<#
.SYNOPSIS
    Removes Windows user profiles that haven't been used in a set number of days, the
    supported way: through Win32_UserProfile, never by deleting folders.
.DESCRIPTION
    Lists local profiles with CIM, skips special (system) profiles, loaded profiles, the
    account running the script and anything matching -ExcludeUser, then removes the rest
    that are older than -Days with Remove-CimInstance. That deletes the folder AND the
    ProfileList registry entry together, so Windows doesn't hand the user a TEMP profile
    next time. Age comes from the profile's last unload time where Windows records it,
    and falls back to LastUseTime. Supports -WhatIf; always run that first.
.PARAMETER Days
    Profiles unused for longer than this are removed. Default: 90.
.PARAMETER ExcludeUser
    Account names to never touch. Wildcards work. Matched against DOMAIN\user and user.
.EXAMPLE
    .\Remove-StaleUserProfile.ps1 -Days 60 -WhatIf
.EXAMPLE
    .\Remove-StaleUserProfile.ps1 -Days 120 -ExcludeUser 'CONTOSO\svc-*', 'labadmin' -Confirm:$false
#>
[CmdletBinding(SupportsShouldProcess, ConfirmImpact = 'High')]
param(
    [ValidateRange(14, 3650)]
    [int]$Days = 90,

    [string[]]$ExcludeUser = @('Administrator', 'defaultuser*')
)

$cutoff = (Get-Date).AddDays(-$Days)
$me = [System.Security.Principal.WindowsIdentity]::GetCurrent().User.Value
$profileList = 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList'

function Get-LastUsed {
    param($UserProfile)
    # Newer Windows builds record when the profile was last unloaded (logoff). It's a much
    # better signal than LastUseTime, which all sorts of things can bump.
    $reg = Get-ItemProperty -LiteralPath (Join-Path $profileList $UserProfile.SID) -ErrorAction SilentlyContinue
    if ($reg -and $null -ne $reg.LocalProfileUnloadTimeHigh -and $null -ne $reg.LocalProfileUnloadTimeLow) {
        # Registry DWORDs come back as signed Int32, so reinterpret the bits before combining.
        $high = [BitConverter]::ToUInt32([BitConverter]::GetBytes([int32]$reg.LocalProfileUnloadTimeHigh), 0)
        $low  = [BitConverter]::ToUInt32([BitConverter]::GetBytes([int32]$reg.LocalProfileUnloadTimeLow), 0)
        $ft = ([uint64]$high -shl 32) -bor [uint64]$low
        if ($ft -gt 0) { return [pscustomobject]@{ When = [datetime]::FromFileTime([int64]$ft); Source = 'UnloadTime' } }
    }
    if ($UserProfile.LastUseTime) { return [pscustomobject]@{ When = $UserProfile.LastUseTime; Source = 'LastUseTime' } }
    [pscustomobject]@{ When = $null; Source = 'Unknown' }
}

$profiles = Get-CimInstance -ClassName Win32_UserProfile -Filter 'Special = FALSE AND Loaded = FALSE'

foreach ($p in $profiles) {
    if ($p.SID -eq $me) { continue }

    try {
        $account = ([System.Security.Principal.SecurityIdentifier]$p.SID).Translate([System.Security.Principal.NTAccount]).Value
    }
    catch {
        # The account was deleted from AD, or this machine can't reach a DC. Use the folder name.
        $account = Split-Path $p.LocalPath -Leaf
    }
    $shortName = $account.Split('\')[-1]

    if ($ExcludeUser | Where-Object { $account -like $_ -or $shortName -like $_ }) {
        Write-Verbose "Excluded: $account"
        continue
    }

    $used = Get-LastUsed -UserProfile $p
    if (-not $used.When -or $used.When -ge $cutoff) {
        Write-Verbose ("Keeping {0} (last used {1}, {2})" -f $account, $used.When, $used.Source)
        continue
    }

    $row = [pscustomobject]@{
        Account   = $account
        LocalPath = $p.LocalPath
        LastUsed  = $used.When
        AgeSource = $used.Source
        DaysIdle  = [int]((Get-Date) - $used.When).TotalDays
        Action    = $null
    }

    if ($PSCmdlet.ShouldProcess("$account ($($p.LocalPath)), idle $($row.DaysIdle) days", 'Remove user profile')) {
        try {
            Remove-CimInstance -InputObject $p -Confirm:$false -ErrorAction Stop
            $row.Action = 'Removed'
        }
        catch {
            $row.Action = "Failed: $($_.Exception.Message)"
        }
    }
    else {
        $row.Action = if ($WhatIfPreference) { 'WouldRemove' } else { 'Skipped' }
    }
    $row
}