statistics_controller.rb

# app/controllers/statistics_controller.rb
class StatisticsController < ApplicationController
  # ...
  def weekly
    @weekly = []

    get_date.each do |date_obj|
      day = date_obj[:start_day].strftime('%A %d-%m-%Y')
      orders = get_orders(date_obj)
      orders_sum = orders.map(&:price).reduce(:+)
      pizza_count = orders
                    .map { |order| order.items.where(type: :pizza).count }
                    .reduce(:+)

      pizza_arr = get_pizza_arr(orders)
      users_arr = get_users_arr(orders)

      @weekly.push(
        day: day,
        pizza_count: pizza_count,
        orders_sum: orders_sum,
        users: users_arr,
        pizza: pizza_arr
      )
    end
  end

  private

  ##
  # returns array
  # like this
  # [ { pizza: <Item>, count: 10},
  #   { pizza: <Item>, count: 8},
  #   { pizza: <Item>, count: 7},]

  def get_pizza_arr(orders, pizza_count)
    pizza_hash = Hash.new(0)
    orders
      .map { |order| order.items.where(type: :pizza) }
      .reduce(:+).each { |item| pizza_hash[item.id] += 1 }
    pizza_hash = pizza_hash.sort_by { |k, v| v }.reverse.to_h
    Hash[pizza_hash.sort_by { |k,v| -v }[0..2]].map do |k,v|
      {
        pizza: Item.find(k),
        count: v
      }
    end
  end

  ##
  # return array like this
  # [ {user: <User>, sum: 1000},
  #   {user: <User>, sum: 900},
  #   {user: <User>, sum: 850}]

  def get_users_arr(orders)
    users_hash = Hash.new(0)
    orders.each { |order| users_hash[order.user_id] += order.price }
    users_hash = users_hash.sort_by { |k, v| v }.reverse.to_h
    Hash[users_hash.sort_by { |k,v| -v }[0..2]].map do |k,v|
      {
        user: User.find(k),
        sum: v
      }
    end
  end

  def get_orders(date_obj)
    Order.preload(:user, :items).where(
      'created_at >= :start_day AND created_at < :end_day',
      start_day: date_obj[:start_day],
      end_day: date_obj[:end_day]
    )
  end

  ##
  # it returns something like this
  # [ {start_day: Mon, 08 May 2017 00:00:00 +0300,
  #     end_day:  Tue, 09 May 2017 00:00:00 +0300},
  #   {start_day: Tue, 09 May 2017 00:00:00 +0300,
  #     end_day:  Wed, 10 May 2017 00:00:00 +0300},
  #   {start_day: Wed, 10 May 2017 00:00:00 +0300,
  #     end_day:  Thu, 11 May 2017 00:00:00 +0300},
  #   {start_day: Thu, 11 May 2017 00:00:00 +0300,
  #     end_day:  Fri, 12 May 2017 00:00:00 +0300},
  #   {start_day: Fri, 12 May 2017 00:00:00 +0300,
  #     end_day:  Sat, 13 May 2017 00:00:00 +0300},
  #   {start_day: Sat, 13 May 2017 00:00:00 +0300,
  #     end_day:  Sun, 14 May 2017 00:00:00 +0300},
  #   {start_day: Sun, 14 May 2017 00:00:00 +0300,
  #     end_day:  Mon, 15 May 2017 00:00:00 +0300}]

  def get_date
    arr = []
    start_day = nil
    loop do
      unless start_day.present?
        start_day = DateTime.current.beginning_of_week
      else
        start_day += 1.day
      end
      end_day = start_day + 1.day

      arr.push(
        start_day: start_day,
        end_day: end_day
      )
      break if end_day > DateTime.current.end_of_week
    end
    arr
  end
# ...
end