# Apply-MachineNumber.ps1 - SYSTEM-context worker for the two-task machine
# number flow. Triggered on-demand by Prompt-MachineNumber.ps1 via
# `schtasks /run /tn "WT-Apply-MachineNumber"`. Reads the requested number
# from a file the GUI script wrote, invokes Update-MachineNumber as SYSTEM
# (full HKLM + ProgramData access), writes a result JSON for the GUI to
# display, then cleans up.
#
# Why SYSTEM:
#   The eDNC reg key (HKLM:\SOFTWARE\WOW6432Node\GE Aircraft Engines\DNC\
#   General\MachineNo) and UDC settings JSON live in HKLM + ProgramData
#   respectively - both require admin to write. The OLD design granted
#   BUILTIN\Users SetValue + Modify via 02-MachineNumberACLs.ps1, but that
#   was fragile (timing race with eDNC install, ACL silently failed on
#   some bays) AND a security hole (any user could mess with the machine
#   identity). Two-task design: GUI gathers input as logged-in user, SYSTEM
#   does the actual write.
#
# Files:
#   C:\Logs\SFLD\machine-number-request.txt - input, single line, new number
#   C:\Logs\SFLD\machine-number-result.json - output, status fields for GUI
#   C:\Logs\SFLD\Apply-MachineNumber.log    - transcript

$ErrorActionPreference = 'Continue'

$logDir = 'C:\Logs\SFLD'
if (-not (Test-Path -LiteralPath $logDir)) {
    try { New-Item -ItemType Directory -Path $logDir -Force | Out-Null } catch { $logDir = $env:TEMP }
}
$transcript = Join-Path $logDir 'Apply-MachineNumber.log'
try { Start-Transcript -Path $transcript -Append -Force | Out-Null } catch {}

$requestFile = Join-Path $logDir 'machine-number-request.txt'
$resultFile  = Join-Path $logDir 'machine-number-result.json'

function Write-Result {
    param([hashtable]$Body)
    $Body | ConvertTo-Json -Depth 5 | Set-Content -LiteralPath $resultFile -Encoding ascii -Force
}

Write-Host "Apply-MachineNumber.ps1 starting $(Get-Date -Format 'yyyy-MM-dd HH:mm:ss')"
Write-Host "Running as: $([System.Security.Principal.WindowsIdentity]::GetCurrent().Name)"

try {
    if (-not (Test-Path -LiteralPath $requestFile)) {
        Write-Warning "No request file at $requestFile - nothing to apply."
        Write-Result @{ Status = 'NoRequest'; Errors = @("request file missing: $requestFile") }
        exit 0
    }
    $newNumber = (Get-Content -LiteralPath $requestFile -First 1 -ErrorAction Stop).Trim()
    Write-Host "Requested new machine number: $newNumber"

    if ($newNumber -notmatch '^\d+$') {
        Write-Warning "Request is not digits-only: '$newNumber'"
        Write-Result @{ Status = 'BadInput'; Requested = $newNumber; Errors = @("Not digits only: '$newNumber'") }
        Remove-Item -LiteralPath $requestFile -Force -ErrorAction SilentlyContinue
        exit 1
    }

    # Dot-source the shared helper. Update-MachineNumber.ps1 now has
    # -ErrorAction Stop on the writes so failures actually throw.
    . "$PSScriptRoot\lib\Get-PCProfile.ps1"
    . "$PSScriptRoot\lib\Update-MachineNumber.ps1"

    $site = if ($siteConfig) { $siteConfig.siteName } else { 'West Jefferson' }
    $mnResult = Update-MachineNumber -NewNumber $newNumber -Site $site

    $resultBody = @{
        Status         = if ($mnResult.Errors.Count -eq 0) { 'OK' } else { 'PartialErrors' }
        Requested      = $newNumber
        Site           = $site
        UdcUpdated     = [bool]$mnResult.UdcUpdated
        EdncUpdated    = [bool]$mnResult.EdncUpdated
        OldUdc         = $mnResult.OldUdc
        OldEdnc        = $mnResult.OldEdnc
        UdcSettingsRestored = [bool]$mnResult.UdcSettingsRestored
        UdcRestored    = [bool]$mnResult.UdcRestored
        MTConnectUpdated = $mnResult.MTConnectUpdated
        MachineNumberTxtUpdated = [bool]$mnResult.MachineNumberTxtUpdated
        Errors         = $mnResult.Errors
        AppliedAt      = (Get-Date -Format 'o')
        AppliedAs      = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name
    }
    Write-Result -Body $resultBody

    Write-Host "Update-MachineNumber result:"
    Write-Host "  UdcUpdated  = $($mnResult.UdcUpdated)"
    Write-Host "  EdncUpdated = $($mnResult.EdncUpdated)"
    Write-Host "  Errors      = $($mnResult.Errors.Count)"
    if ($mnResult.Errors) { $mnResult.Errors | ForEach-Object { Write-Host "    FAILED: $_" } }

    Remove-Item -LiteralPath $requestFile -Force -ErrorAction SilentlyContinue

    # On clean success, also unregister the Prompt logon task. Prompt itself
    # tries to self-unregister but it runs as a Limited user (BUILTIN\Users)
    # and silently fails on Unregister-ScheduledTask (no delete right on a
    # SYSTEM-registered task). We're running as SYSTEM here, so we can.
    # Idempotent if Prompt already unregistered itself somehow.
    if ($mnResult.Errors.Count -eq 0 -and $mnResult.EdncUpdated) {
        try {
            if (Get-ScheduledTask -TaskName 'Prompt Machine Number' -ErrorAction SilentlyContinue) {
                Unregister-ScheduledTask -TaskName 'Prompt Machine Number' -Confirm:$false -ErrorAction Stop
                Write-Host "Unregistered 'Prompt Machine Number' task (SYSTEM cleanup)."
            }
        } catch {
            Write-Host "Could not unregister 'Prompt Machine Number': $_"
        }
    }

    Write-Host "Apply-MachineNumber.ps1 finished $(Get-Date -Format 'yyyy-MM-dd HH:mm:ss')"
} catch {
    Write-Warning "Apply threw: $_"
    Write-Result @{ Status = 'Exception'; Errors = @("$_") }
} finally {
    try { Stop-Transcript | Out-Null } catch {}
}