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/*
 * Copyright © 2017 camunda services GmbH ([email protected])
 *
 * 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.zeebe.logstreams.processor;

import io.zeebe.logstreams.log.LoggedEvent;
import io.zeebe.logstreams.spi.SnapshotSupport;

/**
 * Process events from a log stream.
 */
public interface StreamProcessor
{
    /**
     * Returns the resource which holds the state of the processor.
     *
     * @return the processor state resource
     */
    SnapshotSupport getStateResource();

    /**
     * Returns a specific processor to process the event which is read from the
     * log stream, if available.
     *
     * @param event
     *            the event to process
     *
     * @return specific processor to process the event, or null if the event can't  be processed
     */
    EventProcessor onEvent(LoggedEvent event);

    /**
     * Callback which is invoked by the controller when it opens. An
     * implementation can provide any setup logic here.
     */
    default void onOpen(StreamProcessorContext context)
    {
        // do nothing
    }

    /**
     * Callback which is invoked by the controller when the recovery is done.
     * Implementation could contain logic which should not be done on recovery, but afterwards.
     */
    default void onRecovered()
    {

    }

    /**
     * Callback which is invoked by the controller when it closes. An
     * implementation can provide any clean up logic here.
     */
    default void onClose()
    {
        // no nothing
    }

}