"""任务域模型（M1）：item / tag / item_tag / comment / activity。

约定与 M0 一致：uuid 主键、通用列、`workspace_id NOT NULL`。

两个刻意的取舍：
- **M1 只有一个负责人 `assignee_id`**，不做 `item_assignee` 多对多。M1 是"自己的待办"，
  多人协作在 M2 工单里才真正需要；提前建多对多表和对应 UI 是过度设计，等真要用再迁移。
- **`kind` 列现在就加上**（默认 `task`）。M2 的工单、M3 的知识都是同一条 item 流，
  现在加一列只是默认值，将来加 `ticket_ext` / `knowledge_doc` 时不用改主表。
"""

from __future__ import annotations

import uuid
from datetime import datetime

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

from .models import Base, Timestamps, new_uuid

ITEM_STATUSES: tuple[str, ...] = ("inbox", "todo", "doing", "done", "blocked", "canceled")


class Item(Base, Timestamps):
    """任务/工单/知识的统一载体。M1 只用 `kind='task'`。"""

    __tablename__ = "item"
    __table_args__ = (
        Index("ix_item_ws_status_due", "workspace_id", "status", "due_at"),
        Index("ix_item_ws_assignee", "workspace_id", "assignee_id", "status"),
        Index("ix_item_ws_updated", "workspace_id", "updated_at"),
        Index("ix_item_ws_sort", "workspace_id", "status", "sort_order"),
    )

    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
    )
    kind: Mapped[str] = mapped_column(String(16), nullable=False, default="task")
    title: Mapped[str] = mapped_column(String(200), nullable=False)
    body_md: Mapped[str] = mapped_column(Text, nullable=False, default="")
    status: Mapped[str] = mapped_column(String(16), nullable=False, default="inbox")
    priority: Mapped[int] = mapped_column(nullable=False, default=0)
    creator_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="RESTRICT"), nullable=False
    )
    assignee_id: Mapped[uuid.UUID | None] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="SET NULL")
    )
    due_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    completed_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    sort_order: Mapped[int] = mapped_column(nullable=False, default=0)
    deleted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))


class Tag(Base, Timestamps):
    __tablename__ = "tag"
    __table_args__ = (
        UniqueConstraint("workspace_id", "name", name="uq_tag_ws_name"),
        Index("ix_tag_ws", "workspace_id", "name"),
    )

    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
    )
    name: Mapped[str] = mapped_column(String(32), nullable=False)
    color: Mapped[str] = mapped_column(String(16), nullable=False, default="")


class ItemTag(Base, Timestamps):
    __tablename__ = "item_tag"
    __table_args__ = (
        UniqueConstraint("item_id", "tag_id", name="uq_item_tag"),
        Index("ix_item_tag_ws_tag", "workspace_id", "tag_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
    )
    item_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="CASCADE"), nullable=False
    )
    tag_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("tag.id", ondelete="CASCADE"), nullable=False
    )


class Comment(Base, Timestamps):
    __tablename__ = "comment"
    __table_args__ = (Index("ix_comment_ws_item_created", "workspace_id", "item_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
    )
    item_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="CASCADE"), nullable=False
    )
    author_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="RESTRICT"), nullable=False
    )
    body_md: Mapped[str] = mapped_column(Text, nullable=False, default="")
    deleted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))


class Activity(Base):
    """事件流：item 的每一次实质变更都落一条。

    这是"这条任务怎么走到今天的"唯一真相源，M4 的 LLM 沉淀、M3 的知识都从这里取料。
    只增不改，所以没有 version / updated_at。
    """

    __tablename__ = "activity"
    __table_args__ = (
        Index("ix_activity_ws_item_created", "workspace_id", "item_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
    )
    item_id: Mapped[uuid.UUID] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("item.id", ondelete="CASCADE"), nullable=False
    )
    actor_id: Mapped[uuid.UUID | None] = mapped_column(
        PgUUID(as_uuid=True), ForeignKey("app_user.id", ondelete="SET NULL")
    )
    action: Mapped[str] = mapped_column(String(32), nullable=False)
    payload: Mapped[dict | None] = mapped_column(JSONB)
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, server_default=func.now()
    )


TASK_TENANT_TABLES: tuple[str, ...] = ("item", "tag", "item_tag", "comment", "activity")