Node.js bootstrapper in PowerShell.

GetNode.ps1

$nodeUrl = "http://nodejs.org/dist/v0.10.22/x64/node-v0.10.22-x64.msi"
$nodeSha = "c3c169304c6371ee7bd119151bcbced61a322394"
 
function DownloadIt($url, $path)
{
    Start-BitsTransfer -Source $url -Destination $path
}
 
function TestHash($path, $sha)
{
    $bytes = [System.IO.File]::ReadAllBytes($path)
    $hasher = [System.Security.Cryptography.SHA1]::Create()
    $hash = $hasher.ComputeHash($bytes)
    $hasher.Dispose()
    $hashAsHex = ($hash.GetEnumerator() | Foreach-Object { "{0:x2}" -f $_ }) -Join ""
    if($hashAsHex -ne $sha) {
        throw "Hash for '$path' is incorrect. Was '$hashAsHex' but should be '$sha'."
    }
}
 
function IsElevated()
{
    ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).
        IsInRole([Security.Principal.WIndowsBuiltInRole]::Administrator)
}
 
function ElevateIfNecessary([ScriptBlock]$script, $workingDirectory)
{
    if(!(IsElevated)) {
        Write-Host "Elevating..."
        Start-Process "$PSHome\powershell" `
            -Verb runAs `
            -Wait `
            -ArgumentList "-ExecutionPolicy unrestricted -NoProfile -Command & { Set-Location $workingDirectory; $script }"
    }
    else
    {
        Push-Location $workingDirectory
        try
        {
            & $script
        }
        finally
        {
            Pop-Location
        }
    }
}
 
function FindPath($paths)
{
    foreach($path in $paths)
    {
        if(Test-Path $path)
        {
            $resolvedPaths = @(Resolve-Path $path)
            if($resolvedPaths.Length -gt 1)
            {
                throw "Too many files match '$path'."
            }
            return $resolvedPaths[0]
        }
    }
    throw "Failed to find a match for paths '$($paths -join ", ")'."
}
 
function RunNPM($cmdline)
{
    $npmPath = FindPath "$env:ProgramFiles\nodejs\npm.cmd"
    $p = (Start-Process $npmPath -ArgumentList $cmdline -NoNewWindow -Wait -PassThru)
    if($p.ExitCode -ne 0)
    {
        throw "NPM returned nonzero exit code: $($p.ExitCode)"
    }
}

function FixupEnvironment
{
    $pathParts = $env:Path -split ";"
    $pathParts += [System.Environment]::GetEnvironmentVariable("Path", "Machine") -split ";"
    $pathParts += [System.Environment]::GetEnvironmentVariable("Path", "User") -split ";"
    
    $pathParts = $pathParts | Where { ![string]::IsNullOrWhitespace($_) } | Select-Object -Unique
    $env:Path = $pathParts -join ";"
}

try
{
    # Configure directories and paths
    $thisScript = $MyInvocation.MyCommand.Path
    $curDir = Split-Path $thisScript
    $tempDir = Join-Path $curDir NodeTemp
    $nodeMsi = Join-Path $tempDir "node.msi"
    
    if(!(Test-Path $tempDir)) {
        New-Item $tempDir -ItemType Directory | Out-Null
    }
    Get-ChildItem $tempDir -exclude node.msi | Remove-Item
 
    if(!(Test-Path $nodeMsi))
    {
        Write-Host "Downloading Node.js..."
        DownloadIt $nodeUrl $nodeMsi
    }
 
    Write-Host "Verifying Node.js installer hash..."
    TestHash $nodeMsi $nodeSha
    
    ElevateIfNecessary { 
        try { 
            Write-Host 'Uninstalling Node.js (if needed)...'
            Start-Process msiexec -ArgumentList '/x Node.msi /quiet /l* uninstall.log' -NoNewWindow -Wait
            Write-Host 'Installing Node.js...'
            $p = (Start-Process msiexec -ArgumentList '/i Node.msi /quiet /l* install.log' -NoNewWindow -Wait -PassThru)
            $p.ExitCode | Set-Content MsiExecExitCode.txt 
        } catch { 
            $_ | Set-Content ElevatedError.txt
            $_
        } 
    } $tempDir
    # Check the results from msiexec
    $elevatedErrorPath = Join-Path $tempDir ElevatedError.txt
    if(Test-Path $elevatedErrorPath) {
        throw "Failed in elevated shell: $(Get-Content $elevatedErrorPath)"
    }
    $msiExecExitCode = [int](Get-Content (Join-Path $tempDir MsiExecExitCode.txt))
    if($msiExecExitCode -ne 0)
    {
        throw "Failed while running msiexec with exit code $msiExecExitCode."
    }
    
    Write-Host "Installing jslint..."
    RunNPM "install jslint"
    
    Write-Host "Fixing up local environment Path..."
    FixupEnvironment
    
    Write-Host "Successfully installed Node.js."
}
catch
{
    throw $_
}