gistfile1.rb

class AuditHelper
  def self.rebuild_from_audit(audit)
    changes_in_order = Audit.find(:all, :conditions => ['auditable_id = ? AND auditable_type = ? AND version <= ?', audit.auditable_id, audit.auditable_type, audit.version], :order => "version")
    current_attributes = {}
    changes_in_order.each do |audit|
      current_attributes.merge!(audit.changes || {})
      current_attributes.merge!(:version => audit.version)
    end
    
    obj = audit.auditable_type.constantize.new(current_attributes)
  end
  
  def self.revision_at(model, date_or_time)
    max_audit = model.audits.find(:first, :conditions => ["created_at <= ?", date_or_time], :order => "created_at DESC")
    return nil unless max_audit
    changes_in_order = model.audits.find(:all, :conditions => ['version <= ?', max_audit.version], :order => "version")
    current_attributes = {}
    changes_in_order.each do |audit|
      current_attributes.merge!(audit.changes || {})
      current_attributes.merge!(:version => audit.version)
    end
    
    obj = model.dup    
    # obj.send :instance_variable_set, '@attributes', model.attributes_before_type_cast
    obj.attributes = current_attributes
      
    # Remove any association proxies so that they will be recreated
    # and reference the correct object for this revision. The only way
    # to determine if an instance variable is a proxy object is to
    # see if it responds to certain methods, as it forwards almost
    # everything to its target.
    for ivar in obj.instance_variables
      proxy = obj.instance_variable_get ivar
      if !proxy.nil? and proxy.respond_to? :proxy_respond_to?
        obj.instance_variable_set ivar, nil
      end
    end
    obj
  end
end