from __future__ import unicode_literals

import datetime
import itertools

from django.core.exceptions import ObjectDoesNotExist
from django.core.exceptions import ValidationError
from django.contrib.auth.models import User
from django.db import models
from django.db.models import F, Q
from django.utils import timezone
from django.utils.encoding import python_2_unicode_compatible
from django.utils.translation import ugettext_lazy as _
from model_utils.managers import InheritanceManager


# User models

@python_2_unicode_compatible
class Attendee(models.Model):
    ''' Miscellaneous user-related data. '''

    def __str__(self):
        return "%s" % self.user

    @staticmethod
    def get_instance(user):
        ''' Returns the instance of attendee for the given user, or creates
        a new one. '''
        try:
            return Attendee.objects.get(user=user)
        except ObjectDoesNotExist:
            return Attendee.objects.create(user=user)

    user = models.OneToOneField(User, on_delete=models.CASCADE)
    # Badge/profile is linked
    completed_registration = models.BooleanField(default=False)
    highest_complete_category = models.IntegerField(default=0)


class AttendeeProfileBase(models.Model):
    ''' Information for an attendee's badge and related preferences.
    Subclass this in your Django site to ask for attendee information in your
    registration progess.
     '''

    objects = InheritanceManager()

    @classmethod
    def name_field(cls):
        ''' This is used to pre-fill the attendee's name from the
        speaker profile. If it's None, that functionality is disabled. '''
        return None

    def invoice_recipient(self):
        ''' Returns a representation of this attendee profile for the purpose
        of rendering to an invoice. Override in subclasses. '''

        # Manual dispatch to subclass. Fleh.
        slf = AttendeeProfileBase.objects.get_subclass(id=self.id)
        # Actually compare the functions.
        if type(slf).invoice_recipient != type(self).invoice_recipient:
            return type(slf).invoice_recipient(slf)

        # Return a default
        return slf.attendee.user.username

    attendee = models.OneToOneField(Attendee, on_delete=models.CASCADE)


# Inventory Models

@python_2_unicode_compatible
class Category(models.Model):
    ''' Registration product categories '''

    class Meta:
        verbose_name_plural = _("categories")

    def __str__(self):
        return self.name

    RENDER_TYPE_RADIO = 1
    RENDER_TYPE_QUANTITY = 2

    CATEGORY_RENDER_TYPES = [
        (RENDER_TYPE_RADIO, _("Radio button")),
        (RENDER_TYPE_QUANTITY, _("Quantity boxes")),
    ]

    name = models.CharField(
        max_length=65,
        verbose_name=_("Name"),
    )
    description = models.CharField(
        max_length=255,
        verbose_name=_("Description"),
    )
    limit_per_user = models.PositiveIntegerField(
        null=True,
        blank=True,
        verbose_name=_("Limit per user"),
        help_text=_("The total number of items from this category one "
                    "attendee may purchase."),
    )
    required = models.BooleanField(
        blank=True,
        help_text=_("If enabled, a user must select an "
                    "item from this category."),
    )
    order = models.PositiveIntegerField(
        verbose_name=("Display order"),
        db_index=True,
    )
    render_type = models.IntegerField(
        choices=CATEGORY_RENDER_TYPES,
        verbose_name=_("Render type"),
        help_text=_("The registration form will render this category in this "
                    "style."),
    )


@python_2_unicode_compatible
class Product(models.Model):
    ''' Registration products '''

    def __str__(self):
        return "%s - %s" % (self.category.name, self.name)

    name = models.CharField(
        max_length=65,
        verbose_name=_("Name"),
    )
    description = models.CharField(
        max_length=255,
        verbose_name=_("Description"),
        null=True,
        blank=True,
    )
    category = models.ForeignKey(
        Category,
        verbose_name=_("Product category")
    )
    price = models.DecimalField(
        max_digits=8,
        decimal_places=2,
        verbose_name=_("Price"),
    )
    limit_per_user = models.PositiveIntegerField(
        null=True,
        blank=True,
        verbose_name=_("Limit per user"),
    )
    reservation_duration = models.DurationField(
        default=datetime.timedelta(hours=1),
        verbose_name=_("Reservation duration"),
        help_text=_("The length of time this product will be reserved before "
                    "it is released for someone else to purchase."),
    )
    order = models.PositiveIntegerField(
        verbose_name=("Display order"),
        db_index=True,
    )


@python_2_unicode_compatible
class Voucher(models.Model):
    ''' Registration vouchers '''

    # Vouchers reserve a cart for a fixed amount of time, so that
    # items may be added without the voucher being swiped by someone else
    RESERVATION_DURATION = datetime.timedelta(hours=1)

    def __str__(self):
        return "Voucher for %s" % self.recipient

    @classmethod
    def normalise_code(cls, code):
        return code.upper()

    def save(self, *a, **k):
        ''' Normalise the voucher code to be uppercase '''
        self.code = self.normalise_code(self.code)
        super(Voucher, self).save(*a, **k)

    recipient = models.CharField(max_length=64, verbose_name=_("Recipient"))
    code = models.CharField(max_length=16,
                            unique=True,
                            verbose_name=_("Voucher code"))
    limit = models.PositiveIntegerField(verbose_name=_("Voucher use limit"))


# Product Modifiers

@python_2_unicode_compatible
class DiscountBase(models.Model):
    ''' Base class for discounts. Each subclass has controller code that
    determines whether or not the given discount is available to be added to
    the current cart. '''

    objects = InheritanceManager()

    def __str__(self):
        return "Discount: " + self.description

    def effects(self):
        ''' Returns all of the effects of this discount. '''
        products = self.discountforproduct_set.all()
        categories = self.discountforcategory_set.all()
        return itertools.chain(products, categories)

    description = models.CharField(
        max_length=255,
        verbose_name=_("Description"),
        help_text=_("A description of this discount. This will be included on "
                    "invoices where this discount is applied."),
        )


@python_2_unicode_compatible
class DiscountForProduct(models.Model):
    ''' Represents a discount on an individual product. Each Discount can
    contain multiple products and categories. Discounts can either be a
    percentage or a fixed amount, but not both. '''

    def __str__(self):
        if self.percentage:
            return "%s%% off %s" % (self.percentage, self.product)
        elif self.price:
            return "$%s off %s" % (self.price, self.product)

    def clean(self):
        if self.percentage is None and self.price is None:
            raise ValidationError(
                _("Discount must have a percentage or a price."))
        elif self.percentage is not None and self.price is not None:
            raise ValidationError(
                _("Discount may only have a percentage or only a price."))

        prods = DiscountForProduct.objects.filter(
            discount=self.discount,
            product=self.product)
        cats = DiscountForCategory.objects.filter(
            discount=self.discount,
            category=self.product.category)
        if len(prods) > 1:
            raise ValidationError(
                _("You may only have one discount line per product"))
        if len(cats) != 0:
            raise ValidationError(
                _("You may only have one discount for "
                    "a product or its category"))

    discount = models.ForeignKey(DiscountBase, on_delete=models.CASCADE)
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    percentage = models.DecimalField(
        max_digits=4, decimal_places=1, null=True, blank=True)
    price = models.DecimalField(
        max_digits=8, decimal_places=2, null=True, blank=True)
    quantity = models.PositiveIntegerField()


@python_2_unicode_compatible
class DiscountForCategory(models.Model):
    ''' Represents a discount for a category of products. Each discount can
    contain multiple products. Category discounts can only be a percentage. '''

    def __str__(self):
        return "%s%% off %s" % (self.percentage, self.category)

    def clean(self):
        prods = DiscountForProduct.objects.filter(
            discount=self.discount,
            product__category=self.category)
        cats = DiscountForCategory.objects.filter(
            discount=self.discount,
            category=self.category)
        if len(prods) != 0:
            raise ValidationError(
                _("You may only have one discount for "
                    "a product or its category"))
        if len(cats) > 1:
            raise ValidationError(
                _("You may only have one discount line per category"))

    discount = models.ForeignKey(DiscountBase, on_delete=models.CASCADE)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    percentage = models.DecimalField(
        max_digits=4,
        decimal_places=1)
    quantity = models.PositiveIntegerField()


class TimeOrStockLimitDiscount(DiscountBase):
    ''' Discounts that are generally available, but are limited by timespan or
    usage count. This is for e.g. Early Bird discounts. '''

    class Meta:
        verbose_name = _("Promotional discount")

    start_time = models.DateTimeField(
        null=True,
        blank=True,
        verbose_name=_("Start time"),
        help_text=_("This discount will only be available after this time."),
    )
    end_time = models.DateTimeField(
        null=True,
        blank=True,
        verbose_name=_("End time"),
        help_text=_("This discount will only be available before this time."),
    )
    limit = models.PositiveIntegerField(
        null=True,
        blank=True,
        verbose_name=_("Limit"),
        help_text=_("This discount may only be applied this many times."),
    )


class VoucherDiscount(DiscountBase):
    ''' Discounts that are enabled when a voucher code is in the current
    cart. '''

    voucher = models.OneToOneField(
        Voucher,
        on_delete=models.CASCADE,
        verbose_name=_("Voucher"),
        db_index=True,
    )


class IncludedProductDiscount(DiscountBase):
    ''' Discounts that are enabled because another product has been purchased.
    e.g. A conference ticket includes a free t-shirt. '''

    class Meta:
        verbose_name = _("Product inclusion")

    enabling_products = models.ManyToManyField(
        Product,
        verbose_name=_("Including product"),
        help_text=_("If one of these products are purchased, the discounts "
                    "below will be enabled."),
    )


class RoleDiscount(object):
    ''' Discounts that are enabled because the active user has a specific
    role. This is for e.g. volunteers who can get a discount ticket. '''
    # TODO: implement RoleDiscount
    pass


@python_2_unicode_compatible
class EnablingConditionBase(models.Model):
    ''' This defines a condition which allows products or categories to
    be made visible. If there is at least one mandatory enabling condition
    defined on a Product or Category, it will only be enabled if *all*
    mandatory conditions are met, otherwise, if there is at least one enabling
    condition defined on a Product or Category, it will only be enabled if at
    least one condition is met. '''

    objects = InheritanceManager()

    def __str__(self):
        return self.description

    def effects(self):
        ''' Returns all of the items enabled by this condition. '''
        return itertools.chain(self.products.all(), self.categories.all())

    description = models.CharField(max_length=255)
    mandatory = models.BooleanField(
        default=False,
        help_text=_("If there is at least one mandatory condition defined on "
                    "a product or category, all such conditions must be met. "
                    "Otherwise, at least one non-mandatory condition must be "
                    "met."),
    )
    products = models.ManyToManyField(
        Product,
        blank=True,
        help_text=_("Products that are enabled if this condition is met."),
    )
    categories = models.ManyToManyField(
        Category,
        blank=True,
        help_text=_("Categories whose products are enabled if this condition "
                    "is met."),
    )


class TimeOrStockLimitEnablingCondition(EnablingConditionBase):
    ''' Registration product ceilings '''

    class Meta:
        verbose_name = _("ceiling")

    start_time = models.DateTimeField(
        null=True,
        blank=True,
        help_text=_("Products included in this condition will only be "
                    "available after this time."),
    )
    end_time = models.DateTimeField(
        null=True,
        blank=True,
        help_text=_("Products included in this condition will only be "
                    "available before this time."),
    )
    limit = models.PositiveIntegerField(
        null=True,
        blank=True,
        help_text=_("The number of items under this grouping that can be "
                    "purchased."),
    )


@python_2_unicode_compatible
class ProductEnablingCondition(EnablingConditionBase):
    ''' The condition is met because a specific product is purchased. '''

    def __str__(self):
        return "Enabled by products: " + str(self.enabling_products.all())

    enabling_products = models.ManyToManyField(
        Product,
        help_text=_("If one of these products are purchased, this condition "
                    "is met."),
    )


@python_2_unicode_compatible
class CategoryEnablingCondition(EnablingConditionBase):
    ''' The condition is met because a product in a particular product is
    purchased. '''

    def __str__(self):
        return "Enabled by product in category: " + str(self.enabling_category)

    enabling_category = models.ForeignKey(
        Category,
        help_text=_("If a product from this category is purchased, this "
                    "condition is met."),
    )


@python_2_unicode_compatible
class VoucherEnablingCondition(EnablingConditionBase):
    ''' The condition is met because a Voucher is present. This is for e.g.
    enabling sponsor tickets. '''

    def __str__(self):
        return "Enabled by voucher: %s" % self.voucher

    voucher = models.OneToOneField(Voucher)


# @python_2_unicode_compatible
class RoleEnablingCondition(object):
    ''' The condition is met because the active user has a particular Role.
    This is for e.g. enabling Team tickets. '''
    # TODO: implement RoleEnablingCondition
    pass


# Commerce Models

@python_2_unicode_compatible
class Cart(models.Model):
    ''' Represents a set of product items that have been purchased, or are
    pending purchase. '''

    class Meta:
        index_together = [
            ("active", "time_last_updated"),
            ("active", "released"),
            ("active", "user"),
            ("released", "user"),
        ]

    def __str__(self):
        return "%d rev #%d" % (self.id, self.revision)

    user = models.ForeignKey(User)
    # ProductItems (foreign key)
    vouchers = models.ManyToManyField(Voucher, blank=True)
    time_last_updated = models.DateTimeField(
        db_index=True,
    )
    reservation_duration = models.DurationField()
    revision = models.PositiveIntegerField(default=1)
    active = models.BooleanField(
        default=True,
        db_index=True,
    )
    released = models.BooleanField(
        default=False,
        db_index=True
    )  # Refunds etc

    @classmethod
    def reserved_carts(cls):
        ''' Gets all carts that are 'reserved' '''
        return Cart.objects.filter(
            (Q(active=True) &
                Q(time_last_updated__gt=(
                    timezone.now()-F('reservation_duration')
                                        ))) |
            (Q(active=False) & Q(released=False))
        )


@python_2_unicode_compatible
class ProductItem(models.Model):
    ''' Represents a product-quantity pair in a Cart. '''

    def __str__(self):
        return "product: %s * %d in Cart: %s" % (
            self.product, self.quantity, self.cart)

    cart = models.ForeignKey(Cart)
    product = models.ForeignKey(Product)
    quantity = models.PositiveIntegerField(db_index=True)


@python_2_unicode_compatible
class DiscountItem(models.Model):
    ''' Represents a discount-product-quantity relation in a Cart. '''

    def __str__(self):
        return "%s: %s * %d in Cart: %s" % (
            self.discount, self.product, self.quantity, self.cart)

    cart = models.ForeignKey(Cart)
    product = models.ForeignKey(Product)
    discount = models.ForeignKey(DiscountBase)
    quantity = models.PositiveIntegerField()


@python_2_unicode_compatible
class Invoice(models.Model):
    ''' An invoice. Invoices can be automatically generated when checking out
    a Cart, in which case, it is attached to a given revision of a Cart. '''

    STATUS_UNPAID = 1
    STATUS_PAID = 2
    STATUS_REFUNDED = 3
    STATUS_VOID = 4

    STATUS_TYPES = [
        (STATUS_UNPAID, _("Unpaid")),
        (STATUS_PAID, _("Paid")),
        (STATUS_REFUNDED, _("Refunded")),
        (STATUS_VOID, _("VOID")),
    ]

    def __str__(self):
        return "Invoice #%d" % self.id

    def clean(self):
        if self.cart is not None and self.cart_revision is None:
            raise ValidationError(
                "If this is a cart invoice, it must have a revision")

    @property
    def is_unpaid(self):
        return self.status == self.STATUS_UNPAID

    @property
    def is_void(self):
        return self.status == self.STATUS_VOID

    @property
    def is_paid(self):
        return self.status == self.STATUS_PAID

    @property
    def is_refunded(self):
        return self.status == self.STATUS_REFUNDED

    # Invoice Number
    user = models.ForeignKey(User)
    cart = models.ForeignKey(Cart, null=True)
    cart_revision = models.IntegerField(
        null=True,
        db_index=True,
    )
    # Line Items (foreign key)
    status = models.IntegerField(
        choices=STATUS_TYPES,
        db_index=True,
    )
    recipient = models.CharField(max_length=1024)
    issue_time = models.DateTimeField()
    due_time = models.DateTimeField()
    value = models.DecimalField(max_digits=8, decimal_places=2)


@python_2_unicode_compatible
class LineItem(models.Model):
    ''' Line items for an invoice. These are denormalised from the ProductItems
    and DiscountItems that belong to a cart (for consistency), but also allow
    for arbitrary line items when required. '''

    def __str__(self):
        return "Line: %s * %d @ %s" % (
            self.description, self.quantity, self.price)

    invoice = models.ForeignKey(Invoice)
    description = models.CharField(max_length=255)
    quantity = models.PositiveIntegerField()
    price = models.DecimalField(max_digits=8, decimal_places=2)
    product = models.ForeignKey(Product, null=True, blank=True)


@python_2_unicode_compatible
class PaymentBase(models.Model):
    ''' The base payment type for invoices. Payment apps should subclass this
    class to handle implementation-specific issues. '''

    objects = InheritanceManager()

    def __str__(self):
        return "Payment: ref=%s amount=%s" % (self.reference, self.amount)

    invoice = models.ForeignKey(Invoice)
    time = models.DateTimeField(default=timezone.now)
    reference = models.CharField(max_length=255)
    amount = models.DecimalField(max_digits=8, decimal_places=2)


class ManualPayment(PaymentBase):
    ''' Payments that are manually entered by staff. '''
    pass