"""unique index on user.wechat_openid (一个微信只绑一个账号)

Revision ID: a7c8d9e0f1b2
Revises: f5b2d3c4e6a7
Create Date: 2026-05-25 19:10:00.000000

注意:升级前需保证 wechat_openid 无重复值(NULL 不算重复)。
本仓库 data/app.db 升级前已手动清掉重复 openid(保留最近绑定的账号)。
"""
from typing import Sequence, Union

from alembic import op


# revision identifiers, used by Alembic.
revision: str = 'a7c8d9e0f1b2'
down_revision: Union[str, Sequence[str], None] = 'f5b2d3c4e6a7'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # nullable 列上的唯一索引:SQLite / Postgres 都允许多个 NULL,只约束非空值唯一
    with op.batch_alter_table('user', schema=None) as batch_op:
        batch_op.create_index(
            batch_op.f('ix_user_wechat_openid'), ['wechat_openid'], unique=True
        )


def downgrade() -> None:
    with op.batch_alter_table('user', schema=None) as batch_op:
        batch_op.drop_index(batch_op.f('ix_user_wechat_openid'))
