#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : Hyper-V checkpoints will not merge, and the disk fills
    Fix   : Free enough space for the merge to run
    Source: https://jbtecwiz.com/support/srv-clu-checkpoint

    Run as     : Elevated PowerShell on the host
    Expect     : 60 minutes
    Risk       : high
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    The volume is nearly full. A merge needs working space and will not
    start without it.

    HOW TO UNDO IT
    None. Take a backup before starting if the data matters.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 5"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  Hyper-V checkpoints will not merge, and the disk fills' -ForegroundColor White
Write-Host '  Free enough space for the merge to run' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: high   Reversible   60 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'Establish the size of the chain and the free space.' -Command {
    Get-VM | Get-VMHardDiskDrive | ForEach-Object { Get-VHD $_.Path } | Format-Table Path,VhdType,FileSize,Size,ParentPath -AutoSize
    Get-Volume | Format-Table DriveLetter,FileSystemLabel,SizeRemaining,Size
}

Invoke-Step -Number 2 -Do 'Do not delete .avhdx files by hand. They are a chain, and removing one destroys everything after it.' -Why 'This is the single most damaging thing that can be done in this situation, and it is a common instinct when a disk is full. Each differencing disk holds only the changes since its parent; deleting one in the middle makes the whole chain unrecoverable.' -Manual

Invoke-Step -Number 3 -Do 'Move something else off the volume -- an ISO library, an old export, another virtual machine -- to create room.' -Manual

Invoke-Step -Number 4 -Do 'Or move the virtual machine''s storage to a volume with space, which can be done while it runs.' -Command {
    Move-VMStorage -VMName VM01 -DestinationStoragePath D:\VMs\VM01
}

Invoke-Step -Number 5 -Do 'Then start the merge.' -Command {
    Get-VMSnapshot -VMName VM01 | Remove-VMSnapshot
    Get-VM VM01 | Format-List Name,Status
}

Write-Rule "  Confirm it worked"
Show-Prose 'The chain collapses to a single VHDX and free space returns.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-VM VM01 | Get-VMHardDiskDrive | ForEach-Object { Get-VHD $_.Path } | Format-List Path,VhdType,ParentPath
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/srv-clu-checkpoint' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: None. Take a backup before starting if the data matters.' 'DarkGray'
Write-Rule