/*
    * Copyright (C) 2012-2025 RRiBbit.org
    *
    * 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.rribbit;
  
  import org.rribbit.dispatching.RequestDispatcher;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.List;
  import java.util.concurrent.CopyOnWriteArrayList;
  
  /**
   * Default implementation of {@link RequestResponseBus}. Provides all behaviour specified in that interface.
   * <p />
   * The {@link DefaultRequestResponseBus} supports multiple {@link RequestDispatcher}s and every request will be sent to ALL of them. The responses will then be aggregated. Please keep
   * performance considerations in mind when adding multiple {@link RequestDispatcher}s to a {@link DefaultRequestResponseBus}, especially when using RRiBbit Remoting. In that case,
   * every request will be sent to ALL remote machines and the {@link DefaultRequestResponseBus} will have to wait until all of them have returned.
   * <p />
   * If this is undesirable, an alternative is to create multiple {@link DefaultRequestResponseBus}es, each with its own {@link RequestDispatcher}. This does however, require the sender
   * of the request to have knowledge about where the receiver is located (i.e. which {@link RequestResponseBus} to call). Although this contradicts the principle behind event buses (in that
   * the sender does not have to know anything about the receiver), it could be a worthwile sacrifice for performance considerations.
   *
   * @author G.J. Schouten
   *
   */
  public class DefaultRequestResponseBus implements RequestResponseBus {
  
  	private static final Logger log = LoggerFactory.getLogger(DefaultRequestResponseBus.class);
  
  	protected List<RequestDispatcher> requestDispatchers;
  
  	/**
  	 * Whenever you use this constructor, be sure to set the {@link RequestDispatcher} with the setter provided by this class.
  	 * If you don't, runtime {@link NullPointerException}s will occur.
  	 */
  	public DefaultRequestResponseBus() {
  		requestDispatchers = new CopyOnWriteArrayList<>();
  	}
  
  	/**
  	 * This constructor is recommended, since it forces you to specify a {@link RequestDispatcher}. Passing a null value will result in a
  	 * runtime {@link NullPointerException} whenever the {@link DefaultRequestResponseBus} is used.
  	 *
  	 * @param requestDispatchers The {@link RequestDispatcher}s to be used by this {@link DefaultRequestResponseBus}
  	 */
  	public DefaultRequestResponseBus(RequestDispatcher... requestDispatchers) {
  		this();
  		this.requestDispatchers.addAll(Arrays.asList(requestDispatchers));
  	}
  
  	@Override
  	public <T> T sendForSingleOfClass(Class<T> returnType, Object... parameters) {
  
  		log.info("Sending request for single object of class: '{}'", returnType.getName());
  
  		log.debug("Creating Request object");
  		Request request = new Request(returnType, null, parameters);
  
  		log.debug("Dispatching Request");
  		List<T> returnValues = this.dispatchRequestAndProcessResponse(request);
  		return returnValues.isEmpty() ? null : returnValues.getFirst();
  	}
  
  	@Override
  	public <T> Collection<T> sendForMultipleOfClass(Class<T> returnType, Object... parameters) {
  
  		log.info("Sending request for multiple objects of class: '{}'", returnType.getName());
  
  		log.debug("Creating Request object");
  		Request request = new Request(returnType, null, parameters);
  
  		log.debug("Dispatching Request");
  		return this.dispatchRequestAndProcessResponse(request);
  	}
  
  	@Override
  	public void sendForNothing(Object... parameters) {
  
  		log.info("Sending request for nothing");
  
  		log.debug("Creating Request object");
  		Request request = new Request(null, null, parameters);
  
 		log.debug("Dispatching Request");
 		this.dispatchRequestAndProcessResponse(request);
 	}
 
 	@Override
 	public <T> T sendForSingleWithHint(String hint, Object... parameters) {
 
 		log.info("Sending request for single object with hint '{}'", hint);
 
 		log.debug("Creating Request object");
 		Request request = new Request(null, hint, parameters);
 
 		log.debug("Dispatching Request");
 		List<T> returnValues = this.dispatchRequestAndProcessResponse(request);
 		return returnValues.isEmpty() ? null : returnValues.getFirst();
 	}
 
 	@Override
 	public <T> Collection<T> sendForMultipleWithHint(String hint, Object... parameters) {
 
 		log.info("Sending request for multiple objects with hint '{}'", hint);
 
 		log.debug("Creating Request object");
 		Request request = new Request(null, hint, parameters);
 
 		log.debug("Dispatching Request");
 		return this.dispatchRequestAndProcessResponse(request);
 	}
 
 	@Override
 	public void sendForNothingWithHint(String hint, Object... parameters) {
 
 		log.info("Sending request for nothing with hint '{}'", hint);
 
 		log.debug("Creating Request object");
 		Request request = new Request(null, hint, parameters);
 
 		log.debug("Dispatching Request");
 		this.dispatchRequestAndProcessResponse(request);
 	}
 
 	@Override
 	public <T> T sendForSingleOfClassWithHint(Class<T> returnType, String hint, Object... parameters) {
 
 		log.info("Sending request for single object of class '{}' and with hint '{}'", returnType.getName(), hint);
 
 		log.debug("Creating Request object");
 		Request request = new Request(returnType, hint, parameters);
 
 		log.debug("Dispatching Request");
 		List<T> returnValues = this.dispatchRequestAndProcessResponse(request);
 		return returnValues.isEmpty() ? null : returnValues.getFirst();
 	}
 
 	@Override
 	public <T> Collection<T> sendForMultipleOfClassWithHint(Class<T> returnType, String hint, Object... parameters) {
 
 		log.info("Sending request for multiple objects of class '{}' and with hint '{}'", returnType.getName(), hint);
 
 		log.debug("Creating Request object");
 		Request request = new Request(returnType, hint, parameters);
 
 		log.debug("Dispatching Request");
 		return this.dispatchRequestAndProcessResponse(request);
 	}
 
 	@Override
 	public <T> T send(String hint, Object... parameters) {
 
 		return this.sendForSingleWithHint(hint, parameters);
 	}
 
 	/**
 	 * Sends the given {@link Request} to all available {@link RequestDispatcher}s and aggregates the {@link Response}s. If there are any {@link Throwable}s, then
 	 * an {@link Exception} is thrown, otherwise, the aggregated return values are returned.
 	 *
 	 * @param request	The {@link Request} to be dispatched to the {@link RequestDispatcher}s
 	 * @return			All return values returned by all {@link RequestDispatcher}s
 	 */
 	protected <T> List<T> dispatchRequestAndProcessResponse(Request request) {
 
 		//Dispatch Request to all RequestDispatchers and aggregate results
 		List<T> returnValues = new ArrayList<>();
 		Collection<Throwable> throwables = new ArrayList<>();
 		for(RequestDispatcher requestDispatcher : requestDispatchers) {
 			Response<T> response = requestDispatcher.dispatchRequest(request);
 			returnValues.addAll(response.getReturnValues());
 			throwables.addAll(response.getThrowables());
 		}
 
 		//Process Throwables
 		log.debug("Processing Responses");
 		if(throwables.size() == 1) {
 			this.throwAny(throwables.iterator().next());
 		} else if(!throwables.isEmpty()) {
 			throw new MultipleThrowablesOccurredException(throwables);
 		}
 
 		//Return returnValues
 		return returnValues;
 	}
 
 	/**
 	 * Nice little trick to throw checked {@link Throwable}s without declaring them. It works, because generics are erased at runtime and the bound for E is Throwable.
 	 * A cast to {@link RuntimeException} is not included by the compiler.
 	 *
 	 * @param e
 	 * @throws E
 	 */
 	private <E extends Throwable> void throwAny(Throwable e) throws E {
 		throw (E) e;
 	}
 
 	/**
 	 * Returns all {@link RequestDispatcher}s that are used by this {@link DefaultRequestResponseBus}.
 	 *
 	 * @return  All {@link RequestDispatcher}s that are used by this {@link DefaultRequestResponseBus}
 	 */
 	public List<RequestDispatcher> getRequestDispatchers() {
 		return requestDispatchers;
 	}
 
 	/**
 	 * Adds a {@link RequestDispatcher} to this {@link DefaultRequestResponseBus}.
 	 *
 	 * @param requestDispatcher The {@link RequestDispatcher} that needs to be added to this {@link DefaultRequestResponseBus}
 	 */
 	public void addRequestDispatcher(RequestDispatcher requestDispatcher) {
 		requestDispatchers.add(requestDispatcher);
 	}
 
 	/**
 	 * Removes all {@link RequestDispatcher}s from this {@link DefaultRequestResponseBus} and adds only the given one. After invoking this method, only the given
 	 * {@link RequestDispatcher} will be used by this {@link DefaultRequestResponseBus}.
 	 *
 	 * @param requestDispatcher The {@link RequestDispatcher} that must be the sole {@link RequestDispatcher} used by this {@link DefaultRequestResponseBus}
 	 */
 	public void setRequestDispatcher(RequestDispatcher requestDispatcher) {
 		requestDispatchers.clear();
 		requestDispatchers.add(requestDispatcher);
 	}
 }