import uuid

from django.conf import settings
from django.db import models
from django.db.models import Q


class WorkItemStatus(models.TextChoices):
    ACTIVE = "active", "待处理"
    COMPLETED = "completed", "已完成"
    CANCELLED = "cancelled", "已取消"


class WorkItemType(models.TextChoices):
    TICKET_MISSING_INFO = "ticket_missing_info", "工单信息待补全"
    TICKET_INTAKE_FAILED = "ticket_intake_failed", "智能受理待人工接管"
    TICKET_CUSTOMER_REPLY = "ticket_customer_reply", "客户回复待确认"
    TICKET_CLOSE = "ticket_close", "工单待人工关闭"
    TICKET_CUSTOMER_CONFIRMATION = "ticket_customer_confirmation", "客户解决反馈待确认"
    SUPPORT_ANALYSIS_FAILED = "support_analysis_failed", "支持分析待人工接管"
    KNOWLEDGE_DISTILLATION_FAILED = (
        "knowledge_distillation_failed",
        "知识蒸馏待人工接管",
    )
    ASSET_REVIEW = "asset_review", "知识资产待审核"
    TOOL_CONFIRMATION = "tool_confirmation", "高风险工具待确认"


class WorkItem(models.Model):
    public_id = models.UUIDField(default=uuid.uuid4, unique=True, editable=False)
    task_type = models.CharField(max_length=64, choices=WorkItemType.choices)
    status = models.CharField(
        max_length=24,
        choices=WorkItemStatus.choices,
        default=WorkItemStatus.ACTIVE,
    )
    object_type = models.CharField(max_length=64)
    object_id = models.CharField(max_length=80)
    ticket = models.ForeignKey(
        "tickets.Ticket",
        null=True,
        blank=True,
        on_delete=models.CASCADE,
        related_name="work_items",
    )
    title = models.CharField(max_length=200)
    description = models.TextField(blank=True)
    payload = models.JSONField(default=dict, blank=True)
    assignee = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="assigned_work_items",
    )
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="created_work_items",
    )
    completed_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="completed_work_items",
    )
    completed_at = models.DateTimeField(null=True, blank=True)
    due_at = models.DateTimeField(null=True, blank=True, db_index=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ["-created_at"]
        constraints = [
            models.UniqueConstraint(
                fields=["task_type", "object_type", "object_id"],
                condition=Q(status=WorkItemStatus.ACTIVE),
                name="unique_active_work_item_target",
            )
        ]
        indexes = [
            models.Index(fields=["status", "task_type", "created_at"]),
            models.Index(fields=["object_type", "object_id"]),
            models.Index(fields=["assignee", "status", "created_at"]),
        ]