application_progress.rb

# NOTE: There are Application pages we need to calculate progress for.
#       Every page has specific rules/conditions how to estimate progress.
#       Rules have scores/weights and they are used to calculate progress.
#       pages = {
#         home_page: { home_page_rule => score },
#         info_page: { info_page_rule_1 => score_1, info_page_rule_2 => score_2 }
#       }

module ApplicationProgress
  module Rules
    def self.present?(attr, data)
      !data[attr].nil?
    end

    def self.present_or(*attrs)
      lambda do |data|
        attrs.reduce(false) { |acc, attr| acc || present?(attr, data) }
      end
    end

    def self.present_and(*attrs)
      lambda do |data|
        attrs.reduce(true) { |acc, attr| acc && present?(attr, data) }
      end
    end
  end

  module FirstPage
    def self.rules
      { Rules.present_and(:age) => 1,
        Rules.present_or(:sex, :gender) => 3 }
    end
  end

  module SecondPage
    def self.rules
      { Rules.present_and(:first_name, :last_name) => 2 }
    end
  end
  
  def self.calculate(pages, application)
    score = lambda do |rules, data|
      rules
        .select { |rule, _| rule.call(data) }
        .values
        .reduce(:+)
    end

    pages.reduce({}) do |acc, (page_name, rules)|
      acc.merge(page_name => score.call(rules, application))
    end
  end
end

# main
pages = { first_page: ApplicationProgress::FirstPage.rules,
          second_page: ApplicationProgress::SecondPage.rules }
application = { age: 28, first_name: 'Maxim', last_name: 'K', sex: 'M' }

ApplicationProgress.calculate(pages, application) # => { first_page: 4, second_page: 2 }