subresource-integrity-generater.rb

require 'digest'
require 'base64'

WD = ARGV[0]

# sha256 sha384 sha512
HASH_ALGO = "sha384"

allow_file_type = [".css", ".js"]
short_hash_length = 7

def generate_hash(file)
  case HASH_ALGO
  when "sha512"
    Base64.encode64(Digest::SHA512.digest(file)).delete("\n")
  when "sha384"
    Base64.encode64(Digest::SHA384.digest(file)).delete("\n")
  when "sha256"
    Base64.encode64(Digest::SHA256.digest(file)).delete("\n")
  else
    puts("ERROR: unkown hash algo. #{HASH_ALGO}")
    exit(3)
  end
end

def generate_html_tag(path, ext, hash)
  case ext
  when ".css"
    "<link rel=\"stylesheet\" href=\"#{path}\" crossorigin=\"anonymous\" integrity=\"#{HASH_ALGO}-#{hash}\">"
  when ".js"
    "<script src=\"#{path}\" crossorigin=\"anonymous\" integrity=\"#{HASH_ALGO}-#{hash}\"></script>"
  end
end

files = Dir.glob(WD + "/**/*")
hashs = files.map do |file_path|
  if allow_file_type.include?(File.extname(file_path))
    [file_path, generate_hash(File.open(file_path).read)]
  end
end.compact

hashs.each do |file_path, hash|
  file_ext = File.extname(file_path)

  # delete unnecesaary path
  file_path = file_path.split(WD).last.gsub(/^\//, '')

  # add URI query for cache update
  file_path = file_path + "?#{HASH_ALGO}=#{hash[0, short_hash_length]}"

  tag = generate_html_tag(file_path, file_ext, hash)
  puts(tag)
end