/*
 * Copyright (c) 2001 Matthew Feldt. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided the copyright notice above is
 * retained.
 *
 * THIS SOFTWARE IS PROVIDED ''AS IS'' AND WITHOUT ANY EXPRESSED OR
 * IMPLIED WARRANTIES.
 */

/**
 * DirectoryList.java
 *
 * Java Examples In A Nutshell Copyright (c) 2000 David Flanagan
 * Exercise 3-5:
 * Write a program that lists all of the files and subdirectories in a
 * specified directory, along with their sizes and modification dates.
 * By default, the output should be sorted by name. If invoked with the
 * -s option, however, output should be sorted by size from largest to
 * smallest. If invoked with the -d option, output should be sorted by
 * date, from most recent to least. Use the sort() method of
 * java.util.Collections to help with the sorting.
 *
 * @author Matthew Feldt <developer@feldt.com>
 * @version 1.0, 01/31/2001 22:18
 */

package com.feldt.examples.io;
import java.lang.*;
import java.io.*;
import java.util.*;
import java.text.*;

class DirectoryList {
	/** implementation of Comparator that sorts by file size */
	static class FileSizeComparator implements Comparator {
		public int compare(Object a, Object b) {
			return (int)(((File)a).length() - ((File)b).length());
		}

		public boolean equals(Object a) {
			return (compare(this, a) == 0);
		}
	}

	/** implementation of Comparator that sorts by file modification time */
	static class FileDateComparator implements Comparator {
		public int compare(Object a, Object b) {
			return (int)(((File)a).lastModified() - ((File)b).lastModified());
		}

		public boolean equals(Object a) {
			return (compare(this, a) == 0);
		}
	}

	/**
	 * Static method to print a pleasing list of files and subdirectories
	 * from a specified directory sorted by name, date or size.
	 */
	public static void printList(File dir, int sortby)
			throws IllegalArgumentException {
		final int WIDTH = 13;
		final char[] spaces = "             ".toCharArray();
		SimpleDateFormat df = new SimpleDateFormat("MM/dd/yyyy  hh:mm:ss a  ");
		DecimalFormat nf = new DecimalFormat("#,##0  ");
		StringBuffer result;
		FieldPosition pos = new FieldPosition(NumberFormat.INTEGER_FIELD);
		List dirList = new Vector();
		long total = 0;

		// validate directory argument
		if (! dir.exists())
			throw new IllegalArgumentException(dir + " does not exist.");
		if (! dir.canRead())
			throw new IllegalArgumentException(dir + " read protected.");

		// populate List with files from the specified directory
		File[] entries = dir.listFiles();
		for (int i = 0; i < entries.length; i++) {
			dirList.add(entries[i]);
		}

		// determine which sort to use and sort List
		switch (sortby) {
			case 0:
				java.util.Collections.sort(dirList);
				break;
			case 1:
				java.util.Collections.sort(dirList, new FileSizeComparator());
				break;
			case 2:
				java.util.Collections.sort(dirList, new FileDateComparator());
				break;
		}

		// print the result using SimpleDateFormat and DecimalFormat
		// to condition the output
		for (int i = 0; i < dirList.size(); i++) {
			result = new StringBuffer(32);
			File f = (File)dirList.get(i);
			System.out.print(df.format(new Date(f.lastModified()))); // date

			if (f.isDirectory()) System.out.print(" <DIR> "); // directory
			else System.out.print("       ");

			nf.format(f.length(), result, pos); // size
			if (pos.getEndIndex() < WIDTH) // align with spaces if necessary
				result.insert(0, spaces, 0, WIDTH-pos.getEndIndex());
			System.out.print(result);
			System.out.println(f.getName()); // name
		}
	}

	/** test class */
	static class Test {
		public static void main (String args[]) {
			final String usage = "Usage: java DirectoryList$Test [[-s] || [-d]] dir";
			int sortby = 0, fileNameIndex = 0;

			switch (args.length) {
				case 1: {
					// use option and fileNameIndex defaults
					break;
				}
				case 2: {
					if (args[0].equals("-s")) { // sort by size
						sortby = 1;
						fileNameIndex = 1;
						break;
					} else if (args[0].equals("-d")) { // sort by date
						sortby = 2;
						fileNameIndex = 1;
						break;
					} // otherwise fall through to the error message
				}
				default: {
					System.err.println(usage);
					System.exit(-1);
				}
			}

			// print the directory listing
			DirectoryList.printList(new File(args[fileNameIndex]), sortby);
		}
	}
}