module ActiveExt
  module DataStructures
    class Columns
      include Enumerable

      # This collection is referenced by other parts of ActiveExt and by methods within this DataStructure.
      # IT IS NOT MEANT FOR PUBLIC USE (but if you know what you're doing, go ahead)
      def _inheritable=(value)
        @sorted = true
        @_inheritable = value
      end

      # This accessor is used by ActionColumns to create new Column objects without adding them to this set
      attr_reader :active_record_class

      def initialize(active_record_class, *args)
        @active_record_class = active_record_class
        @_inheritable = []
        @excluded_columns = []
        @set = []

        self.add *args
      end

      # the way to add columns to the set. this is primarily useful for virtual columns.
      # note that this also makes columns inheritable
      def add(*args)
        args.flatten! # allow [] as a param
        args = args.collect { |a| a.to_sym }

        # make the columns inheritable
        @_inheritable.concat(args)
        # then add columns to @set (unless they already exist)
        args.each { |a| @set << ActiveExt::DataStructures::Column.new(a.to_sym, @active_record_class) unless find_by_name(a) }
      end

      alias_method :<<, :add

      def exclude(*args)
        # only remove columns from _inheritable. we never want to completely forget about a column.
        args.each { |a| @_inheritable.delete a }
        @excluded_columns.concat(args)
      end

      # returns an array of columns with the provided names
      def find_by_names(*names)
        @set.find_all { |column| names.include? column.name }
      end

      # returns the column of the given name.
      def find_by_name(name)
        # this works because of `def column.=='
        column = @set.find { |c| c.name == name }
        column
      end

      alias_method :[], :find_by_name

      def each
        @set.each { |i| yield i }
      end

      def exclude_column?(name)
        @excluded_columns.include?(name)
      end

    end
  end
end