#  Copyright (c) 2012-2021, Jungwacht Blauring Schweiz. This file is part of
#  hitobito and licensed under the Affero General Public License version 3
#  or later. See the COPYING file at the top-level directory or at
#  https://github.com/hitobito/hitobito.

class Event::Filter
  attr_reader :type, :filter, :group, :year, :sort_expression

  def initialize(group, type, filter, year, sort_expression)
    @group = group
    @type = type
    @filter = filter
    @year = year
    @sort_expression = sort_expression
    @sort_expression = Arel.sql(sort_expression) if sort_expression.is_a?(String)
  end

  def list_entries
    if sort_expression.is_a?(String)
      sort_expression_query_value = sort_expression.gsub(/\b\w+\./, "")
    elsif sort_expression.is_a?(Hash)
      sort_expression_query_value =
        "#{sort_expression.keys[0].gsub(/\b\w+\./, "")} #{sort_expression.values[0]}"
    end

    sort_expression ? scope.reorder(Arel.sql(sort_expression_query_value)) : scope
  end

  def scope
    # This must run as an explicite separate query.
    # If you merge this in the following relation, activerecord+kaminari
    # will mess up the queries (pagination is run on the wrong query).
    event_ids_for_relevant_groups_and_dates = Event.with_group_id(relevant_group_ids).in_year(year).pluck(:id)

    Event # nesting restricts to parent, we want more
      .where(id: event_ids_for_relevant_groups_and_dates)
      .list
      .where(type: type)
      .includes(:groups, :events_groups)
      .preload_all_dates
      .select(:id)
  end

  def to_h
    {year: year,
     type: type,
     filter: filter,
     sort_expression: sort_expression}
  end

  private

  def relevant_group_ids
    case filter
    when "layer" then [group.id] + descendants(layer: true).pluck(:id)
    else [group.id] + descendants.pluck(:id) # handles 'all' also
    end
  end

  def descendants(layer: false)
    scope = group.descendants
    layer ? scope.where(layer_group_id: group.layer_group_id) : scope
  end
end
