class CourseSessionController < ApplicationController
  def index
    @sessions = CourseSession.
                  search(params[:q]).
                  by_course_type(params[:course_type_id]).
                  by_role(params[:role_id]).
                  paginate(page_params).
                  order(ordering_params)
  end
end

class CourseSessionController < ApplicationController
  def index
    @sessions = rubanok_process(
      # pass input
      CourseSession.all,
      # pass params
      params,
      # provide a processor to use
      with: CourseSessionsProcessor
    )
  end
end

class CourseSessionController < ApplicationController
  def index
    @sessions = rubanok_process(CourseSession.all)
  end
end

gem "rubanok"

class CourseSessionsProcessor < Rubanok::Processor
  # You can map keys
  map :q do |q:|
    # `raw` is an accessor for input data
    raw.search(q)
  end
end

# The following code
CourseSessionsProcessor.call(CourseSession.all, q: "xyz")

# is equal to
CourseSession.all.search("xyz")

class CourseSessionsProcessor < Rubanok::Processor
  DEFAULT_PAGE_SIZE = 25

  map :page, :per_page do |page:, per_page: DEFAULT_PAGE_SIZE|
    raw.paginate(page: page, per_page: per_page)
  end
end

class CourseSessionsProcessor < Rubanok::Processor
  SORT_ORDERS = %w(asc desc).freeze
  SORTABLE_FIELDS = %w(id name created_at).freeze

  match :sort_by, :sort do
    having "course_id", "desc" do
      raw.joins(:courses).order("courses.id desc nulls last")
    end

    having "course_id", "asc" do
      raw.joins(:courses).order("courses.id asc nulls first")
    end

    # Match any value for the second arg
    having "type" do |sort: "asc"|
      # Prevent SQL injections
      raise "Possible injection: #{sort}" unless SORT_ORDERS.include?(sort)
      raw.joins(:course_type).order("course_types.name #{sort}")
    end

    # Match any value
    default do |sort_by:, sort: "asc"|
      raise "Possible injection: #{sort}" unless SORT_ORDERS.include?(sort)
      raise "The field is not sortable: #{sort_by}" unless SORTABLE_FIELDS.include?(sort_by)
      raw.order(sort_by => sort)
    end
  end

  # strict matching; if Processor will not match parameter, it will raise Rubanok::UnexpectedInputError
  # You can handle it in controller, for example, with sending 422 Unprocessable Entity to client
  match :filter, fail_when_no_matches: true do
    having "active" do
      raw.active
    end

    having "finished" do
      raw.finished
    end
  end
end

class CourseSessionController < ApplicationController
  def index
    @sessions = rubanok_process(CourseSession.all)
    # Returns the Hash of params recognized by the CourseSessionProcessor.
    # For example:
    #
    #    params == {q: "search", role_id: 2, date: "2019-08-22"}
    #    @session_filter == {q: "search", role_id: 2}
    @sessions_filter = rubanok_scope(
      params.permit(:q, :role_id),
      with: CourseSessionProcessor
    )

    # You can omit all the arguments
    @sessions_filter = rubanok_scope #=> equals to rubanok_scope(params, with: implicit_rubanok_class)
  end
end

# Always apply the rule; use default values for keyword args
map :page, :per_page, activate_always: true do |page: 1, per_page: 2|
  raw.page(page).per(per_page)
end

# Only require `sort_by` to be preset to activate sorting rule
match :sort_by, :sort, activate_on: :sort_by do
 # ...
end

# For example, with RSpec
RSpec.describe CourseSessionsProcessor do
  let(:input ) { CourseSession.all }
  let(:params) { {} }

  subject { described_class.call(input, params) }

  specify "searching" do
    params[:q] = "wood"

    expect(subject).to eq input.search("wood")
  end
end

RSpec.describe CourseSessionController do
  subject { get :index }

  specify do
    expect { subject }.to have_rubanok_processed(CourseSession.all).
      with(CourseSessionsProcessor)
  end
end

require "rubanok/rspec"

class ApplicationController < ActionController::Smth
  # override the `implicit_rubanok_class` method
  def implicit_rubanok_class
    "#{controller_path.classify.pluralize}Scoper".safe_constantize
  end
end

class CourseSessionsController < ApplicationController
  def index
    @sessions = rubanok_process(CourseSession.all, params)
    # which equals to
    @sessions = CourseSessionsScoper.call(CourseSession.all, params.to_unsafe_h)
  end
end