from datetime import datetime

from sqlalchemy import JSON, Column, DateTime, ForeignKey, Integer, String, UniqueConstraint

from app.database import Base


class Exam(Base):
    """A study objective — the top of the hierarchy, above systems and disciplines.

    A question can sit under more than one exam (paediatric cardiology counts for
    both a paediatrics board and a step exam), so membership is a link table
    rather than a column on the question.
    """

    __tablename__ = "exams"

    id = Column(Integer, primary_key=True, index=True)
    slug = Column(String(80), unique=True, nullable=False, index=True)
    name = Column(String(160), nullable=False)
    sort_order = Column(Integer, default=100)
    is_active = Column(Integer, default=1)  # 0 hides it from the switcher
    # Objectives are picked from families — USMLE, COMLEX, boards — because a
    # flat list of every exam is not a choice anyone can make.
    family = Column(String(80), nullable=True)
    description = Column(String(300), nullable=True)
    # Which article views 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. Null means all of them.
    article_views = Column(JSON, nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)


class QuestionExamLink(Base):
    __tablename__ = "question_exam_links"
    __table_args__ = (UniqueConstraint("question_id", "exam_id", name="uq_question_exam"),)

    id = Column(Integer, primary_key=True, index=True)
    question_id = Column(Integer, ForeignKey("questions.id", ondelete="CASCADE"), nullable=False, index=True)
    exam_id = Column(Integer, ForeignKey("exams.id", ondelete="CASCADE"), nullable=False, index=True)