module Arel
  module Nodes
    class Case < Arel::Nodes::Node
      include Arel::OrderPredications
      include Arel::Predications
      include Arel::AliasPredication

      attr_accessor :case, :conditions, :default

      def initialize expression = nil, default = nil
        @case = expression
        @conditions = []
        @default = default
      end

      def when condition, expression = nil
        @conditions << When.new(Nodes.build_quoted(condition), expression)
        self
      end

      def then expression
        @conditions.last.right = Nodes.build_quoted(expression)
        self
      end

      def else expression
        @default = Else.new Nodes.build_quoted(expression)
        self
      end

      def initialize_copy other
        super
        @case = @case.clone if @case
        @conditions = @conditions.map { |x| x.clone }
        @default = @default.clone if @default
      end

      def hash
        [@case, @conditions, @default].hash
      end

      def eql? other
        self.class == other.class &&
          self.case == other.case &&
          self.conditions == other.conditions &&
          self.default == other.default
      end
      alias :== :eql?
    end

    class When < Binary # :nodoc:
    end

    class Else < Unary # :nodoc:
    end
  end
end
