"""instance identity — the id lineage a backup carries

Revision ID: 0127
Revises: 0126
Create Date: 2026-11-05

One row naming this database's id lineage. Every full backup carries it, a
restore into a fresh instance adopts it (the restore keeps the original ids),
and rolling a live instance back requires the backup's to match, so a backup's
ids never land on unrelated rows. Made here with a random value, so every
instance has one before its first account exists.
"""
import sqlalchemy as sa
from alembic import op

revision = "0127"
down_revision = "0126"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.create_table(
        "instance_identity",
        sa.Column("id", sa.Integer(), primary_key=True),
        sa.Column("instance_id", sa.Text(), nullable=False),
        sa.Column(
            "created_at", sa.DateTime(timezone=True), nullable=False,
            server_default=sa.func.now(),
        ),
        sa.CheckConstraint("id = 1", name="ck_instance_identity_single_row"),
    )
    op.execute(
        "INSERT INTO instance_identity (id, instance_id) VALUES (1, gen_random_uuid()::text)"
    )


def downgrade() -> None:
    op.drop_table("instance_identity")