import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;

import javax.swing.JFileChooser;

import interfaces.*;

/**
 * An input iterator for City objects from file input.
 * 
 * @(#)TraversalInFile 22 March 2006
 * @author Viera K. Proulx
 */
public class TraversalInFile implements Traversal<City>{

  /*-------------------------------------------------------- 
   Member data
   *------------------------------------------------------*/

  /** the input reader */
  protected BufferedReader buffer;

  /** one line of input at a time */
  protected String line;

  /** a city object to hold values */
  protected City c;

  /** determines whether the general dialog has been closed */
  protected boolean closed = true;

  /** determines whether new city data has been submitted */
  protected boolean submitted = false;

  /*-------------------------------------------------------- 
   Constructor
   *------------------------------------------------------*/    
  /**
   * Select a file from which the data will be read, make sure 
   * it can be opened. 
   */
  public TraversalInFile() {

    /** build a file chooser 
     and have the user choose a file, 
     quitting this operation 
     if the user cancelled the choice */
    JFileChooser chooser = new JFileChooser(".");

    /** set the file extension to be .txt */
    //chooser.setFileFilter(new FileView.ExtensionFileFilter("txt"));

    closed = false;

    /** see if file was selected - quit if user canceled */
    if (chooser.showOpenDialog(null) != JFileChooser.APPROVE_OPTION){
      closed = true;
      return;
    }
    try{
      buffer = new BufferedReader(
          new FileReader(chooser.getSelectedFile()));
    }
    catch(FileNotFoundException e){
      System.out.println("File not found exception: " + e);
      closed = true;        
    }


    /** read one line of input from the selected file */
    /** and extract values for the first city */
    getnext();
  }
  
  /*--------------------------------------------------------
   Methods to implement the Traversal interface
   *------------------------------------------------------*/

  /** process next item, if available */
  public void getnext() {

    if (!closed)
      try{
        if (buffer.ready()){

          line = new String(buffer.readLine());
          if ((line == null)||(line == "")){     
            buffer.close();
            closed = true;
          }
          else{ 
            read(line);
          }            
        }
        else{
          buffer.close();
          closed = true;
        }
      }
    catch(Exception e) {
      System.out.println("Error in reading line exception: " + e);
      closed = true;
    }

  }

  /** produce a traversal for the rest of this list */
  public Traversal<City> getRest(){
    getnext();
    return this;
  }

  /** return the most recent submission - if available */
  public City getFirst() {

    if (!closed)
      return c;
    else{
      closed = true;
      return null;
    }
  }

  /** verify that new submission is available */
  public boolean isEmpty() {
    return (closed); 
  }

  /** extract next City object from the input string */
  public void read(String s){

    try {
      c = new City();
      c.fromStringData(line);
    }
    catch(java.text.ParseException e){
      System.out.println(e.getMessage() + 
          " parse exception in line\n" + 
          line);
      c = null;
      closed = true;
    }

  }

  /** Self Test */
  public static void main(String argv[]){

    System.out.println("Examples of CitiesList-s:");
    Traversal<City> tr = new TraversalInFile();

    while (!tr.isEmpty()){
      System.out.println(tr.getFirst().toString());
      tr = tr.getRest(); 
    }
    System.out.println("End of the list.");
  }
}