"""Make users.email the unique login identifier (NOT NULL + unique index).

Backfills any missing/blank email from username first, so existing rows
(e.g. the seeded admin, which historically had no email) never violate
the new constraint.

Revision ID: b067
Revises: b066
Create Date: 2026-07-23
"""

from alembic import op
import sqlalchemy as sa

revision = "b067"
down_revision = "b066"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.execute(
        "UPDATE users SET email = username WHERE email IS NULL OR email = ''"
    )
    op.alter_column("users", "email", existing_type=sa.String(), nullable=False)
    op.create_unique_constraint("uq_users_email", "users", ["email"])
    op.create_index("ix_users_email", "users", ["email"])


def downgrade() -> None:
    op.drop_index("ix_users_email", table_name="users")
    op.drop_constraint("uq_users_email", "users", type_="unique")
    op.alter_column("users", "email", existing_type=sa.String(), nullable=True)