puppetlabs/facter

# frozen_string_literal: true

require 'timeout'

# The resolvable mixin defines behavior for evaluating and returning fact
# resolutions.
#
# Classes including this mixin should implement a #name method describing
# the value being resolved and a #resolve_value that actually executes the code
# to resolve the value.
module LegacyFacter
  module Core
    module Resolvable
      # The timeout, in seconds, for evaluating this resolution.
      # @return [Integer]
      # @api public
      attr_accessor :timeout
      attr_reader :logger

      # Return the timeout period for resolving a value.
      # (see #timeout)
      # @return [Numeric]
      # @comment requiring 'timeout' stdlib class causes Object#timeout to be
      #   defined which delegates to Timeout.timeout. This method may potentially
      #   overwrite the #timeout attr_reader on this class, so we define #limit to
      #   avoid conflicts.
      def limit
        @timeout || 0
      end

      ##
      # on_flush accepts a block and executes the block when the resolution's value
      # is flushed.  This makes it possible to model a single, expensive system
      # call inside of a Ruby object and then define multiple dynamic facts which
      # resolve by sending messages to the model instance.  If one of the dynamic
      # facts is flushed then it can, in turn, flush the data stored in the model
      # instance to keep all of the dynamic facts in sync without making multiple,
      # expensive, system calls.
      #
      # Please see the Solaris zones fact for an example of how this feature may be
      # used.
      #
      # @see Facter::Util::Fact#flush
      # @see Facter::Util::Resolution#flush
      #
      # @api public
      def on_flush(&block)
        @on_flush_block = block
      end

      ##
      # flush executes the block, if any, stored by the {on_flush} method
      #
      # @see Facter::Util::Fact#flush
      # @see Facter::Util::Resolution#on_flush
      #
      # @api private
      def flush
        @on_flush_block&.call
      end

      # Resolves the fact's value or loggs an error if the value
      # couldn't be resolved.
      #
      # @raise Facter::ResolveCustomFactError if an error was raised
      # (except Timeout::Error or Narmalization::NarmalizationError
      # in which case an error message is logged and the execution
      # isn't suspended).
      #
      # @return value (hash, string, int, array, etc) or nil
      #
      # @api private
      def value
        result = nil

        with_timing do
          Timeout.timeout(limit) do
            result = resolve_value
          end
        end

        LegacyFacter::Util::Normalization.normalize(result)
      rescue Timeout::Error => e
        Facter.log_exception(e, "Timed out after #{limit} seconds while resolving #{qualified_name}")

        nil
      rescue LegacyFacter::Util::Normalization::NormalizationError => e
        Facter.log_exception(e, "Fact resolution #{qualified_name} resolved to an invalid value: #{e.message}")

        nil
      rescue StandardError => e
        Facter.log_exception(e, "Error while resolving custom fact #{qualified_name}: #{e.message}")

        raise Facter::ResolveCustomFactError
      end

      private

      def with_timing
        starttime = Time.now.to_f

        yield

        finishtime = Time.now.to_f
        ms = (finishtime - starttime) * 1000
        Facter::Log.show_time format('%<qn>s: %<ms>.2fms', qn: qualified_name, ms: ms)
      end

      def qualified_name
        "fact='#{@fact.name}', resolution='#{@name || '<anonymous>'}'"
      end
    end
  end
end