"""users password_hash nullable

Revision ID: 5bb055a1593e
Revises: b1fad5ddf357
Create Date: 2026-05-06 07:23:21.480252

"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision: str = '5bb055a1593e'
down_revision: Union[str, None] = 'b1fad5ddf357'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.alter_column(
        "users",
        "password_hash",
        existing_type=sa.String(255),
        nullable=True,
    )


def downgrade() -> None:
    # NOTE: downgrade is non-trivial if any OAuth-only users exist.
    # This downgrade fails fast in that case rather than corrupting data.
    conn = op.get_bind()
    null_count = conn.execute(
        sa.text("SELECT COUNT(*) FROM users WHERE password_hash IS NULL")
    ).scalar()
    if null_count and null_count > 0:
        raise RuntimeError(
            f"Cannot downgrade: {null_count} OAuth-only users have NULL password_hash. "
            "Set passwords or delete those rows before downgrading."
        )
    op.alter_column(
        "users",
        "password_hash",
        existing_type=sa.String(255),
        nullable=False,
    )