# accounts/signals.py
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.db import transaction
from django.utils.text import slugify

from hr.models import Employee
from .models import User


@receiver(post_save, sender=User)
def create_employee_for_user(sender, instance: User, created: bool, **kwargs):
    """
    Auto-create an Employee profile when a User is created.
    Idempotent, tenant-aligned, and makes a unique employee_number per tenant.
    """
    if not created:
        return

    def _make_employee():
        # Generate a readable employee_number from username/email, unique within tenant
        base = (instance.username or (instance.email or 'user')).split('@')[0]
        candidate = slugify(base)[:16] or 'emp'
        suffix = 1
        emp_no = candidate
        while Employee.objects.filter(tenant=instance.tenant, employee_number=emp_no).exists():
            suffix += 1
            emp_no = f"{candidate}-{suffix}"

        # Create with basic info mirrored from User
        Employee.objects.create(
            tenant=instance.tenant,
            user=instance,
            employee_number=emp_no,
            first_name=instance.first_name or '',
            last_name=instance.last_name or '',
            email=instance.email
        )

    # Defer until after outer transaction commits (avoids race conditions in tests/views)
    transaction.on_commit(_make_employee)