import cs1705.*;
import java.io.*;


// -------------------------------------------------------------------------
/**
 *  A Rot-13 decryption class.
 *  This in-class demo is based on the Lab 06 assignment.
 *
 *  @author  Stephen Edwards
 *  @version 2003.10.07
 */
public class RotDecryptor
{
    //~ Instance/static variables .............................................



    //~ Constructor ...........................................................



    //~ Methods ...............................................................

    // ----------------------------------------------------------
    /**
     * Compute the Rot-13 version of the character (or return the character
     * unchanged if it is not a letter).
     * 
     * @ return the Rot-13 encoding of the character
     */
    public int rotateCharacter( int chr )
    {
        if ( Character.isLowerCase( (char)chr ) )
        {
            return ( chr - 'a' + 13 ) % 26 + 'a';
        }
        else if ( Character.isUpperCase( (char)chr ) )
        {
            return ( chr - 'A' + 13 ) % 26 + 'A';
        }
        else
        {
            return chr;
        }
    }


    // ----------------------------------------------------------
    /**
     * Read all input from the provided input stream, and write the
     * equivalent Rot-13 translation on the given output stream.
     * 
     * @param in   the input stream to read from
     * @param out  the output stream to write to
     */
    public void decrypt( BufferedReader in,
                         PrintWriter    out )
        throws Exception
    {
        int chr = in.read();
        while ( chr != -1 )
        {
            out.write( rotateCharacter( chr ) );
            chr = in.read();
        }
    }


    // ----------------------------------------------------------
    /**
     * Read all input from the provided input file, and write the
     * equivalent Rot-13 translation on the given output file.
     * 
     * @param inFile   the name of the file to read from
     * @param outFile  the name of the file to write to
     */
    public void decryptFile( String inFile, String outFile )
    {
        try
        {
            // First, set up the streams
            BufferedReader in  =
                IOHelper.createBufferedReader( inFile );
            PrintWriter    out =
                IOHelper.createPrintWriter( outFile );

            // Now, call the real operation to do the work
            decrypt( in, out );
            
            // Now clean up
            in.close();
            out.close();
        }
        catch ( Exception e )
        {
            e.printStackTrace();
        }
    }
}