/*
 * Copyright 2002-2017 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.messaging.simp.config;

import java.util.Arrays;
import java.util.Collection;

import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.SubscribableChannel;
import org.springframework.messaging.simp.broker.SimpleBrokerMessageHandler;
import org.springframework.messaging.simp.stomp.StompBrokerRelayMessageHandler;
import org.springframework.util.Assert;
import org.springframework.util.PathMatcher;

/**
 * A registry for configuring message broker options.
 *
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @since 4.0
 */
public class MessageBrokerRegistry {

        private final SubscribableChannel clientInboundChannel;

        private final MessageChannel clientOutboundChannel;

        private SimpleBrokerRegistration simpleBrokerRegistration;

        private StompBrokerRelayRegistration brokerRelayRegistration;

        private final ChannelRegistration brokerChannelRegistration = new ChannelRegistration();

        private String[] applicationDestinationPrefixes;

        private String userDestinationPrefix;

        private PathMatcher pathMatcher;

        private Integer cacheLimit;


        public MessageBrokerRegistry(SubscribableChannel clientInboundChannel, MessageChannel clientOutboundChannel) {
                Assert.notNull(clientInboundChannel, "Inbound channel must not be null");
                Assert.notNull(clientOutboundChannel, "Outbound channel must not be null");
                this.clientInboundChannel = clientInboundChannel;
                this.clientOutboundChannel = clientOutboundChannel;
        }


        /**
         * Enable a simple message broker and configure one or more prefixes to filter
         * destinations targeting the broker (e.g. destinations prefixed with "/topic").
         */
        public SimpleBrokerRegistration enableSimpleBroker(String... destinationPrefixes) {
                this.simpleBrokerRegistration = new SimpleBrokerRegistration(
                                this.clientInboundChannel, this.clientOutboundChannel, destinationPrefixes);
                return this.simpleBrokerRegistration;
        }

        /**
         * Enable a STOMP broker relay and configure the destination prefixes supported by the
         * message broker. Check the STOMP documentation of the message broker for supported
         * destinations.
         */
        public StompBrokerRelayRegistration enableStompBrokerRelay(String... destinationPrefixes) {
                this.brokerRelayRegistration = new StompBrokerRelayRegistration(
                                this.clientInboundChannel, this.clientOutboundChannel, destinationPrefixes);
                return this.brokerRelayRegistration;
        }

        /**
         * Customize the channel used to send messages from the application to the message
         * broker. By default, messages from the application to the message broker are sent
         * synchronously, which means application code sending a message will find out
         * if the message cannot be sent through an exception. However, this can be changed
         * if the broker channel is configured here with task executor properties.
         */
        public ChannelRegistration configureBrokerChannel() {
                return this.brokerChannelRegistration;
        }

        protected ChannelRegistration getBrokerChannelRegistration() {
                return this.brokerChannelRegistration;
        }

        protected String getUserDestinationBroadcast() {
                return (this.brokerRelayRegistration != null ?
                                this.brokerRelayRegistration.getUserDestinationBroadcast() : null);
        }

        protected String getUserRegistryBroadcast() {
                return (this.brokerRelayRegistration != null ?
                                this.brokerRelayRegistration.getUserRegistryBroadcast() : null);
        }

        /**
         * Configure one or more prefixes to filter destinations targeting application
         * annotated methods. For example destinations prefixed with "/app" may be
         * processed by annotated methods while other destinations may target the
         * message broker (e.g. "/topic", "/queue").
         * <p>When messages are processed, the matching prefix is removed from the destination
         * in order to form the lookup path. This means annotations should not contain the
         * destination prefix.
         * <p>Prefixes that do not have a trailing slash will have one automatically appended.
         */
        public MessageBrokerRegistry setApplicationDestinationPrefixes(String... prefixes) {
                this.applicationDestinationPrefixes = prefixes;
                return this;
        }

        protected Collection<String> getApplicationDestinationPrefixes() {
                return (this.applicationDestinationPrefixes != null ?
                                Arrays.asList(this.applicationDestinationPrefixes) : null);
        }

        /**
         * Configure the prefix used to identify user destinations. User destinations
         * provide the ability for a user to subscribe to queue names unique to their
         * session as well as for others to send messages to those unique,
         * user-specific queues.
         * <p>For example when a user attempts to subscribe to "/user/queue/position-updates",
         * the destination may be translated to "/queue/position-updatesi9oqdfzo" yielding a
         * unique queue name that does not collide with any other user attempting to do the same.
         * Subsequently when messages are sent to "/user/{username}/queue/position-updates",
         * the destination is translated to "/queue/position-updatesi9oqdfzo".
         * <p>The default prefix used to identify such destinations is "/user/".
         */
        public MessageBrokerRegistry setUserDestinationPrefix(String destinationPrefix) {
                this.userDestinationPrefix = destinationPrefix;
                return this;
        }

        protected String getUserDestinationPrefix() {
                return this.userDestinationPrefix;
        }

        /**
         * Configure the PathMatcher to use to match the destinations of incoming
         * messages to {@code @MessageMapping} and {@code @SubscribeMapping} methods.
         * <p>By default {@link org.springframework.util.AntPathMatcher} is configured.
         * However applications may provide an {@code AntPathMatcher} instance
         * customized to use "." (commonly used in messaging) instead of "/" as path
         * separator or provide a completely different PathMatcher implementation.
         * <p>Note that the configured PathMatcher is only used for matching the
         * portion of the destination after the configured prefix. For example given
         * application destination prefix "/app" and destination "/app/price.stock.**",
         * the message might be mapped to a controller with "price" and "stock.**"
         * as its type and method-level mappings respectively.
         * <p>When the simple broker is enabled, the PathMatcher configured here is
         * also used to match message destinations when brokering messages.
         * @since 4.1
         * @see org.springframework.messaging.simp.broker.DefaultSubscriptionRegistry#setPathMatcher
         */
        public MessageBrokerRegistry setPathMatcher(PathMatcher pathMatcher) {
                this.pathMatcher = pathMatcher;
                return this;
        }

        protected PathMatcher getPathMatcher() {
                return this.pathMatcher;
        }

        /**
         * Configure the cache limit to apply for registrations with the broker.
         * <p>This is currently only applied for the destination cache in the
         * subscription registry. The default cache limit there is 1024.
         * @since 4.3.2
         * @see org.springframework.messaging.simp.broker.DefaultSubscriptionRegistry#setCacheLimit
         */
        public MessageBrokerRegistry setCacheLimit(int cacheLimit) {
                this.cacheLimit = cacheLimit;
                return this;
        }


        protected SimpleBrokerMessageHandler getSimpleBroker(SubscribableChannel brokerChannel) {
                if (this.simpleBrokerRegistration == null && this.brokerRelayRegistration == null) {
                        enableSimpleBroker();
                }
                if (this.simpleBrokerRegistration != null) {
                        SimpleBrokerMessageHandler handler = this.simpleBrokerRegistration.getMessageHandler(brokerChannel);
                        handler.setPathMatcher(this.pathMatcher);
                        handler.setCacheLimit(this.cacheLimit);
                        return handler;
                }
                return null;
        }

        protected StompBrokerRelayMessageHandler getStompBrokerRelay(SubscribableChannel brokerChannel) {
                if (this.brokerRelayRegistration != null) {
                        return this.brokerRelayRegistration.getMessageHandler(brokerChannel);
                }
                return null;
        }

}