"""document reviewer

An author can delegate approval: `documents.reviewer_id` names the user asked
to review a pending document. Nullable (self-approval leaves it null), SET NULL
so a document survives the reviewer leaving.

Revision ID: c4f7a1b2e9d3
Revises: a71e3c92fd45
Create Date: 2026-07-22 00:00:00.000000

"""

from typing import Sequence, Union

import sqlalchemy as sa

from alembic import op

# revision identifiers, used by Alembic.
revision: str = "c4f7a1b2e9d3"
down_revision: Union[str, Sequence[str], None] = "a71e3c92fd45"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    """Upgrade schema."""
    op.add_column("documents", sa.Column("reviewer_id", sa.Uuid(), nullable=True))
    op.create_foreign_key(
        "documents_reviewer_id_fkey",
        "documents",
        "users",
        ["reviewer_id"],
        ["id"],
        ondelete="SET NULL",
    )


def downgrade() -> None:
    """Downgrade schema."""
    op.drop_constraint("documents_reviewer_id_fkey", "documents", type_="foreignkey")
    op.drop_column("documents", "reviewer_id")