class Phlex::SGML

def __styles__(styles)
	case styles
	when Array, Set
		styles.filter_map do |s|
			case s
			when String
				if s == "" || s.end_with?(";")
					s
				else
					"#{s};"
				end
			when Phlex::SGML::SafeObject
				value = s.to_s
				value.end_with?(";") ? value : "#{value};"
			when Hash
				next __styles__(s)
			when nil
				next nil
			else
				raise Phlex::ArgumentError.new("Invalid style: #{s.inspect}.")
			end
		end.join(" ")
	when Hash
		buffer = +""
		i = 0
		styles.each do |k, v|
			prop = case k
			when String
				k
			when Symbol
				k.name.tr("_", "-")
			else
				raise Phlex::ArgumentError.new("Style keys should be Strings or Symbols.")
			end
			value = case v
			when String
				v
			when Symbol
				v.name.tr("_", "-")
			when Integer, Float, Phlex::SGML::SafeObject
				v.to_s
			when nil
				nil
			else
				raise Phlex::ArgumentError.new("Invalid style value: #{v.inspect}")
			end
			if value
				if i == 0
					buffer << prop << ": " << value << ";"
				else
					buffer << " " << prop << ": " << value << ";"
				end
			end
			i += 1
		end
		buffer
	end
end