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Integration with Grails' GORM API
There is a newer version: 0.6.1
package com.github.rahulsom.grooves.grails;

import com.github.rahulsom.grooves.api.AggregateType;
import com.github.rahulsom.grooves.api.events.BaseEvent;
import com.github.rahulsom.grooves.api.snapshots.Snapshot;
import com.github.rahulsom.grooves.queries.QuerySupport;
import com.github.rahulsom.grooves.queries.internal.BaseQuery;
import grails.gorm.rx.RxEntity;
import rx.Observable;

import java.util.Date;
import java.util.List;

import static com.github.rahulsom.grooves.grails.QueryUtil.*;
import static org.codehaus.groovy.runtime.InvokerHelper.invokeStaticMethod;
import static rx.Observable.from;

/**
 * Supplies Events from an Rx Gorm Source.
 *
 * @param   The aggregate over which the query executes
 * @param     The type of the Event's id field
 * @param       The type of the Event
 * @param  The type of the Snapshot's id field
 * @param    The type of the Snapshot
 *
 * @author Rahul Somasunderam
 */
public interface RxEventSource<
        AggregateIdT,
        AggregateT extends AggregateType,
        EventIdT,
        EventT extends BaseEvent &
                RxEntity,
        SnapshotIdT,
        SnapshotT extends Snapshot,
        QueryT extends BaseQuery
        > extends QuerySupport {

    Class getEventClass();

    @Override
    default Observable getUncomputedEvents(
            AggregateT aggregate, SnapshotT lastSnapshot, long version) {
        final long position = lastSnapshot == null || lastSnapshot.getLastEventPosition() == null ?
                0 : lastSnapshot.getLastEventPosition();

        //noinspection unchecked
        return (Observable) invokeStaticMethod(
                getEventClass(),
                UNCOMPUTED_EVENTS_BY_VERSION,
                new Object[]{aggregate, position, version, INCREMENTAL_BY_POSITION});
    }

    @Override
    default Observable getUncomputedEvents(
            AggregateT aggregate, SnapshotT lastSnapshot, Date snapshotTime) {
        final Date lastEventTimestamp = lastSnapshot.getLastEventTimestamp();
        final String method = lastEventTimestamp == null ?
                UNCOMPUTED_EVENTS_BEFORE_DATE :
                UNCOMPUTED_EVENTS_BY_DATE_RANGE;
        final Object[] params = lastEventTimestamp == null ?
                new Object[]{aggregate, snapshotTime, INCREMENTAL_BY_TIMESTAMP} :
                new Object[]{aggregate, lastEventTimestamp, snapshotTime, INCREMENTAL_BY_TIMESTAMP};

        //noinspection unchecked
        return (Observable) invokeStaticMethod(getEventClass(), method, params);
    }

    /**
     * Hook to turn a proxy for an aggregate into an aggregate.
     *
     * @param aggregate The aggregate that may or may not be a proxy
     *
     * @return An observable of the aggregate
     */
    Observable reattachAggregate(AggregateT aggregate);

}