"""Add ``alert_rules`` JSON column to ``cmdb_cloud_scopes``.

Revision ID: 055
Revises: 054
Create Date: 2026-04-23

Per-scope cost alerts — each scope carries a list of rules the
billing sweep evaluates against that day's + month-to-date cost.
Shape:

```
[
  {"type": "daily",   "threshold_usd": 100, "cc_person_ids": ["..."], "active": true},
  {"type": "monthly", "threshold_usd": 2000, "cc_person_ids": ["..."], "active": true}
]
```

The scope owner + additional ``cc_person_ids`` get Feishu + email
when the rule fires. Idempotency is per-(rule-index, day) for daily
and per-(rule-index, month) for monthly so repeated sweeps don't
re-alert.

Simpler than a dedicated ``scope_alerts`` table because rules are
almost always <= 4 per scope and never queried cross-scope; JSON
column keeps the write + read path trivial.
"""
from __future__ import annotations

import sqlalchemy as sa
from alembic import op

revision = "055"
down_revision = "054"
branch_labels = None
depends_on = None


def _column_exists(bind, table: str, col: str) -> bool:
    return bind.execute(
        sa.text(
            "SELECT 1 FROM information_schema.COLUMNS "
            "WHERE TABLE_SCHEMA = DATABASE() "
            "AND TABLE_NAME = :t AND COLUMN_NAME = :c"
        ),
        {"t": table, "c": col},
    ).scalar() is not None


def upgrade() -> None:
    bind = op.get_bind()
    if not _column_exists(bind, "cmdb_cloud_scopes", "alert_rules"):
        op.add_column(
            "cmdb_cloud_scopes",
            sa.Column("alert_rules", sa.JSON, nullable=True),
        )


def downgrade() -> None:
    bind = op.get_bind()
    if _column_exists(bind, "cmdb_cloud_scopes", "alert_rules"):
        op.drop_column("cmdb_cloud_scopes", "alert_rules")