"""采购模型：PurchaseOrder（订单）+ PurchaseBill（进货单/收货入库单）。"""

from decimal import Decimal

from django.db import models

from apps.core.base_models import TenantScopedModel


class PurchaseOrder(TenantScopedModel):
    """采购订单（可选，预先订货流程）。"""

    STATE_CHOICES = [
        ("draft", "草稿"),
        ("confirmed", "已确认"),
        ("received", "已收货"),
        ("cancelled", "已取消"),
    ]

    bill_no = models.CharField(max_length=64)
    supplier = models.ForeignKey(
        "partner.Supplier",
        on_delete=models.PROTECT,
        related_name="purchase_orders",
    )
    warehouse = models.ForeignKey(
        "inventory.Warehouse",
        on_delete=models.PROTECT,
        related_name="purchase_orders",
    )
    bill_date = models.DateField()
    expected_date = models.DateField(null=True, blank=True)
    total_amount = models.DecimalField(max_digits=18, decimal_places=4, default=0)
    state = models.CharField(max_length=16, choices=STATE_CHOICES, default="draft")
    remark = models.TextField(blank=True, default="")

    class Meta:
        db_table = "purchase_order"
        unique_together = [("tenant", "bill_no")]
        ordering = ["-bill_date", "-id"]
        verbose_name_plural = "采购订单"


class PurchaseOrderLine(TenantScopedModel):
    order = models.ForeignKey(
        PurchaseOrder, on_delete=models.CASCADE, related_name="lines"
    )
    product = models.ForeignKey(
        "catalog.Product", on_delete=models.PROTECT, related_name="po_lines"
    )
    source_unit = models.ForeignKey(
        "catalog.Unit",
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="%(class)s_lines",
        help_text="录入单位（空=按基本单位）",
    )
    source_quantity = models.DecimalField(
        max_digits=18, decimal_places=4, null=True, blank=True,
        help_text="录入数量（按录入单位；quantity 恒为基本单位数量）",
    )

    quantity = models.DecimalField(max_digits=18, decimal_places=4)
    unit_price = models.DecimalField(max_digits=18, decimal_places=4)
    amount = models.DecimalField(max_digits=18, decimal_places=4, default=0)
    received_qty = models.DecimalField(max_digits=18, decimal_places=4, default=0)

    class Meta:
        db_table = "purchase_order_line"
        ordering = ["id"]


class PurchaseBill(TenantScopedModel):
    """进货单（实际收货入库时生成）。"""

    STATE_CHOICES = [
        ("draft", "草稿"),
        ("confirmed", "已过账"),
        ("cancelled", "已取消"),
    ]

    bill_no = models.CharField(max_length=64)
    supplier = models.ForeignKey(
        "partner.Supplier",
        on_delete=models.PROTECT,
        related_name="purchase_bills",
    )
    warehouse = models.ForeignKey(
        "inventory.Warehouse",
        on_delete=models.PROTECT,
        related_name="purchase_bills",
    )
    order = models.ForeignKey(
        PurchaseOrder,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="bills",
    )
    bill_date = models.DateField()
    total_amount = models.DecimalField(max_digits=18, decimal_places=4, default=0)
    state = models.CharField(max_length=16, choices=STATE_CHOICES, default="draft")
    remark = models.TextField(blank=True, default="")

    class Meta:
        db_table = "purchase_bill"
        unique_together = [("tenant", "bill_no")]
        ordering = ["-bill_date", "-id"]
        verbose_name_plural = "进货单"


class PurchaseBillLine(TenantScopedModel):
    bill = models.ForeignKey(
        PurchaseBill, on_delete=models.CASCADE, related_name="lines"
    )
    product = models.ForeignKey(
        "catalog.Product", on_delete=models.PROTECT, related_name="bill_lines"
    )
    batch_no = models.CharField(
        max_length=64, blank=True, default="", help_text="批次号（批次管理商品必填）"
    )
    production_date = models.DateField(null=True, blank=True)
    expiry_date = models.DateField(null=True, blank=True)

    source_unit = models.ForeignKey(
        "catalog.Unit",
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="%(class)s_lines",
        help_text="录入单位（空=按基本单位）",
    )
    source_quantity = models.DecimalField(
        max_digits=18, decimal_places=4, null=True, blank=True,
        help_text="录入数量（按录入单位；quantity 恒为基本单位数量）",
    )

    quantity = models.DecimalField(max_digits=18, decimal_places=4)
    unit_price = models.DecimalField(max_digits=18, decimal_places=4)
    amount = models.DecimalField(max_digits=18, decimal_places=4, default=0)

    tax_rate = models.DecimalField(
        max_digits=6, decimal_places=4, default=0,
        help_text="行税率（0.13 = 13%）；价内口径：amount 为含税额",
    )
    tax_amount = models.DecimalField(
        max_digits=18, decimal_places=4, default=0,
        help_text="行税额（从含税额中拆出）",
    )

    class Meta:
        db_table = "purchase_bill_line"
        ordering = ["id"]