Rename files based on lookup hashtable - powershell

Question

I have a list of .txt files inside a folder with the following naming: firstname[dot]lastname[underscore]nationality[underscore]date.txt
Examples:
charles.pearson_FR_08-11-2021.txt
lena.smith_GB_11-12-2019.txt
paul.miller_XX_08-03-2017.txt
I would like to replace the filenames of the files that have a 'XX' as nationality by the nationality coming from a lookup table.
What I have tried so far:
$sqlcn = New-Object System.Data.SqlClient.SqlConnection
$sqlcn.ConnectionString = "MyData; MyCatalog;"
$sqlcn.Open()
$sqlcmd = $sqlcn.CreateCommand()
$query = "select username, nationality from mytable"
$sqlcmd.CommandText = $query
$adp = New-Object System.Data.SqlClient.SqlDataAdapter $sqlcmd
$data = New-Object System.Data.DataSet
$adp.Fill($data) | Out-Null
# create a lookup Hashtable
$lookup = #{}
# build up the $lookup hash
foreach ($item in $data.Tables) {
$lookup[$item.username] = $item.nationality
}
[string]$rootPathForFiles = Join-Path -Path $env:USERPROFILE -ChildPath 'Desktop\testFolder'
[string[]]$listOfFilesToRename = Get-ChildItem -Path $rootPathForFiles -Filter '*_XX_*.txt' | Select-Object -ExpandProperty FullName
$listOfFilesToRename | ForEach-Object {
#get the filename without the directory
[string]$newName = Split-Path -Path $_ -Leaf
#NEEDED: Lookup on the hashtable and rename the file
}
It correctly lists all .txt files that have _XX_ in the name but I miss the lookup on the hashtable and the renaming.
For information, $data looks like this:
username nationality
-------- -----------
lena.jeankins
paul.mirabel GB
mickael.mudik GB
paul.miller FR
...

Answer 1

What you can do here is to not just select the files FullName, but instead keep the complete FileInfo object and use the .BaseName and .Extensions properties like this:
$rootPathForFiles = Join-Path -Path $env:USERPROFILE -ChildPath 'Desktop\testFolder'
(Get-ChildItem -Path $rootPathForFiles -Filter '*.*_XX_*.txt' -File) | ForEach-Object {
$userName,$nationality,$date = $_.BaseName -split '_'
if ($lookup.ContainsKey($userName)) {
$newName = '{0}_{1}_{2}{3}' -f $userName, $lookup[$username], $date, $_.Extension
$_ | Rename-Item -NewName $newName
}
else {
Write-Warning "Could not retrieve nationality for user $userName"
}
}