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Camel Consul support
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.camel.component.consul.endpoint;

import java.util.List;
import java.util.Optional;

import org.apache.camel.Exchange;
import org.apache.camel.Message;
import org.apache.camel.Processor;
import org.apache.camel.component.consul.ConsulConfiguration;
import org.apache.camel.component.consul.ConsulConstants;
import org.apache.camel.component.consul.ConsulEndpoint;
import org.kiwiproject.consul.Consul;
import org.kiwiproject.consul.KeyValueClient;
import org.kiwiproject.consul.async.ConsulResponseCallback;
import org.kiwiproject.consul.model.ConsulResponse;
import org.kiwiproject.consul.model.kv.Value;
import org.kiwiproject.consul.option.QueryOptions;

public final class ConsulKeyValueConsumer extends AbstractConsulConsumer {

    public ConsulKeyValueConsumer(ConsulEndpoint endpoint, ConsulConfiguration configuration, Processor processor) {
        super(endpoint, configuration, processor, Consul::keyValueClient);
    }

    @Override
    protected Runnable createWatcher(KeyValueClient client) throws Exception {
        return configuration.isRecursive() ? new RecursivePathWatcher(client) : new PathWatcher(client);
    }

    // *************************************************************************
    // Watch
    // *************************************************************************

    private abstract class AbstractPathWatcher extends AbstractWatcher implements ConsulResponseCallback {
        protected AbstractPathWatcher(KeyValueClient client) {
            super(client);
        }

        protected QueryOptions queryOptions() {
            return QueryOptions.blockSeconds(configuration.getBlockSeconds(), index.get()).build();
        }

        @Override
        public void onComplete(ConsulResponse consulResponse) {
            if (isRunAllowed()) {
                onResponse(consulResponse.getResponse());
                setIndex(consulResponse.getIndex());
                watch();
            }
        }

        @Override
        public void onFailure(Throwable throwable) {
            onError(throwable);
        }

        protected void onValue(Value value) {
            final Exchange exchange = createExchange(false);
            try {
                final Message message = exchange.getIn();

                message.setHeader(ConsulConstants.CONSUL_KEY, value.getKey());
                message.setHeader(ConsulConstants.CONSUL_RESULT, true);
                message.setHeader(ConsulConstants.CONSUL_FLAGS, value.getFlags());
                message.setHeader(ConsulConstants.CONSUL_CREATE_INDEX, value.getCreateIndex());
                message.setHeader(ConsulConstants.CONSUL_LOCK_INDEX, value.getLockIndex());
                message.setHeader(ConsulConstants.CONSUL_MODIFY_INDEX, value.getModifyIndex());

                if (value.getSession().isPresent()) {
                    message.setHeader(ConsulConstants.CONSUL_SESSION, value.getSession().get());
                }

                message.setBody(
                        configuration.isValueAsString()
                                ? value.getValueAsString().orElse(null) : value.getValue().orElse(null));

                getProcessor().process(exchange);
            } catch (Exception e) {
                getExceptionHandler().handleException("Error processing exchange", exchange, e);
            } finally {
                releaseExchange(exchange, false);
            }
        }

        protected abstract void onResponse(T consulResponse);
    }

    private class PathWatcher extends AbstractPathWatcher> {
        PathWatcher(KeyValueClient client) {
            super(client);
        }

        @Override
        public void watch(KeyValueClient client) {
            client.getValue(key, queryOptions(), this);
        }

        @Override
        public void onResponse(Optional value) {
            value.ifPresent(this::onValue);
        }
    }

    private class RecursivePathWatcher extends AbstractPathWatcher> {
        RecursivePathWatcher(KeyValueClient client) {
            super(client);
        }

        @Override
        public void watch(KeyValueClient client) {
            client.getValues(key, queryOptions(), this);
        }

        @Override
        public void onResponse(List values) {
            values.forEach(this::onValue);
        }
    }
}