#Requires -Version 5.1
#Requires -RunAsAdministrator
<#
.SYNOPSIS
    Creates a timestamped backup of the CI template VM directory.

.DESCRIPTION
    Run before any template refresh (toolchain update, KMS re-activation, snapshot
    rebuild). The act_runner service is stopped for the duration so no vmrun clone
    races the file copy, then restarted automatically.

    Restore procedure (after a bad refresh):
        Stop-Service act_runner
        Remove-Item 'F:\CI\Templates\WinBuild' -Recurse -Force
        Copy-Item 'F:\CI\Backups\Template_<stamp>' 'F:\CI\Templates\WinBuild' -Recurse
        Start-Service act_runner

.PARAMETER TemplatePath
    Directory containing the template VM files (.vmx, .vmdk, snapshots).
    Default: F:\CI\Templates\WinBuild

.PARAMETER BackupBaseDir
    Directory under which timestamped backup folders are created.
    Default: F:\CI\Backups

.PARAMETER KeepCount
    Number of most-recent backups to retain. Older ones are deleted.
    Default: 3

.PARAMETER SkipRunnerStop
    Skip stopping/restarting act_runner. Use when the service is already stopped
    or when called from a maintenance window where the runner is offline.

.EXAMPLE
    # Standard pre-refresh backup (run elevated)
    .\Backup-CITemplate.ps1

    # Dry run to preview what would happen
    .\Backup-CITemplate.ps1 -WhatIf

    # Keep 5 backups
    .\Backup-CITemplate.ps1 -KeepCount 5
#>
[CmdletBinding(SupportsShouldProcess)]
param(
    [string] $TemplatePath  = 'F:\CI\Templates\WinBuild',

    [string] $BackupBaseDir = 'F:\CI\Backups',

    [ValidateRange(1, 20)]
    [int] $KeepCount = 3,

    [switch] $SkipRunnerStop
)

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

if (-not (Test-Path $TemplatePath -PathType Container)) {
    throw "Template directory not found: $TemplatePath"
}

$timestamp  = Get-Date -Format 'yyyyMMdd_HHmmss'
$backupDest = Join-Path $BackupBaseDir "Template_$timestamp"

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

# ── Step 1: Stop runner ──────────────────────────────────────────────────────
$runnerWasRunning = $false
if (-not $SkipRunnerStop) {
    $svc = Get-Service -Name act_runner -ErrorAction SilentlyContinue
    if ($svc -and $svc.Status -eq 'Running') {
        if ($PSCmdlet.ShouldProcess('act_runner', 'Stop service before backup')) {
            Write-Host "[Backup-CITemplate] Stopping act_runner..."
            Stop-Service -Name act_runner -Force
            $runnerWasRunning = $true
            Write-Host "[Backup-CITemplate] act_runner stopped."
        }
    }
}

try {
    # ── Step 2: Copy template directory ───────────────────────────────────────
    if ($PSCmdlet.ShouldProcess($TemplatePath, "Copy to $backupDest")) {
        Write-Host "[Backup-CITemplate] Copying $TemplatePath -> $backupDest ..."
        $sw = [System.Diagnostics.Stopwatch]::StartNew()
        Copy-Item -Path $TemplatePath -Destination $backupDest -Recurse -Force
        $sw.Stop()

        # Size sum without Measure-Object.Sum (Set-StrictMode safe)
        $backupFiles = Get-ChildItem $backupDest -Recurse -File -ErrorAction SilentlyContinue
        $totalBytes  = [long]0
        if ($backupFiles) { foreach ($f in $backupFiles) { $totalBytes += $f.Length } }
        $sizeMB = [math]::Round($totalBytes / 1MB, 0)

        Write-Host "[Backup-CITemplate] Backup complete: $backupDest ($sizeMB MB, $($sw.Elapsed.TotalSeconds.ToString('F0'))s)"
    }

    # ── Step 3: Prune old backups ──────────────────────────────────────────────
    $existing = Get-ChildItem $BackupBaseDir -Directory -ErrorAction SilentlyContinue |
        Where-Object { $_.Name -like 'Template_????????_??????' } |
        Sort-Object LastWriteTime -Descending

    if ($existing.Count -gt $KeepCount) {
        $toRemove = $existing | Select-Object -Skip $KeepCount
        foreach ($old in $toRemove) {
            if ($PSCmdlet.ShouldProcess($old.FullName, 'Remove old backup')) {
                Write-Host "[Backup-CITemplate] Pruning old backup: $($old.Name)"
                Remove-Item $old.FullName -Recurse -Force
            }
        }
        Write-Host "[Backup-CITemplate] Retained $KeepCount backup(s)."
    }
}
finally {
    # ── Step 4: Restart runner ────────────────────────────────────────────────
    if ($runnerWasRunning) {
        if ($PSCmdlet.ShouldProcess('act_runner', 'Start service after backup')) {
            Write-Host "[Backup-CITemplate] Restarting act_runner..."
            Start-Service -Name act_runner
            $newStatus = (Get-Service -Name act_runner).Status
            Write-Host "[Backup-CITemplate] act_runner status: $newStatus"
        }
    }
}