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

from apps.core.models import BaseModel


class SupportTicket(BaseModel):
    CATEGORY_CHOICES = (
        ("account", "Account"),
        ("payment", "Payment"),
        ("order", "Order"),
        ("kyc", "KYC"),
        ("technical", "Technical"),
        ("other", "Other"),
    )

    PRIORITY_CHOICES = (
        ("low", "Low"),
        ("medium", "Medium"),
        ("high", "High"),
        ("urgent", "Urgent"),
    )

    STATUS_CHOICES = (
        ("open", "Open"),
        ("in_progress", "In Progress"),
        ("resolved", "Resolved"),
        ("closed", "Closed"),
    )

    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="support_tickets")
    ticket_number = models.CharField(max_length=30, unique=True, db_index=True)
    subject = models.CharField(max_length=255)
    description = models.TextField()
    category = models.CharField(max_length=30, choices=CATEGORY_CHOICES, default="other", db_index=True)
    priority = models.CharField(max_length=20, choices=PRIORITY_CHOICES, default="medium", db_index=True)
    status = models.CharField(max_length=20, choices=STATUS_CHOICES, default="open", db_index=True)
    assigned_to = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="assigned_support_tickets",
    )

    first_response_at = models.DateTimeField(null=True, blank=True, db_index=True)
    resolved_at = models.DateTimeField(null=True, blank=True, db_index=True)
    closed_at = models.DateTimeField(null=True, blank=True, db_index=True)
    last_user_reply_at = models.DateTimeField(null=True, blank=True)
    last_admin_reply_at = models.DateTimeField(null=True, blank=True)
    reopened_count = models.PositiveIntegerField(default=0)
    first_response_due_at = models.DateTimeField(null=True, blank=True, db_index=True)
    resolution_due_at = models.DateTimeField(null=True, blank=True, db_index=True)
    sla_breached_at = models.DateTimeField(null=True, blank=True, db_index=True)
    escalated_at = models.DateTimeField(null=True, blank=True, db_index=True)
    escalation_level = models.PositiveSmallIntegerField(default=0, db_index=True)

    class Meta:
        indexes = [
            models.Index(fields=["status", "priority", "created_at"], name="support_tic_status_302a08_idx"),
            models.Index(fields=["user", "status"], name="support_tic_user_id_46c31d_idx"),
            models.Index(fields=["assigned_to", "status"], name="support_tic_assigne_0b42dd_idx"),
            models.Index(fields=["status", "first_response_due_at"], name="support_tic_status_b03e2b_idx"),
            models.Index(fields=["status", "resolution_due_at"], name="support_tic_status_655ec3_idx"),
        ]

    def __str__(self):
        return f"{self.ticket_number} - {self.subject}"

    @staticmethod
    def generate_ticket_number():
        prefix = timezone.now().strftime("TWM-%Y%m%d-")
        suffix = "".join(random.choices(string.digits, k=5))
        return f"{prefix}{suffix}"

    def save(self, *args, **kwargs):
        if not self.ticket_number:
            for _ in range(10):
                candidate = self.generate_ticket_number()
                if not SupportTicket.objects.filter(ticket_number=candidate).exists():
                    self.ticket_number = candidate
                    break
        super().save(*args, **kwargs)


class SupportTicketMessage(BaseModel):
    ticket = models.ForeignKey(SupportTicket, on_delete=models.CASCADE, related_name="messages")
    sender = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="support_messages")
    message = models.TextField()
    is_internal = models.BooleanField(default=False, db_index=True)

    class Meta:
        ordering = ["created_at"]
        indexes = [
            models.Index(fields=["ticket", "created_at"], name="support_tic_ticket__d8d570_idx"),
            models.Index(fields=["is_internal", "created_at"], name="support_tic_is_inte_7875e1_idx"),
        ]

    def __str__(self):
        return f"{self.ticket.ticket_number} message by {self.sender_id}"


class SupportTicketAttachment(BaseModel):
    ticket = models.ForeignKey(SupportTicket, on_delete=models.CASCADE, related_name="attachments")
    message = models.ForeignKey(
        SupportTicketMessage,
        on_delete=models.CASCADE,
        related_name="attachments",
        null=True,
        blank=True,
    )
    uploaded_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="support_attachments",
    )
    file = models.FileField(upload_to="support/attachments/%Y/%m/%d/")
    file_name = models.CharField(max_length=255)
    content_type = models.CharField(max_length=120, blank=True)
    file_size = models.PositiveIntegerField(default=0)

    class Meta:
        indexes = [
            models.Index(fields=["ticket", "created_at"], name="support_tic_ticket__6c8c03_idx"),
            models.Index(fields=["message", "created_at"], name="support_tic_message_05d7f0_idx"),
        ]

    def __str__(self):
        return f"{self.ticket.ticket_number} attachment {self.file_name}"