path: root/activesupport/lib/active_support/file_update_checker.rb

module ActiveSupport
  # This class is responsible to track files and invoke the given block
  # whenever one of these files are changed. For example, this class
  # is used by Rails to reload routes whenever they are changed upon
  # a new request.
  #
  #   routes_reloader = ActiveSupport::FileUpdateChecker.new(paths) do
  #     paths.each { |p| load(p) }
  #     Rails::Application.routes.reload!
  #   end
  #
  #   ActionDispatch::Callbacks.to_prepare do
  #     routes_reloader.execute_if_updated
  #   end
  #
  class FileUpdateChecker
    attr_reader :paths, :last_update_at

    def initialize(paths, calculate=false, &block)
      @paths = paths
      @block = block
      @last_update_at = calculate ? updated_at : nil
    end

    def updated_at
      paths.map { |path| File.stat(path).mtime }.max
    end

    def execute_if_updated
      current_update_at = self.updated_at
      if @last_update_at != current_update_at
        @last_update_at = current_update_at
        @block.call
      end
    end
  end
end