from decimal import Decimal
from django.db import models
from flower.common import ModelBase
from basic_info import models as basic_info_models


class PurchaseOrderKindEnum(models.IntegerChoices):
    """采购单类型"""
    WHOLESALE = 1, '大货'
    SAMPLE = 2, '样板'


class PurchaseOrderStatusEnum(models.IntegerChoices):
    """采购单状态"""
    PENDING = 1, '审批中'
    APPROVED = 2, '审批通过'
    CANCELLED = 3, '作废'


class PurchaseOrder(ModelBase):
    """采购单模型（业务模块）"""

    id = models.BigAutoField(primary_key=True)
    merchant = models.ForeignKey(
        basic_info_models.Merchant,
        on_delete=models.PROTECT,
        related_name='purchase_orders',
        verbose_name='所属商户',
    )
    supplier = models.ForeignKey(
        basic_info_models.Supplier,
        on_delete=models.PROTECT,
        related_name='purchase_orders',
        verbose_name='供应商',
    )
    purchase_date = models.DateField(verbose_name='采购日期')
    kind = models.IntegerField(
        choices=PurchaseOrderKindEnum.choices, 
        default=PurchaseOrderKindEnum.WHOLESALE, 
        verbose_name='采购单类型',
    )
    operator = models.ForeignKey(
        basic_info_models.Employee,
        on_delete=models.PROTECT,
        related_name='purchase_orders',
        verbose_name='经办人',
    )
    warehouse = models.ForeignKey(
        basic_info_models.WareHouse,
        on_delete=models.PROTECT,
        related_name='purchase_orders',
        verbose_name='仓库',
    )
    status = models.IntegerField(
        choices=PurchaseOrderStatusEnum.choices, 
        default=PurchaseOrderStatusEnum.PENDING, 
        verbose_name='状态',
    )
    remarks = models.TextField(blank=True, null=True, verbose_name='备注')

    def __str__(self):
        return f'采购订单 {self.id} - {self.supplier.name}'

    class Meta:
        verbose_name = '采购单'
        verbose_name_plural = '采购单'

    def get_total_amount(self) -> Decimal:
        return sum(item.total_amount() for item in self.items.all())

    def get_total_quantity(self) -> Decimal:
        return sum(item.quantity for item in self.items.all())

    def get_total_diff_quantity(self) -> Decimal:
        return sum(item.diff_quantity() for item in self.items.all())


class PurchaseOrderItem(ModelBase):
    """采购单明细模型"""

    id = models.BigAutoField(primary_key=True)
    purchase_order = models.ForeignKey(
        PurchaseOrder,
        on_delete=models.CASCADE,
        related_name='items',
        verbose_name='采购单',
    )
    product = models.ForeignKey(
        basic_info_models.Product,
        on_delete=models.PROTECT,
        related_name='purchase_order_items',
        verbose_name='产品',
    )
    price = models.DecimalField(max_digits=15, decimal_places=2, verbose_name='单价')
    color = models.CharField(max_length=50, null=True, blank=True, verbose_name='颜色')
    quantity = models.DecimalField(max_digits=10, decimal_places=2, verbose_name='数量')
    unit = models.CharField(max_length=50, verbose_name='单位')
    spec = models.CharField(max_length=100, null=True, blank=True, verbose_name='规格')
    empty_diff_percent = models.DecimalField(
        max_digits=15, 
        decimal_places=2, 
        verbose_name='空差百分比',
    )
    # if purchase_order.warehouse.mode != WarehouseModeEnum.UNRESTRICTED, then quantity_of_rolls is required
    quantity_of_rolls = models.CharField(
        max_length=255,
        null=True,
        blank=True,
        verbose_name='各条数数量',
    )
    num_of_rolls = models.PositiveIntegerField(default=1, verbose_name='条数')
    batch_number = models.CharField(null=True, blank=True, max_length=100, verbose_name='批次号')
    remarks = models.TextField(blank=True, null=True, verbose_name='备注')

    class Meta:
        verbose_name = '采购单明细'
        verbose_name_plural = '采购单明细'

    def real_quantity(self):
        return round(self.quantity * (1 - self.empty_diff_percent / 100), 2)

    def diff_quantity(self):
        return round(self.quantity * (self.empty_diff_percent / 100), 2)

    def total_amount(self):
        return round(self.price * self.real_quantity(), 2)