Install-Chocolatey.ps1

<#
.SYNOPSIS
Can be used on new machines to install Chocolately. If already installed then
checks if it is outdated and prompts to update.

.PARAMETER Upgrade
Check if Chocolatey is outdated and update if it is.
#>

param ([switch] $Upgrade)

if (-not (Get-Command 'choco' -ErrorAction:Ignore))
{
	$installer = (New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1')
	$signature = Get-AuthenticodeSignature -Content ([Text.Encoding]::Unicode.GetBytes($installer)) -SourcePathOrExtension 'install.ps1'

	if ($signature.Status -ne 'Valid')
 	{
		throw 'Got invalid signature on Chocolatey install.ps1'
	}

	if ($signature.SignerCertificate.Subject -ne 'CN="Chocolatey Software, Inc.", O="Chocolatey Software, Inc.", L=Topeka, S=Kansas, C=US')
 	{
		throw "Got untrusted Chocolatey signer $($signature.SignerCertificateSubject)"
	}
	Write-Host 'Install'
	Invoke-Expression $installer
}
elseif ($Upgrade)
{
	(choco outdated -r) | % { $_ -match 'chocolatey\|'} | % `
	{
		choco upgrade chocolatey -y
	}
}