require "rss/1.0"

module RSS

	SY_PREFIX = 'sy'
	SY_URI = "http://purl.org/rss/1.0/modules/syndication/"

	RDF.install_ns(SY_PREFIX, SY_URI)

	module SyndicationModel
		
		extend BaseModel
		
		ELEMENTS = []
		
		def self.append_features(klass)
			super
			
			klass.module_eval(<<-EOC)
				%w(updatePeriod updateFrequency).each do |x|
					install_text_element("\#{SY_PREFIX}_\#{x}")
				end

				%w(updateBase).each do |x|
					install_date_element("\#{SY_PREFIX}_\#{x}", 'w3cdtf', x)
				end

				alias_method(:_sy_updatePeriod=, :sy_updatePeriod=)
				def sy_updatePeriod=(new_value)
					new_value = new_value.strip
					validate_sy_updatePeriod(new_value) if @do_validate
					self._sy_updatePeriod = new_value
				end

				alias_method(:_sy_updateFrequency=, :sy_updateFrequency=)
				def sy_updateFrequency=(new_value)
					new_value = new_value.strip
					validate_sy_updateFrequency(new_value) if @do_validate
					self._sy_updateFrequency = new_value.to_i
				end
			EOC
		end

		def sy_validate(tags)
			counter = {}
			ELEMENTS.each do |x|
				counter[x] = 0
			end

			tags.each do |tag|
				key = "#{SY_PREFIX}_#{tag}"
				raise UnknownTagError.new(tag, SY_URI)  unless counter.has_key?(key)
				counter[key] += 1
				raise TooMuchTagError.new(tag, tag_name) if counter[key] > 1
			end
		end

		private
		SY_UPDATEPERIOD_AVAILABLE_VALUES = %w(hourly daily weekly monthly yearly)
		def validate_sy_updatePeriod(value)
			unless SY_UPDATEPERIOD_AVAILABLE_VALUES.include?(value)
				raise NotAvailableValueError.new("updatePeriod", value)
			end
		end

		SY_UPDATEFREQUENCY_AVAILABLE_RE = /\A\s*\+?\d+\s*\z/
		def validate_sy_updateFrequency(value)
			if SY_UPDATEFREQUENCY_AVAILABLE_RE !~ value
				raise NotAvailableValueError.new("updateFrequency", value)
			end
		end

	end

	class RDF
		class Channel; include SyndicationModel; end
	end

	prefix_size = SY_PREFIX.size + 1
	SyndicationModel::ELEMENTS.uniq!
	SyndicationModel::ELEMENTS.each do |x|
		BaseListener.install_get_text_element(x[prefix_size..-1], SY_URI, "#{x}=")
	end

end