#!/usr/bin/perl -w

#
# Reads contents of a directory
# in array context.
#
# Usage:
#  readdir4.pl source_directory, destination_directory
#

use File::Copy;

# remove the comment below if you want to read in the directory from and arg 
 $name1 = $ARGV[0];
 $name2 = $ARGV[1];
 

opendir(SOURCE, $name1)
			 or die "Can't open $name1 due to $!";
@source_entries = readdir(SOURCE);

closedir(SOURCE);

# Lets get the destination now
		 
opendir(DESTINATION, $name2)
			 or die "Can't open $name2 due to $!";
			 
@dest_entries = readdir(DESTINATION); 

closedir (DESTINATION);

# Sort Results.
@sourcesorted = sort(@source_entries);
@destsorted = sort (@dest_entries);

# Make a hash out of them
foreach $filename1 (@sourcesorted) {
		%hashsource = ($filename1,$filename1);
}

foreach $filename2 (@destsorted) {
		%hashdest = ($filename2,$filename2);
}

# At this point we have two sorted arrays that we can use to do compares with
# The idea now is to compare Source with Destination first.
# If the file exist in Source and not in Destination then copy it over to Destination
# If the file exist in both then do nothing.
# Then compare Destination with Source. If the file exist in Destination and not in source
# then erase it from Destination.

# this routine will seperate all the files into two arrays
    @union = @intersection = @difference = ();
    %count = ();
    foreach $element (@sourcesorted, @destsorted) { $count{$element}++ }
    foreach $element (keys %count) {
        push @union, $element;
        push @{ $count{$element} > 1 ? \@intersection : \@difference }, $element;
    }

# Sorting the difference array
@diffsorted = sort(@difference);
	
# Now lets compare the files. We can ignore all the files in the intersection list
# and compare only the files in the difference list.
# The trick is to use the @difference array correctly


foreach $filename (@diffsorted) {
		# now that we are going through each element in the @difference array lets
		# do some checking.
		# Now for every file in the sorted source list see if it is not equal to a file
		# file in the differences list. If it is in the differences list and it is not in the
		# source list then it should be deleted from the destination directory.
		
		unless ( exists $hashdest{$filename}){
		   if ( exists $hashsource{$filename}){
		   print "$filename exist in the source directory.\n";
		   print "Not in the destination directory, so copy it.\n\n";
		   
		   #now to do actual work in here.
		   chdir($name1);
		   print "Now copying, $filename.\n";
		   #copy($filename,$name2.$filename) or die
		   #		"Can't copy $filename to $name2$filename due to $!.\n";
		   }
		   } 
		   
}

foreach $filename (@diffsorted) {
		# continuation of above test. This one checks for stragglers in the
		# destination directory
		
		if ( exists $hashdest{$filename}){
			   unless ( exists $hashsource{$filename}) {
		   	   print "$filename exist in destination directory.\n";
		   	   print "Not in the source directory, so delete it. \n\n";
			   # Lets change to the right directory
			   # chdir($name2);
			   # and delete
			   unlink($name.$filename);
			   print "Deleted $filename.\n";
		   	   }
		}
}
foreach $entry (@sourcesorted) {
		print "Source: \t$entry\n";
}

foreach $entrydest (@destsorted) {
		print "Destination: \t$entrydest\n";
}

foreach $entryinter (@intersection) {
		print "Intersection: \t$entryinter\n";
}

foreach $entrydiff (@diffsorted) {
		print "Differences: \t$entrydiff\n";
}


# readdir4.pl