/* Author: Julie Romm
 * Course: COM3336
 * Professor: Karl Lieberherr
 * Homework 3, part 2
 */
 
 /* File: URLDiffThread.java
  * Classes implemented: URLDiffThread
  *
  * Purpose:
  *   This class compares to files using UNIX diff command.
  *   The result of the comparison is written into a file.
  *   In case diff produces output, the EMail object is
  *   instantiated, and the diff file is sent to the
  *   RECIPIENT (a constant defined in WebWatch.java)
  *   After that, the diff file is removed.
  */
 
 
import java.io.*;

public class URLDiffThread extends Thread{
  private String oldname;
  private String newname;
  private String diffname;
  private String filename;
  private Process p;
  private Runtime r;
  private BufferedWriter bw;
  
  public URLDiffThread(String filename) {
    this.filename = filename;
    oldname = filename + ".old";
    newname = filename + ".new";
    diffname = filename + ".diff";
  }

  public void run() {
    r = Runtime.getRuntime();
    try {p = r.exec("diff " + oldname + " " + newname);}
    catch (IOException e) {
      System.err.println("URLDiffThread: error: " + e);
    }

    try { bw = new BufferedWriter(new FileWriter(diffname));}
    catch (IOException e){}; 
    
    //need to capture the output of the command into the file
    InputStream is = p.getInputStream();
    try {
      int i = is.read();
      while (i != -1) {
      	bw.write(i);
        i = is.read();
      }
      bw.close();
    }
    catch (IOException e){};

    File difffile = new File(diffname);
    //for debug: System.out.println(difffile.length());
	if (difffile.length() != 0) {
	  sendEMail(filename);
	  System.out.println("Mail was sent to " + WebWatch.RECIPIENT);
	}
	else
	  System.out.println("WebWatch detected no changes in http://" + filename);
	  
	//remove the diff file
	difffile.delete();
  }
  
  private void sendEMail(String filename) {
    try {
	  BufferedReader br = new BufferedReader(new FileReader(filename + ".diff"));
	  EMail email = new EMail();
	
	  System.out.println("WebWatch detected changes in http://" + filename);
	  email.sendMail( WebWatch.MAILSERVER, WebWatch.SENDER, WebWatch.RECIPIENT,
                    "WebWatch detected changes in http://" + filename, br);
      } catch (FileNotFoundException e) {
	    System.out.println("Error: File not found: " + filename);
      }
  } //sendEMail  
}  //URLDiffThread