[CmdletBinding(SupportsShouldProcess = $true)]
param(
    [switch]$Remove,
    [switch]$AllUsers,
    [switch]$StartNow
)

Set-StrictMode -Version Latest
$ErrorActionPreference = "Stop"

$scriptDir = Split-Path -Parent $PSCommandPath
$backendScript = Join-Path $scriptDir "start_backend.ps1"
$vbsLauncher = Join-Path $scriptDir "start_backend_hidden.vbs"
$shortcutName = "ScreenJob Backend.lnk"

if (-not (Test-Path -LiteralPath $backendScript)) {
    throw "Backend launcher script not found: $backendScript"
}

if (-not (Test-Path -LiteralPath $vbsLauncher)) {
    throw "Hidden backend launcher file not found: $vbsLauncher"
}

function Test-IsAdministrator {
    $identity = [Security.Principal.WindowsIdentity]::GetCurrent()
    $principal = New-Object Security.Principal.WindowsPrincipal($identity)
    return $principal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)
}

$legacyService = Get-Service -Name "ScreenJobBackend" -ErrorAction SilentlyContinue
if ($null -ne $legacyService) {
    if (Test-IsAdministrator) {
        if ($PSCmdlet.ShouldProcess("ScreenJobBackend", "Remove legacy Windows service")) {
            if ($legacyService.Status -ne "Stopped") {
                Stop-Service -Name "ScreenJobBackend" -Force -ErrorAction Stop
            }

            & sc.exe delete ScreenJobBackend | Out-Null
            if ($LASTEXITCODE -ne 0) {
                throw "Failed to delete legacy service 'ScreenJobBackend' (sc.exe exit code $LASTEXITCODE)."
            }

            Write-Host "Removed legacy Windows service: ScreenJobBackend"
        }
    } else {
        Write-Warning "Legacy Windows service 'ScreenJobBackend' is still installed. Run uninstall_backend_service.ps1 from an elevated PowerShell session once to remove it."
    }
}

$startupFolder = if ($AllUsers) {
    [Environment]::GetFolderPath("CommonStartup")
} else {
    [Environment]::GetFolderPath("Startup")
}

$shortcutPath = Join-Path $startupFolder $shortcutName

if ($Remove) {
    if (Test-Path -LiteralPath $shortcutPath) {
        if ($PSCmdlet.ShouldProcess($shortcutPath, "Remove backend startup shortcut")) {
            Remove-Item -LiteralPath $shortcutPath -Force
            Write-Host "Removed backend startup shortcut: $shortcutPath"
        }
    } else {
        Write-Host "No backend startup shortcut found at: $shortcutPath"
    }
    return
}

if ($PSCmdlet.ShouldProcess($shortcutPath, "Create backend startup shortcut")) {
    $shell = New-Object -ComObject WScript.Shell
    $shortcut = $shell.CreateShortcut($shortcutPath)
    $shortcut.TargetPath = "$env:SystemRoot\System32\wscript.exe"
    $shortcut.Arguments = '"' + $vbsLauncher + '"'
    $shortcut.WorkingDirectory = $scriptDir
    $shortcut.Description = "Launch ScreenJob backend at sign-in in the current user session."
    $shortcut.Save()
    Write-Host "Created backend startup shortcut: $shortcutPath"
}

if ($StartNow) {
    Start-Process -FilePath "$env:SystemRoot\System32\wscript.exe" -ArgumentList @($vbsLauncher) -WorkingDirectory $scriptDir | Out-Null
    Write-Host "Started backend launcher now."
}