learningtapestry/lcms-engine

# frozen_string_literal: true

module Lcms
  module Engine
    class HierarchicalPosition
      RESOURCE_TYPE_ORDER = %w(resource media quick_reference_guide text_set).freeze

      attr_reader :resource

      def initialize(resource)
        @resource = resource
      end

      # Position mask:
      # - We use 7 blocks of 2 numbers for:
      #     subject, resource_types, grades (average if more than one), module, unit,
      #     lesson, num_of_grades
      # - The last position is the number of different grades covered, i.e:
      #   a resource with 3 different grades show after one with 2, (more specific
      #   at the top, more generic at the bottom)
      def position
        return default_position if dettached_resource?

        [
          subject_position, # subject
          resource_type_position, # resource_type
          resource.grades.average_number, # grades
          module_position, # module
          unit_position, # unit
          lesson_position, # lesson
          resource.grades.list.size # number of grades
        ].map { |v| v.to_s.rjust(2, '0') }.join(' ')
      end

      private

      def dettached_resource?
        resource.resource? && !resource.tree?
      end

      def default_position
        @default_position ||= Array.new(7, '99').join(' ')
      end

      def subject_position
        return 99 if resource.generic?

        val = Resource::SUBJECTS.index(resource.subject)
        val ? val + 1 : 99
      end

      def resource_type_position
        type = resource.media? ? 'media' : resource.resource_type
        RESOURCE_TYPE_ORDER.index(type)
      end

      def module_position
        position_for :module?
      end

      def unit_position
        position_for :unit?
      end

      def position_for(type)
        val = if !resource.persisted? && resource.send(type)
                resource.level_position
              else
                resource.self_and_ancestors_not_persisted.detect { |res| res.send type }&.level_position
              end
        val ? val + 1 : 0
      end

      def lesson_position
        val =  resource.lesson? ? resource.level_position : nil
        return val if val

        resource.metadata['lesson'].to_s.match(/(\d+)/)&.captures&.first.to_i
      end
    end
  end
end