"""任务模型 — 支持无限嵌套、任务裂变分支、返工闭环"""
import uuid
from datetime import datetime, timezone
from sqlalchemy import String, DateTime, Boolean, ForeignKey
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.models.base import Base

# 任务状态常量
TASK_STATUS_PENDING = "PENDING"       # 待接收
TASK_STATUS_WIP = "WIP"               # 进行中
TASK_STATUS_COMPLETED = "COMPLETED"   # 已完成
TASK_STATUS_REJECTED = "REJECTED"     # 已驳回
TASK_STATUS_ARCHIVED = "ARCHIVED"     # 已入库


class Task(Base):
    __tablename__ = "tasks"

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4,
    )

    # ---- 物理外键（关联本库 products） ----
    product_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True), ForeignKey("products.id"), nullable=False, comment="所属产品ID",
    )

    # ---- 物理外键（自引用：无限嵌套父子任务 / 裂变分支） ----
    parent_task_id: Mapped[uuid.UUID | None] = mapped_column(
        UUID(as_uuid=True), ForeignKey("tasks.id"), nullable=True, index=True, comment="父任务ID(用于任务裂变树)",
    )

    task_name: Mapped[str] = mapped_column(
        String(200), nullable=False, comment="任务名称",
    )

    # ---- 逻辑外键（关联老系统用户表，仅存储 ID，无物理约束） ----
    assignee_id: Mapped[str | None] = mapped_column(
        String(64), nullable=True, comment="负责人ID(逻辑外键→老系统)",
    )

    status: Mapped[str] = mapped_column(
        String(50), nullable=False, default=TASK_STATUS_PENDING,
        comment="任务状态: PENDING(待接收) | WIP(进行中) | COMPLETED(已完成) | REJECTED(已驳回) | ARCHIVED(已入库)",
    )

    notify_parent_on_complete: Mapped[bool] = mapped_column(
        Boolean, default=False, comment="完成后是否通知父任务",
    )

    # ---- 时间追踪 ----
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), comment="创建时间",
    )
    received_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True, comment="操作员确认接收时间",
    )
    completed_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True, comment="任务完工转交时间",
    )

    # ---- 驳回/返工 ----
    reject_reason: Mapped[str | None] = mapped_column(
        String(500), nullable=True, comment="驳回原因",
    )
    is_rework: Mapped[bool] = mapped_column(
        Boolean, default=False, comment="是否为返工任务",
    )

    # ---- 关系 ----
    product: Mapped["Product"] = relationship("Product", lazy="selectin")
    parent_task: Mapped["Task | None"] = relationship(
        "Task", remote_side="Task.id", back_populates="child_tasks", lazy="selectin",
    )
    child_tasks: Mapped[list["Task"]] = relationship(
        "Task", back_populates="parent_task", lazy="selectin",
    )

    def __repr__(self) -> str:
        return f"<Task {self.task_name}>"