from sqlalchemy import Column, ForeignKey, Integer, String, Text, UniqueConstraint

from app.database import Base


class QuestionMedia(Base):
    """One figure on a question.

    A figure is a row rather than a path so it can be labelled, ordered, and
    reused: the same radiograph can illustrate two questions without being
    stored twice, and the bank knows where each one is used.
    """

    __tablename__ = "question_media"
    __table_args__ = (UniqueConstraint("question_id", "media_id", "role", name="uq_question_media"),)

    id = Column(Integer, primary_key=True, index=True)
    question_id = Column(Integer, ForeignKey("questions.id", ondelete="CASCADE"), nullable=False, index=True)
    media_id = Column(Integer, ForeignKey("media_assets.id", ondelete="CASCADE"), nullable=False, index=True)
    # stem | explanation. A figure that gives the answer away must never sit
    # beside the question, which is the mistake this area started with.
    role = Column(String(20), nullable=False, default="stem")
    # What the prose calls it, so "shown in Figure 1" refers to something.
    label = Column(String(80), nullable=True)
    caption = Column(Text, nullable=True)
    position = Column(Integer, default=0)