gistfile1.txt

grammar Interpolation
  rule document
    (text / variable / object / space)* {
      def content
        elements.map { |e| e.content }
      end
    }
  end

  ######################################################################
  # Main Literals

  rule text
    [^{:%]+ <TextLiteral>
  end

  rule variable
    space? "%{" name "}" space? <VariableLiteral>
  end

  rule object
    space? "%{" object_name assignment "}" space? <ObjectLiteral>
  end

  rule assignment
    '[' attribute_name space? '=' space? attribute_value ']' <AssignmentLiteral>
  end

  ######################################################################
  # Common Literals

  rule space
    [\s]+
  end

  rule name
    [A-Z:]+ {
      def content
        text_value
      end
    }
  end

  rule object_name
    [A-Z] 1..1 [A-Za-z:]+ {
      def content
        text_value
      end
    }
  end

  rule attribute_name
    '$' [a-z]+ {
      def content
        elements[1].text_value
      end
    }
  end

  rule attribute_value
    [^\]]+ {
      def content
        text_value
      end
    }
  end
end