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ddd-common
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//   Copyright 2012,2013 Vaughn Vernon
//
//   Licensed under the Apache License, Version 2.0 (the "License");
//   you may not use this file except in compliance with the License.
//   You may obtain a copy of the License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
//   Unless required by applicable law or agreed to in writing, software
//   distributed under the License is distributed on an "AS IS" BASIS,
//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//   See the License for the specific language governing permissions and
//   limitations under the License.

package io.dddspring.common.notification;

import io.dddspring.common.domain.model.DomainEvent;
import io.dddspring.common.event.EventStore;
import io.dddspring.common.event.StoredEvent;

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

public class NotificationLogFactory {

    // this could be a configuration
    private static final int NOTIFICATIONS_PER_LOG = 20;

    private EventStore eventStore;

    public static int notificationsPerLog() {
        return NOTIFICATIONS_PER_LOG;
    }

    public NotificationLogFactory(EventStore anEventStore) {
        super();

        this.setEventStore(anEventStore);
    }

    public NotificationLog createCurrentNotificationLog() {
        return this.createNotificationLog(
                this.calculateCurrentNotificationLogId(eventStore));
    }

    public NotificationLog createNotificationLog(
            NotificationLogId aNotificationLogId) {

        long count = this.eventStore().countStoredEvents();

        NotificationLogInfo info = new NotificationLogInfo(aNotificationLogId, count);

        return this.createNotificationLog(info);
    }

    private NotificationLogInfo calculateCurrentNotificationLogId(
            EventStore anEventStore) {

        long count = anEventStore.countStoredEvents();

        long remainder = count % NOTIFICATIONS_PER_LOG;

        if (remainder == 0 && count > 0) {
            remainder = NOTIFICATIONS_PER_LOG;
        }

        long low = count - remainder + 1;

        // ensures a minted id value even though there may
        // not be a full set of notifications at present
        long high = low + NOTIFICATIONS_PER_LOG - 1;

        return new NotificationLogInfo(new NotificationLogId(low, high), count);
    }

    private NotificationLog createNotificationLog(
            NotificationLogInfo aNotificationLogInfo) {

        List storedEvents =
            this.eventStore().allStoredEventsBetween(
                    aNotificationLogInfo.notificationLogId().low(),
                    aNotificationLogInfo.notificationLogId().high());

        boolean archivedIndicator =
                aNotificationLogInfo.notificationLogId().high() < aNotificationLogInfo.totalLogged();

        NotificationLogId next = archivedIndicator ?
                aNotificationLogInfo.notificationLogId().next(NOTIFICATIONS_PER_LOG) :
                null;

        NotificationLogId previous =
                aNotificationLogInfo.notificationLogId().previous(NOTIFICATIONS_PER_LOG);

        NotificationLog notificationLog =
            new NotificationLog(
                    aNotificationLogInfo.notificationLogId().encoded(),
                    NotificationLogId.encoded(next),
                    NotificationLogId.encoded(previous),
                    this.notificationsFrom(storedEvents),
                    archivedIndicator);

        return notificationLog;
    }

    private List notificationsFrom(List aStoredEvents) {
        List notifications =
            new ArrayList(aStoredEvents.size());

        for (StoredEvent storedEvent : aStoredEvents) {
            DomainEvent domainEvent = storedEvent.toDomainEvent();

            Notification notification =
                new Notification(storedEvent.eventId(), domainEvent);

            notifications.add(notification);
        }

        return notifications;
    }

    private EventStore eventStore() {
        return eventStore;
    }

    private void setEventStore(EventStore anEventStore) {
        this.eventStore = anEventStore;
    }
}