from django.db import models
from django.utils import timezone
from django.core.exceptions import ValidationError
from django_choices_field import TextChoicesField
from core.models.base import BaseModel, Address, Contact
from core.models.customer import Customer
from core.models.enums import StatusChoices


class Account(BaseModel):
    """Account model belonging to a customer"""
    customer = models.ForeignKey(Customer, on_delete=models.PROTECT, related_name='accounts')
    name = models.CharField(max_length=200)
    status = TextChoicesField(choices_enum=StatusChoices, default=StatusChoices.ACTIVE,
                              help_text="Current status of the account")
    start_date = models.DateField(default=timezone.now)
    end_date = models.DateField(blank=True, null=True)

    class Meta:
        ordering = ['name']
        verbose_name = "Account"
        verbose_name_plural = "Accounts"
        indexes = [
            models.Index(fields=['customer', 'status']),
            models.Index(fields=['status', 'start_date'])
        ]
        constraints = [
            models.UniqueConstraint(
                fields=['customer', 'name'],
                name='unique_account_name_per_customer'
            )
        ]

    def __str__(self):
        return f"{self.name} ({self.customer.name})"

    @property
    def is_active(self):
        """Check if the account is currently active based on dates and status"""
        today = timezone.now().date()
        return self.status == 'ACTIVE' and self.start_date <= today and (
                self.end_date is None or self.end_date >= today)

    @property
    def primary_address(self):
        """Get the primary address for this account"""
        return self.addresses.filter(is_primary=True, is_active=True).first()

    def clean(self):
        """Validate account data"""
        if self.end_date and self.start_date and self.end_date < self.start_date:
            raise ValidationError("End date cannot be earlier than start date")


class AccountAddress(Address):
    """Physical address information for an account"""
    account = models.ForeignKey('Account', on_delete=models.PROTECT, related_name='addresses')
    name = models.CharField(max_length=200, blank=True)
    is_active = models.BooleanField(default=True)
    is_primary = models.BooleanField(default=False)
    notes = models.TextField(blank=True)

    class Meta:
        verbose_name = "Account Address"
        verbose_name_plural = "Account Addresses"
        indexes = [
            models.Index(fields=['account', 'is_active']),
        ]
        constraints = [
            models.UniqueConstraint(
                fields=['account'],
                condition=models.Q(is_primary=True, is_active=True),
                name='unique_primary_address_per_account'
            )
        ]

    def save(self, *args, **kwargs):
        if self.is_active and not AccountAddress.objects.filter(
                account=self.account,
                is_active=True
        ).exclude(pk=self.pk).exists():
            self.is_primary = True
        super().save(*args, **kwargs)

    def clean(self):
        """Validate address data"""
        if self.is_primary and not self.is_active:
            raise ValidationError("Primary address must be active")

    def __str__(self):
        primary_indicator = " (Primary)" if self.is_primary else ""
        return f"{self.account.name} - {self.street_address}{primary_indicator}"


class AccountContact(Contact):
    """Contact information for an account"""
    account = models.ForeignKey('Account', on_delete=models.PROTECT, related_name='contacts')
    email = models.EmailField(blank=True)
    is_active = models.BooleanField(default=True)
    is_primary = models.BooleanField(default=False)
    notes = models.TextField(blank=True)

    class Meta:
        verbose_name = "Account Contact"
        verbose_name_plural = "Account Contacts"
        indexes = [
            models.Index(fields=['account', 'is_active']),
        ]
        constraints = [
            # Only one primary contact per account
            models.UniqueConstraint(
                fields=['account'],
                condition=models.Q(is_primary=True, is_active=True),
                name='unique_primary_contact_per_account'
            ),
            # Prevent duplicate phone numbers for the same account
            models.UniqueConstraint(
                fields=['account', 'phone'],
                condition=models.Q(is_active=True, phone__isnull=False) & ~models.Q(phone=''),
                name='unique_phone_per_account'
            ),
            # Prevent duplicate emails for the same account (when email provided)
            models.UniqueConstraint(
                fields=['account', 'email'],
                condition=models.Q(is_active=True, email__isnull=False) & ~models.Q(email=''),
                name='unique_email_per_account'
            )
        ]

    def save(self, *args, **kwargs):
        # Auto-set first active contact as primary
        if self.is_active and not AccountContact.objects.filter(
                account=self.account,
                is_active=True
        ).exclude(pk=self.pk).exists():
            self.is_primary = True
        super().save(*args, **kwargs)

    def clean(self):
        """Validate contact data"""
        # Ensure primary contacts are active
        if self.is_primary and not self.is_active:
            raise ValidationError("Primary contact must be active")

        # Ensure we have at least phone or email
        if not self.phone and not self.email:
            raise ValidationError("Contact must have either phone number or email address")

    def __str__(self):
        primary_indicator = " (Primary)" if self.is_primary else ""
        return f"{self.full_name} - {self.account.name}{primary_indicator}"