from django.db import models
from django.conf import settings
from django.utils import timezone

from core.models.directories import directory_default


class Ticket(models.Model):
    number      = models.CharField('Номер', max_length=20, unique=True, editable=False)
    title       = models.CharField('Заголовок', max_length=200)
    ticket_type = models.ForeignKey(
        'core.Directory', on_delete=models.PROTECT,
        limit_choices_to={'directory_type__code': 'ticket_type', 'is_active': True},
        related_name='tickets_by_type', verbose_name='Тип',
    )
    priority = models.ForeignKey(
        'core.Directory', on_delete=models.PROTECT,
        limit_choices_to={'directory_type__code': 'ticket_priority', 'is_active': True},
        related_name='tickets_by_priority', verbose_name='Приоритет',
        default=directory_default('ticket_priority', 'medium'),
    )
    status = models.ForeignKey(
        'core.Directory', on_delete=models.PROTECT,
        limit_choices_to={'directory_type__code': 'ticket_status', 'is_active': True},
        related_name='tickets_by_status', verbose_name='Статус',
        default=directory_default('ticket_status', 'new'),
    )

    requester = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.PROTECT,
        related_name='created_tickets', verbose_name='Заявитель',
    )
    assignee = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.SET_NULL,
        null=True, blank=True,
        related_name='assigned_tickets', verbose_name='Исполнитель',
    )
    equipment = models.ForeignKey(
        'it_manager.Equipment', on_delete=models.SET_NULL,
        null=True, blank=True,
        related_name='tickets', verbose_name='Оборудование',
    )
    location = models.ForeignKey(
        'locations.Location', on_delete=models.SET_NULL,
        null=True, blank=True,
        related_name='it_tickets', verbose_name='Локация',
    )

    description = models.TextField('Описание проблемы')
    resolution  = models.TextField('Решение', blank=True)

    created_at  = models.DateTimeField(auto_now_add=True, db_index=True)
    updated_at  = models.DateTimeField(auto_now=True)
    resolved_at = models.DateTimeField('Решена в', null=True, blank=True)
    closed_at   = models.DateTimeField('Закрыта в', null=True, blank=True)

    class Meta:
        verbose_name        = 'Заявка'
        verbose_name_plural = 'Заявки'
        ordering = ['-created_at']

    def __str__(self):
        return f'[{self.number}] {self.title}'

    def save(self, *args, **kwargs):
        if not self.number:
            self.number = self._generate_number()
        if self.status.code == 'resolved' and not self.resolved_at:
            self.resolved_at = timezone.now()
        if self.status.code == 'closed' and not self.closed_at:
            self.closed_at = timezone.now()
        super().save(*args, **kwargs)

    def _generate_number(self):
        today = timezone.now()
        prefix = f'IT-{today.year}{today.month:02d}'
        last = (
            Ticket.objects
            .filter(number__startswith=prefix)
            .order_by('-number')
            .values_list('number', flat=True)
            .first()
        )
        seq = int(last.split('-')[-1]) + 1 if last else 1
        return f'{prefix}-{seq:04d}'

    @property
    def is_overdue(self):
        if self.status.code in ('resolved', 'closed'):
            return False
        sla_hours = {'critical': 4, 'high': 8, 'medium': 24, 'low': 72}
        limit = sla_hours.get(self.priority.code, 24)
        return (timezone.now() - self.created_at).total_seconds() / 3600 > limit


class TicketComment(models.Model):
    ticket      = models.ForeignKey(
        Ticket, on_delete=models.CASCADE,
        related_name='comments', verbose_name='Заявка',
    )
    author      = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.PROTECT,
        related_name='ticket_comments', verbose_name='Автор',
    )
    text        = models.TextField('Комментарий')
    is_internal = models.BooleanField(
        'Внутренний', default=False,
        help_text='Виден только сотрудникам IT',
    )
    created_at  = models.DateTimeField(auto_now_add=True)

    class Meta:
        verbose_name        = 'Комментарий'
        verbose_name_plural = 'Комментарии'
        ordering = ['created_at']

    def __str__(self):
        return f'{self.ticket.number} / {self.author} / {self.created_at:%d.%m.%Y %H:%M}'