osem-fcy/app/controllers/concerns/datatable_serverside_processing.rb

module DatatableServersideProcessing
  extend ActiveSupport::Concern

  def datatable_response(data)
    {
      sEcho: params[:sEcho].to_i,
      iTotalRecords: @collection.count,
      iTotalDisplayRecords: records.count,
      aaData: data
    }
  end

  def filtered_records(collection, search_columns, sort_columns)
    @collection = collection
    @search_columns = search_columns
    @sort_columns = sort_columns
    paginate(records)
  end

  private

  def records
    @records ||= fetch_records
  end

  def fetch_records
    sort_direction = params[:sSortDir_0] == 'desc' ? 'desc' : 'asc'
    sort_column = @sort_columns[params[:iSortCol_0].to_i]
    records = @collection.order("#{sort_column} #{sort_direction}")

    if params[:sSearch].present? && @search_columns.present?
      search_query = @search_columns.map{ |column|  "#{column} like :search" }.join(' or ')
      records = records.where(search_query, search: "%#{params[:sSearch]}%")
    end

    records
  end

  def paginate(records)
    per_page = params[:iDisplayLength].to_i > 0 ? params[:iDisplayLength].to_i : 10
    page = params[:iDisplayStart].to_i / per_page + 1
    records.offset((page - 1) * per_page).limit(per_page)
  end
end