npm3 custom cache

npmcache.ps1

# This is a custom implementation of npm cache.
# It is significantly faster then original implementation and restores packages almost instantaneously.

$ErrorActionPreference = "Stop"

if (-not (Test-Path ".\node_modules")) {
  Write-Host "node_modules folder is missing. Creating cache entry and junction point correspondingly."
  $md5 = New-Object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
  # Calculating hash from package.json. We are using it as a key in our cache.
  # todo: Currently we assume that there will be no collisions in MD5 cache. Ideally we should store package.json in cache and perform full comparison between files.
  $hash = [System.BitConverter]::ToString($md5.ComputeHash([System.IO.File]::ReadAllBytes("package.json")))
  Write-Host "Md5 from package.json: $($hash)"
  # Cache is stored globally in %APPDATA% folder.
  $npmCacheFolder = "$($env:APPDATA)\npm-quick-cache\$($hash)\node_modules"
  New-Item -ItemType Directory -Force -Path $npmCacheFolder
  # Creating junction point.
  cmd /c mklink /j "node_modules" $npmCacheFolder
  if (-not $?) {
    throw "Failed to create junction point.";
  }
}

$npmInstalledMarker = ".\.npm_installed";
# Performance optimization. it takes 9 seconds for npm to verify dependencies. We are creating folder that indicates that installation was performed already.
if (-not (Test-Path -LiteralPath $npmInstalledMarker)) {
  # Install [email protected] if required ([email protected] the most stable version in the moment)
  $npm = Test-Path -LiteralPath ".\node_modules\.bin\npm"
  npm install [email protected]
  if (-not $?) {
    throw "Npm Install failed";
  }

  # Install node packages
  .\node_modules\.bin\npm install
  if (-not $?) {
    throw "Npm install failed";
  }
  New-Item -ItemType Directory -Force -Path $npmInstalledMarker
}