CrossJoin-Csv, cartesian product on flat files

crossjoin-csv.ps1

# Cross-Join between two flat files
# By Joannes Vermorel, 2015-12-11
#
# Syntax:
# Crossjoin-Csv .\sample.csv .\sample.csv "Name" 

function Crossjoin-Csv
{
    param
    (
        [string] $file1,
        [string] $file2,
        [string] $pivot
    )

    # adjusting the delimiter automatically
    if($file1.ToLower().EndsWith(".tsv"))
    {
        $t1 = Import-Csv -Delimiter "`t" $file1;
    }
    else
    {
        $t1 = Import-Csv $file1;
    }

    if($file2.ToLower().EndsWith(".tsv"))
    {
        $t2 = Import-Csv -Delimiter "`t" $file2;
    }
    else
    {
        $t2 = Import-Csv $file2;
    }

    $lookup = $t2 | Group-Object -AsHashTable -AsString -Property $pivot;

    $f1 = $t1 | Get-Member | Where-Object {$_.MemberType -eq "NoteProperty"} | Foreach-Object{$_.Name};
    $f2 = $t2 | Get-Member | Where-Object {$_.MemberType -eq "NoteProperty"} | Foreach-Object{$_.Name} | Where-Object{$_ -ne $pivot}; 

    # writing the fields for the first line
    ($f1 + $f2) | & {$ofs=',';"$input"};


    Foreach($a in $t1)
    {
        Foreach($b in $lookup[$a.$pivot])
        {
            (($f1 | ForEach-Object{$a.$_}) + ($f2 | ForEach-Object{$b.$_})) | & {$ofs=',';"$input"};
        }
    }
}