"""DNS write control — decouple DNS requests from the prod-cloud freeze.

Revision ID: 386
Revises: 385
Create Date: 2026-07-06

Why this exists
---------------
Self-service DNS requests (create / update / delete a record via the
Feishu approval → execute path) used to gate their cloud write on
``cmdb.prod_cloud_writes_enabled`` — the prod-IAM kill-switch. That
coupled two unrelated things: an incident freeze meant to stop
accidental prod-IAM mutation ALSO failed every already-approved DNS
change, with no auto-resume, stranding requests at ``failed``.

A DNS record edit is low blast-radius and trivially reversible, so it
gets its own switch: ``cmdb.dns_writes_enabled``. Unlike the IAM lock,
its safe/normal posture is ENABLED — it is seeded ``true`` and the
enforcement code (``app/domains/cmdb/prod_write_lock.dns_writes_enabled``)
treats a MISSING row as enabled too, so DNS requests execute by default.
Flipping it to ``false`` freezes DNS writes specifically, without
touching cloud-IAM writes.

Idempotency
-----------
``INSERT ... ON DUPLICATE KEY UPDATE description`` so re-running refreshes
the description without overwriting an admin's flipped value.
"""
from __future__ import annotations

import json

import sqlalchemy as sa

from alembic import op

revision = "386"
down_revision = "385"
branch_labels = None
depends_on = None


SETTING_KEY = "cmdb.dns_writes_enabled"
DEFAULT_VALUE = True
DESCRIPTION = (
    "DNS 解析记录写操作总开关。true(默认)= 允许:已审批通过的 DNS 新增 / "
    "修改 / 删除申请会正常执行。false = 锁定:已审批的 DNS 变更不会执行,"
    "失败的申请可在 IT 管理员解除锁定后点「重跑」恢复(审批仍有效,无需"
    "重新发起)。此开关与生产云账号写开关(cmdb.prod_cloud_writes_enabled)"
    "相互独立 —— 冻结云 IAM 写操作不再会连带停掉 DNS 变更。系统自动化不受影响。"
)


def _table_exists(bind, name: str) -> bool:
    return bind.execute(
        sa.text(
            "SELECT 1 FROM information_schema.TABLES "
            "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :n"
        ),
        {"n": name},
    ).scalar() is not None


def upgrade() -> None:
    bind = op.get_bind()
    if not _table_exists(bind, "platform_settings"):
        return
    bind.execute(
        sa.text(
            "INSERT INTO platform_settings (`key`, value, description, "
            "created_at, updated_at) "
            "VALUES (:k, :v, :d, NOW(), NOW()) "
            "ON DUPLICATE KEY UPDATE "
            "description = VALUES(description), updated_at = NOW()"
        ),
        {
            "k": SETTING_KEY,
            "v": json.dumps(DEFAULT_VALUE),
            "d": DESCRIPTION,
        },
    )


def downgrade() -> None:
    bind = op.get_bind()
    if not _table_exists(bind, "platform_settings"):
        return
    bind.execute(
        sa.text("DELETE FROM platform_settings WHERE `key` = :k"),
        {"k": SETTING_KEY},
    )