# GPOWdac.ps1
# Lightweight WDAC (Windows Defender Application Control) policy deployment via GPO.
# Copies .p7b policy to SYSVOL and sets the registry pointer.
# Depends on: GPOCore.ps1 (Get-GPOSysvolPath)

function Set-GPOWdacPolicy {
    <#
    .SYNOPSIS
        Deploys a WDAC policy file to a GPO.
        If source is .xml, converts to .p7b with ConvertFrom-CIPolicy.
        Copies .p7b to SYSVOL and sets the DeployConfigCIPolicy registry key.
    #>
    param(
        [Parameter(Mandatory)]
        [string]$GPOName,

        [Parameter(Mandatory)]
        [hashtable]$WDACPolicy,

        [Parameter(Mandatory)]
        [string]$SourceDir,

        [string]$Domain = (Get-ADDomain).DNSRoot
    )

    Write-Host "  Applying WDAC policy..." -ForegroundColor Yellow

    $policyFile = $WDACPolicy.PolicyFile
    $sourcePath = Join-Path $SourceDir $policyFile

    if (-not (Test-Path $sourcePath)) {
        throw "WDAC policy file not found: $sourcePath"
    }

    $sysvolPath = Get-GPOSysvolPath -GPOName $GPOName -Domain $Domain
    $deviceGuardDir = Join-Path $sysvolPath 'Machine\Microsoft\Windows\DeviceGuard'

    if (-not (Test-Path $deviceGuardDir)) {
        New-Item -ItemType Directory -Path $deviceGuardDir -Force | Out-Null
    }

    $extension = [System.IO.Path]::GetExtension($sourcePath).ToLower()

    if ($extension -eq '.xml') {
        # Convert XML to .p7b
        $destPath = Join-Path $deviceGuardDir 'SIPolicy.p7b'
        ConvertFrom-CIPolicy -XmlFilePath $sourcePath -BinaryFilePath $destPath | Out-Null
        Write-Host "    Converted $policyFile -> SIPolicy.p7b" -ForegroundColor Green
    } elseif ($extension -eq '.p7b') {
        # Copy directly
        $destPath = Join-Path $deviceGuardDir 'SIPolicy.p7b'
        Copy-Item -Path $sourcePath -Destination $destPath -Force
        Write-Host "    Copied $policyFile -> SIPolicy.p7b" -ForegroundColor Green
    } else {
        throw "WDAC policy file must be .xml or .p7b, got: $extension"
    }

    # Set registry key to enable WDAC via GPO
    $regKey = 'HKLM\SOFTWARE\Policies\Microsoft\Windows\DeviceGuard'
    Set-GPRegistryValue -Name $GPOName -Key $regKey -ValueName 'DeployConfigCIPolicy' `
        -Type DWord -Value 1 -Domain $Domain | Out-Null

    Write-Host "  [OK] WDAC policy deployed to $GPOName" -ForegroundColor Green
}

function Compare-GPOWdacPolicy {
    <#
    .SYNOPSIS
        Compares desired WDAC policy against current GPO state.
        Checks registry key and .p7b file existence/hash.
    #>
    param(
        [Parameter(Mandatory)]
        [string]$GPOName,

        [Parameter(Mandatory)]
        [hashtable]$WDACPolicy,

        [Parameter(Mandatory)]
        [string]$SourceDir,

        [string]$Domain = (Get-ADDomain).DNSRoot
    )

    $diffs = @()

    Write-Host "  Comparing WDAC policy..." -ForegroundColor Yellow

    # Check registry key
    $regKey = 'HKLM\SOFTWARE\Policies\Microsoft\Windows\DeviceGuard'
    $currentRegValue = $null
    try {
        $regResult = Get-GPRegistryValue -Name $GPOName -Key $regKey -ValueName 'DeployConfigCIPolicy' `
            -Domain $Domain -ErrorAction Stop
        $currentRegValue = $regResult.Value
    } catch {
        $currentRegValue = $null
    }

    if ($currentRegValue -ne 1) {
        $display = if ($null -eq $currentRegValue) { '(not set)' } else { $currentRegValue }
        Write-Host "    [DRIFT] DeployConfigCIPolicy: $display -> 1" -ForegroundColor Red
        $diffs += [PSCustomObject]@{
            Type    = 'WDAC'
            Setting = 'DeployConfigCIPolicy'
            Status  = "Registry: $display -> 1"
        }
    } else {
        Write-Host "    [OK] DeployConfigCIPolicy = 1" -ForegroundColor Green
    }

    # Check .p7b file exists in SYSVOL
    $sysvolPath = Get-GPOSysvolPath -GPOName $GPOName -Domain $Domain
    $p7bPath = Join-Path $sysvolPath 'Machine\Microsoft\Windows\DeviceGuard\SIPolicy.p7b'

    if (-not (Test-Path $p7bPath)) {
        Write-Host "    [DRIFT] Missing: SIPolicy.p7b" -ForegroundColor Red
        $diffs += [PSCustomObject]@{
            Type    = 'WDAC'
            Setting = 'SIPolicy.p7b'
            Status  = 'Missing'
        }
    } else {
        # Compare file hashes if source exists
        $policyFile = $WDACPolicy.PolicyFile
        $sourcePath = Join-Path $SourceDir $policyFile

        if (Test-Path $sourcePath) {
            $sourceExt = [System.IO.Path]::GetExtension($sourcePath).ToLower()

            if ($sourceExt -eq '.p7b') {
                $sourceHash = (Get-FileHash -Path $sourcePath -Algorithm SHA256).Hash
                $deployedHash = (Get-FileHash -Path $p7bPath -Algorithm SHA256).Hash

                if ($sourceHash -ne $deployedHash) {
                    Write-Host "    [DRIFT] SIPolicy.p7b hash mismatch (source updated)" -ForegroundColor Red
                    $diffs += [PSCustomObject]@{
                        Type    = 'WDAC'
                        Setting = 'SIPolicy.p7b'
                        Status  = 'Hash mismatch'
                    }
                } else {
                    Write-Host "    [OK] SIPolicy.p7b hash matches" -ForegroundColor Green
                }
            } else {
                # Source is .xml -- convert to temp .p7b and compare
                $tempP7b = [System.IO.Path]::GetTempFileName()
                try {
                    ConvertFrom-CIPolicy -XmlFilePath $sourcePath -BinaryFilePath $tempP7b | Out-Null
                    $sourceHash = (Get-FileHash -Path $tempP7b -Algorithm SHA256).Hash
                    $deployedHash = (Get-FileHash -Path $p7bPath -Algorithm SHA256).Hash

                    if ($sourceHash -ne $deployedHash) {
                        Write-Host "    [DRIFT] SIPolicy.p7b hash mismatch (source XML updated)" -ForegroundColor Red
                        $diffs += [PSCustomObject]@{
                            Type    = 'WDAC'
                            Setting = 'SIPolicy.p7b'
                            Status  = 'Hash mismatch'
                        }
                    } else {
                        Write-Host "    [OK] SIPolicy.p7b matches source XML" -ForegroundColor Green
                    }
                } catch {
                    Write-Host "    [WARN] Cannot convert source XML for comparison: $($_.Exception.Message)" -ForegroundColor Yellow
                } finally {
                    Remove-Item $tempP7b -Force -ErrorAction SilentlyContinue
                }
            }
        } else {
            Write-Host "    [OK] SIPolicy.p7b exists (source file not found for hash comparison)" -ForegroundColor Green
        }
    }

    if ($diffs.Count -eq 0) {
        Write-Host "  [OK] WDAC policy matches desired state" -ForegroundColor Green
    } else {
        Write-Host "  [DRIFT] $($diffs.Count) WDAC difference(s) found" -ForegroundColor Red
    }

    return $diffs
}