module ActiveRecord
  module Associations
    class Preloader
      class Association
        def query_scope(ids)
          # CPK
          # scope.where(association_key.in(ids))

          if reflection.foreign_key.is_a?(Array)
            predicate = cpk_in_predicate(table, reflection.foreign_key, ids)
            scope.where(predicate)
          else
            scope.where(association_key.in(ids))
          end
        end

        def associated_records_by_owner(preloader)
          owners_map = owners_by_key
          # CPK
          # owner_keys = owners_map.keys.compact
          owner_keys = if reflection.foreign_key.is_a?(Array)
            owners.map do |owner|
              Array(owner_key_name).map do |owner_key|
                owner[owner_key]
              end
            end.compact.uniq
          else
            owners_map.keys.compact
          end

          # Each record may have multiple owners, and vice-versa
          records_by_owner = owners.each_with_object({}) do |owner,h|
            h[owner] = []
          end

          if owner_keys.any?
            # Some databases impose a limit on the number of ids in a list (in Oracle it's 1000)
            # Make several smaller queries if necessary or make one query if the adapter supports it
            sliced  = owner_keys.each_slice(klass.connection.in_clause_length || owner_keys.size)

            records = load_slices sliced
            records.each do |record, owner_key|
              owners_map[owner_key].each do |owner|
                records_by_owner[owner] << record
              end
            end
          end

          records_by_owner
        end

        def load_slices(slices)
          @preloaded_records = slices.flat_map { |slice|
            records_for(slice)
          }

          @preloaded_records.map { |record|
            # CPK
            #[record, record[association_key_name]]
            owner_key = Array(association_key_name).map do |key_name|
              record[key_name]
            end.join(CompositePrimaryKeys::ID_SEP)
            [record, owner_key]
          }
        end

        def owners_by_key
          @owners_by_key ||= if key_conversion_required?
                               owners.group_by do |owner|
                                 # CPK
                                 # owner[owner_key_name].to_s
                                 key = Array(owner_key_name).map do |key_name|
                                   owner[key_name]
                                 end.join(CompositePrimaryKeys::ID_SEP)
                               end
                             else
                               owners.group_by do |owner|
                                 # CPK
                                 # owner[owner_key_name]
                                 key = Array(owner_key_name).map do |key_name|
                                   owner[key_name]
                                 end.join(CompositePrimaryKeys::ID_SEP)
                               end
                             end
                             
        end
      end
    end
  end
end