## the problem is with the Imt <> Lesson relationship.
## When asking for lesson.imt it errors out looking for imt_id in the table ( which doesn't exist as it's users id )
## So should I be using class_name, table_name, set_table_name or finder_sql or what.. ?
## and, it's possible to have different validations and assoications subclassed like this?
## e.g. all user types ( Student, Imt, etc ) validates_presence_of :first_name. But only Imt has_many :lessons..


## lesson.rb :
class Lesson < ActiveRecord::Base
	validates_presence_of :instrument, :name, :cost, :status
	belongs_to :imt, :class_name => "User"
	has_many :bookings
	has_many :enrolments
end
## user.rb
class User < ActiveRecord::Base
	require 'digest/sha2'
	#validates_uniqueness_of :username
	attr_accessor :skip_password
	attr_accessor :tmp_password
	validates_confirmation_of :password, :on => :create #:if => :password_required?
        validates_length_of :password, :within => 5..40, :on => :create #:if => :password_required?
        validates_presence_of :password, :password_confirmation, :on => :create #:if => :password_required?
	validates_presence_of :first_name, :last_name
	def name
		first_name + " " + last_name
	end
	def self.getuser(id)
		find(id)
	end
	def self.authenticate(username, password)
		user = User.find(:first, :conditions => ['username = ?', username])
		if user.blank? || Digest::SHA256.hexdigest(password + user.password_salt) != user.password_hash
			raise "Username or password invalid"
		end
		user
	end
	def password=(pass)
	   self.tmp_password = pass
	   unless pass.nil?
             salt = [Array.new(6){rand(256).chr}.join].pack("m").chomp
             self.password_salt, self.password_hash =
             salt, Digest::SHA256.hexdigest(pass + salt)

	   end
	end
	def password
		self.tmp_password
        end
	protected
        def password_required?
          @skip_password != true
        end

end

class Imt < User
	has_many :lessons
end

class Student < User
	validates_presence_of :form_class,  :student_id
	validates_uniqueness_of :student_id
	has_many :enrolments, :dependent => :destroy
	has_many :bookings, :dependent => :destroy
	def before_validation
		self.username = self.student_id
	end
end

class Teacher < User
end

class Admin < User
end