"""M2 工单域：ticket_ext / item_link / notification + 扩宽 item.status 取值。

三个需要注意的点：

1. **item 的 status CHECK 必须重写**。0002 里只允许任务的六个状态，
   工单的 `open/accepted/in_progress/pending_verify` 会直接被约束拦下。
   这里改成任务 ∪ 工单的并集，而不是按 kind 做条件约束——PostgreSQL 的 CHECK 不能引用其它行，
   而"任务不该有工单状态"这件事由状态机（`app/domain/*.py`）保证，不靠数据库。
2. **新表同样开 RLS**。通知是"谁的"、工单附加信息是"哪个租户的"，漏一张就等于开了一个洞。
3. **downgrade 会删掉所有工单数据**（kind='ticket' 的 item 及其扩展）。这是有意的：
   旧约束容纳不下工单状态，不回删就无法回到 0002。已在函数注释里写明。
"""

from __future__ import annotations

from collections.abc import Sequence

import sqlalchemy as sa
from alembic import op
from sqlalchemy.dialects import postgresql

revision: str = "0003"
down_revision: str | None = "0002"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None

APP_ROLE = "dadao_app"

TENANT_TABLES_0003: tuple[str, ...] = ("ticket_ext", "item_link", "notification")

TASK_STATUSES = ("inbox", "todo", "doing", "done", "blocked", "canceled")
TICKET_STATUSES = ("open", "accepted", "in_progress", "pending_verify", "done", "canceled")


def _ws_fk() -> sa.Column:
    return sa.Column(
        "workspace_id",
        postgresql.UUID(as_uuid=True),
        sa.ForeignKey("workspace.id", ondelete="CASCADE"),
        nullable=False,
    )


def _user_fk(name: str, *, ondelete: str, nullable: bool = False) -> sa.Column:
    return sa.Column(
        name,
        postgresql.UUID(as_uuid=True),
        sa.ForeignKey("app_user.id", ondelete=ondelete),
        nullable=nullable,
    )


def _item_fk(name: str, *, ondelete: str, nullable: bool = False) -> sa.Column:
    return sa.Column(
        name,
        postgresql.UUID(as_uuid=True),
        sa.ForeignKey("item.id", ondelete=ondelete),
        nullable=nullable,
    )


def upgrade() -> None:
    # 1) 放宽 item.status：任务 ∪ 工单
    op.execute("ALTER TABLE item DROP CONSTRAINT IF EXISTS ck_item_status")
    statuses = ",".join(f"'{s}'" for s in (*TASK_STATUSES, *TICKET_STATUSES))
    op.execute(
        f"ALTER TABLE item ADD CONSTRAINT ck_item_status CHECK (status IN ({statuses}))"
    )

    # 2) 工单扩展：item_id 既是主键也是外键，天然 1:1
    op.create_table(
        "ticket_ext",
        sa.Column(
            "item_id",
            postgresql.UUID(as_uuid=True),
            sa.ForeignKey("item.id", ondelete="CASCADE"),
            primary_key=True,
        ),
        _ws_fk(),
        _user_fk("requester_id", ondelete="RESTRICT"),
        _user_fk("assignee_id", ondelete="RESTRICT"),
        _item_fk("parent_item_id", ondelete="SET NULL", nullable=True),
        sa.Column("accepted_at", sa.DateTime(timezone=True)),
        sa.Column("submitted_at", sa.DateTime(timezone=True)),
        sa.Column("verified_at", sa.DateTime(timezone=True)),
        _user_fk("verified_by", ondelete="SET NULL", nullable=True),
        sa.Column("reject_count", sa.Integer, nullable=False, server_default="0"),
        sa.Column("resolution_md", sa.Text, nullable=False, server_default=""),
        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("version", sa.Integer, nullable=False, server_default="1"),
        sa.CheckConstraint("reject_count >= 0", name="ck_ticket_reject_count"),
    )
    op.create_index("ix_ticket_ws_assignee", "ticket_ext", ["workspace_id", "assignee_id"])
    op.create_index("ix_ticket_ws_requester", "ticket_ext", ["workspace_id", "requester_id"])

    # 3) 事项关系（子任务 / 相关）
    op.create_table(
        "item_link",
        sa.Column("id", postgresql.UUID(as_uuid=True), primary_key=True),
        _ws_fk(),
        _item_fk("from_item_id", ondelete="CASCADE"),
        _item_fk("to_item_id", ondelete="CASCADE"),
        sa.Column("link_type", sa.String(16), nullable=False, server_default="related"),
        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("version", sa.Integer, nullable=False, server_default="1"),
        sa.UniqueConstraint("from_item_id", "to_item_id", "link_type", name="uq_item_link"),
        sa.CheckConstraint("from_item_id <> to_item_id", name="ck_item_link_not_self"),
        sa.CheckConstraint("link_type IN ('parent','related')", name="ck_item_link_type"),
    )
    op.create_index("ix_item_link_ws_from", "item_link", ["workspace_id", "from_item_id"])
    op.create_index("ix_item_link_ws_to", "item_link", ["workspace_id", "to_item_id"])

    # 4) 站内通知
    op.create_table(
        "notification",
        sa.Column("id", postgresql.UUID(as_uuid=True), primary_key=True),
        _ws_fk(),
        _user_fk("user_id", ondelete="CASCADE"),
        sa.Column("kind", sa.String(32), nullable=False),
        _item_fk("item_id", ondelete="CASCADE", nullable=True),
        sa.Column("title", sa.String(120), nullable=False),
        sa.Column("body", sa.String(300), nullable=False, server_default=""),
        sa.Column("read_at", sa.DateTime(timezone=True)),
        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("version", sa.Integer, nullable=False, server_default="1"),
    )
    op.create_index("ix_notification_ws_user_read", "notification", ["workspace_id", "user_id", "read_at"])
    op.create_index("ix_notification_ws_created", "notification", ["workspace_id", "created_at"])

    for statement in _POLICY_STATEMENTS:
        op.execute(statement)
    for statement in _GRANT_STATEMENTS:
        op.execute(statement)


def downgrade() -> None:
    # 旧约束容纳不下工单状态，回退必须先清掉工单数据（含它们的 ticket_ext）。
    # 这是破坏性操作，只在回滚迁移时发生；生产环境回滚前请先导出 kanban/ticket 数据。
    op.execute("DELETE FROM item WHERE kind = 'ticket'")

    for table in TENANT_TABLES_0003:
        op.execute(f"DROP POLICY IF EXISTS {table}_isolation ON {table}")

    op.drop_index("ix_notification_ws_created", table_name="notification")
    op.drop_index("ix_notification_ws_user_read", table_name="notification")
    op.drop_table("notification")

    op.drop_index("ix_item_link_ws_to", table_name="item_link")
    op.drop_index("ix_item_link_ws_from", table_name="item_link")
    op.drop_table("item_link")

    op.drop_index("ix_ticket_ws_requester", table_name="ticket_ext")
    op.drop_index("ix_ticket_ws_assignee", table_name="ticket_ext")
    op.drop_table("ticket_ext")

    statuses = ",".join(f"'{s}'" for s in TASK_STATUSES)
    op.execute("ALTER TABLE item DROP CONSTRAINT IF EXISTS ck_item_status")
    op.execute(
        f"ALTER TABLE item ADD CONSTRAINT ck_item_status CHECK (status IN ({statuses}))"
    )


_POLICY_STATEMENTS: tuple[str, ...] = tuple(
    statement
    for table in TENANT_TABLES_0003
    for statement in (
        f"ALTER TABLE {table} ENABLE ROW LEVEL SECURITY;",
        f"""
        CREATE POLICY {table}_isolation ON {table}
          USING (workspace_id = app_ws_id())
          WITH CHECK (workspace_id = app_ws_id());
        """,
    )
)

_GRANT_STATEMENTS: tuple[str, ...] = (
    f"GRANT SELECT, INSERT, UPDATE, DELETE ON {', '.join(TENANT_TABLES_0003)} TO {APP_ROLE};",
)