class Dependency < ActiveRecord::Base

  # Extending surveyor
  include "#{self.name}Extensions".constantize if Surveyor::Config['extend'].include?(self.name.underscore)

  # Associations
  belongs_to :question
  belongs_to :question_group
  has_many :dependency_conditions
  
  # Validations
  validates_presence_of :rule
  validates_format_of :rule, :with => /^(?:and|or|\)|\(|[A-Z]|\s)+$/ #TODO properly formed parenthesis etc.
  validates_numericality_of :question_id, :if => Proc.new { |d| d.question_group_id.nil? }
  validates_numericality_of :question_group_id, :if => Proc.new { |d| d.question_id.nil? }
  
  # Attribute aliases
  alias_attribute :dependent_question_id, :question_id
  
  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