/*
 * 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.avro;

import java.net.InetSocketAddress;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.apache.avro.Protocol;
import org.apache.avro.Schema;
import org.apache.avro.ipc.Server;
import org.apache.avro.ipc.netty.NettyServer;
import org.apache.avro.ipc.specific.SpecificResponder;
import org.apache.avro.specific.SpecificData;
import org.apache.camel.CamelContext;
import org.apache.camel.Exchange;
import org.apache.camel.ExchangePattern;
import org.apache.camel.ExtendedCamelContext;
import org.apache.camel.component.avro.spi.AvroRpcHttpServerFactory;
import org.apache.camel.spi.FactoryFinder;
import org.apache.camel.support.ExchangeHelper;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.apache.camel.component.avro.AvroConstants.AVRO_HTTP_TRANSPORT;
import static org.apache.camel.component.avro.AvroConstants.AVRO_NETTY_TRANSPORT;

/**
 * This class holds server that listen to given protocol:host:port combination and dispatches messages to different
 * routes mapped.
 */
public class AvroListener {

    private static final Logger LOGGER = LoggerFactory.getLogger(AvroListener.class);

    private ConcurrentMap<String, AvroConsumer> consumerRegistry = new ConcurrentHashMap<>();
    private AvroConsumer defaultConsumer;
    private final Server server;

    public AvroListener(AvroEndpoint endpoint) throws Exception {
        server = initAndStartServer(endpoint.getConfiguration(), endpoint.getCamelContext());
    }

    /**
     * Initializes and starts http or netty server on basis of transport protocol from configuration.
     *
     *
     * @param  configuration
     * @return                     Initialized and started server
     * @throws java.io.IOException
     */
    private Server initAndStartServer(AvroConfiguration configuration, CamelContext camelContext) throws Exception {
        SpecificResponder responder;
        Server server;

        if (configuration.isReflectionProtocol()) {
            responder = new AvroReflectResponder(configuration.getProtocol(), this);
        } else {
            responder = new AvroSpecificResponder(configuration.getProtocol(), this);
        }

        if (AVRO_HTTP_TRANSPORT.equalsIgnoreCase(configuration.getTransport().name())) {
            AvroRpcHttpServerFactory factory = camelContext
                    .adapt(ExtendedCamelContext.class)
                    .getFactoryFinder(FactoryFinder.DEFAULT_PATH)
                    .newInstance("avro-rpc-http-server-factory", AvroRpcHttpServerFactory.class)
                    .orElseThrow(() -> new IllegalStateException(
                            "AvroRpcHttpServerFactory is neither set on this endpoint neither found in Camel Registry or FactoryFinder."));
            server = factory.create(responder, configuration.getPort());
        } else if (AVRO_NETTY_TRANSPORT.equalsIgnoreCase(configuration.getTransport().name())) {
            server = new NettyServer(responder, new InetSocketAddress(configuration.getHost(), configuration.getPort()));
        } else {
            throw new IllegalArgumentException("Unknown transport " + configuration.getTransport());
        }

        server.start();

        return server;
    }

    /**
     * Registers consumer by appropriate message name as key in registry.
     *
     * @param  messageName            message name
     * @param  consumer               avro consumer
     * @throws AvroComponentException
     */
    public void register(String messageName, AvroConsumer consumer) throws AvroComponentException {
        if (messageName == null) {
            if (this.defaultConsumer != null) {
                throw new AvroComponentException(
                        "Default consumer already registered for uri: " + consumer.getEndpoint().getEndpointUri());
            }
            this.defaultConsumer = consumer;
        } else {
            if (consumerRegistry.putIfAbsent(messageName, consumer) != null) {
                throw new AvroComponentException(
                        "Consumer already registered for message: " + messageName + " and uri: "
                                                 + consumer.getEndpoint().getEndpointUri());
            }
        }
    }

    /**
     * Unregisters consumer by message name. Stops server in case if all consumers are unregistered and default consumer
     * is absent or stopped.
     *
     * @param  messageName message name
     * @return             true if all consumers are unregistered and defaultConsumer is absent or null. It means that
     *                     this responder can be unregistered.
     */
    public boolean unregister(String messageName) {
        if (!StringUtils.isEmpty(messageName)) {
            if (consumerRegistry.remove(messageName) == null) {
                LOGGER.warn("Consumer with message name {} was already unregistered.", messageName);
            }
        } else {
            defaultConsumer = null;
        }

        if (defaultConsumer == null && consumerRegistry.isEmpty()) {
            if (server != null) {
                server.close();
            }
            return true;
        }
        return false;
    }

    public Object respond(Protocol.Message message, Object request, SpecificData data) throws Exception {
        AvroConsumer consumer = this.defaultConsumer;
        if (this.consumerRegistry.containsKey(message.getName())) {
            consumer = this.consumerRegistry.get(message.getName());
        }

        if (consumer == null) {
            throw new AvroComponentException("No consumer defined for message: " + message.getName());
        }

        Object params = extractParams(message, request, consumer.getEndpoint().getConfiguration().isSingleParameter(), data);

        return processExchange(consumer, message, params);
    }

    /**
     * Extracts parameters from RPC call to List or converts to object of appropriate type if only one parameter set.
     *
     * @param  message         Avro message
     * @param  request         Avro request
     * @param  singleParameter Indicates that called method has single parameter
     * @param  dataResolver    Extracts type of parameters in call
     * @return                 Parameters of RPC method invocation
     */
    private static Object extractParams(
            Protocol.Message message, Object request, boolean singleParameter, SpecificData dataResolver) {

        if (singleParameter) {
            Schema.Field field = message.getRequest().getFields().get(0);
            return dataResolver.getField(request, field.name(), field.pos());
        } else {
            int i = 0;
            Object[] params = new Object[message.getRequest().getFields().size()];
            for (Schema.Field param : message.getRequest().getFields()) {
                params[i] = dataResolver.getField(request, param.name(), param.pos());
                i++;
            }
            return params;
        }
    }

    /**
     * Creates exchange and processes it.
     *
     * @param  consumer  Holds processor and exception handler
     * @param  message   Message on which exchange is created
     * @param  params    Params of exchange
     * @return           Response of exchange processing
     * @throws Exception
     */
    private static Object processExchange(AvroConsumer consumer, Protocol.Message message, Object params) throws Exception {
        Object response;
        Exchange exchange = createExchange(consumer, message, params);

        try {
            consumer.getProcessor().process(exchange);
        } catch (Exception e) {
            consumer.getExceptionHandler().handleException(e);
        }

        if (ExchangeHelper.isOutCapable(exchange)) {
            response = exchange.getOut().getBody();
        } else {
            response = null;
        }

        boolean failed = exchange.isFailed();
        if (failed) {
            if (exchange.getException() != null) {
                throw exchange.getException();
            } else {
                // failed and no exception, must be a fault
                throw new AvroComponentException("Camel processing error.");
            }
        }
        return response;
    }

    protected static Exchange createExchange(AvroConsumer consumer, Protocol.Message message, Object request) {
        ExchangePattern pattern = ExchangePattern.InOut;
        if (message.getResponse().getType().equals(Schema.Type.NULL)) {
            pattern = ExchangePattern.InOnly;
        }
        Exchange exchange = consumer.createExchange(true);
        exchange.setPattern(pattern);
        exchange.getIn().setBody(request);
        exchange.getIn().setHeader(AvroConstants.AVRO_MESSAGE_NAME, message.getName());
        return exchange;
    }

}
