How to use a condition when writing to a .txt file - powershell

Question

I am trying to create myself a powershell script that has mainly two tasks - one after the other.
Initial assumptions: it runs where it performs the following tasks.
Trace all the files, those that are folders - make a zip of them, then after making the archive, delete them. Objective accomplished.
Write to the file the names of all files in the folder (after completing point 1) but check if the given file has the extension of *.zip
a) if it has extension of *.zip then it should be saved in .txt file like "uresoruce = foo/file.zip"
b) if it doesn't have extension *.zip then it should be saved to a .txt file like this "resoruce = foo/file2.jar"
c) since the script is started from the place where all the files are, it will probably also be saved to a file, I would like to avoid this
Suppose we have some files in a folder after compiling, and we don't have any folder inside. The .txt file should look like the following:
uresource = plugins/Liula_1.0.0.0.zip
uresource = plugins/Liborts_3.7.1.0.zip
uresource = plugins/Liwer_1.2.0.0.zip
resource = plugins/o0.I20100512-1500.jar
resource = plugins/or.v20100505-1235.jar
The script I managed to write so far:
## set current path
$path = (Resolve-Path .\).Path
## dirs in a path
$source = Get-ChildItem -Path $path -Filter "" -Directory
$files = Get-ChildItem $path
Add-Type -assembly "system.io.compression.filesystem"
Foreach ($s in $source) {
$destination = Join-path -path $path -ChildPath "$($s.name).zip"
[io.compression.zipfile]::CreateFromDirectory($s.fullname, $destination)
Remove-Item $s -Recurse
}
# This does not working!!! :/
Foreach ($f in $files) {
$extn = [IO.Path]::GetExtension($f)
if ($extn -eq ".zip" ) {
$outfile = "uresource = plugins/" + $f.Name
}
else {
$outfile = "resource = plugins/" + $f.Name
}
}

Answer 1

As #Santiago Squarzon rightly pointed out I did not do anything with this variable. I got a little confused because before I did it only for out-file I didn't use -append and in fact I got the last value in .txt. Now I made my first script in ph, it works like a dream ;)
## set current path
$path = (Resolve-Path .\).Path
## dirs in a path
$source = Get-ChildItem -Path $path -Filter "" -Directory
$files = Get-ChildItem $path
Add-Type -assembly "system.io.compression.filesystem"
## create zip and delete other dirs
Foreach ($s in $source) {
$destination = Join-path -path $path -ChildPath "$($s.name).zip"
[io.compression.zipfile]::CreateFromDirectory($s.fullname, $destination)
Remove-Item $s -Recurse
}
## output filename in .txt
$logFile = "$pwd\logfile.txt"
Foreach ($f in $files) {
$extn = [IO.Path]::GetExtension($f)
if ($extn -eq ".zip" ) {$outfile = "uresource = plugins/$f"}
else {$outfile = "resource = plugins/$f"}
$outfile | Out-File -Append $logFile
}