upload direct s3 helpers

upload_helpers.rb

# Helpers
  def uploader
      @uploader ||= ImageUploader.new
  end
      def policy
      conditions = [
        ["starts-with", "$utf8", ""],
        # Change this path if you need, but adjust the javascript config
        ["starts-with", "$key", "uploads"],
        ["starts-with", "$filename", ""],
        { "bucket" => "neufert-tmp-cdn.archdaily.net" },
        { "acl" => uploader.acl }
      ]

      policy = {
        # Valid for 3 hours. Change according to your needs
        'expiration' => (Time.now.utc + 3600 * 24).iso8601,
        'conditions' => conditions
      }

      Base64.encode64(JSON.dump(policy)).gsub("\n","")
    end

    def signature
      Base64.encode64(
        OpenSSL::HMAC.digest(
          OpenSSL::Digest::Digest.new('sha1'),
          uploader.aws_secret_access_key, policy
        )
      ).gsub("\n","")
    end