Powershell Script: prompt a file (by mask) and use that file in a command line - powershell

Question

Disclaimer: I don't know enough about ps to accomplish this in a reasonable amount of time, so yes, I am asking someone else to do my dirty job.
I want to be able to run a web.config transformation without opening a command line.
I have following files in a folder:
web.config - actual web config
web.qa.config - web config transformation for qa env
web.production.config - web config transformation for production env
transform.ps1 - powershell script I want to use to run transformation
Here is what I want:
PS file shall enumerate current directory using .*\.(?<env>.*?)\.config and let me choose which <env> I am interested in generate web.config for. In my example I will be presented with two options: "qa", "production".
After I (user) select the environment (let's say it is "qa", selected environment is stored as $env, and corresponding filename will be stored as $transformation) script shall do following:
backup original web.config as web.config.bak
execute following command:
.
echo applying $transformation...
[ctt][1].exe source:web.config transformation:$transformation destination:web.config preservewhitespaces verbose
echo done.
ctt.exe is a tool based on XDT that runs web.config transformation from command line.

Answer 1

Okay, looks simple enough, I'll do your dirty job for you. ;)
Save the following as transform.ps1:
$environments = #()f
gci | %{if ($_ -match '.*\.(?<env>.*?)\.config') {$environments += $matches.env}}
Write-Host "`nEnvironments:"
for ($i = 0; $i -lt $environments.Length; $i++) {Write-Host "[$($i + 1)] $($environments[$i])"}
Write-Host
do {
$selection = [int](Read-Host "Please select an environment")
if ($selection -gt 0 -and $selection -le $environments.Length) {
$continue = $true
} else {
Write-Host "Invalid selection. Please enter the number of the environment you would like to select from the list."
}
} until ($continue)
$transformation = "web.$($environments[$selection - 1]).config"
if (Test-Path .\web.config) {
cpi .\web.config .\web.config.bak
} else {
Write-Warning "web.config does not exist. No backup will be created."
}
if ($?) {
Write-Host "`nApplying $transformation..."
[ctt][1].exe source:web.config transformation:$transformation destination:web.config preservewhitespaces verbose
Write-Host "Done.`n"
} else {
Write-Error "Failed to create a backup of web.config. Transformation aborted."
}