#Requires -Version 3.0 -Modules NetAdapter

# Example:
#  - to disable ICS
#     Set-ICS -VMSwitch minikube
#  - to enable ICS (and create the internal VM switch if it doesn't exist yet)
#     Set-ICS -VMSwitch minikube Enabled
# Purposes:
#  - Create the VM switch if it doesn't exist
#  - Share the internet with the VM Switch using ICS (Internet Connection Sharing)
# Outcomes:
#  - ICS deploys its own DHCP server within the internal network connected to the VM switch 
#  - Each VM will be given an IP address associated to a hostname defined as <VM Name>.mshome.net
#  - IP addresses and associated hostnames are written to C:\Windows\System32\drivers\etc\hosts.ics

param (
	[Parameter(Mandatory)]
	[string]$VMSwitch,
	[switch]$Enabled
)

regsvr32.exe /s hnetcfg.dll
$pHNetShare = New-Object -ComObject HNetCfg.HNetShare
try 
{
	# always disable the sharing first, Internet Connection Sharing doesn't support well a reboot and doesn't support more than one sharing
	$pHNetShare.EnumEveryConnection | ForEach-Object {
		$sConnectionName = $pHNetShare.NetConnectionProps.Invoke($_).Name
		$pSharingConfiguration = $pHNetShare.INetSharingConfigurationForINetConnection.Invoke($_)
		if ($pSharingConfiguration.SharingEnabled)
		{
			$pSharingConfiguration.DisableSharing()
			Write-Host "Disabled pre-existing ICS on '$sConnectionName'."
		}
	}

	if ($Enabled) {
		# get the internet connection name
		$pInternetConnection = Get-NetConnectionProfile | 
			Where-Object  {$_.IPv4Connectivity -eq 'Internet'}
		if ($pInternetConnection -eq $null)
		{
			Write-Warning -Message "Could not find any NetConnectionProfile currently connected to the internet, please connect to the internet."
			Exit 1
		}
		$sInternetConnectionName = $pInternetConnection.InterfaceAlias
		
		# get the internet connection configuration object
		$pInternetConnection = $pHNetShare.EnumEveryConnection | 
			Where-Object {$pHNetShare.NetConnectionProps.Invoke($_).Name -eq "$sInternetConnectionName"}
		$pInternetSharingConfiguration = $pHNetShare.INetSharingConfigurationForINetConnection.Invoke($pInternetConnection)

		# get the VM switch, create it if it doesn't exist
		$pVMSwitchConnection = $pHNetShare.EnumEveryConnection |
			Where-Object {$pHNetShare.NetConnectionProps.Invoke($_).Name -like "*$VMSwitch*"}
		if ($pVMSwitchConnection -eq $null)
		{
			# create a new internal VM switch if it doesn't exist yet
			try
			{
				New-VMSwitch -Name $VMSwitch -SwitchType Internal
			}
			catch
			{
				Write-Warning -Message "Could not create the VM switch $VMSwitch. Create with powershell 'New-VMSwitch -Name $VMSwitch' -SwitchType Internal."	
				Exit 1
			}
			$pVMSwitchConnection = $pHNetShare.EnumEveryConnection |
				Where-Object {$pHNetShare.NetConnectionProps.Invoke($_).Name -like "*$VMSwitch*"}
			if ($pVMSwitchConnection -eq $null)
			{
				Write-Warning -Message "Could not find a NetConnection matching VM switch $VMSwitch. Create with powershell 'New-VMSwitch -Name $VMSwitch' -SwitchType Internal."	
				Exit 1
			}
			Write-Host "Created internal VM Switch '$VMSwitch'."
		}

		# get the VM switch configuration object
		if ($pVMSwitchConnection.Count -ne 1)
		{
			Write-Warning -Message "Found too many NetConnection matching the VM switch $VMSwitch. Remove with powershell 'Remove-VMSwitch -Name $VMSwitch'."
			Exit 1
		}
		$pVMSwitchSharingConfiguration = $pHNetShare.INetSharingConfigurationForINetConnection.Invoke($pVMSwitchConnection)

		$pInternetSharingConfiguration.EnableSharing(0)
		$pVMSwitchSharingConfiguration.EnableSharing(1)
		Write-Host "Shared internet from connection '$sInternetConnectionName' to VM Switch '$VMSwitch'."
	}
}
catch {
	Write-Warning -Message "An unexpected error has occurred!"
	Throw
}