//HttpProxy.java
/*************************************
* 一個基礎的代理服務器類
*************************************
*/
import java.net.*;
import java.io.*;

public class HttpProxy extends Thread {
    static public int CONNECT_RETRIES=5;
    static public int CONNECT_PAUSE=5;
    static public int TIMEOUT=50;
    static public int BUFSIZ=1024;
    static public boolean logging = false;
    static public OutputStream log=null;
    // 傳入數據用的Socket
    protected Socket socket;
    // 上級代理服務器，可選
    static private String parent=null;
    static private int parentPort=-1;
    static public void setParentProxy(String name, int pport) {
		parent=name;
		parentPort=pport;
    }
	
    // 在給定Socket上創建一個代理線程。
    public HttpProxy(Socket s) { socket=s; start(); }
	
    public void writeLog(int c, boolean browser) throws IOException {
		log.write(c);
    }
	
    public void writeLog(byte[] bytes,int offset, int len, boolean browser) throws IOException {
		for (int i=0;i<len;i++) writeLog((int)bytes[offset+i],browser);
    }
	
	
    // 默認情況下，日志信息輸出到
    // 標準輸出設備
    // 派生類可以覆蓋它
    public String processHostName(String url, String host, int port, Socket sock) {
		java.text.DateFormat cal=java.text.DateFormat.getDateTimeInstance();
		System.out.println(cal.format(new java.util.Date()) + " - " + url + " " 
			+ sock.getInetAddress()+"\n");
		return host;
    }
	
	
	
    // 執行操作的線程
    public void run() {
		String line;
		String host;
		int port=80;
        Socket outbound=null;
		try {
			socket.setSoTimeout(TIMEOUT);
			InputStream is=socket.getInputStream();
			OutputStream os=null;
			try {
                // 獲取請求行的內容
				line="";
				host="";
				int state=0;
				boolean space;
				while (true) {
					int c=is.read();
					if (c==-1) break;
					if (logging) writeLog(c,true);
					space=Character.isWhitespace((char)c); 
					switch (state) {
					case 0:
						if (space) continue; 
						state=1;
					case 1:
						if (space) {
							state=2;
							continue;
						}
						line=line+(char)c;
						break;
					case 2:
						if (space) continue; // 跳過多個空白字符
						state=3;
					case 3:
						if (space) {
							state=4; 
                            // 只取出主機名稱部分
							String host0=host;
							int n;
							n=host.indexOf("//");
							if (n!=-1) host=host.substring(n+2);
							n=host.indexOf('/');
							if (n!=-1) host=host.substring(0,n);
                            // 分析可能存在的端口號
							n=host.indexOf(":");
							if (n!=-1) { 
								port=Integer.parseInt(host.substring(n+1));
								host=host.substring(0,n);
							}
							host=processHostName(host0,host,port,socket);
							if (parent!=null) {
								host=parent;
								port=parentPort;
							}
							int retry=CONNECT_RETRIES;
							while (retry--!=0) {
								try {
									outbound=new Socket(host,port);
									break;
				} catch (Exception e) { }
				// 等待
				Thread.sleep(CONNECT_PAUSE);
							}
							if (outbound==null) break;
							outbound.setSoTimeout(TIMEOUT);
							os=outbound.getOutputStream();
							os.write(line.getBytes());
							os.write(' ');
							os.write(host0.getBytes());
							os.write(' ');
							pipe(is,outbound.getInputStream(),os,socket.getOutputStream());
							break;
						}
						host=host+(char)c;
						break;
					}
				}
			}
			catch (IOException e) { }
			
    } catch (Exception e) { }
    finally {
		try { socket.close();} catch (Exception e1) {}
		try { outbound.close();} catch (Exception e2) {}
	}
    }
	
	
    void pipe(InputStream is0, InputStream is1,
		OutputStream os0,  OutputStream os1) throws IOException {
		try {
			int ir;
			byte bytes[]=new byte[BUFSIZ];
			while (true) {
				try {
					if ((ir=is0.read(bytes))>0) {
						os0.write(bytes,0,ir);
						if (logging) writeLog(bytes,0,ir,true);
					}
					else if (ir<0)
						break;
		} catch (InterruptedIOException e) { }
		try {
			if ((ir=is1.read(bytes))>0) {
				os1.write(bytes,0,ir);
				if (logging) writeLog(bytes,0,ir,false);
			}
			else if (ir<0) 
				break;
		} catch (InterruptedIOException e) { }
			}
		} catch (Exception e0) {
			System.out.println("Pipe異常: " + e0);
		}
    }
	
	
    static public void startProxy(int port,Class clobj) {
		ServerSocket ssock;
		Socket sock;
        try {
			ssock=new ServerSocket(port);
			while (true) {
				Class [] sarg = new Class[1];
				Object [] arg= new Object[1];
				sarg[0]=Socket.class;
				try {
					java.lang.reflect.Constructor cons = clobj.getDeclaredConstructor(sarg);
					arg[0]=ssock.accept();
					cons.newInstance(arg); // 創建HttpProxy或其派生類的實例
				} catch (Exception e) { 
					Socket esock = (Socket)arg[0];
					try { esock.close(); } catch (Exception ec) {}
				}
			}
		} catch (IOException e) {
		}
    }
	
	
    // 測試用的簡單main方法
    static public void main(String args[]) {
		System.out.println("在端口808啟動代理服務器\n");
		HttpProxy.log=System.out;
		HttpProxy.logging=false;
		HttpProxy.startProxy(808,HttpProxy.class);
	}
}