import random
import logging

from odoo import api, fields, models, _
from odoo.exceptions import UserError

_logger = logging.getLogger(__name__)


class HrEmployee(models.Model):
    _inherit = 'hr.employee'

    employee_pin = fields.Char(
        string='Employee PIN',
        size=6,
        copy=False,
        help='Unique 6-digit PIN for this employee. '
             'Globally unique across all companies.',
    )

    _sql_constraints = [
        (
            'employee_pin_unique',
            'UNIQUE(employee_pin)',
            'The Employee PIN must be unique across all employees and companies.',
        )
    ]

    # ------------------------------------------------------------------
    # Helpers
    # ------------------------------------------------------------------

    @api.model
    def _generate_unique_pin(self):
        """Return a random 6-digit string that is not yet used by any employee."""
        existing = set(
            self.sudo().search([('employee_pin', '!=', False)]).mapped('employee_pin')
        )
        for _attempt in range(1000):
            pin = '{:06d}'.format(random.randint(0, 999999))
            if pin not in existing:
                return pin
        raise UserError(
            _('Could not generate a unique PIN after 1000 attempts. '
              'The PIN pool may be exhausted.')
        )

    # ------------------------------------------------------------------
    # ORM overrides
    # ------------------------------------------------------------------

    @api.model_create_multi
    def create(self, vals_list):
        for vals in vals_list:
            if not vals.get('employee_pin'):
                vals['employee_pin'] = self._generate_unique_pin()
        return super().create(vals_list)

    # ------------------------------------------------------------------
    # Actions
    # ------------------------------------------------------------------

    def action_regenerate_pin(self):
        """Regenerate a new unique PIN for this employee (called from button)."""
        self.ensure_one()
        new_pin = self._generate_unique_pin()
        self.employee_pin = new_pin
        return {
            'type': 'ir.actions.client',
            'tag': 'display_notification',
            'params': {
                'title': _('PIN Regenerated'),
                'message': _('New PIN for %s: %s') % (self.name, new_pin),
                'type': 'success',
                'sticky': False,
            },
        }