# coding: utf-8
require 'set'

require 'category'

class Page
	# Page is an abstract class.
	#
	# Implementors must implement several methods:
	#
	#     def url => URI
	#     def atom_title => String
	#     def atom_author => Person
	#     def atom_content => html | nil
	#     def atom_rights => html | nil
	#
	#     def page_categories => String | Enumerable<String>
	#
	#     def page_published => DateTime | nil
	#     def page_updated => DateTime | nil
	#     def page_years => Enumerable<Fixnum>

	def atom_categories # => Enumerable<Category>
		if @categories.nil?
			raw = page_categories
			if raw.is_a?(String)
				raw = raw.split
			end
			@categories = raw.map{|abbr|Category.new(abbr)}
		end
		@categories
	end

	def atom_published # => DateTime | nil
		if @published.nil?
			unless page_published.nil?
				@published = page_published
			else
				unless page_updated.nil?
					@published = page_updated
				end
			end
			# sanity check
			unless page_published.nil? or page_updated.nil?
				if page_updated < page_published
					@published = page_updated
				end
			end
		end
		@published
	end

	def atom_updated # => DateTime | nil
		if @updated.nil?
			unless page_updated.nil?
				@updated = page_updated
			else
				unless page_published.nil?
					@updated = page_published
				end
			end
		end
		@updated
	end

	def years # => Enumerable<Fixnum>
		if @years.nil?
			if published.nil? || updated.nil?
				@years = Set[]
			else
				first = published.year
				last = updated.year

				years = page_years
				years.add(first)
				years.add(last)

				@years = Set[*years.select{|i|i >= first && i <= last}]
			end
		end
		@years
	end
end