import java.io.*;
import java.util.*;
import javax.swing.*;

/** Class to demo reading of files */
public class Reading {
    
    /** Yields: the number of lines in a file chosen by the caller */
    public static int lines() throws IOException {
        BufferedReader bf= getReader(null);
        String lin= bf.readLine();
        int n= 0;
        // invariant: n is the number of lines that precede line lin, and
        //            lin is the next line to process (null if no more).
        while (lin != null) {
            // Process line lin
            n= n + 1;
            
            lin= bf.readLine();
        }
        
        return n;
    }
    
    /** Yields: "a line of a file chosen by the user contains s" */
    public static boolean contains(String s) {
        return false; // STUB RETURN.  Replace.
    }
    
    
    /** Obtain a file name from the user using a JFileChooser
     *  and return a reader that is linked to it. If p is not null
     *  (it can be), start the JFileChooser at the path given by p*/
    public static BufferedReader getReader(String p) {
        try {
            JFileChooser jd;
            if (p == null) {
                jd= new JFileChooser();
            }
            else {
                jd= new JFileChooser(p);
            }
            jd.setDialogTitle("Choose input file");
            jd.showOpenDialog(null);
            
            FileReader fr= new FileReader(jd.getSelectedFile());
            return new BufferedReader(fr);
        }
        catch (IOException e) {
            return null;
        }
    }
    
    /** Obtain a file name from the user, using a JFileChooser, and return
     *  a PrintStream that is linked to it. Return null if the user cancels. */
    public static PrintStream getWriter() throws IOException {
        JFileChooser jd= new JFileChooser();
        jd.setDialogTitle("Choose output file");
        jd.showSaveDialog(null);
        File f= jd.getSelectedFile();
        if (f == null) {
            return null;
        }
        return new PrintStream(new FileOutputStream(f));
    }
    
    /** Read in a file of Peoplesoft netids for CS1110 and a file of CMS
     *  netids for CS1110 (both using a JFileChooser to retrieve the files).
     *   
     *  Obtain from the user an output file name to write (using a JFileChooser)
     * 
     *  Write on the output file all netids that are in both input files.
     * 
     *  Precondition: both files are in sorted order. */
    public static void netIds() throws IOException {
        /*Note: We give a series of comment-statements stating what the body is to do.
                Implement each comment-statement UNDERNEATH that comment-statement. and
                put a blank line after the implementation. This way, you can read the
                program on two levels --the high-level comment-statements or their
                implementations. */
        
        // Obtain a BufferedReader peop for the Peoplesoft file.
        
        
        
        // Obtain a BufferedReader cms for the cms file.
        
        
        
        // Obtain a PrintStream out for the output file.
        
        
        
        // Loop through the two input files in a kind of synchronized
        // fashion (remember, they are sorted), and put the lines
        // that are in both of them on file out, using out.println(...);
        
        
        
        
      
        
        // Close file out
        
        
    }
}