package MTdownload;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.net.*;
import java.io.*;

public class DLFrame extends JFrame{
	private JPanel contentPane;
	private TextField textField1 = new TextField();//輸入url和端口
	private TextField textField2 = new TextField();//輸入保存路徑
	private Button button = new Button();//啟動下載活動的按鈕
	private Label label1 = new Label();//提示輸入下載的url
	private Label label2 = new Label();//提示輸入保存路徑和文件名
    private TextArea textArea = new TextArea();//輸出用戶交互的提示信息
	private String dlURL = new String();//要下載的目標文件的完整url
	private String saveFileAs = new String();//文件保存的路徑和名稱
	
	public DLFrame() {
		enableEvents(AWTEvent.WINDOW_EVENT_MASK);
		try{
			toInit();	
		}
		catch(Exception e){
			e.printStackTrace();
		}
	}
	
	private void toInit() throws Exception{//初始化窗體
		contentPane = (JPanel) this.getContentPane();
		contentPane.setLayout(null);
		this.setSize(new Dimension(380,320));
		this.setTitle("多線程下載");
		textField1.setBounds(new Rectangle(150,200,200,20));
		textField1.setText("http://localhost:8080/try.rar");
		textField2.setBounds(new Rectangle(150,240,150,20));
		textField2.setText("f:\\temp\\try.rar");
		label1.setBounds(new Rectangle(20,200,120,20));
		label1.setText("下載的目標文件為:");
		label2.setBounds(new Rectangle(20,240,120,20));
		label2.setText("下載的文件另存為:");
		button.setBounds(new Rectangle(310,240,40,20));
		button.setLabel("下載");
		button.addActionListener(new java.awt.event.ActionListener() {
      		public void actionPerformed(ActionEvent ee) {
        		button_actionPerformed(ee);
      		}
    	});
    	textArea.setBounds(new Rectangle(20,20,330,170));
    	textArea.setEditable(false);
    	contentPane.add(textField1,null);
    	contentPane.add(textField2,null);
    	contentPane.add(label1,null);
    	contentPane.add(label2,null);
    	contentPane.add(button,null);
    	contentPane.add(textArea,null);
    	
    	dlURL = "http://localhost:8080/try.rar";//默認的下載目標
    	saveFileAs = "f:\\temp\\rar.zip";//默認的存儲位置和名字
	}
	
	protected void processWindowEvent(WindowEvent e){
		super.processWindowEvent(e);
		if (e.getID() == WindowEvent.WINDOW_CLOSING){
			System.exit(0);	
		}	
	}
	
	void button_actionPerformed(ActionEvent ee){//啟動下載文件的主線程
		try{
			dlURL = textField1.getText();
			saveFileAs = textField2.getText();
			if(dlURL.compareTo("") == 0 && saveFileAs.compareTo("") == 0 ) {
				textArea.setText("請輸入要下載的文件和保存文件完整地址\n然后點擊下載鍵重新下載");
			}
			else{
				DownFile fileFetch = new DownFile(dlURL,saveFileAs,5,textArea);
				fileFetch.start();	
				textArea.append("\n主線程啟動....");
			}
		}
		catch(Exception e){
			e.printStackTrace ();
			textArea.append("\nError0:" + e);	
		}
	}
}


class DownFileSplitter extends Thread {
  String dlURL; 										// 定義文件傳輸時服務器的URL
  long startPos; 									// 分段的開始位置
  long endPos; 									// 分段的結束位置
  int threadID; 									// 子線程ID
  TextArea textArea = new TextArea();
  boolean done = false;						 // 文件傳輸完成
  boolean stop = false; 							// 文件傳輸被終止
  RandomAccessFile file;

  public DownFileSplitter(String dlURL,String saveAs,long nStart,long nEnd,int id,TextArea textArea) throws IOException{
    this.dlURL = dlURL;
    this.startPos = nStart;
    this.endPos = nEnd;
    threadID = id;
	this.textArea = textArea;
    file = new RandomAccessFile(saveAs,"rw");
    file.seek(startPos);
  }

  public void run(){
    while(startPos < endPos && !stop){
      try{
        URL url = new URL(dlURL);
        HttpURLConnection httpConnection = (HttpURLConnection)url.openConnection ();
        String sProperty = "bytes="+startPos+"-";
        httpConnection.setRequestProperty("RANGE",sProperty);//請求傳輸的開始位置
        System.out.println("線程" + threadID + " 下載文件......請等待" );
        textArea.append("\n線程" + threadID + "下載文件......請等待");
        InputStream input = httpConnection.getInputStream();
        byte[] b = new byte[1024];
        int offset;
        offset = (int)endPos - (int)startPos;
        if(offset>1024) offset = 1024;
        while(input.read(b,0,offset)> 0 && startPos < endPos && !stop){
          offset = (int)endPos - (int)startPos;
          if(offset>1024) offset = 1024;
          System.out.println("started " + startPos + " offset: " + offset);
          file.write(b,0,offset);
          startPos += offset;//下一次開始寫的位置
        }
        System.out.println("線程 " + threadID + " 下載完畢!!");
        done = true;
        textArea.append("\n線程" + threadID + " 下載完畢！");
        file.close();
      }
      catch(Exception e){
        e.printStackTrace ();
      }
    }
  }

  public void splitterStop(){
    stop = true;
  }
}


class DownFile extends Thread {   // 傳輸文件線程類
  String dlURL;
  String saveFileAs;
  int nthread;
  String info = new String();
  TextArea textArea = new TextArea();
  
  long[] position;
  long[] startPos; //開始位置
  long[] endPos; //結束位置
  DownFileSplitter[] downFileSplitter; //子線程對象
  long fileLength; //文件長度
  boolean stop = false; //停止標志
  DataOutputStream output; //輸出到文件的輸出流

  public DownFile(String sURL,String saveFileAs,int nthread,TextArea textArea) throws IOException{
    this.dlURL = sURL;
    this.saveFileAs = saveFileAs;
    this.nthread = nthread;
    this.textArea = textArea;

    startPos = new long[nthread];//各個線程的開始位置
    endPos = new long[nthread];//各個線程的結束位置
  }

  public void run(){
    info = "目標文件: " + dlURL;
    System.out.println(info);
    textArea.append("\n" + info);
    info = "文件存為: " + saveFileAs;
    System.out.println(info);    
    textArea.append("\n" + info);
    info = "\n線程總數: " + nthread;
    System.out.println(info);
    textArea.append("\n" + info);
    
    try{
        fileLength = getFileSize();
        if(fileLength == -1){
          System.err.println("不可知的文件長度!");
          textArea.append("\n不可知的文件長度");
        }
        else
          if(fileLength == -2){
            System.err.println("文件無法獲取!");
            textArea.append("\n文件無法獲取");
          }
          else{
            for(int i=0;i<startPos.length;i++){//文件劃分成和進程數相同的小塊
              startPos[i] = (long)(i*(fileLength/startPos.length));
            }
            for(int i=0;i<endPos.length-1;i++){
              endPos[i] = startPos[i+1];
            }
            endPos[endPos.length-1] = fileLength;
            for(int i=0;i<startPos.length;i++){
              info = "線程" + i + " 下載范圍： " + startPos[i] + " -- " +endPos[i];
              System.out.println(info);
              textArea.append("\n" + info);
      		}
          }

      downFileSplitter = new DownFileSplitter[startPos.length];//啟動一組子線程
      for(int i=0;i<startPos.length;i++){
        downFileSplitter[i] = new DownFileSplitter(dlURL,saveFileAs,startPos[i],endPos[i],i,textArea);
        info = "線程" + i + " 啟動";
        textArea.append("\n" + info);
        downFileSplitter[i].start();
        System.out.println(info);
        
      }
 
      boolean breakWhile = false;
      while(!stop){//等待整個下下載過程結束
        Thread.sleep(500);
        breakWhile = true;
        for(int i=0;i<startPos.length;i++){//檢測每條線程都已經完成則整個下載完成
          if(!downFileSplitter[i].done){
          breakWhile = false;
          break;
        }
      }
      if(breakWhile)
        break;
      }
      System.out.println("文件傳輸結束！");//文件傳輸結束
      textArea.append("\n文件傳輸結束！");
    }
    catch(Exception e){
      e.printStackTrace ();
    }
  }

  
  public long getFileSize(){//獲得文件長度
    int fileLength = -1;
    try{
      URL url = new URL(dlURL);
      HttpURLConnection httpConnection = (HttpURLConnection)url.openConnection ();
      int responseCode=httpConnection.getResponseCode();
      if(responseCode>=400){
        processErrorCode(responseCode);
        return -2; //Web服務器響應錯誤
      }
      String sHeader;
      for(int i=1;;i++){//查找標識文件長度的文件頭，獲取文件長度
        sHeader=httpConnection.getHeaderFieldKey(i);
        if(sHeader!=null){
          if(sHeader.equals("Content-Length")){
            fileLength = Integer.parseInt(httpConnection.getHeaderField(sHeader));
            break;
          }
        }
        else
          break;
      }
    }
    catch(IOException e){e.printStackTrace ();}
    catch(Exception e){e.printStackTrace ();}
    return fileLength;
  }

  private void processErrorCode(int nErrorCode){
    System.err.println("Error Code : " + nErrorCode);
  }

  //停止文件傳輸
  public void siteStop(){
    stop = true;
    for(int i=0;i<startPos.length;i++)
      downFileSplitter[i].splitterStop();
  }
}