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/*
 * Copyright (C) 2020 Graylog, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the Server Side Public License, version 1,
 * as published by MongoDB, Inc.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * Server Side Public License for more details.
 *
 * You should have received a copy of the Server Side Public License
 * along with this program. If not, see
 * .
 */
package org.graylog.events.processor.storage;

import com.google.common.collect.ImmutableList;
import org.graylog.events.event.EventWithContext;

import javax.inject.Inject;
import javax.inject.Singleton;
import java.util.List;
import java.util.Map;

/**
 * The event handler engine is responsible for executing handlers on events.
 */
@Singleton
public class EventStorageHandlerEngine {
    private final Map storageHandlerFactories;

    @Inject
    public EventStorageHandlerEngine(Map storageHandlerFactories) {
        this.storageHandlerFactories = storageHandlerFactories;
    }

    /**
     * Run storage handlers. These persist events into a storage system and they must run after the notification
     * handler has run.
     *
     * @param eventsWithContext events to run the handlers on
     * @param handlerConfigs    event definition
     */
    public void handleEvents(List eventsWithContext, ImmutableList handlerConfigs) throws EventStorageHandlerException {
        for (final EventStorageHandler.Config config : handlerConfigs) {
            final EventStorageHandler.Factory storageHandlerFactory = storageHandlerFactories.get(config.type());

            if (storageHandlerFactory == null) {
                throw new EventStorageHandlerException("Couldn't find storage handler for type <" + config.type() + ">", config);
            }

            try {
                final EventStorageHandler storageHandler = storageHandlerFactory.create(config);
                final EventStorageHandlerCheckResult checkResult = storageHandler.checkPreconditions();

                if (checkResult.canExecute()) {
                    storageHandler.handleEvents(eventsWithContext);
                } else {
                    throw new EventStorageHandlerException("Precondition for storage handler <" + config.type() + "> failed: " + checkResult.message(), config);
                }
            } catch (Exception e) {
                throw new EventStorageHandlerException("Couldn't execute storage handler <" + config.type() + ">", config, e);
            }
        }
    }
}