/**
 * QQ聊天室服務器端
 */
import java.net.*;
import java.io.*;
import java.util.*;

public class Server implements Protocol {
	/*
	 * 用戶名存入key,線程存入對應value
	 */
	private static Map users = new HashMap();

	/**
	 * 用戶線程類,每個用戶一個線程
	 */
	static class UserThread extends Thread {
		private Socket s;

		private String username = "";

		private PrintWriter out;

		private static int online;// 統計在線人數

		private static String lock = "";

		public UserThread(Socket s) {
			this.s = s;
		}

		public void run() {
			try {
				/*
				 * 創建流
				 */
				InputStream is = s.getInputStream();
				InputStreamReader ir = new InputStreamReader(is, "GBK");
				// java.nio.charset.Charset.defaultCharset());
				BufferedReader in = new BufferedReader(ir);
				OutputStream os = s.getOutputStream();
				OutputStreamWriter or = new OutputStreamWriter(os, "GBK");
				out = new PrintWriter(or);
				out.println(VERSION);
				out.flush();
				/*
				 * 判斷版本是否過期
				 */
				if (!in.readLine().equals(VERSION)) {
					throw new Exception("版本過期");
				}
				this.username = in.readLine();
				synchronized (lock) {
					/*
					 * 讀取用戶名,并判斷是否已經存在
					 */
					if (isExist(this.username)) {
						throw new ExistException();
					}
					/*
					 * 登陸成功
					 */
					out.println(SYSTEM_MSG);
					out.flush();
					/*
					 * 通知所有人有新用戶登陸
					 */
					sendAll(SYSTEM_MSG + ADD_USER + this.username);
					/*
					 * 刷新在線人數
					 */
					System.out.print("\rOnline:" + ++online);
					/*
					 * 給本線程用戶發送在線用戶列表
					 */
					listAll();
					/*
					 * 將本用戶加入集合
					 */
					users.put(this.username, this);
				}
				String msg = "";
				String touser = "All";
				while (!s.isClosed()) {
					while (!s.isClosed() && (msg = in.readLine()) != null
							&& msg.length() > 0) {
						/*
						 * 收到用戶退出的系統信息,刪除集合中對應項,通知所有用戶
						 */
						if (msg.startsWith(SYSTEM_MSG + USER_LOGOUT)) {
							synchronized (lock) {
								users.remove(this.username);
							}
							sendAll(SYSTEM_MSG + DELETE_USER + this.username);
							s.close();
							System.out.print("\rOnline:" + --online + " ");
						}
						/*
						 * 收到聊天信息,解析出發送對象和信息內容,并發送
						 */
						else {
							touser = msg.substring(0, msg.indexOf(NAME_END));
							msg = msg.replaceFirst(touser + NAME_END, "");
							send(msg, touser);
						}
					}
				}
			}
			/*
			 * 登陸時出現用戶名已存在情況,通知用戶
			 */
			catch (ExistException e) {
				out.println(SYSTEM_MSG + USER_EXIST);
				out.flush();
			} catch (Exception e) {
			} finally {
				try {
					s.close();
				} catch (Exception e) {
				}
			}
		}

		/**
		 * 發送信息給所有用戶
		 */
		private void sendAll(String msg) {
			Set s = users.keySet();
			Iterator it = s.iterator();
			while (it.hasNext()) {
				UserThread t = (UserThread) users.get(it.next());
				if (t != this)
					t.sendUser(msg);
			}
		}

		/**
		 * 給本線程發送在線用戶列表
		 */
		private void listAll() {
			Set s = users.keySet();
			Iterator it = s.iterator();
			while (it.hasNext()) {
				this.sendUser(SYSTEM_MSG + EXIST_USERS + it.next());
			}
		}

		/**
		 * 判斷用戶名是否已經有人使用
		 */
		private boolean isExist(String name) {
			Set s = users.keySet();
			Iterator it = s.iterator();
			while (it.hasNext()) {
				if (name.equals((String) it.next())) {
					return true;
				}
			}
			return false;
		}

		/**
		 * 給本線程對應的用戶發信息
		 */
		private void sendUser(String msg) {
			out.println(msg);
			out.flush();
			// System.out.println("to " + this.username + ": " + msg);// 調試用代碼
		}

		/**
		 * 給指定對象發送信息
		 */
		private void send(String msg, String touser) {
			/*
			 * 調用相應函數,給所有人發信息時
			 */
			if (touser.equals("All")) {
				sendAll(this.username + NAME_END + msg);
				return;
			}
			/*
			 * 根據發送目標的名字獲得相應線程,調用目標線程的函數給目標發送信息
			 */
			if (users.containsKey(touser))// 加判斷,防止用戶已經離線
				((UserThread) users.get(touser)).sendUser(MSG_FROM
						+ this.username + NAME_END + msg);
		}
	}

	/**
	 * 主方法:啟動服務器
	 */
	public static void main(String[] args) {
		/*
		 * 根據參數的情況,獲得端口號,無效時使用默認值,并返回相應信息
		 */
		int port = Integer.parseInt(DEFAULT_PORT);
		if (args.length > 0) {
			int newport;
			try {
				newport = Integer.parseInt(args[0]);
				/*
				 * 無效端口
				 */
				if (newport > 65535 || newport < 0) {
					System.out.println("The port " + newport + " is invalid.");
				}
				/*
				 * 操作系統預留端口
				 */
				else if (newport <= 1024) {
					System.out.println("The port 0~1024 is not allowed.");
				} else {
					port = newport;
				}
			}
			/*
			 * 不能轉換成整數的參數
			 */
			catch (NumberFormatException e) {
				System.out.println("Invalid port number!");
			}
		}
		try {
			ServerSocket ss = new ServerSocket(port);
			System.out.print("Server is running.\nPort:" + port + "\nOnline:0");
			while (true) {
				Socket s = ss.accept();
				Thread t = new UserThread(s);
				t.start();
			}
		}
		/*
		 * 端口綁定失敗
		 */
		catch (IOException e) {
			System.out.println("Failed to bind " + port + "port.");
		}
	}
}