require 'yaml'

require 'facet/object/constant'

require 'glue/attribute'
require 'glue/hash'
require 'glue/flexob'

# A Configuration holds a group of Settings organized by
# Owners.
#--
# TODO: implement with annotations.
#++

class Configuration

	# A hash of setting owners. Use double @'s to allow for
	# the Settings alias.
	#--
	# TODO: find a better name.
	#++
		
	@@owners = Glue::SafeHash.new	

	# A datastructure to store Settings metadata.
	
	class Setting
		attr_accessor :owner, :name, :type, :value, :options
		
		def initialize(owner, name, options)
			raise ArgumentError.new('A default value is required') unless options.key?(:default)
			@owner, @name = owner, name
			@options = options
			@value = options[:default]
			@type = options[:type] = options[:type] || @value.class
		end

		def value=(value)
			@value = value
			constant(@owner).module_eval %{
				@@#{@name} = #{value.inspect}
			}
		end

		def to_s
			@value.to_s
		end
	end
	
	class << self
	
		def setup(options)
			options.each do |owner, ss|
				owner = constant(owner)
				ss.each do |name, s|
					@@owners[owner][name.to_sym].value = s
					owner.module_eval %{
						@@#{name} = #{s.inspect}
					}
				end 
			end
		end

		def parse(options)
			temp = YAML::load(options)
			options = {}
			temp.each { |k, v| options[constant(k.gsub(/\./, '::').to_sym)] = v }
			setup(options)
		end
		
		def load(filename)
			parse(File.read(filename))
		end
		
		def add_setting(owner, name, options)
			s = @@owners[owner] || {}
			s[name] = Setting.new(owner, name, options)
			@@owners[owner] = s
		end
		
		def settings(owner = nil)
			if owner
				@@owners[owner]
			else
				@@owners.values.inject([]) { |memo, obj| memo.concat(obj.values) }
			end
		end
		alias_method :all, :settings
		alias_method :[], :settings

		def method_missing(sym)
			if sym.to_s =~ /[A-Z]/ # facet's capitalized? is buggy at the moment.
				Flexob.new(self[constant(sym)])
			end
		end
	end
	
end

# Alias for the Configuration class (shorter).

class Settings < Configuration
end

class Module

	# Defines a configuration setting.
	#--
	# TODO: implement with annotations.
	#++
	
	def setting(sym, options = {})
		Configuration.add_setting(self, sym, options)
		module_eval %{
			mattr_accessor sym, options[:default]
			
      def self.#{sym.id2name}=(obj)
        @@#{sym.id2name} = obj
        Configuration[#{self}][:#{sym}].value = obj
      end
		}
	end
	
end

# * George Moschovitis <gm@navel.gr>