class Sesion(Workflow, ModelSQL, ModelView):
    "Sesion"
    _name = 'academia.sesion'

    def __init__(self):
        super(Sesion, self).__init__()

        self._error_messages.update({
            'sold_out': 'You have no seets availables !',
            })

        self._transitions |= set((
            ('draft', 'confirmed'),
            ('confirmed', 'done'),
            ('done', 'cancel'),

            ))
        self._buttons.update({
            #'confirm': {
                #'invisible': ~Eval('state').in_(['confirmed', 'done','cancel']),
                #},
            'done': {
                'invisible': ~Eval('state').in_(['draft', 'cancel']),
                'icon': If(Eval('state') == 'cancel', 'tryton-clear',
                'tryton-go-previous'),
                    },
            'cancel': {
                'invisible': Eval('state') != 'done',
                }  })

    def on_change_alumnos(self,vals):
        res = {}
        alumnos = vals.get('alumnos')
        num_of_seats = vals.get('num_of_seats')
        print "Alumnos", alumnos
        if alumnos and len(alumnos)>num_of_seats:
            self.raise_user_error('sold_out')

        print "INGRESO A ONCHANGE",vals
        res['num_of_seats'] = num_of_seats
        return res



    name = fields.Char('Name')
    start_date = fields.Date('Start Date')
    duration = fields.Float('Duration')
    num_of_seats = fields.Integer('Number of Seats')
    course = fields.Many2One('academia.curso', 'Course')
    instructor = fields.Many2One('party.party', 'Instructor', domain=[('instructor', '=', True)])
    alumnos = fields.One2Many('academia.alumno', 'session', 'Alumnos', on_change=['alumnos','num_of_seats'])
    state = fields.Selection([
        ('draft', 'Draft'),
        ('confirmed', 'Confirmed'),
        ('done', 'Done'),
        ('cancel', 'Canceled'),
        ], 'State', readonly=True)


    def default_state(self):
        return 'draft'

    #@ModelView.button
    #@Workflow.transition('draft')
    #def confirm(self, ids):
        #print "INGRESO A FUNCIoN CONFIRM"
        #pass


    @ModelView.button
    @Workflow.transition('confirmed')
    def confirmed(self, ids):
        print "INGRESO A FUNCIoN CONFIRM"
        pass


Sesion()