class Budget
  class Stats

    def initialize(budget)
      @budget = budget
    end

    def generate
      stats = %w[total_participants total_participants_support_phase total_participants_vote_phase total_budget_investments total_votes
                 total_selected_investments total_unfeasible_investments total_male_participants total_female_participants total_supports
                 total_unknown_gender_or_age age_groups male_percentage female_percentage headings]
      stats.map { |stat_name| [stat_name.to_sym, send(stat_name)] }.to_h
    end

    private

      def total_participants
        stats_cache("total_participants") { participants.distinct.count }
      end

      def total_participants_support_phase
        stats_cache("total_participants_support_phase") { voters.uniq.count }
      end

      def total_participants_vote_phase
        stats_cache("total_participants_vote_phase") { balloters.uniq.count }
      end

      def total_budget_investments
        stats_cache("total_budget_investments") { @budget.investments.count }
      end

      def total_votes
        stats_cache("total_votes") { @budget.ballots.map(&:lines).count }
      end

      def total_selected_investments
        stats_cache("total_selected_investments") { @budget.investments.selected.count }
      end

      def total_unfeasible_investments
        stats_cache("total_unfeasible_investments") { @budget.investments.unfeasible.count }
      end

      def total_male_participants
        stats_cache("total_male_participants") { participants.where(gender: "male").count }
      end

      def total_female_participants
        stats_cache("total_female_participants") { participants.where(gender: "female").count }
      end

      def total_supports
        stats_cache("total_supports") { supports(@budget).count }
      end

      def total_unknown_gender_or_age
        stats_cache("total_unknown_gender_or_age") do
          participants.where("gender IS NULL OR date_of_birth is NULL").uniq.count
        end
      end

      def age_groups
        stats_cache("age_groups") do
          groups = Hash.new(0)
          ["16 - 19",
           "20 - 24",
           "25 - 29",
           "30 - 34",
           "35 - 39",
           "40 - 44",
           "45 - 49",
           "50 - 54",
           "55 - 59",
           "60 - 64",
           "65 - 69",
           "70 - 140"].each do |group|
            start, finish = group.split(" - ")
            group_name = (group == "70 - 140" ? "+ 70" : group)
            groups[group_name] = User.where(id: participants)
                                     .where("date_of_birth > ? AND date_of_birth < ?",
                                            finish.to_i.years.ago.beginning_of_year,
                                            start.to_i.years.ago.end_of_year).count
          end
          groups
        end
      end

      def male_percentage
        stats_cache("male_percentage") { total_male_participants / total_participants_with_gender.to_f * 100 }
      end

      def female_percentage
        stats_cache("female_percentage") { total_female_participants / total_participants_with_gender.to_f * 100 }
      end

      def participants
        stats_cache("participants") { User.where(id: (authors + voters + balloters).uniq) }
      end

      def authors
        stats_cache("authors") { @budget.investments.pluck(:author_id) }
      end

      def voters
        stats_cache("voters") { supports(@budget).pluck(:voter_id) }
      end

      def balloters
        stats_cache("balloters") { @budget.ballots.where("ballot_lines_count > ?", 0).pluck(:user_id) }
      end

      def total_participants_with_gender
        stats_cache("total_participants_with_gender") { participants.where.not(gender: nil).distinct.count }
      end

      def balloters_by_heading(heading_id)
        stats_cache("balloters_by_heading_#{heading_id}") do
          @budget.ballots.joins(:lines).where(budget_ballot_lines: {heading_id: heading_id}).pluck(:user_id)
        end
      end

      def voters_by_heading(heading)
        stats_cache("voters_by_heading_#{heading.id}") do
          supports(heading).pluck(:voter_id)
        end
      end

      def headings
        stats_cache("headings") do
          groups = Hash.new(0)
          @budget.headings.order("id ASC").each do |heading|
            groups[heading.id] = Hash.new(0).merge(calculate_heading_totals(heading))
          end

          groups[:total] = Hash.new(0)
          groups[:total][:total_participants_support_phase] = groups.collect {|_k, v| v[:total_participants_support_phase]}.sum
          groups[:total][:total_participants_vote_phase] = groups.collect {|_k, v| v[:total_participants_vote_phase]}.sum
          groups[:total][:total_participants_all_phase] = groups.collect {|_k, v| v[:total_participants_all_phase]}.sum

          @budget.headings.each do |heading|
            groups[heading.id].merge!(calculate_heading_stats_with_totals(groups[heading.id], groups[:total], heading.population))
          end

          groups[:total][:percentage_participants_support_phase] = groups.collect {|_k, v| v[:percentage_participants_support_phase]}.sum
          groups[:total][:percentage_participants_vote_phase] = groups.collect {|_k, v| v[:percentage_participants_vote_phase]}.sum
          groups[:total][:percentage_participants_all_phase] = groups.collect {|_k, v| v[:percentage_participants_all_phase]}.sum

          groups
        end
      end

      def calculate_heading_totals(heading)
        {
          total_participants_support_phase: voters_by_heading(heading).uniq.count,
          total_participants_vote_phase: balloters_by_heading(heading.id).uniq.count,
          total_participants_all_phase: voters_and_balloters_by_heading(heading)
        }
      end

      def calculate_heading_stats_with_totals(heading_totals, groups_totals, population)
        {
          percentage_participants_support_phase: participants_percent(heading_totals, groups_totals, :total_participants_support_phase),
          percentage_district_population_support_phase: population_percent(population, heading_totals[:total_participants_support_phase]),
          percentage_participants_vote_phase: participants_percent(heading_totals, groups_totals, :total_participants_vote_phase),
          percentage_district_population_vote_phase: population_percent(population, heading_totals[:total_participants_vote_phase]),
          percentage_participants_all_phase: participants_percent(heading_totals, groups_totals, :total_participants_all_phase),
          percentage_district_population_all_phase: population_percent(population, heading_totals[:total_participants_all_phase])
        }
      end

      def voters_and_balloters_by_heading(heading)
        (voters_by_heading(heading) + balloters_by_heading(heading.id)).uniq.count
      end

      def participants_percent(heading_totals, groups_totals, phase)
        calculate_percentage(heading_totals[phase], groups_totals[phase])
      end

      def population_percent(population, participants)
        return "N/A" unless population.to_f.positive?
        calculate_percentage(participants, population)
      end

      def calculate_percentage(fraction, total)
        percent = fraction / total.to_f
        percent.nan? ? 0.0 : (percent * 100).round(2)
      end

      def supports(supportable)
        ActsAsVotable::Vote.where(votable_type: "Budget::Investment", votable_id: supportable.investments.pluck(:id))
      end

      def stats_cache(key, &block)
        Rails.cache.fetch("budgets_stats/#{@budget.id}/#{key}/v10", &block)
      end
  end
end