/* Author: Julie Romm
 * Course: COM3336
 * Professor: Karl Lieberherr
 * Homework 3, part 2
 */
 
 /* File: URLThread.java
  * Classes implemented: URLThread
  *
  * Purpose:
  *   This class attempts to access the URL object constructed with urlpath.
  *   Once the connections is successfully made, the HTML source code of the
  *   page is writen into a file.  Also, the run method of this class 
  *   instantiate URLDiffThread object, and starts its run() method,
  *   which determines whether the current version of this page differs
  *   from the previous one.
  */
  
import java.io.*;
import java.util.*;
import java.net.*;

public class URLThread extends Thread {
  private String urlpath;
  private boolean status = false;
  private URL url;
  private BufferedReader br;
  private BufferedWriter bw;
  private String filename;
  private File oldfile;
  private File newfile;
  private Process p;
  private Runtime r;
  private String line;

  //constructor
  public URLThread (String urlpath) {
    this.urlpath = urlpath;
    filename = urlpath.substring(7);
    oldfile = new File(filename + ".old");
    newfile = new File(filename + ".new");
  }

  //public accessor
  public boolean getStatus() {
    return status;
  }

  public synchronized void run() {
    //System.out.println("URLThread: starting run()");
    try {url = new URL(urlpath);}
	catch (MalformedURLException e){};
    
	
    //The following  fragment of code renames 
    //the new file into old file
    r = Runtime.getRuntime();
    try {p = r.exec("mv " + newfile.toString() + " " + oldfile.toString());}
    catch (IOException e) {
      System.err.println("URLThread: Error: " + e);
    }

    try {
    br = new BufferedReader(new InputStreamReader(url.openConnection().getInputStream()));
    bw = new BufferedWriter(new FileWriter(filename + ".new"));
    }
    catch (IOException e){};

    //access the url and retrieve the html source code of the page
    while (br == null) {
      try {
      br = new BufferedReader(new InputStreamReader(url.openConnection().getInputStream()));
      }
      catch (IOException e){};
      if (isInterrupted()) {
        status = false;
        return;
      }
    }      

    //write the source code of the page into a file
    String line;
    try {
      while ((line = br.readLine()) != null) {
        //System.out.println(line);
        bw.write(line + "\n");
      }//while
      bw.close();
      br.close();
    } //try
    catch (IOException e){};
	
    System.out.println("URLThread: successfully retrieved " + urlpath);
	//diff it with the previous version of this page
    URLDiffThread dm = new URLDiffThread(filename);
    dm.start();
    status = true;

  }//run
}//URLThread