from datetime import datetime

from sqlalchemy import JSON, Column, DateTime, ForeignKey, Integer, Numeric, 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)


class ArticleExamLink(Base):
    """Which reading belongs to which objective.

    An article reached an exam only by inference through its category, which
    cannot express the case that matters: the same article belongs to a basic
    science step and to a clinical one, showing different views in each.
    `Exam.article_views` decides what is shown once you are there; this decides
    whether it is in the group at all.
    """

    __tablename__ = "article_exam_links"
    __table_args__ = (UniqueConstraint("article_id", "exam_id", name="uq_article_exam"),)

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


class ExamBlueprint(Base):
    """One line of an examining board's published content outline.

    A real exam is not a uniform draw from a bank: the ABP publishes that 12%
    of a general paediatrics paper is preventive care and 2% is rheumatology.
    Without that, a forty-question block is forty coin flips and tells a
    learner nothing about how they would do on the day.

    `code` is the board's own numbering ("1", "4.A") so a domain can be matched
    back to the published outline, and `weight` is a percentage of the whole
    paper — set on domains, left null on the subdomains beneath them.
    """

    __tablename__ = "exam_blueprints"
    __table_args__ = (UniqueConstraint("exam_id", "code", name="uq_exam_blueprint_code"),)

    id = Column(Integer, primary_key=True, index=True)
    exam_id = Column(Integer, ForeignKey("exams.id", ondelete="CASCADE"), nullable=False, index=True)
    parent_id = Column(Integer, ForeignKey("exam_blueprints.id", ondelete="CASCADE"), nullable=True, index=True)
    code = Column(String(16), nullable=False)
    title = Column(String(240), nullable=False)
    #: Percent of the paper. Null on a subdomain, which inherits its domain's share.
    weight = Column(Numeric(5, 2), nullable=True)
    sort_order = Column(Integer, default=0)
    created_at = Column(DateTime, default=datetime.utcnow)


class BlueprintCategoryLink(Base):
    """Which of our categories feed one blueprint line.

    The taxonomy is not reshaped to match a board's outline — it is arranged
    for studying, and theirs is arranged for examining. This maps one onto the
    other, so both can be right.
    """

    __tablename__ = "blueprint_category_links"
    __table_args__ = (UniqueConstraint("blueprint_id", "category_id", name="uq_blueprint_category"),)

    id = Column(Integer, primary_key=True, index=True)
    blueprint_id = Column(Integer, ForeignKey("exam_blueprints.id", ondelete="CASCADE"), nullable=False, index=True)
    category_id = Column(Integer, ForeignKey("question_categories.id", ondelete="CASCADE"), nullable=False, index=True)