from datetime import datetime

from sqlalchemy import Column, DateTime, ForeignKey, Integer

from app.database import Base


class CategoryGrant(Base):
    """Scoped editorial access for a non-moderator.

    A grant names any combination of exam, discipline tag and category, and
    covers the questions matching *all* the dimensions it sets — so "Step 1"
    plus "Cardiology" grants exactly Step 1 cardiology questions. An unset
    dimension means "any". It is access, not a role: the holder can create, edit
    and delete the questions it covers, and nothing else.

    A folder is the fourth dimension and the odd one out: the other three
    describe questions, so a grant over them keeps covering whatever is filed
    there later, while a folder is a list somebody wrote by hand. It is here
    rather than in a table of its own because a grant is a grant — one place to
    read what a person holds, and one predicate that answers what they reach.
    """

    __tablename__ = "category_grants"
    id = Column(Integer, primary_key=True, index=True)
    # Each dimension is optional and means "any". A grant must name at least one,
    # or it would silently mean "everything".
    category_id = Column(Integer, ForeignKey("question_categories.id", ondelete="CASCADE"), nullable=True, index=True)
    exam_id = Column(Integer, ForeignKey("exams.id", ondelete="CASCADE"), nullable=True, index=True)
    tag_id = Column(Integer, nullable=True, index=True)  # question_tags is raw DDL
    folder_id = Column(Integer, ForeignKey("question_folders.id", ondelete="CASCADE"), nullable=True, index=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    granted_by = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)