"""消息通知与智能预警模型：
1. Notification 站内消息/通知
2. AlertRule 业务预警规则（库存低限预警、应收账款逾期催收预警等）
"""

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


class Notification(TenantScopedModel):
    """消息通知。"""

    CATEGORY_CHOICES = [
        ("info", "系统通知"),
        ("warning", "业务预警"),
        ("error", "异常提醒"),
        ("audit", "审批待办"),
    ]

    recipient = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.CASCADE,
        related_name="notifications",
        help_text="接收人（为空表示租户内广播）",
    )
    title = models.CharField(max_length=128)
    content = models.TextField()
    category = models.CharField(max_length=16, choices=CATEGORY_CHOICES, default="info")
    link = models.CharField(max_length=255, blank=True, default="", help_text="跳转路由")
    is_read = models.BooleanField(default=False)
    read_at = models.DateTimeField(null=True, blank=True)
    extra_data = models.JSONField(default=dict, blank=True)

    class Meta:
        db_table = "notify_notification"
        indexes = [
            models.Index(fields=["tenant", "recipient", "is_read"]),
            models.Index(fields=["tenant", "-created_at"]),
        ]
        ordering = ["-created_at"]

    def __str__(self):
        return f"[{self.get_category_display()}] {self.title} (已读: {self.is_read})"


class AlertRule(TenantScopedModel):
    """业务预警规则配置。"""

    RULE_TYPE_CHOICES = [
        ("inventory_low", "库存缺货/下限预警"),
        ("receivable_overdue", "应收账款逾期催款预警"),
        ("stock_backlog", "商品呆滞积压预警"),
        ("batch_expiry", "批次近效期预警"),
        ("risk_score", "AI 应收风险预警（threshold=风险分数线）"),
    ]

    code = models.CharField(max_length=64, help_text="规则代码")
    name = models.CharField(max_length=128, help_text="预警规则名称")
    rule_type = models.CharField(max_length=32, choices=RULE_TYPE_CHOICES)
    threshold = models.DecimalField(max_digits=18, decimal_places=4, default=10, help_text="预警阈值（如天数或数量）")
    is_enabled = models.BooleanField(default=True)
    channels = models.JSONField(default=list, blank=True, help_text="通知渠道 ['in_app', 'webhook']")

    class Meta:
        db_table = "notify_alert_rule"
        unique_together = [("tenant", "code")]
        verbose_name_plural = "业务预警规则"
        ordering = ["code"]

    def __str__(self):
        return f"{self.name} (阈值: {self.threshold}) [{ '启用' if self.is_enabled else '停用' }]"