# code: 
# * George Moschovitis  <gm@navel.gr>
#
# (c) 2004 Navel, all rights reserved.
# $Id: meta.rb 124 2004-11-01 12:34:17Z gmosx $

module N

# = OgMetaUtils
#
# Some useful meta-language utilities.
#
module OgMetaUtils # :nodoc: all

	# Conver the klass to a string representation
	# The leading module if available is removed.
	#
	def self.expand(klass)
		return klass.name.gsub(/^.*::/, "").gsub(/::/, "_").downcase
	end

end

# = OgMetaLanguage
#
# Implements a meta-language for manipulating og-managed objects
# and defining their relationships. The original idea comes
# from the excellent ActiveRecord library.
#
# Many more useful relations will be available soon.
#
module OgMetaLanguage

	# Implements a 'belongs_to' relation.
	# Automatically enchants the calling class with helper methods.
	# 
	# Example:
	#
	# class MyObject
	#		belongs_to AnotherObject, :parent
	# end
	#
	# creates the code:
	#
	# prop_accessor Fixnum, :parent_oid
	# def parent; ... end
	# def parent=(obj_or_oid); ... end
	#
	def belongs_to(klass, name, options = {})
		module_eval %{
			prop_accessor Fixnum, :#{name}_oid 
			
			def #{name}
				$og.load_by_oid(@#{name}_oid, #{klass})
			end
			
			def #{name}=(obj_or_oid)
				@#{name}_oid = obj_or_oid.to_i
			end
		}
	end

	# Implements a 'has_many' relation.
	# Automatically enchants the calling class with helper methods.
	#
	# NOT IMPLEMENTED.
	# 
	# Example:
	#
	# class MyObject
	#		has_many AnotherObject, :children
	# end
	#
	# creates the code:
	#
	# def children; ... end
	#
	def has_one(klass, name, options = {})
		module_eval %{
			def #{name}(extrasql = nil)
				$og.select_one("article_oid=\#\@oid \#\{extrasql\}", #{klass})
			end			
		}
	end	
	
	# Implements a 'has_many' relation.
	# Automatically enchants the calling class with helper methods.
	# 
	# Example:
	#
	# class MyObject
	#		has_many AnotherObject, :children
	# end
	#
	# creates the code:
	#
	# def children; ... end
	#
	def has_many(klass, name, options = {})
		# linkback is the property of the child object that 'links back' 
		# to this object. 
		linkback = options[:linkback] || "#{N::OgMetaUtils.expand(self)}_oid"
		
		module_eval %{
			@@og_descendants ||= {}
			@@og_descendants[#{klass}] = :#{linkback} 
	
			unless defined?(og_descendants)
				def self.og_descendants
					@@og_descendants
				end
			end
			
			def #{name}(extrasql = nil)
				$og.select("#{linkback}=\#\@oid \#\{extrasql\}", #{klass})
			end			
		}
	end
	
end

end # module

class Module # :nodoc: all
	include N::OgMetaLanguage
end