path: root/activerecord/lib/active_record/associations/alias_tracker.rb

# frozen_string_literal: true

require "active_support/core_ext/string/conversions"

module ActiveRecord
  module Associations
    # Keeps track of table aliases for ActiveRecord::Associations::JoinDependency
    class AliasTracker # :nodoc:
      def self.create(connection, initial_table, joins)
        if joins.empty?
          aliases = Hash.new(0)
        else
          aliases = Hash.new { |h, k|
            h[k] = initial_count_for(connection, k, joins)
          }
        end
        aliases[initial_table] = 1
        new(connection, aliases)
      end

      def self.initial_count_for(connection, name, table_joins)
        quoted_name = nil

        counts = table_joins.map do |join|
          if join.is_a?(Arel::Nodes::StringJoin)
            # quoted_name should be case ignored as some database adapters (Oracle) return quoted name in uppercase
            quoted_name ||= connection.quote_table_name(name)

            # Table names + table aliases
            join.left.scan(
              /JOIN(?:\s+\w+)?\s+(?:\S+\s+)?(?:#{quoted_name}|#{name})\sON/i
            ).size
          elsif join.is_a?(Arel::Nodes::Join)
            join.left.name == name ? 1 : 0
          elsif join.is_a?(Hash)
            join[name]
          else
            raise ArgumentError, "joins list should be initialized by list of Arel::Nodes::Join"
          end
        end

        counts.sum
      end

      # table_joins is an array of arel joins which might conflict with the aliases we assign here
      def initialize(connection, aliases)
        @aliases    = aliases
        @connection = connection
      end

      def aliased_table_for(table_name, aliased_name, type_caster)
        if aliases[table_name].zero?
          # If it's zero, we can have our table_name
          aliases[table_name] = 1
          Arel::Table.new(table_name, type_caster: type_caster)
        else
          # Otherwise, we need to use an alias
          aliased_name = @connection.table_alias_for(aliased_name)

          # Update the count
          aliases[aliased_name] += 1

          table_alias = if aliases[aliased_name] > 1
            "#{truncate(aliased_name)}_#{aliases[aliased_name]}"
          else
            aliased_name
          end
          Arel::Table.new(table_name, type_caster: type_caster).alias(table_alias)
        end
      end

      attr_reader :aliases

      private
        def truncate(name)
          name.slice(0, @connection.table_alias_length - 2)
        end
    end
  end
end