ExternalPreferredListener.java

package gov.usgs.earthquake.indexer;

import java.util.HashMap;
import java.util.Map;

import gov.usgs.earthquake.product.Product;

/**
 * (Experimental) Notify external processes when preferred product change within events.
 *
 * @author jmfee
 *
 */
public class ExternalPreferredListener extends ExternalIndexerListener {

    /** Argument for Preferred action */
    public static final String PREFERRED_ACTION_ARGUMENT = "--preferred-action=";

    /**
     * Types of preferred product actions.
     */
    public static enum PreferredAction {
        /** Preferred added product enum */
        PREFERRED_ADDED,
        /** Preferred changed product enum */
        PREFERRED_CHANGED,
        /** Preferred removed product enum */
        PREFERRED_REMOVED
    };

    /**
     * Skip parent class processing, except autoArchiving.
     */
    @Override
    public boolean accept(final IndexerEvent event) {
        return false;
    }

    /**
     * Handle indexer events.
     */
    @Override
    public void onIndexerEvent(final IndexerEvent event) throws Exception {
        for (IndexerChange change : event.getIndexerChanges()) {
            if (!accept(event, change)) {
                // ignoreArchive, processOnlyWhenEventChanged checks
                continue;
            }

            Map<ProductSummary, PreferredAction> changes = getIndexerChangePreferredActions(change);
            for (ProductSummary changedProduct : changes.keySet()) {
                if (!accept(changedProduct.getId())) {
                    continue;
                }

                Event changedEvent = change.getNewEvent();
                if (changedEvent == null) {
                    // event archived...
                    changedEvent = change.getOriginalEvent();
                }

                String command = getProductSummaryCommand(changedEvent, changedProduct);

                // indexer action
                command = command + " " +
                        ExternalIndexerListener.EVENT_ACTION_ARGUMENT +
                        change.getType().toString();

                // preferred product action
                command = command + " " +
                        PREFERRED_ACTION_ARGUMENT +
                        changes.get(changedProduct).toString();

                // pass product content as input to command
                Product product = null;
                try {
                    // this product is not necessarily the product that triggered the change.
                    product = storeProduct(event.getIndexer().getProductStorage().getProduct(changedProduct.getId()));
                } catch (Exception e) {
                    // ignore, just leave null
                }

                runProductCommand(command, product);
            }
        }

        super.onIndexerEvent(event);
    }

    /**
     * Compare preferred products before/after IndexerChange was applied.
     *
     * @param change indexer change to evaluate.
     * @return map of preferred products that were changed.
     */
    public static Map<ProductSummary, PreferredAction> getIndexerChangePreferredActions(final IndexerChange change) {
        Map<ProductSummary, PreferredAction> changes = new HashMap<ProductSummary, PreferredAction>();

        // only event types
        IndexerChange.IndexerChangeType changeType = change.getType();
        if (changeType != IndexerChange.EVENT_ADDED &&
                changeType != IndexerChange.EVENT_DELETED &&
                changeType != IndexerChange.EVENT_MERGED &&
                changeType != IndexerChange.EVENT_SPLIT &&
                changeType != IndexerChange.EVENT_UPDATED) {
            return changes;
        }

        Map<String, ProductSummary> newProducts = getPreferredProducts(change.getNewEvent());
        Map<String, ProductSummary> originalProducts = getPreferredProducts(change.getOriginalEvent());

        // check all currently preferred products
        for (String type : newProducts.keySet()) {
            ProductSummary newProduct = newProducts.get(type);
            ProductSummary originalProduct = originalProducts.get(type);

            if (originalProduct == null) {
                // no product of this type previously existed
                changes.put(newProduct,
                        PreferredAction.PREFERRED_ADDED);
            } else if (!newProduct.getId().equals(originalProduct.getId())) {
                // different from previous preferred product of same type
                changes.put(newProduct,
                        PreferredAction.PREFERRED_CHANGED);
            }
        }

        for (String type : originalProducts.keySet()) {
            if (newProducts.get(type) == null) {
                // no product of this type exists anymore
                changes.put(originalProducts.get(type),
                        PreferredAction.PREFERRED_REMOVED);
            }
        }

        return changes;
    }

    /**
     * Get a map of preferred products from an event.
     *
     * @param event the event.
     * @return preferred products, or empty hashmap if event is null.
     */
    public static Map<String, ProductSummary> getPreferredProducts(final Event event) {
        if (event == null) {
            return new HashMap<String, ProductSummary>();
        }
        return event.getPreferredProducts();
    }

}