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/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.elasticsearch.transport;

import org.elasticsearch.tasks.Task;
import org.elasticsearch.tasks.TaskManager;

import java.lang.reflect.Constructor;
import java.util.concurrent.Callable;
import java.io.IOException;

/**
 *
 */
public class RequestHandlerRegistry {

    private final String action;
    private final TransportRequestHandler handler;
    private final boolean forceExecution;
    private final boolean canTripCircuitBreaker;
    private final String executor;
    private final Callable requestFactory;
    private final TaskManager taskManager;

    RequestHandlerRegistry(String action, Class request, TaskManager taskManager, TransportRequestHandler handler,
                           String executor, boolean forceExecution, boolean canTripCircuitBreaker) {
        this(action, new ReflectionFactory<>(request), taskManager, handler, executor, forceExecution, canTripCircuitBreaker);
    }

    public RequestHandlerRegistry(String action, Callable requestFactory, TaskManager taskManager, TransportRequestHandler handler, String executor, boolean forceExecution, boolean canTripCircuitBreaker) {
        this.action = action;
        this.requestFactory = requestFactory;
        assert newRequest() != null;
        this.handler = handler;
        this.forceExecution = forceExecution;
        this.canTripCircuitBreaker = canTripCircuitBreaker;
        this.executor = executor;
        this.taskManager = taskManager;
    }

    public String getAction() {
        return action;
    }

    public Request newRequest() {
        try {
            return requestFactory.call();
        } catch (Exception e) {
            throw new IllegalStateException("failed to instantiate request ", e);
        }
    }

    public void processMessageReceived(Request request, TransportChannel channel) throws Exception {
        final Task task = taskManager.register(channel.getChannelType(), action, request);
        if (task == null) {
            handler.messageReceived(request, channel);
        } else {
            boolean success = false;
            try {
                handler.messageReceived(request, new TransportChannelWrapper(taskManager, task, channel), task);
                success = true;
            } finally {
                if (success == false) {
                    taskManager.unregister(task);
                }
            }
        }
    }

    public boolean isForceExecution() {
        return forceExecution;
    }

    public boolean canTripCircuitBreaker() {
        return canTripCircuitBreaker;
    }

    public String getExecutor() {
        return executor;
    }

    private final static class ReflectionFactory implements Callable {
        private final Constructor requestConstructor;

        public ReflectionFactory(Class request) {
            try {
                this.requestConstructor = request.getDeclaredConstructor();
            } catch (NoSuchMethodException e) {
                throw new IllegalStateException("failed to create constructor (does it have a default constructor?) for request " + request, e);
            }
        }

        @Override
        public Request call() throws Exception {
            try {
                return requestConstructor.newInstance();
            } catch (IllegalAccessException e) {
                throw new IllegalStateException("Could not access '" + requestConstructor + "'. Implementations must be a public class and have a public no-arg ctor.", e);
            }
        }
    }

    @Override
    public String toString() {
        return handler.toString();
    }

    private static class TransportChannelWrapper extends DelegatingTransportChannel {

        private final Task task;

        private final TaskManager taskManager;

        public TransportChannelWrapper(TaskManager taskManager, Task task, TransportChannel channel) {
            super(channel);
            this.task = task;
            this.taskManager = taskManager;
        }

        @Override
        public void sendResponse(TransportResponse response) throws IOException {
            endTask();
            super.sendResponse(response);
        }

        @Override
        public void sendResponse(TransportResponse response, TransportResponseOptions options) throws IOException {
            endTask();
            super.sendResponse(response, options);
        }

        @Override
        public void sendResponse(Throwable error) throws IOException {
            endTask();
            super.sendResponse(error);
        }

        private void endTask() {
            taskManager.unregister(task);
        }
    }
}