package com.expgiga.NIO;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Date;
import java.util.Iterator;
import java.util.Scanner;

/**
 * 一、使用NIO完成网络通信的三个核心：
 * 1.通道Channel：负责连接
 * java.nio.channels.Channel接口:
 * |--SelectableChannel
 *    |--SocketChannel
 *    |--ServerSocketChannel
 *    |--DatagramChannel
 * <p>
 *    |--Pipe.SinkChannel
 *    |--Pipe.SourceChannel
 * <p>
 * 2.缓冲区Buffer：负责数据的存取
 * <p>
 * 3.选择器Selector：是SelectableChannel的多路复用器。用于监控SelectableChannel的IO状况。
 */
public class TestNonBlockingNIO {

    //客户端
    public void client() throws IOException {

        //1.获取通道
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));

        //2.切换成非阻塞模式
        sChannel.configureBlocking(false);

        //3.分配指定大小的缓冲区
        ByteBuffer buf = ByteBuffer.allocate(1024);

        //4.发送数据给服务端
        Scanner scan = new Scanner(System.in);

        while (scan.hasNext()) {
            String str = scan.next();
            buf.put((new Date().toString() + "\n" + str).getBytes());
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }

        //5.关闭通道
        sChannel.close();
    }


    //服务端
    public void server() throws IOException {
        //1.获取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();

        //2.切换成非阻塞模式
        ssChannel.configureBlocking(false);

        //3.绑定连接
        ssChannel.bind(new InetSocketAddress(9898));

        //4.获取选择器Selector
        Selector selector = Selector.open();

        //5.将通道注册到选择器上，并且指定“监听接受事件”
        ssChannel.register(selector, SelectionKey.OP_ACCEPT);

        //6.轮询式获取选择器上已经准备就绪的事件
        while (selector.select() > 0) {
            //7.获取当前选择器中所有注册的选择键(已就绪的监听事件)
            Iterator<SelectionKey> it = selector.selectedKeys().iterator();

            while (it.hasNext()) {
                //8.获取准备就绪的事件
                SelectionKey sk = it.next();

                //9.判断具体是什么事件准备就绪
                if (sk.isAcceptable()) {
                    //10.若“接收就绪”,获取客户端连接
                    SocketChannel sChannel = ssChannel.accept();

                    //11.切换成非阻塞的模式
                    sChannel.configureBlocking(false);

                    //12.将该通道注册到选择器上
                    sChannel.register(selector, SelectionKey.OP_READ);
                } else if (sk.isReadable()) {
                    //13.获取当前选择器上的"读就绪"状态的通道
                    SocketChannel sChannel = (SocketChannel) sk.channel();

                    //14.读取数据
                    ByteBuffer buf = ByteBuffer.allocate(1024);

                    int len = 0;
                    while ((len = sChannel.read(buf)) > 0) {
                        buf.flip();
                        System.out.println(new String(buf.array(), 0, len));
                        buf.clear();
                    }
                }

                //15.取消选择键SelectionKey
                it.remove();
            }
        }
    }

}