2008 Scripting Games, Solution 8

# Advanced Event 8: Making Beautiful Music
# http://www.microsoft.com/technet/scriptcenter/funzone/games/games08/aevent8.mspx

param($minminutes=75,$maxminutes=80,$artistMax=2)

if ($minminutes -ge $maxminutes) {
    throw "Min minutes must be smaller than max minutes"
}
# If only this file had header rows!
# Load the csv, convert each line to an object and
# convert the duration to timespans
$songs=type c:\scripts\songlist.csv | % {
    $obj="" | select Artist,Song,Duration
    # Multi assignment - each variable gets a value assigned
    $obj.Artist,$obj.Song,$duration=$_.split(",")
    $min,$sec=$duration.split(":")
    $obj.Duration=new-timespan -min $min -sec $sec
    $obj
}
# Randomizer
$random=new-object random

do {
    $listOk=$false
    write-verbose "Generating list.."
    # Randomize the list
    $songs=$songs | sort {$random.next()}

    # Pick only $artistMax numbers per artist
    $songs=$songs | group Artist | % {
        $_.group[0..($random.next($artistMax))] | % { $_ }
    }

    # See if we can build a list
    $burnSongs=@()
    $burnDuration=New-Timespan
    $brokeOut=$false
    foreach($song in $songs) {
        $burnSongs+=$song
        # += does not work on timespan objects
        $burnDuration=$burnDuration+$song.Duration
        if ($burnDuration.totalMinutes -ge $minminutes -and `
            $burnDuration.totalMinutes -le $maxminutes) {
            # Is with-in constraints, exit
            $listOk=$true
            $brokeOut=$true
            break
        }
        elseif ($burnDuration.TotalMinutes -gt $maxminutes) {
            $brokeOut=$true
            break # No need to spent more time on this list
        }
    }
    if (!$brokeOut) {
        throw "Songlist does not contain material that can fullfill the constraints"
    }
} until ($listOk)
# Output duration as m:ss - the default hh:mm:ss does not seem to meet the requirements
$burnSongs | Format-Table Artist,Song,@{Label="Duration"; `
                          Expression={"{0}:{1:00}" -f $_.Duration.Minutes,$_.Duration.Seconds}}
# And again m:ss format
"Total music time {0}:{1}" -f [math]::truncate($burnDuration.TotalMinutes),$burnDuration.Seconds