Clean up PSReadLine history file (with backup)

clean-up-psreadline-history.ps1

$historyPath = (Get-PSReadLineOption).HistorySavePath

$directory = (Get-Item $historyPath).DirectoryName
$basename = (Get-Item $historyPath).Basename
$extension = (Get-Item $historyPath).Extension
$timestamp = (Get-Date).ToString("yyyy-MM-ddTHH-mm-ssZ")

$backupPath = "$directory\$basename-$timestamp-backup$extension"

Copy-Item $historyPath $backupPath

$uniqueHistory = @()
$history = Get-Content $historyPath

[Array]::Reverse($history)

$history | Foreach-Object {
  if (-Not $uniqueHistory.Contains($_)) {
    $uniqueHistory += $_
  }
}

[Array]::Reverse($uniqueHistory)

Clear-Content $historyPath

$uniqueHistory | Out-File -Append $historyPath