<#
.SYNOPSIS
    Lists PC names and MCZ Machine IDs as CSV, ready to upload at https://mcz.software/Buy

.DESCRIPTION
    The MCZ Machine ID is the same value "mcz license" shows on each computer: the first 80 bits of
    SHA-256 over "<MachineGuid>|<system volume serial>|MegaCompressorZip", in base32 (XXXX-XXXX-XXXX-XXXX).
    Works on Windows PowerShell 5.1 and PowerShell 7. Reading MachineGuid needs no elevation.

.EXAMPLE
    .\Get-MczMachineId.ps1
    This computer only, printed as CSV.

.EXAMPLE
    .\Get-MczMachineId.ps1 -ComputerName (Get-Content .\pcs.txt) -OutFile .\machines.csv
    Remote PCs over PowerShell remoting (WinRM); unreachable PCs are reported as warnings.

.EXAMPLE
    .\Get-MczMachineId.ps1 -OutDirectory \\server\share\mcz
    For a GPO startup script or Intune: each PC writes <PCNAME>.csv to the share. Merge them with
    Get-ChildItem \\server\share\mcz\*.csv | Import-Csv | Export-Csv machines.csv -NoTypeInformation
#>
[CmdletBinding(DefaultParameterSetName = 'Local')]
param(
    [Parameter(ParameterSetName = 'Remote', Mandatory)] [string[]] $ComputerName,
    [System.Management.Automation.PSCredential] $Credential,
    [string] $OutFile,
    [Parameter(ParameterSetName = 'Local')] [string] $OutDirectory
)

$collect = {
    $b32 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
    $hklm = [Microsoft.Win32.RegistryKey]::OpenBaseKey('LocalMachine', [Microsoft.Win32.RegistryView]::Registry64)
    $guid = $hklm.OpenSubKey('SOFTWARE\Microsoft\Cryptography').GetValue('MachineGuid')
    $drive = $env:SystemRoot.Substring(0, 2)
    $disk = Get-CimInstance -ClassName Win32_LogicalDisk -Filter "DeviceID='$drive'"
    $serial = [Convert]::ToUInt32($disk.VolumeSerialNumber, 16)
    $material = "$guid|$serial|MegaCompressorZip"
    $sha = [System.Security.Cryptography.SHA256]::Create()
    $hash = $sha.ComputeHash([System.Text.Encoding]::UTF8.GetBytes($material))
    $acc = [uint64]0; $bits = 0; $chars = New-Object System.Text.StringBuilder
    for ($i = 0; $i -lt 10; $i++) {
        $acc = (($acc -shl 8) -bor $hash[$i]) -band [uint64]65535; $bits += 8
        while ($bits -ge 5) { $bits -= 5; [void]$chars.Append($b32[[int](($acc -shr $bits) -band 31)]) }
    }
    $s = $chars.ToString()
    [pscustomobject]@{
        PcName    = $env:COMPUTERNAME
        MachineId = '{0}-{1}-{2}-{3}' -f $s.Substring(0, 4), $s.Substring(4, 4), $s.Substring(8, 4), $s.Substring(12, 4)
    }
}

if ($PSCmdlet.ParameterSetName -eq 'Remote') {
    $params = @{ ComputerName = $ComputerName; ScriptBlock = $collect; ErrorAction = 'SilentlyContinue'; ErrorVariable = 'failed' }
    if ($Credential) { $params.Credential = $Credential }
    $rows = Invoke-Command @params | Select-Object PcName, MachineId
    foreach ($f in $failed) { Write-Warning "$($f.TargetObject): $($f.Exception.Message)" }
} else {
    $rows = & $collect
}

if ($OutDirectory) {
    New-Item -ItemType Directory -Force -Path $OutDirectory | Out-Null
    $rows | Export-Csv -Path (Join-Path $OutDirectory "$env:COMPUTERNAME.csv") -NoTypeInformation -Encoding UTF8
} elseif ($OutFile) {
    $rows | Sort-Object PcName | Export-Csv -Path $OutFile -NoTypeInformation -Encoding UTF8
    Write-Host "$(@($rows).Count) computer(s) written to $OutFile"
} else {
    $rows | ConvertTo-Csv -NoTypeInformation
}