"""工单域模型（M2）：ticket_ext / item_link / notification。

三条设计约束（对应 PRODUCT-PLAN 的 D1/D2）：

1. **工单不是新表，是 `item` 的一个 kind**。标题、正文、截止、标签、评论、事件流
   全部复用，M1 写的每一处代码对工单依然成立；`ticket_ext` 只补"谁请谁、验没验收"。
2. **升级不是搬家**。原任务留在原地并进入 `blocked`（它确实被卡住了），工单是**新建**的一条
   item，通过 `TicketExt.parent_item_id` 指回去。工单验收通过时把原任务从 blocked 拉回 todo，
   这就是"闭环回流"——任务那条时间线完整保留，历史不被搬来搬去。
3. **通知只记录"发生了什么"，不做已读以外的状态机**。通知看错、漏看是常态，
   真正的状态永远以 item 为准，通知只是提醒，不能变成第二份真相。
"""

from __future__ import annotations

import uuid
from datetime import datetime

from sqlalchemy import (
    CheckConstraint,
    DateTime,
    ForeignKey,
    Index,
    Integer,
    String,
    Text,
    UniqueConstraint,
    func,
)
from sqlalchemy.dialects.postgresql import UUID as PgUUID
from sqlalchemy.orm import Mapped, mapped_column

from .models import Base, Timestamps, new_uuid

# 工单状态机（与任务共用 item.status 这一列，但取值集合不同）
TICKET_STATUSES: tuple[str, ...] = (
    "open",
    "accepted",
    "in_progress",
    "pending_verify",
    "done",
    "canceled",
)

LINK_TYPES: tuple[str, ...] = ("parent", "related")


class TicketExt(Base, Timestamps):
    """工单的附加信息，与 item 一比一。"""

    __tablename__ = "ticket_ext"
    __table_args__ = (
        Index("ix_ticket_ws_assignee", "workspace_id", "assignee_id"),
        Index("ix_ticket_ws_requester", "workspace_id", "requester_id"),
        CheckConstraint("reject_count >= 0", name="ck_ticket_reject_count"),
    )

    # item_id 既是主键又是外键：一条 item 最多一条 ticket_ext，天然 1:1
    item_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="CASCADE"), primary_key=True
    )
    workspace_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("workspace.id", ondelete="CASCADE"), nullable=False
    )
    # 谁提的这件事（下单的人）
    requester_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="RESTRICT"), nullable=False
    )
    # 谁在办（冗余一份，免得每次查工单都要回 item 表；两处必须一致，改指派时同时写）
    assignee_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="RESTRICT"), nullable=False
    )
    # 从哪条任务升级来的；独立创建的工单为空
    parent_item_id: Mapped[uuid.UUID | None] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="SET NULL")
    )
    accepted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    submitted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    verified_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    verified_by: Mapped[uuid.UUID | None] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="SET NULL")
    )
    # 被驳回次数：不是为了考核，是为了让提需求的人知道"这事返工过几次"
    reject_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    # 办完的结论：写什么由办理人决定，M3 从这里长知识草稿
    resolution_md: Mapped[str] = mapped_column(Text, nullable=False, default="")


class ItemLink(Base, Timestamps):
    """事项之间的关系。M2 只做两种：父子（子任务）与相关。

    `from_item_id → to_item_id` 是有方向的：parent 表示 from 是 to 的子项。
    """

    __tablename__ = "item_link"
    __table_args__ = (
        UniqueConstraint("from_item_id", "to_item_id", "link_type", name="uq_item_link"),
        CheckConstraint("from_item_id <> to_item_id", name="ck_item_link_not_self"),
        CheckConstraint("link_type IN ('parent','related')", name="ck_item_link_type"),
        Index("ix_item_link_ws_from", "workspace_id", "from_item_id"),
        Index("ix_item_link_ws_to", "workspace_id", "to_item_id"),
    )

    id: Mapped[uuid.UUID] = mapped_column(PgUUID(as_uuid=True), primary_key=True, default=new_uuid)
    workspace_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("workspace.id", ondelete="CASCADE"), nullable=False
    )
    from_item_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="CASCADE"), nullable=False
    )
    to_item_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="CASCADE"), nullable=False
    )
    link_type: Mapped[str] = mapped_column(String(16), nullable=False, default="related")


class Notification(Base, Timestamps):
    """站内通知。收件人维度，不是工作区里的公共消息流。"""

    __tablename__ = "notification"
    __table_args__ = (
        Index("ix_notification_ws_user_read", "workspace_id", "user_id", "read_at"),
        Index("ix_notification_ws_created", "workspace_id", "created_at"),
    )

    id: Mapped[uuid.UUID] = mapped_column(PgUUID(as_uuid=True), primary_key=True, default=new_uuid)
    workspace_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("workspace.id", ondelete="CASCADE"), nullable=False
    )
    user_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="CASCADE"), nullable=False
    )
    kind: Mapped[str] = mapped_column(String(32), nullable=False)
    item_id: Mapped[uuid.UUID | None] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="CASCADE")
    )
    title: Mapped[str] = mapped_column(String(120), nullable=False)
    body: Mapped[str] = mapped_column(String(300), nullable=False, default="")
    read_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, server_default=func.now()
    )


TICKET_TENANT_TABLES: tuple[str, ...] = ("ticket_ext", "item_link", "notification")