from decimal import Decimal
from secrets import token_urlsafe
from typing import Type

from django.conf import settings
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import models, transaction
from django.db.models import TextChoices
from django.http import HttpRequest
from django.utils.functional import cached_property
from django.utils.text import Truncator, slugify
from django.utils.translation import gettext_lazy as _

from salesman.basket.models import Basket
from salesman.conf import app_settings
from salesman.core.models import JSONField

from .signals import status_changed

try:
    # Add support for Wagtail admin.
    from modelcluster.models import ClusterableModel
    from modelcluster.fields import ParentalKey
except ImportError:  # pragma: no cover
    ClusterableModel = models.Model
    ParentalKey = models.ForeignKey


class ParentalForeignKey(ParentalKey):
    """
    Use this foreign key to add support for Wagtail
    in case modelcluster is installed.
    """


class OrderManager(models.Manager):
    def create_from_request(self, request: HttpRequest, **kwargs) -> 'Order':
        """
        Create new order with reference. Items are still in basket and should
        be added using ``order.populate_from_basket(basket, request)`` method.

        Returns:
            Order: Order instance
        """
        generate_ref = app_settings.SALESMAN_ORDER_REFERENCE_GENERATOR
        kwargs['ref'] = slugify(generate_ref(request))
        return super().create(**kwargs)

    def create_from_basket(
        self, basket: Basket, request: HttpRequest, **kwargs
    ) -> 'Order':
        """
        Create and populate new order from basket.

        Returns:
            Order: Order instance
        """
        order = self.create_from_request(request, **kwargs)
        order.populate_from_basket(basket, request)
        return order


class Order(ClusterableModel):
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        verbose_name=_("User"),
    )

    # A unique reference to this order, could be used as order number.
    ref = models.SlugField(
        _("Reference"),
        max_length=128,
        unique=True,
        help_text=_("A unique order reference."),
    )

    # Current order status.
    status = models.CharField(
        _("Status"),
        max_length=128,
        default='NEW',
        help_text=_("Changing order status might trigger a notification to customer."),
    )

    # A unique token to allow non-authenticated user access to order.
    token = models.CharField(
        _("Token"),
        max_length=128,
        unique=True,
        default=token_urlsafe,
        help_text=_(
            "Allow non-authenticated customer to access the order with token. "
            "To access order suply a '?token={token}' in url querystring."
        ),
    )

    # Customer contact info.
    email = models.EmailField(_("Email"), blank=True)
    shipping_address = models.TextField(_("Shipping address"), blank=True)
    billing_address = models.TextField(_("Billing address"), blank=True)

    subtotal = models.DecimalField(
        _("Subtotal"), max_digits=18, decimal_places=2, default=Decimal(0)
    )
    total = models.DecimalField(
        _("Total"), max_digits=18, decimal_places=2, default=Decimal(0)
    )
    _extra = JSONField(_("Extra"), blank=True)

    date_created = models.DateTimeField(_("Date created"), auto_now_add=True)
    date_updated = models.DateTimeField(_("Date updated"), auto_now=True)

    objects = OrderManager()

    # Separate rows from `_extra` to `extra_rows`.
    extra = None
    extra_rows = None

    _current_status = None

    class Meta:
        verbose_name = _("Order")
        verbose_name_plural = _("Orders")
        ordering = ['-date_created']

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.extra = self._extra
        self.extra_rows = self.extra.pop('rows', [])
        self._current_status = self.status

    def __str__(self):
        return self.ref

    def save(self, *args, **kwargs):
        self._extra = dict(self.extra, rows=self.extra_rows)
        if 'extra' in kwargs.get('update_fields', []):
            kwargs['update_fields'].remove('extra')
            kwargs['update_fields'].append('_extra')
        new_status, old_status = self.status, self._current_status
        super().save(*args, **kwargs)
        # Send signal if status changed.
        if new_status != old_status:
            status_changed.send(
                Order, order=self, new_status=new_status, old_status=old_status
            )

    def pay(
        self, amount: Decimal, transaction_id: str, payment_method: str = ''
    ) -> 'OrderPayment':
        """
        Create a new payment for order.

        Args:
            amount (Decimal): Amount to add
            transaction_id (str): ID of transaction
            payment_method (str, optional): Payment method identifier. Defaults to ''.

        Returns:
            OrderPayment: New order payment instance
        """
        return OrderPayment.objects.create(
            order=self,
            amount=amount,
            transaction_id=transaction_id,
            payment_method=payment_method,
        )

    @transaction.atomic
    def populate_from_basket(
        self, basket: Basket, request: HttpRequest, **kwargs,
    ) -> None:
        """
        Populate order with items from basket.

        Args:
            basket (Basket): Basket instance
            request (HttpRequest): Django request
        """
        from salesman.basket.serializers import ProductField, ExtraRowsField

        if not hasattr(basket, 'total'):
            basket.update(request)

        self.user = basket.owner
        self.email = basket.extra.pop('email', '')
        self.shipping_address = basket.extra.pop('shipping_address', '')
        self.billing_address = basket.extra.pop('billing_address', '')
        self.subtotal = basket.subtotal
        self.total = basket.total
        self.extra = basket.extra
        self.extra_rows = ExtraRowsField().to_representation(basket.extra_rows)
        if self.status == self.statuses.NEW:
            self.status = self.statuses.CREATED
        for attr, value in kwargs.items():
            setattr(self, attr, value)
        self.save()

        for item in basket.get_items():
            # Store serialized product with `name` and `code`.
            product_data = ProductField().to_representation(item.product)
            product_data.update({'name': item.product.name, 'code': item.product.code})

            extra_rows = ExtraRowsField().to_representation(item.extra_rows)
            OrderItem.objects.create(
                order=self,
                product_type=item.product._meta.label,
                product_content_type=item.product_content_type,
                product_id=item.product_id,
                product_data=product_data,
                unit_price=item.unit_price,
                subtotal=item.subtotal,
                total=item.total,
                quantity=item.quantity,
                _extra=dict(item.extra, rows=extra_rows),
            )

    @property
    def status_display(self) -> str:
        """
        Returns display label for current status.
        """
        return str(dict(self.get_statuses().choices).get(self.status, self.status))

    status_display.fget.short_description = _("Status")
    status_display.fget.admin_order_field = 'status'

    @property
    def statuses(self) -> Type[TextChoices]:
        """
        Shorthand on order instance to get statuses enum.
        """
        return self.get_statuses()

    @cached_property
    def amount_paid(self) -> Decimal:
        """
        Returns amount already paid for this order.
        """
        aggr = self.payments.aggregate(amount=models.Sum('amount'))
        return Decimal(aggr['amount'] or 0)

    @property
    def amount_outstanding(self) -> Decimal:
        """
        Returns amount still needed for order to be paid.
        """
        return Decimal(self.total - self.amount_paid)

    @property
    def is_paid(self) -> bool:
        """
        Returns if order is paid in full.
        """
        return self.amount_paid >= self.total

    @classmethod
    def get_statuses(cls) -> Type[TextChoices]:
        """
        Return order status enum from settings.
        Defaults to ``salesman.orders.status.OrderStatus``.
        """
        return app_settings.SALESMAN_ORDER_STATUS


class OrderItem(models.Model):
    order = ParentalForeignKey(
        Order, on_delete=models.CASCADE, related_name='items', verbose_name=_("Order"),
    )

    product_type = models.CharField(_("Product type"), max_length=128)

    # Generic relation to product (optional).
    product_content_type = models.ForeignKey(
        ContentType, on_delete=models.SET_NULL, null=True
    )
    product_id = models.PositiveIntegerField(_("Product id"), null=True)
    product = GenericForeignKey('product_content_type', 'product_id')

    # Stored product serializer data at the moment of purchase.
    product_data = JSONField(_("Product data"), blank=True)

    unit_price = models.DecimalField(_("Unit price"), max_digits=18, decimal_places=2)
    subtotal = models.DecimalField(_("Subtotal"), max_digits=18, decimal_places=2)
    total = models.DecimalField(_("Total"), max_digits=18, decimal_places=2)
    quantity = models.PositiveIntegerField(_("Quantity"))
    _extra = JSONField(_("Extra"), blank=True)

    # Separate rows from `_extra` to `extra_rows`.
    extra = None
    extra_rows = None

    class Meta:
        verbose_name = _("Item")
        verbose_name_plural = _("Items")

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.extra = self._extra
        self.extra_rows = self.extra.pop('rows', [])

    def __str__(self):
        return f'{self.quantity}x {self.name} ({self.code})'

    def save(self, *args, **kwargs):
        self._extra = dict(self.extra, rows=self.extra_rows)
        if 'extra' in kwargs.get('update_fields', []):
            kwargs['update_fields'].remove('extra')
            kwargs['update_fields'].append('_extra')
        super().save(*args, **kwargs)

    @property
    def name(self):
        """
        Returns product `name` from stored data.
        """
        return self.product_data.get('name', "(no name)")

    @property
    def code(self):
        """
        Returns product `name` from stored data.
        """
        return self.product_data.get('code', "(no code)")


class OrderPayment(models.Model):
    order = ParentalForeignKey(
        Order,
        on_delete=models.CASCADE,
        related_name='payments',
        verbose_name=_("Order"),
    )

    amount = models.DecimalField(_("Amount"), max_digits=18, decimal_places=2)
    transaction_id = models.CharField(_("Transaction ID"), max_length=128)
    payment_method = models.CharField(_("Payment method"), max_length=128, blank=True)

    date_created = models.DateTimeField(_("Date created"), auto_now_add=True)

    class Meta:
        verbose_name = _("Payment")
        verbose_name_plural = _("Payments")
        unique_together = ('order', 'transaction_id')

    def __str__(self):
        return f'{self.amount} ({self.transaction_id})'

    def get_payment_method(self):
        """
        Returns payment method instance.
        """
        from salesman.checkout.payment import payment_methods_pool

        return payment_methods_pool.get_payment(self.payment_method)

    @property
    def payment_method_display(self):
        """
        Returns display label for payment method.
        """
        payment = self.get_payment_method()
        return payment.label if payment else self.payment_method

    payment_method_display.fget.short_description = _("Payment method")


class OrderNote(models.Model):
    order = ParentalForeignKey(
        Order, on_delete=models.CASCADE, related_name='notes', verbose_name=_("Order"),
    )

    message = models.TextField(_("Message"))
    public = models.BooleanField(
        _("Public"), default=False, help_text=_("Is accessible to the customer?")
    )

    date_created = models.DateTimeField(_("Date created"), auto_now_add=True)

    class Meta:
        verbose_name = _("Note")
        verbose_name_plural = _("Notes")

    def __str__(self):
        return Truncator(self.message).words(3)
