/*
 * 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.sysds.runtime.controlprogram.federated;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;
import io.netty.util.concurrent.Promise;
import org.apache.sysds.common.Types;
import org.apache.sysds.conf.DMLConfig;
import org.apache.sysds.runtime.DMLRuntimeException;
import org.apache.sysds.runtime.controlprogram.federated.FederatedRequest.RequestType;
import org.apache.sysds.utils.Statistics;

import java.net.InetSocketAddress;
import java.util.concurrent.Future;


public class FederatedData {
	private Types.DataType _dataType;
	private InetSocketAddress _address;
	private String _filepath;
	/**
	 * The ID of default matrix/tensor on which operations get executed if no other ID is given.
	 */
	private long _varID = -1; // -1 is never valid since varIDs start at 0
	private int _nrThreads = Integer.parseInt(DMLConfig.DEFAULT_NUMBER_OF_FEDERATED_WORKER_THREADS);


	public FederatedData(Types.DataType dataType, InetSocketAddress address, String filepath) {
		_dataType = dataType;
		_address = address;
		_filepath = filepath;
	}
	
	/**
	 * Make a copy of the <code>FederatedData</code> metadata, but use another varID (refer to another object on worker)
	 * @param other the <code>FederatedData</code> of which we want to copy the worker information from
	 * @param varID the varID of the variable we refer to
	 */
	public FederatedData(FederatedData other, long varID) {
		this(other._dataType, other._address, other._filepath);
		_varID = varID;
	}
	
	public InetSocketAddress getAddress() {
		return _address;
	}
	
	public void setVarID(long varID) {
		_varID = varID;
	}
	
	public long getVarID() {
		return _varID;
	}
	
	public String getFilepath() {
		return _filepath;
	}
	
	public boolean isInitialized() {
		return _varID != -1;
	}
	
	public synchronized Future<FederatedResponse> initFederatedData(long id) {
		if(isInitialized())
			throw new DMLRuntimeException("Tried to init already initialized data");
		if(!_dataType.isMatrix() && !_dataType.isFrame())
			throw new DMLRuntimeException("Federated datatype \"" + _dataType.toString() + "\" is not supported.");
		_varID = id;
		FederatedRequest request = new FederatedRequest(RequestType.READ_VAR, id);
		request.appendParam(_filepath);
		request.appendParam(_dataType.name());
		return executeFederatedOperation(request);
	}
	
	/**
	 * Executes an federated operation on a federated worker.
	 *
	 * @param request the requested operation
	 * @return the response
	 */
	public synchronized Future<FederatedResponse> executeFederatedOperation(FederatedRequest... request) {
		// Careful with the number of threads. Each thread opens connections to multiple files making resulting in 
		// java.io.IOException: Too many open files
		EventLoopGroup workerGroup = new NioEventLoopGroup(_nrThreads);
		try {
			Bootstrap b = new Bootstrap();
			final DataRequestHandler handler = new DataRequestHandler(workerGroup);
			b.group(workerGroup).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
				@Override
				public void initChannel(SocketChannel ch) {
					ch.pipeline().addLast("ObjectDecoder",
						new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.weakCachingResolver(ClassLoader.getSystemClassLoader())))
						.addLast("FederatedOperationHandler", handler)
						.addLast("ObjectEncoder", new ObjectEncoder());
				}
			});
			
			ChannelFuture f = b.connect(_address).sync();
			Promise<FederatedResponse> promise = f.channel().eventLoop().newPromise();
			handler.setPromise(promise);
			f.channel().writeAndFlush(request);
			return promise;
		}
		catch (InterruptedException e) {
			throw new DMLRuntimeException("Could not send federated operation.");
		}
		catch (Exception e) {
			throw new DMLRuntimeException(e);
		}
	}
	
	private static class DataRequestHandler extends ChannelInboundHandlerAdapter {
		private Promise<FederatedResponse> _prom;
		private EventLoopGroup _workerGroup;
		
		public DataRequestHandler(EventLoopGroup workerGroup) {
			_workerGroup = workerGroup;
		}
		
		public void setPromise(Promise<FederatedResponse> prom) {
			_prom = prom;
		}
		
		@Override
		public void channelRead(ChannelHandlerContext ctx, Object msg) {
			if (_prom == null)
				throw new DMLRuntimeException("Read while no message was sent");
			_prom.setSuccess((FederatedResponse) msg);
			ctx.close();
			_workerGroup.shutdownGracefully();
		}
	}
}