#Source		: CodeMonkey Software http://codemonkeysoftware.atlassian.net

param (
	$ServerName = $(throw 'Please specify Virtual Infrastructure ServerName or IP'),
	$User = $(throw 'Please specify username'),
	$Password = $(throw 'Please specify password'),
	$VMName = $(throw 'Please specify VMName'),
	$SnapshotName = $null
)

$s = get-pssnapin | where-object {$_.Name -eq "VMWare.VimAutomation.Core" }
if($s -eq $null)
{
	add-pssnapin VMWare.VimAutomation.Core
}

function ResetSnapshot
{

	if($server -eq $null -or $server.IsConnected -eq $false)
	{
		throw 'Unable to connect to $ServerName'
	}
	$vm = Get-VM -Name $VMName
	if($vm -eq $null)
	{
		throw 'Unable to find specified VM $VMName'
	}	
	$snapShot = $null
	$snapShots = Get-SnapShot -VM $vm
	if($SnapshotName -eq $null)
	{
		if($snapShots -eq $null -or $snapShots.Count -eq 0)
		{
			throw 'No snapshots for specified VM $VMName'
		}
		$snapShot = $snapShots[$snapshots.Count - 1]	
	}
	else
	{
		$snapShot = $snapShots | Where-Object { $_.Name -ieq $SnapshotName }
	}
	if($snapShot -eq $null)
	{
		throw 'No snapshots for specified VM $VMName'
	}
	Write-Host ('Setting snapshot ' + $snapShot.Name + ' on VM ' + $vm.Name)
	Set-VM -VM $vm -Snapshot $snapShot -confirm:$false -ErrorAction:Stop
	$Message = "Restored default machine on " 
	Set-VM -VM $vm -Description $Message $vm.Name -confirm:$false -ErrorAction:Continue  
}

try
{
	cls
	$server = Connect-VIServer -Server $ServerName -User $User -Password $Password
	ResetSnapshot
}
catch
{
	Write-Error $_
	exit 1
}
finally
{
	if($server -ne $null -and $server.IsConnected -eq $true)
	{
		Disconnect-VIServer -Server $server -Confirm:$false
	}
}