module EfficientDownloader

# File lib/efficient_downloader.rb, line 13
def self.download(from, to, headers = nil)
  uri = URI.parse(from)
  raise FileDownloadError, "Invalid URL" unless uri.is_a?(URI::HTTP)

  request = Net::HTTP::Get.new(uri.request_uri)
  headers.each { |header| request[header.first] = header.last } if headers

  redirect_uri = nil
  use_ssl = uri.scheme == "https"

  Net::HTTP.start(uri.host, uri.port, use_ssl: use_ssl) do |http|
    http.request(request) do |response|
      if response.is_a?(Net::HTTPFound)
        redirect_uri = response["location"]
      elsif response.is_a?(Net::HTTPMovedPermanently)
        redirect_uri = response["location"]
      elsif response.is_a?(Net::HTTPTemporaryRedirect)
        redirect_uri = response["location"]
      elsif response.is_a?(Net::HTTPUnauthorized)
        raise FileDownloadError, "File download was not authorised."
      elsif response.is_a?(Net::HTTPForbidden)
        raise FileDownloadError, "File download was not authorised."
      elsif response.is_a?(Net::HTTPNotFound)
        raise FileDownloadError, "Specified file could not be found."
      elsif response.is_a?(Net::HTTPInternalServerError)
        raise FileDownloadError, "Host of specified file returned an error."
      else
        ensure_directory(to)
        File.open(to, "wb") { |io| response.read_body { |chunk| io.write(chunk) } }
      end
    end
  end
  if redirect_uri
    sanitized = sanitized_redirect_uri(redirect_uri, uri)
    download(sanitized, to, headers)
  end
rescue SocketError
  raise FileDownloadError, "The specified host could not be found."
end

# File lib/efficient_downloader.rb, line 60
def self.ensure_directory(to)
  dirname = File.dirname(to)
  FileUtils.mkdir_p(dirname) unless File.directory?(dirname)
end

# File lib/efficient_downloader.rb, line 53
def self.sanitized_redirect_uri(redirect_uri, original_uri)
  uri = URI.parse(redirect_uri)
  return redirect_uri if uri.is_a?(URI::HTTP)
  redirect_path = redirect_uri
  "#{original_uri.scheme}://#{original_uri.host}#{redirect_path}"
end