/* StringsDemo.java
 *
 * This program implements a number of simple string-processing operations for
 * text files.  Upon startup, the user is prompted to choose a particular
 * operation, and then is prompted for the file specification for the input
 * file and for additional parameters as appropriate.  The output is written
 * to standard output.
 *
 * Copyright (c) 2000, 2004 - Russell C. Bjork
 *
 */

import java.io.*;
import javax.swing.*;
import java.awt.event.*;

public class StringsDemo
  {
	/** Search the specified file for all occurrence of the specified
	 *  pattern, printing each such line to standard output
	 *
	 *  @param source the file to search
	 *  @param pattern the pattern to search for
	 *
	 *  This search is case sensitive
	 */
	 
	public static void search(BufferedReader source, String pattern)
			throws IOException
	{
		System.out.println("Starting results of search");
	  	String line = source.readLine();
	  	while (line != null)
	  	{ 
	  	    if (line.indexOf(pattern) >= 0)
	  	    	System.out.println(line);
	  	    line = source.readLine();
	  	}
	  	System.out.println("Done");
	  	System.out.println();
	}
	  
	/** Search the specified file for all occurrence of the specified
	 *  pattern, printing each such line to standard output
	 *
	 *  @param source the file to search
	 *  @param pattern the pattern to search for
	 *
	 *  This search is not case sensitive
	 */
	 
	public static void searchIgnoreCase(BufferedReader source, String pattern)
			throws IOException
	{
		System.out.println("Starting results of case insensitive search");
		pattern = pattern.toUpperCase();
	  	String line = source.readLine();
	  	while (line != null)
	  	{ 
	  	    if (line.toUpperCase().indexOf(pattern) >= 0)
	  	    	System.out.println(line);
	  	    line = source.readLine();
	  	}
	  	System.out.println("Done");
	  	System.out.println();
	}
	  
	/** Substitute a specified replacement for all occurrences of a
	 *	specified pattern within a specified file, writing the modified
	 *  file to standard output
	 *
	 *	@param source the file to search
	 *	@param pattern the pattern to search for
	 *	@param replacement the text to replace it with
	 *
	 *  The search process is case sensitive
	 */
	 
	public static void substitute(BufferedReader source, 
								  String pattern, 
								  String replacement)  throws IOException
	{
		System.out.println("Starting results of substitute");
	  	String line = source.readLine();
	  	while (line != null)
	  	{
			// Replace each occurrence of pattern in the line
			
	  	  	int index = line.indexOf(pattern);
	  	  	while (index >= 0)
	  	  	{
	  	  	  	line = line.substring(0, index) +
	  	  	  		   replacement +
	  	  	  		   line.substring(index + pattern.length(), line.length());
	  	  	  	// Search for next occurrence of pattern, beginning at index + 
	  	  	  	// replacement.length() in case pattern occurs in replacement
	  	  	  	index = line.indexOf(pattern, index + replacement.length()); 
	  	  	}

			// Output the line with any changes that may have been made
			
	  	  	System.out.println(line);
	  	  	
	  	  	// Move on to the next line
	  	  	
	  	  	line = source.readLine();
	  	}
	  	System.out.println("Done");
	  	System.out.println();
	}

	/** Print all the individual words occurring in a specified file, one per
	 *  line, writing the words to standard output
	 *
	 *	@param source the file to break up into words
	 *
	 *	Note: A word is considered to be a sequence of 1 or more alphabetic
     *	characters and/or digits.  Anything else (spaces, punctuation etc.)
     *	is considered to be separators and is not displayed.
	 */
	 
	public static void listWords(BufferedReader source)
			throws IOException
	{
		System.out.println("Starting list of words");
	  	String line = source.readLine();
	  	while (line != null)
		{
		  	// Iterate through line one word at a time.  start marks the 
		  	// beginning position of a word, finish the first character after
		  	// its end
		  	
		  	int start = 0, finish = 0;
		  	while (start < line.length())
		  	{
		  	  	// Find start of next word (next letter, if any)
		  	  	
		  	  	while (start < line.length() && 
		  	  			! Character.isLetter(line.charAt(start)))
		  	  		start ++;
		  	  		
		  	  	// Find finish of this word (next non-letter, if any)
		  	  	
		  	  	finish = start;
		  	  	while (finish < line.length() && 
		  	  			Character.isLetter(line.charAt(finish)))
		  	  		finish ++;
		  	  		
		  	  	// If we found a real word (not some spaces or punctuation at
		  	  	// the end of the line), then output it
		  	  	
		  	  	if (finish > start)
		  	  		System.out.println(line.substring(start, finish));
		  	  		
		  	  	// Next word begins where this one left off
		  	  	
		  	  	start = finish;
			  }
			
			// Move on to next line
			
			line = source.readLine();
		}
	  	System.out.println("Done");
	  	System.out.println();
	}    

    /** Main method.  Get the user's choice of operation and necessary 
     *	information, then call on the appropriate method to do it.
     *
     */
     
    public static void main(String args[]) throws FileNotFoundException, IOException
    {
		// Create the GUI
		
        final JFrame mainWindow = new JFrame("Strings Demo");
        mainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainWindow.getContentPane().setLayout(new BoxLayout(
        	mainWindow.getContentPane(), BoxLayout.Y_AXIS));
        mainWindow.getRootPane().
        	setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));

		JButton searchButton = new JButton("Search for a pattern");
		mainWindow.getContentPane().add(searchButton);
		searchButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event)
			{
				try
				{
					BufferedReader source = getFile(mainWindow);
					if (source == null) return;
					String pattern = JOptionPane.showInputDialog(
						mainWindow, "Pattern to search for");
					if (pattern == null) return;
					search(source, pattern);
				}
				catch(Exception exception)
				{
					exception.printStackTrace();
				}
			}
		});
		
		JButton caseInsensitiveSearchButton = 
							new JButton("Ditto - case insensitive");
		mainWindow.getContentPane().add(caseInsensitiveSearchButton);
		caseInsensitiveSearchButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event)
			{
				try
				{
					BufferedReader source = getFile(mainWindow);
					if (source == null) return;
					String pattern = JOptionPane.showInputDialog(
						mainWindow, "Pattern to search for");
					if (pattern == null) return;
					searchIgnoreCase(source, pattern);
				}
				catch(Exception exception)
				{
					exception.printStackTrace();
				}
			}
		});
		
 		JButton substituteButton =  
 							new JButton("Substitute for a pattern");
		mainWindow.getContentPane().add(substituteButton);
		substituteButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event)
			{
				try
				{
					BufferedReader source = getFile(mainWindow);
					if (source == null) return;
					String pattern = JOptionPane.showInputDialog(
						mainWindow, "Pattern to search for");
					if (pattern == null) return;
					String replacement = JOptionPane.showInputDialog(
						mainWindow, "Replacement");
					if (replacement == null) return;
					substitute(source, pattern, replacement);
				}
				catch(Exception exception)
				{
					exception.printStackTrace();
				}
			}
		});
		
 		JButton listButton =  new JButton("List words");
		mainWindow.getContentPane().add(listButton);
		listButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event)
			{
				try
				{
					BufferedReader source = getFile(mainWindow);
					if (source == null) return;
					listWords(source);
				}
				catch(Exception exception)
				{
					exception.printStackTrace();
				}
			}
		});
		
		mainWindow.pack();
		mainWindow.show();		
    }

	// Auxillary to above - get a file choice from user, then open
	// the specified file.  Return null if the user cancels
	
	private static BufferedReader getFile(JFrame parent) 
						throws FileNotFoundException, IOException
    {
		JFileChooser chooser = new JFileChooser(System.getProperty("user.dir"));
		if (chooser.showOpenDialog(parent) == JFileChooser.APPROVE_OPTION)
		{
			return new BufferedReader(new FileReader(
										chooser.getSelectedFile()));
		}
		else
			return null;
	}
}