wedding-planner/app/queries/expenses/total_query.rb

module Expenses
  class TotalQuery
    def call
      ActiveRecord::Base.connection.execute(query).first
    end

    private

    def query
      <<~SQL
        WITH guest_count AS (#{guest_count_per_status}),
             expense_summary AS (#{expense_summary})
        SELECT expense_summary.fixed,
               expense_summary.fixed_count,
               expense_summary.variable,
               expense_summary.variable_count,
               expense_summary.total_count,
               expense_summary.fixed + expense_summary.variable * guest_count.confirmed as total,
               expense_summary.fixed + expense_summary.variable * guest_count.projected as max_projected,
               (expense_summary.fixed + expense_summary.variable * guest_count.confirmed) / guest_count.confirmed as per_person
        FROM guest_count, expense_summary;
      SQL
    end

    def expense_summary
      <<~SQL
        SELECT coalesce(sum(amount) filter (where pricing_type = 'fixed'), 0) as fixed,
               coalesce(count(amount) filter (where pricing_type = 'fixed'), 0) as fixed_count,
               coalesce(sum(amount) filter (where pricing_type = 'per_person'), 0) as variable,
               coalesce(count(amount) filter (where pricing_type = 'per_person'), 0) as variable_count,
               count(*) as total_count
        FROM expenses
      SQL
    end

    def guest_count_per_status
      <<~SQL
        SELECT COALESCE(count(*) filter(where status = #{Guest.statuses["confirmed"]}), 0) as confirmed,
               COALESCE(count(*) filter(where status IN (#{Guest.statuses.values_at("confirmed", "invited", "tentative").join(",")})), 0) as projected
        FROM guests
      SQL
    end
  end
end