module ActiveRecord
  module Associations
    class JoinDependency
      class Aliases # :nodoc:
        def column_alias(node, column)
          # CPK
          #@alias_cache[node][column]
          if column.kind_of?(Array)
            column.map do |a_column|
              @alias_cache[node][a_column]
            end
          else
            @alias_cache[node][column]
          end
        end
      end

      def instantiate(result_set, &block)
        primary_key = aliases.column_alias(join_root, join_root.primary_key)

        seen = Hash.new { |i, object_id|
          i[object_id] = Hash.new { |j, child_class|
            j[child_class] = {}
          }
        }

        model_cache = Hash.new { |h, klass| h[klass] = {} }
        parents = model_cache[join_root]
        column_aliases = aliases.column_aliases join_root

        message_bus = ActiveSupport::Notifications.instrumenter

        payload = {
            record_count: result_set.length,
            class_name: join_root.base_klass.name
        }

        message_bus.instrument("instantiation.active_record", payload) do
          result_set.each { |row_hash|
            # CPK
            # parent_key = primary_key ? row_hash[primary_key] : row_hash
            # CPK
            parent_key = if primary_key.kind_of?(Array)
                           primary_key.map {|key| row_hash[key]}
                         else
                           primary_key ? row_hash[primary_key] : row_hash
                         end

            parent = parents[parent_key] ||= join_root.instantiate(row_hash, column_aliases, &block)
            construct(parent, join_root, row_hash, seen, model_cache)
          }
        end

        parents.values
      end

      def construct(ar_parent, parent, row, seen, model_cache)
        return if ar_parent.nil?

        parent.children.each do |node|
          if node.reflection.collection?
            other = ar_parent.association(node.reflection.name)
            other.loaded!
          elsif ar_parent.association_cached?(node.reflection.name)
            model = ar_parent.association(node.reflection.name).target
            construct(model, node, row, seen, model_cache)
            next
          end

          key = aliases.column_alias(node, node.primary_key)

          # CPK
          if key.is_a?(Array)
            id = Array(key).map do |column_alias|
              row[column_alias]
            end
            # At least the first value in the key has to be set.  Should we require all values to be set?
            id = nil if id.first.nil?
          else # original
            id = row[key]
          end

          if id.nil? # duplicating this so it is clear what remained unchanged from the original
            nil_association = ar_parent.association(node.reflection.name)
            nil_association.loaded!
            next
          end

          model = seen[ar_parent.object_id][node][id]

          if model
            construct(model, node, row, seen, model_cache)
          else
            model = construct_model(ar_parent, node, row, model_cache, id)

            seen[ar_parent.object_id][node][id] = model
            construct(model, node, row, seen, model_cache)
          end
        end
      end
    end
  end
end