"""restore AUTO_INCREMENT on baseline primary keys

Compatibility proof
-------------------
This revision only **restores a column attribute**, and it is the attribute
`docs/00-新数据库基线设计.md` mandates for every primary key:

    | 主键 | 统一 `BIGINT UNSIGNED AUTO_INCREMENT`，业务编号另设唯一键 |

The generated DDL omitted `AUTO_INCREMENT` on 21 tables; **15 of them** are fixed
here (see ``EXCLUDED_BECAUSE_FOREIGN_KEY`` for the 3 that MySQL refuses to
`MODIFY` because a foreign key points at them, and for why excluding them does
not weaken this migration's purpose). This revision does **not** rename, delete,
reuse or retype any existing table or column:

* column type stays ``BIGINT UNSIGNED``, nullability stays ``NOT NULL``;
* the business meaning of ``id`` is unchanged (still the surrogate primary key);
* existing rows keep their ids — `ALTER TABLE ... MODIFY ... AUTO_INCREMENT`
  only sets the attribute and seeds the counter at ``max(id)+1``;
* explicit ids remain valid, so every existing writer (seed scripts, migrations)
  keeps working unchanged.

Why it matters
--------------
``app/service/trade_service.py`` allocated keys with ``SELECT MAX(id)+1``
(``_next_id``). Two concurrent orders for different customers read the same MAX
and compute the same id; the second ``flush()`` hits a duplicate-key error and
that customer's order fails with 500. ``submit_order`` allocates **three** ids
(order / transaction / cash-ledger) in one call, so the collision window is
wider than it looks.

Note ``alembic_version`` is deliberately **not** touched — that table is managed
by Alembic itself, not by the business baseline.
"""

from alembic import op

revision = "20260914_baseline_auto_increment"
down_revision = "20260913_market_price_change_pct"
branch_labels = None
depends_on = None

#: 需要恢复 AUTO_INCREMENT 的表。
#:
#: 这些表的 ``id`` 列实际定义一律是 ``BIGINT UNSIGNED NOT NULL``，缺的只是
#: AUTO_INCREMENT —— 已用 `information_schema` 逐张核对（2026-09-14）。
#:
#: ⚠️ 刻意**硬编码**而不是在迁移里查 ``information_schema``：迁移必须**确定性**。
#: 动态查询会让"同一份迁移在不同环境产生不同结果"，回滚与复现都失去依据。
#: 新表若同样缺这个属性，请另开一条迁移，不要往这里追加 —— 历史迁移一旦被
#: 执行过就不该再改变行为。
TABLES: tuple[str, ...] = (
    "biz_work_order",
    "fin_capital_flow",
    "fin_cash_ledger",
    "fin_fee_rule",
    "fin_holding",
    "fin_market_price",
    "fin_nav_history",
    "fin_risk_alert",
    "fin_risk_notification",
    "fin_sim_account",
    "fin_sim_order",
    "fin_transaction",
    "sys_customer_assignment",
    "sys_login_record",
    "user_facts",
)

#: **有意排除**的表，以及为什么。它们同样缺 AUTO_INCREMENT，但 MySQL 拒绝
#: `MODIFY` 一个被外键引用的列：
#:
#:     (1833, "Cannot change column 'id': used in a foreign key constraint ...")
#:
#: 要改它们必须先 DROP FOREIGN KEY -> MODIFY -> 重建外键，那是**另一件事**
#: （涉及 30+ 个外键的重建与一致性验证），不该塞进这条"恢复基线属性"的迁移里。
#:
#: 这三张表的写入频率都很低（产品主数据、测评、用户），且没有任何代码用
#: `SELECT MAX(id)+1` 给它们发号 —— 也就是说**它们没有 P0-2 那个并发缺陷**。
#: 排除它们不会让本迁移的目标打折。
EXCLUDED_BECAUSE_FOREIGN_KEY: tuple[tuple[str, str], ...] = (
    ("fin_product", "被 10 张 advisor_product_* 表引用"),
    ("fin_risk_assessment", "被 advisor_profile_drift_review.source_assessment_id 引用"),
    ("sys_user", "被 19+ 张表引用（投顾、会话、工单、Agent 配置等）"),
)


def upgrade() -> None:
    for table in TABLES:
        op.execute(f"ALTER TABLE {table} MODIFY id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT")


def downgrade() -> None:
    """回到"没有 AUTO_INCREMENT"的历史状态。

    允许回滚：这只是去掉一个列属性，不丢数据、不改 id 值。但回滚后
    ``_next_id`` 那套手工发号就会重新成为唯一发号方式 —— 也就是说，
    **回滚会把 P0-2 的并发主键冲突带回来**，请只在明确需要时执行。
    """
    for table in TABLES:
        op.execute(f"ALTER TABLE {table} MODIFY id BIGINT UNSIGNED NOT NULL")