#!perl

use warnings;
use strict;
use Tk;
use Tk::Tree;

my $rootPath = shift;

ShowHelp() if !defined $rootPath;
ShowHelp( -2, "Error finding folder $rootPath\n\n" ) if !-d $rootPath;

my $main = MainWindow->new( -title => "Folder stats for $rootPath" );
my $tree = $main->ScrlTree(
    #-font      => 'FixedSys 8',
    -itemtype  => 'text',
    -separator => '/',

    #  Having scrollbars-only-when-needed-option, 'o', does not make the
    #  scrollbars appear when the content overflows display area (FreeBSD
    #  6-STABLE & Tk-804.027).
    -scrollbars => 'sw'
);

my @pathStack  = (1);
my $maxNesting = 0;
my $totalLines;
my $maxLineLength = 0;
my $currPath      = join "/", @pathStack;

$tree->add( $currPath, -text => $rootPath );
my ( $subDirCount, $subFileCount, $subTotalSize ) =
  buildSubTree( $tree, $rootPath, \@pathStack, \$maxNesting, \$totalLines,
    \$maxLineLength );
$tree->entryconfigure( $currPath,
    -text => annotate( $rootPath, $subDirCount, $subFileCount, $subTotalSize )
);

$totalLines = 40 if $totalLines > 40;
$main->geometry(
    ( $maxLineLength + @pathStack * 4 ) * 5 . 'x' . ( 40 + $totalLines * 20 ) );
closeTree( $tree, '' );

$tree->pack( -fill => 'both', -expand => 1 );

MainLoop;

sub closeTree {
    my $tree = shift;
    my ( $entryPath, $hideChildren ) = @_;
    my @children = $tree->info( children => $entryPath );

    return if !@children;

    for (@children) {
        closeTree( $tree, $_, 1 );
        $tree->hide( 'entry' => $_ ) if $hideChildren;
    }
    $tree->setmode( $entryPath, 'open' ) if length $entryPath;
}

sub buildSubTree {
    my ( $tree, $rootPath, $pathStack, $maxNesting, $totalLines,
        $maxLineLength ) = @_;
    my $dirCount  = 0;
    my $fileCount = 0;
    my $sizeTotal = 0;

    push @$pathStack, 1;
    $$maxNesting = @$pathStack if $$maxNesting < @$pathStack;

    my $dir;
    opendir $dir, $rootPath;

    while ( my $currDir = readdir $dir ) {
        next if $currDir =~ /^\.\.?$/;

        my $path = "$rootPath/$currDir";
        ++$$totalLines;

        my $currPath = join "/", @$pathStack;
        my $nodeText = $path;

        $tree->add( $currPath, -text => $nodeText );

        if ( -d $path && !-l $path ) {
            my ( $subDirCount, $subFileCount, $subTotalSize ) =
              buildSubTree( $tree, $path, $pathStack, $maxNesting, $totalLines,
                $maxLineLength );

            $dirCount  += $subDirCount + 1;
            $fileCount += $subFileCount;
            $sizeTotal += $subTotalSize;

            $tree->entryconfigure(
                $currPath,
                -text => annotate(
                    $nodeText, $subDirCount, $subFileCount, $subTotalSize
                )
            );
        }
        else {
            my $fileSize = -s $path;
            $tree->entryconfigure( $currPath,
                -text => $nodeText . ' (' . size_in_kilobyte($fileSize) . ')' );
            ++$fileCount;
#warn $path unless defined $fileSize;
            $sizeTotal += $fileSize;
        }

        $$maxLineLength = length($nodeText)
          if length($nodeText) > $$maxLineLength;
        ++$pathStack->[-1];
    }

    closedir $dir;
    pop @$pathStack;
    return ( $dirCount, $fileCount, $sizeTotal );
}

sub annotate {
    my ( $path, $dirs, $files, $byte_size ) = @_;
    return
      $path
      . " \t("
      . $dirs . ' dir' . count_to_plural_suffix($dirs) . ', '
      . $files . ' file' . count_to_plural_suffix($files) . ', '
      . size_in_kilobyte($byte_size)
      . ')';
}

sub count_to_plural_suffix {
    return $_[0] > 1 ? 's' : '';
}

sub size_in_kilobyte {
    defined $_[0] ? sprintf( '%0.1f', $_[0] / 1024 ) . ' kB' : 'UNKNOWN SIZE';
}

sub ShowHelp {
    my $exitValue = 0;
    $exitValue = shift if defined $_[0] and $_[0] =~ /^[-+]?\d+$/;

    print $_ while $_ = shift;

    print <<HELP;
FolderStats scans a directory tree starting at the folder given on the command
line and generates an explorer like tree giving folder content stats such as

number of files, their total size, and the count and sizes of sub-folders.

Note that the statistics are not dynamically updated as files and folders are
altered on disk.

Usage:

FolderStats <root folder>

HELP

    exit( $exitValue || -1 );
}