prueba.rb

rails.rb

class Api::CarSearch
  include SearchObject.module(:paging)
  include SearchObject.module(:sorting)

  per_page 1
  min_per_page 1
  max_per_page 50
  sort_by :price

  option(:price_min) { |scope, value| scope.where('price > ?', value)  }
  option(:price_max) { |scope, value| scope.where('price < ?', value)  }

  # https://stackoverflow.com/questions/11823689/how-to-make-sure-a-record-is-always-at-the-top-in-a-given-resultset-in-mysql
  # https://stackoverflow.com/questions/48743316/ruby-on-rails-active-record-sort-and-put-specific-row-to-the-top
  # https://stackoverflow.com/questions/23620615/how-to-sort-activerecord-query-by-specific-prority
  # Implement Priority sending using the order clause.
  # ------
  # With this approach I can paginate easily using SQL and avoid merge manually differents sources of cars and then paginate it manually
  # ------
  # This technique are respeting the price_min and price_max filters but the perfect match and good match
  # will be in the top no matter if the price dont fit with the filter rules 
  def initialize(options={})
    counter_priority = 0
    super options.merge(scope: Car.order(
      Arel.sql(
        "
        CASE
          #{
            options[:top_results_id][:car_perfect_match_ids].map do |id|
              counter_priority += 1
              "WHEN (id = #{id}) THEN #{counter_priority} "
            end.join(' ') + 
            options[:top_results_id][:car_good_match_ids].map do |id|
              counter_priority += 1
              "WHEN (id = #{id}) THEN #{counter_priority} "
            end.join(' ') +
            options[:top_results_id][:car_external_recommendation_ids].map do |id|
              counter_priority += 1
              "WHEN (id = #{id}) THEN #{counter_priority} "
            end.join(' ')
          }
        END ASC"
      )
    ).all)
  end
end

class Api::CarSearchController < ApplicationController
  def index
    @user = User.find(params[:user_id])

    # 1. On top it should be cars with perfect_match label. This cars have match
    #    with user preferred car brands ( user.preferred_brands.include?(car.brand) == true)
    #    and with preferred price (user.preferred_price_range.include?(car.price) == true).

    car_perfect_match_ids  = (20..25).to_a

    # 2. Then we should have good_match offers. These offers have the only user
    #     preferred car brands (user.preferred_brands.include?(car.brand) == true).

    car_good_match_ids  = (40..45).to_a

    # 3. Then goes top 5 cars suggested by external recommendation service API
    #    (they can also be matched as perfect and good matches).

    car_external_recommendation_ids = (60..65).to_a

    # 4. Then goes all other cars sorted by price (ASC).
    @search = Api::CarSearch.new(
      filters: get_search_filter_params.merge(
        { sort: 'price asc' }
      ),
      page: params[:page],
      per_page: params[:per_page],
      top_results_id: {
        car_perfect_match_ids: car_perfect_match_ids,
        car_good_match_ids: car_good_match_ids,
        car_external_recommendation_ids: car_external_recommendation_ids
      }
    )
  end

  private

  def get_search_filter_params
    params.slice(:user_id, :query, :price_min, :price_max, :free)
  end
end