Show-Warning.ps1

[CmdletBinding()]
Param(
    [Parameter(Mandatory,Position = 0)][datetime]$ShutdownTime
)
Function Show-Message {
    Param(
        [Parameter(Mandatory)]
        [ValidateScript({$null -notlike "$_"})]
        [uint16]$iMinutes
    )
    Function Get-Icon {
        Param(
            [Parameter(Mandatory)]
            [string]$Base64String
        )
        $IconByteArray = [System.Convert]::FromBase64String($Base64String)
        $IconStream = New-Object System.IO.MemoryStream($IconByteArray,0,$IconByteArray.Length)
        $IconStream.Write($IconByteArray,0,$IconByteArray.Length)
        $null = [System.Drawing.Image]::FromStream($IconStream,$true)
        return [System.Drawing.Icon]::FromHandle((New-Object System.Drawing.Bitmap -ArgumentList $IconStream).GetHIcon())
    }
    Function Get-Image {
        Param(
            [Parameter(Mandatory)]
            [string]$Base64String
        )
        $ImageByteArray = [System.Convert]::FromBase64String($Base64String)
        $ImageStream = New-Object System.IO.MemoryStream($ImageByteArray,0,$ImageByteArray.Length)
        $ImageStream.Write($ImageByteArray,0,$ImageByteArray.Length)
        return [System.Drawing.Image]::FromStream($ImageStream,$true)
    }
    #Include .NET assembly to create forms
    Add-Type -AssemblyName System.Windows.Forms

    #Graphic image binary data encoded in base64
    [string]$b64Icon = "<paste base64 encoding of .ico here>"
    [string]$b64Logo = "<paste base64 encoding of .jpg/.png/.bmp here>"

    $imgLogo = Get-Image -Base64String $b64Logo

    #Constants
    New-Variable -Name frmTitle     -Value ([string]'Shutdown Warning') -Option Constant
    New-Variable -Name frmWidth     -Value ([uint16]$imgLogo.Width)     -Option Constant
    New-Variable -Name frmHeight    -Value ([uint16]340)                -Option Constant
    New-Variable -Name pnlHeight    -Value ([uint16]40)                 -Option Constant
    New-Variable -Name lblOffset    -Value ([uint16]8)                  -Option Constant

    #Create message box
    $form = New-Object Windows.Forms.Form
        $form.FormBorderStyle = "FixedToolWindow"
        $form.Text = $frmTitle
        $form.StartPosition = "CenterScreen"
        $form.Width = $frmWidth; $form.Height = $frmHeight
        $form.TopMost = $true
        $form.Icon = Get-Icon -Base64String $b64Icon

    #Add button panel with OK button
    $pnlButton = New-Object Windows.Forms.Panel
        $pnlButton.Size = New-Object Drawing.Size @($frmWidth,$pnlHeight)
        $pnlButton.Dock = "Bottom"
        #Create OK button
        $btnOK = New-Object Windows.Forms.Button
            $btnOK.Top = ($pnlButton.Height / 2) - ($btnOK.Height / 2); $btnOK.Left = ($pnlButton.Width  / 2) - ($btnOK.Width / 2)
            $btnOK.Text = 'OK'
            $btnOK.DialogResult = 'OK'
            $btnOK.Anchor = 'Top','Left'
        #Add button to button panel
        $pnlButton.Controls.Add($btnOK)
    #Add panel to form
    $form.Controls.Add($pnlButton)

    #Create logo logo banner
    $picBanner = New-Object Windows.Forms.PictureBox
        $picBanner.Left = 0; $picBanner.Top = 0; $picBanner.Width = $imgLogo.Width; $picBanner.Height = $imgLogo.Height
        $picBanner.Image = $imgLogo

    #Create message labels
    $lblWarning = New-Object System.Windows.Forms.Label
        $lblWarning.Left = $lblOffset; $lblWarning.Top = $picBanner.Top + $picBanner.Height + $lblOffset; $lblWarning.Width = $picBanner.Width - $lblOffset * 2; $lblWarning.Height = 24
        $lblWarning.TextAlign = [System.Drawing.ContentAlignment]::MiddleCenter
        $lblWarning.Font = New-Object System.Drawing.Font("Microsoft Sans Serif",12,[System.Drawing.FontStyle]::Bold)
        $lblWarning.Text = "Windows will shutdown in less than $iMinutes minutes"
    #Create message label
    $lblMessage = New-Object System.Windows.Forms.Label
        $lblMessage.Left = $lblOffset; $lblMessage.Top = $lblWarning.Top + $lblWarning.Height + $lblOffset; $lblMessage.Width = ($picBanner.Width - ($lblOffset * 2)); $lblMessage.Height = $pnlButton.Top - $lblMessage.Top - $lblOffset; $lblMessage.AutoSize = $false
        $lblMessage.TextAlign = [System.Drawing.ContentAlignment]::TopCenter
        $lblMessage.Font = New-Object System.Drawing.Font("Microsoft Sans Serif",10,[System.Drawing.FontStyle]::Regular)
        $lblMessage.Text = "This device has a parking schedule enabled and has an upcoming power down window. Please ensure you save any work as soon as possible. This system will power off in approximately $iMinutes minutes. If you need to continue working, you may reconnect after power down to restart the system."

    $timer = New-Object System.Windows.Forms.Timer
        $timer.Interval = 1000
        $timer.Add_Tick({
            If (($script:ShutdownTime - (Get-Date)) -le (New-TimeSpan -Minutes ($iMinutes - 5))) {
                $form.Close()
            }
        })

    #Add remaining elements to form
    $form.Controls.AddRange(@($picBanner,$lblWarning,$lblMessage))

    #Set default actions
    $form.AcceptButton = $btnOK
    $form.CancelButton = $btnOK

    #Show form
    If (($script:ShutdownTime - (Get-Date)) -gt (New-TimeSpan -Minutes ($iMinutes - 5))) {
        $form.Activate()
        $timer.Start()
        [void]$form.ShowDialog()
    }

    #Stop timer after form is closed
    $timer.Dispose()
    $form.Dispose()

    return $null
}

For ([int16]$Interval = 15; $Interval -ge 0; $Interval -= 5) {
    [bool]$NextIteration = $false
    $TimeSpan = New-TimeSpan -Minutes $Interval
    Do {
        If (($ShutdownTime - (Get-Date)) -le $TimeSpan) {
            If ($Interval -gt 0) {
                Show-Message $Interval
            }
            $NextIteration = $true
        }
        Else {
            Start-Sleep -Seconds 1
        }
    } Until ($NextIteration)
}