module DbCharmer
  module ActiveRecordExtensions
    module ClassMethods

      def establish_real_connection_if_exists(name, should_exist = false)
        name = name.to_s
        config = configurations[RAILS_ENV][name]
        unless config
          if should_exist
            raise ArgumentError, "Invalid connection name (does not exist in database.yml): #{RAILS_ENV}/#{name}"
          end
          return # No need to establish connection - they do not want us to
        end
        # Pass connection name with config
        config[:connection_name] = name
        establish_connection(config)
      end

      #-----------------------------------------------------------------------------
      @@db_charmer_opts = {}
      def db_charmer_opts=(opts)
        @@db_charmer_opts[self.name] = opts
      end

      def db_charmer_opts
        @@db_charmer_opts[self.name] || {}
      end

      #-----------------------------------------------------------------------------
      @@db_charmer_connection_proxies = {}
      def db_charmer_connection_proxy=(proxy)
        @@db_charmer_connection_proxies[self.name] = proxy
      end

      def db_charmer_connection_proxy
        @@db_charmer_connection_proxies[self.name]
      end

      #-----------------------------------------------------------------------------
      @@db_charmer_slaves = {}
      def db_charmer_slaves=(slaves)
        @@db_charmer_slaves[self.name] = slaves
      end

      def db_charmer_slaves
        @@db_charmer_slaves[self.name] || []
      end

      def db_charmer_random_slave
        return nil unless db_charmer_slaves.any?
        db_charmer_slaves[rand(db_charmer_slaves.size)]
      end

      #-----------------------------------------------------------------------------
      @@db_charmer_connection_levels = Hash.new(0)
      def db_charmer_connection_level=(level)
        @@db_charmer_connection_levels[self.name] = level
      end

      def db_charmer_connection_level
        @@db_charmer_connection_levels[self.name] || 0
      end

      def db_charmer_top_level_connection?
        db_charmer_connection_level.zero?
      end

      #-----------------------------------------------------------------------------
      @@db_charmer_database_remappings = Hash.new
      def db_charmer_remapped_connection
        return nil if (db_charmer_connection_level || 0) > 0
        name = :master
        proxy = db_charmer_connection_proxy
        name = proxy.db_charmer_connection_name.to_sym if proxy

        remapped = @@db_charmer_database_remappings[name]
        remapped ? DbCharmer::ConnectionFactory.connect(remapped, true) : nil
      end

      def db_charmer_database_remappings
        @@db_charmer_database_remappings
      end

      def db_charmer_database_remappings=(mappings)
        raise "Mappings must be nil or respond to []" if mappings && (! mappings.respond_to?(:[]))
        @@db_charmer_database_remappings = mappings || { }
      end

      #-----------------------------------------------------------------------------
      def hijack_connection!
        return if self.respond_to?(:connection_with_magic)
        class << self
          def connection_with_magic
            db_charmer_remapped_connection || db_charmer_connection_proxy || connection_without_magic
          end
          alias_method_chain :connection, :magic
        end
      end

    end
  end
end