app/controllers/concerns/pagination_methods.rb

   1 # frozen_string_literal: true
   2
   3 module PaginationMethods
   4   extend ActiveSupport::Concern
   5
   6   private
   7
   8   ##
   9   # limit selected items to one page, get ids of first item before/after the page
  10   def get_page_items(items, includes: [], limit: 20, cursor_column: :id)
  11     param! :before, Integer, :min => 0
  12     param! :after, Integer, :min => 0
  13
  14     qualified_cursor_column = "#{items.table_name}.#{cursor_column}"
  15     page_items = if params[:before]
  16                    items.where("#{qualified_cursor_column} < ?", params[:before]).reorder(cursor_column => :desc)
  17                  elsif params[:after]
  18                    items.where("#{qualified_cursor_column} > ?", params[:after]).reorder(cursor_column => :asc)
  19                  else
  20                    items.reorder(cursor_column => :desc)
  21                  end
  22
  23     page_items = page_items.limit(limit)
  24     page_items = page_items.includes(includes)
  25     page_items = page_items.sort.reverse
  26
  27     newer_items_cursor = page_items.first&.send cursor_column
  28     older_items_cursor = page_items.last&.send cursor_column
  29
  30     [
  31       page_items,
  32       (newer_items_cursor if page_items.any? && items.exists?(["#{qualified_cursor_column} > ?", newer_items_cursor])),
  33       (older_items_cursor if page_items.any? && items.exists?(["#{qualified_cursor_column} < ?", older_items_cursor]))
  34     ]
  35   end
  36 end