for (DSpaceObject o : objectsToUpdate) {
                /* we let all types through here and 
                 * allow the search indexer to make 
                 * decisions on indexing and/or removal
                 */
                DSpaceObject iu = ctx.reloadEntity(o);
                String hdl = iu.getHandle();
                if (hdl != null && !handlesToDelete.contains(hdl)) {
                    try {
                        indexer.indexContent(ctx, iu, true);
                        log.debug("Indexed "
                                + Constants.typeText[iu.getType()]
                                + ", id=" + String.valueOf(iu.getID())
                                + ", handle=" + hdl);
                    }
                    catch (Exception e) {
                        log.error("Failed while indexing object: ", e);
                    }
                }
            }

            for (String hdl : handlesToDelete) {
                try {
                    indexer.unIndexContent(ctx, hdl, true);
                    if (log.isDebugEnabled())
                    {
                        log.debug("UN-Indexed Item, handle=" + hdl);
                    }
                }
                catch (Exception e) {
                    log.error("Failed while UN-indexing object: " + hdl, e);
                }

            }

        }

        // "free" the resources
        objectsToUpdate = null;
        handlesToDelete = null;
    }

    @Override
    public void finish(Context ctx) throws Exception {
        // No-op

    }

}