fluke/devops-service/db/mongo/models/stack_template/stack_template_base.rb

require 'tempfile'
require 'securerandom'

class StackTemplateBase < MongoModel

  attr_accessor :id, :template_url, :template_json, :provider

  # Few words about template_url:
  # In Amazon Cloudformation the template file must be stored on an Amazon S3 bucket,
  # but for Openstack stacks it isn't neccessary (your may use local file).
  # I decided to enforce template_url strategy using in openstack to reach more common
  # interface between different providers' stack templates.

  types id: {type: String, empty: false},
    provider: {type: String, empty: false},
    template_json: {type: String, empty: false},
    template_url: {type: String, empty: false}

  def initialize(attrs)
    self.id = attrs['id']
    self.template_json = attrs['template_json'].to_s
    self.template_url = attrs['template_url']
    self.provider = attrs['provider']
    self
  end

  def to_hash_without_id
    {
      provider: provider,
      template_json: template_json,
      template_url: template_url
    }
  end

  # do not forget to destroy template files on template destroying
  def delete_template_file_from_storage
    raise 'Override me'
  end

  # attrs should include:
  # - id (String)
  # - provider (String)
  # - template_json (String)
  def self.create(attrs)
    json = attrs['template_json']
    attrs['template_url'] = generate_template_file_and_upload_to_storage(attrs['id'], json)
    new(attrs)
  end

  def self.build_from_bson(attrs)
    attrs['id'] = attrs["_id"]
    self.new(attrs)
  end

  class << self
    private

    def generate_template_file_and_upload_to_storage(id, json)
      tempfile = Tempfile.new('foo')
      tempfile.write(json)
      secure_filename = "#{id}-#{SecureRandom.hex}.template"
      upload_file_to_storage(secure_filename, tempfile.path)
    ensure
      tempfile.close
      tempfile.unlink
    end

    def upload_file_to_storage(filename, file_path)
      raise 'Override me'
    end

  end
end