"""客户与供应商（partner）模型。

设计：
- 客户 (Customer) 与供应商 (Supplier) 共享 PriceLevel 价格等级字典
- 联系人 (Contact) 可挂在任一客户/供应商上
- 客户/供应商都有期初应收/应付余额、累计金额、信用额度等
"""

from django.db import models
from apps.core.base_models import TenantScopedModel


class PriceLevel(TenantScopedModel):
    """价格等级（VIP1、VIP2、批发、零售 等）。"""

    code = models.CharField(max_length=32)
    name = models.CharField(max_length=64)
    discount_rate = models.DecimalField(
        max_digits=6, decimal_places=4, default=0, help_text="默认折扣率"
    )
    sort_order = models.IntegerField(default=0)

    class Meta:
        db_table = "partner_price_level"
        unique_together = [("tenant", "code")]
        ordering = ["sort_order", "code"]
        verbose_name_plural = "价格等级"

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


class Contact(TenantScopedModel):
    """联系人（可挂在 customer 或 supplier 上）。"""

    name = models.CharField(max_length=64)
    phone = models.CharField(max_length=32, blank=True, default="")
    email = models.EmailField(blank=True, default="")
    title = models.CharField(max_length=64, blank=True, default="", help_text="职位/称呼")
    customer = models.ForeignKey(
        "Customer",
        null=True,
        blank=True,
        on_delete=models.CASCADE,
        related_name="contacts",
    )
    supplier = models.ForeignKey(
        "Supplier",
        null=True,
        blank=True,
        on_delete=models.CASCADE,
        related_name="contacts",
    )
    is_primary = models.BooleanField(default=False, help_text="是否主联系人")

    class Meta:
        db_table = "partner_contact"
        verbose_name_plural = "联系人"

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


class Customer(TenantScopedModel):
    """客户。"""

    KIND_CHOICES = [
        ("individual", "个人"),
        ("company", "企业"),
    ]

    code = models.CharField(max_length=64, help_text="客户编码（租户内唯一）")
    name = models.CharField(max_length=128)
    kind = models.CharField(max_length=16, choices=KIND_CHOICES, default="company")
    contact_name = models.CharField(max_length=64, blank=True, default="")
    phone = models.CharField(max_length=32, blank=True, default="")
    email = models.EmailField(blank=True, default="")
    address = models.CharField(max_length=255, blank=True, default="")
    tax_number = models.CharField(max_length=64, blank=True, default="", help_text="税号")
    bank_account = models.CharField(max_length=64, blank=True, default="")

    price_level = models.ForeignKey(
        PriceLevel,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="customers",
    )
    credit_limit = models.DecimalField(
        max_digits=18, decimal_places=4, default=0, help_text="信用额度"
    )
    initial_receivable = models.DecimalField(
        max_digits=18, decimal_places=4, default=0, help_text="期初应收"
    )

    is_active = models.BooleanField(default=True)
    remark = models.TextField(blank=True, default="")

    class Meta:
        db_table = "partner_customer"
        unique_together = [("tenant", "code")]
        verbose_name_plural = "客户"
        indexes = [
            models.Index(fields=["tenant", "code"]),
            models.Index(fields=["tenant", "name"]),
            models.Index(fields=["tenant", "phone"]),
        ]
        ordering = ["code"]

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


class Supplier(TenantScopedModel):
    """供应商。"""

    code = models.CharField(max_length=64)
    name = models.CharField(max_length=128)
    contact_name = models.CharField(max_length=64, blank=True, default="")
    phone = models.CharField(max_length=32, blank=True, default="")
    email = models.EmailField(blank=True, default="")
    address = models.CharField(max_length=255, blank=True, default="")
    tax_number = models.CharField(max_length=64, blank=True, default="")
    bank_account = models.CharField(max_length=64, blank=True, default="")

    initial_payable = models.DecimalField(
        max_digits=18, decimal_places=4, default=0, help_text="期初应付"
    )

    is_active = models.BooleanField(default=True)
    remark = models.TextField(blank=True, default="")

    class Meta:
        db_table = "partner_supplier"
        unique_together = [("tenant", "code")]
        verbose_name_plural = "供应商"
        indexes = [
            models.Index(fields=["tenant", "code"]),
            models.Index(fields=["tenant", "name"]),
        ]
        ordering = ["code"]

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


class CustomerProductPrice(TenantScopedModel):
    """客户专属价格本（客户 × 商品 → 成交价，取价优先级最高）。"""

    customer = models.ForeignKey(
        Customer, on_delete=models.CASCADE, related_name="product_prices"
    )
    product = models.ForeignKey(
        "catalog.Product", on_delete=models.CASCADE, related_name="customer_prices"
    )
    price = models.DecimalField(max_digits=18, decimal_places=4)

    class Meta:
        db_table = "partner_customer_product_price"
        unique_together = [("tenant", "customer", "product")]
        verbose_name_plural = "客户专属价"
        ordering = ["customer", "product"]

    def __str__(self):
        return f"{self.customer.code}/{self.product.code} = {self.price}"