"""A study objective decides what a learner is shown, not just what is counted.

Revision ID: c7d8e9f0a1b2
Revises: b6c7d8e9f0a1
"""
import sqlalchemy as sa
from alembic import op
from sqlalchemy import inspect

revision = "c7d8e9f0a1b2"
down_revision = "b6c7d8e9f0a1"
branch_labels = None
depends_on = None


def _has_column(table: str, column: str) -> bool:
    return column in {c["name"] for c in inspect(op.get_bind()).get_columns(table)}


def upgrade():
    # `create_all` at startup may already have added these; each step checks.
    for column in (
        # Objectives are chosen from a list of families — USMLE, COMLEX, boards —
        # because a flat list of every exam is not a choice anyone can make.
        sa.Column("family", sa.String(80), nullable=True),
        sa.Column("description", sa.String(300), nullable=True),
        # Which readings this objective shows. Someone revising a basic-science
        # step has no use for bedside dosing, and a view they can open but must
        # never act on is worse than one they were never offered.
        sa.Column("article_views", sa.JSON, nullable=True),
    ):
        if not _has_column("exams", column.name):
            op.add_column("exams", column)

    op.execute("UPDATE exams SET family = 'Boards' WHERE slug = 'pediatrics-boards' AND family IS NULL")
    op.execute("UPDATE exams SET family = 'USMLE' WHERE slug LIKE 'usmle-%' AND family IS NULL")
    op.execute("UPDATE exams SET family = 'Other' WHERE family IS NULL")


def downgrade():
    for column in ("article_views", "description", "family"):
        if _has_column("exams", column):
            op.drop_column("exams", column)