module Surveyor
  module Models
    module DependencyMethods
      def self.included(base)
        # Associations
        base.send :belongs_to, :question
        base.send :belongs_to, :question_group
        base.send :has_many, :dependency_conditions, :dependent => :destroy

        # Validations
        base.send :validates_presence_of, :rule
        base.send :validates_format_of, :rule, :with => /^(?:and|or|\)|\(|[A-Z]|\s)+$/ #TODO properly formed parenthesis etc.
        base.send :validates_numericality_of, :question_id, :if => Proc.new { |d| d.question_group_id.nil? }
        base.send :validates_numericality_of, :question_group_id, :if => Proc.new { |d| d.question_id.nil? }

        # Attribute aliases
        base.send :alias_attribute, :dependent_question_id, :question_id
      end

      # Instance Methods
      def question_group_id=(i)
        write_attribute(:question_id, nil) unless i.nil?
        write_attribute(:question_group_id, i)
      end

      def question_id=(i)
        write_attribute(:question_group_id, nil) unless i.nil?
        write_attribute(:question_id, i) 
      end

      # Has this dependency has been met in the context of response_set?
      # Substitutes the conditions hash into the rule and evaluates it
      def is_met?(response_set)
        ch = conditions_hash(response_set)
        return false if ch.blank?
        # logger.debug "rule: #{self.rule.inspect}"
        # logger.debug "rexp: #{rgx.inspect}"
        # logger.debug "keyp: #{ch.inspect}"
        # logger.debug "subd: #{self.rule.gsub(rgx){|m| ch[m.to_sym]}}"
        rgx = Regexp.new(self.dependency_conditions.map{|dc| ["a","o"].include?(dc.rule_key) ? "#{dc.rule_key}(?!nd|r)" : dc.rule_key}.join("|")) # exclude and, or
        eval(self.rule.gsub(rgx){|m| ch[m.to_sym]})
      end

      # A hash of the conditions (keyed by rule_key) and their evaluation (boolean) in the context of response_set
      def conditions_hash(response_set)
        hash = {}
        self.dependency_conditions.each{|dc| hash.merge!(dc.to_hash(response_set))}
        return hash
      end    
    end
  end
end