#!/usr/bin/perl

use strict;
use warnings;
use File::Wildcard;
use Getopt::Long;

my $music;
my $output;
my $size = 134217728;   # default 128M selection.

GetOptions(
    'source=s'  => \$music,
    'output=s'  => \$output,
    'size=i'    => \$size,
    );

$music =~ s!/$!!;  #!
my $wc = File::Wildcard->new(
                path => "$music///",
                match => qr(/\d*\s*([^/]+\.(?:wma|mp3))$),
                derive => ["$output/\$1"],
                );
my @allsongs;
my $sum=0;
my $sumsq=0;

while (my $found = $wc->next) {
    my ($song,$dest) = @$found;
    my $siz = (stat $song)[7];
    $sum += $siz;
    $sumsq += $siz * $siz;
    push @allsongs,[$song,$siz,$dest];
}

my $count = scalar @allsongs;
my $mean = $sum / $count;
my $sd = sqrt( $sumsq / $count - $mean * $mean);

my $nsamp = int( $mean / $sd );

my @songs = sort {$a->[1] <=> $b->[1]} @allsongs;
my %seen;

while ($size > 20971520) {
    my $pt = 0;
    $pt += rand for (1..$nsamp);
    my $idx = int( $pt / $nsamp * $count);
    my ($song,$ssize,$dest) = @{$songs[$idx]};
    next if exists $seen{$song};
    $seen{$song}++;
    print $song,"\n";
    symlink $song, $dest;
    $size -= $ssize;
}