#!/usr/bin/perl -w
#
#  Removes an empty folder $1, *without* prompting the user.
#
#  Case 1:  $1 is an empty folder (simple case) -- delete it.
#
#  Case 2:  $1 is not empty, but none of its contents or sub-contents
#           are files (only other empty folders) -- delete it.
#
#  Case 3:  $1 is not empty, and contains at least 1 file (or some folder
#           containing a file at some level) -- open the folder.
#
#  100829 John C. Norton -- created.
#  111230 John C. Norton -- finally got installation working!
##


###############
## Libraries ##
###############
use strict;
use warnings;
use File::Basename;
use File::Copy;
use IO::File;
use Win32::TieRegistry( Delimiter => '/' );


##################
## User-defined ##
##################
my $b_debug = 0;
my $label   = '* Remove Folder(s)';


#############
## Globals ##
#############
my $iam    = basename $0;
my $syntax = qq{
    syntax:  $iam  /install  <dir>
        or:  $iam  /uninstall

    Installs the $iam program into the specified directory <dir> and
    creates a right-click context menu entry "$label" to remove
    a selected folder if it is empty as well as any empty subfolders.  If a
    top-level folder is not empty, it is opened in Explorer so the user can
    see its contents.

    With the argument '/uninstall', the program is removed from the context
    menu instead.

};


##################
## Main Program ##
##################
my $dir = shift or die $syntax;

if ($dir eq '/uninstall') {
    my $h_shell = context_menu_uninstall();
    print "Uninstalled \"$label\"\n";
    exit;
}

if ($dir eq '/install') {
    my $location = shift or die "$iam:  must specify installation dir\n";
    (my $path = $location) =~ s|\\|/|g;
    copy("$0", $path);
    context_menu_install($location);
    print "Installed '$iam' as \"$label\"\n";
    exit;
}

# Quit if argument is not a dir (shouldn't get here though)
(-d $dir) or exit;    

if (remove_subfolders($dir)) {
    # Top folder is empty, so just remove it
    rmdir $dir;
} else {
    # Top folder is not empty; open it
    (chdir "$dir") or exit;    # Can't change to directory
    exec "start .";
}


#################
## Subroutines ##
#################

sub context_menu_uninstall {
    my $h_shell  = $Registry->{"Classes/Directory/shell"};
    my $key      = "$label/";
    delete_key($h_shell, $key);
    return $h_shell;
}


sub context_menu_install {
    my ($target) = @_;

    # Remove previous version (if any)
    my $h_shell = context_menu_uninstall();
    my $key     = "$label/";

    # Create new context menu
    $b_debug and print "[Adding Key '$key']\n";
    my $fullcmd = qq{cmd.exe /C $target\\$iam "%1"};
    $h_shell->{$key} = { "command/" => { "/" => $fullcmd } };
}


sub delete_key {
    my ($h_keys, $key) = @_;

    if ($key =~ m|/$|) {
        my $h_subkey = $h_keys->{$key};
        if (ref $h_subkey) {
            map { delete_key($h_subkey, $_) } keys %$h_subkey;
        }
        $b_debug and print "[Deleting Key '$key']\n";
        delete $h_keys->{$key};
    } else {
        $b_debug and print "[Deleting Data '$key']\n";
        delete $h_keys->{$key};
    }
}


#
#  Inputs:   $1: a folder name
#  Outputs:  Nonzero if all subfolders of the given folder were removed,
#            (ie. no files were found at any level), zero otherwise.
#
sub remove_subfolders {
    my ($dir) = @_;

    my $b_empty = 1;
    my @empty   = ( );
    my $fh = new IO::File;

    opendir($fh, $dir) or exit;
    my @files = readdir($fh);
    closedir $fh;

    foreach my $file (@files) {
        next if ($file eq '.' or $file eq '..');
        my $path = "$dir/$file";
        if (!-d $path) {
            # Not a folder; parent folder is not empty
            $b_empty = 0;
        } else {
            # It's a folder
            if (!remove_subfolders($path)) {
                $b_empty = 0;
            } else {
                push @empty, $path;
            }
        }
    }

    # Remove all empty subfolders
    foreach my $path (@empty) {
        (rmdir $path) or $b_empty = 0;
    }

    return $b_empty;
}