"""Deleting a quiz must not destroy the questions extracted for it.

`questions.quiz_id` was created ON DELETE CASCADE, while the model has long
declared SET NULL and its comment says the column is informational — "which
quiz this question was originally extracted for" — with real membership held
in `quiz_question_links`. The database was the one being obeyed, so removing a
quiz silently erased every question it had produced, along with their attempts,
exam membership, media and article links, and straight past the trash that was
built to make exactly that impossible.

The model's intent is the correct one and is what this applies.

`quizzes.user_id` is the opposite case: the database cascades and the model
said nothing, and here the database is right — deleting an account is
documented as removing what it made. The model is corrected to match rather
than the data.

Revision ID: b8c9d0e1f2a3
Revises: a7b8c9d0e1f2
"""
from alembic import op

revision = "b8c9d0e1f2a3"
down_revision = "a7b8c9d0e1f2"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.drop_constraint("questions_quiz_id_fkey", "questions", type_="foreignkey")
    op.create_foreign_key("questions_quiz_id_fkey", "questions", "quizzes",
                          ["quiz_id"], ["id"], ondelete="SET NULL")


def downgrade() -> None:
    op.drop_constraint("questions_quiz_id_fkey", "questions", type_="foreignkey")
    op.create_foreign_key("questions_quiz_id_fkey", "questions", "quizzes",
                          ["quiz_id"], ["id"], ondelete="CASCADE")