package wadihu.crawl;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;

/** 爬行类，专门负责网页的下载, 以非阻塞方式连接 */
    public class CrawlOrder1 {
        private boolean shutdown = false; // 用于控制Connector线程
        private Selector selector; // 注册选择器
        private Queue<Target> targetLists = new LinkedList<Target>(); // 任务队列
        private Queue<Target> taskLists = new LinkedList<Target>(); // 待抓取任务对列
        public CrawlOrder1() throws IOException {
            selector = Selector.open(); // 打开选择器
            RW rw = new RW();
            rw.start();
            System.out.println("读写线程已启动...");
            receiveTarget();  // 用户提交URL任务输入
        }

        /**用户输入URL请求 */
        public void receiveTarget() throws IOException {
            BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
            String msg = null;
            while((msg = buf.readLine()) != null) {
                if(!msg.equals("bye")) {
                    Target target = new Target(msg);
                    addTarget(target);
                }
                else {
                    shutdown = true;
                    selector.wakeup();
                    System.out.println("系统已经停止");
                    break;
                }
            }
        }

        /** 向任务队列添加任务 
         * @throws IOException */
        public void addTarget(Target target) throws IOException {
            synchronized (targetLists) {
                targetLists.add(target);
            }
            selector.wakeup();
        }

         /** 注册读写事件 */
        public void registerRW() {
            synchronized(targetLists) {
                while(targetLists.size() > 0) {
                    Target target = targetLists.poll();
                    try {
                        target.socketChannel.register(selector, SelectionKey.OP_WRITE|SelectionKey.OP_READ, target);
                    } catch (ClosedChannelException e) {
                        e.printStackTrace();
                    }
                }
            }
        }

        /** 读写就绪事件发生，处理读写的事件
         * @throws IOException */
        public void processSelectdRWKeys() throws IOException {
            for (Iterator<?> it =  selector.selectedKeys().iterator(); it.hasNext();) {
                SelectionKey selectionKey = (SelectionKey) it.next();
                it.remove();
                SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
                if(selectionKey.isWritable()) {
                    String head = "GET / HTTP/1.1\r\nHOST:" + socketChannel.socket().getInetAddress().getHostName() + "\r\n" + "Accept:*/*\r\n" + "User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1;)\r\n\r\n";
                    ByteBuffer buffer = ByteBuffer.wrap(head.getBytes());
                    socketChannel.write(buffer);
                    socketChannel.register(selector, SelectionKey.OP_READ);
                } else if(selectionKey.isReadable()) {
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    int ret = socketChannel.read(buffer);
                    if (ret < 0) {
                        socketChannel.close();
                        selectionKey.cancel();
                    }
                    buffer.flip();
                    Charset ch = Charset.forName("gb2312");
                    System.out.println(ch.decode(buffer));
                }
            }
        }

        /** 建立读写内部类 */
        private class RW extends Thread {
            public void run() {
                while(!shutdown) {
                    try {
                        registerRW();
                        if(selector.select(500) > 0) {
                            processSelectdRWKeys();
                        }
                    } catch (ClosedChannelException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                try {
                    selector.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        public static void main(String[] args) throws IOException {
            new CrawlOrder1();
        }
    }

    /** 一项抓取任务,外部类  */
    class Target {
        SocketAddress address;
        SocketChannel socketChannel;
        public Target(String host) throws IOException {
            address = new InetSocketAddress(InetAddress.getByName(host), 80);
            this.socketChannel = SocketChannel.open(address);
            this.socketChannel.configureBlocking(false);
        }
    }