from datetime import datetime

from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Text
from sqlalchemy.orm import relationship

from app.database import Base
from app.models.quiz_category import QuizCategory  # noqa — ensures mapper resolves "QuizCategory"
from app.models.quiz_question_link import QuizQuestionLink  # noqa

#: `Quiz.origin` for a quiz that backs a study-plan block rather than standing
#: on its own. Kept here because both the study-plan builder that sets it and
#: the session list that filters on it need the same spelling.
PLAN_ORIGIN = "plan"


class Quiz(Base):
    __tablename__ = "quizzes"

    id = Column(Integer, primary_key=True, index=True)
    section_id = Column(Integer, ForeignKey("sections.id", ondelete="SET NULL"), nullable=True)
    # Cascades: deleting an account is documented as removing what it made.
    # Declared here because the database has always done it, and a model that
    # says nothing is a model that will be believed.
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=True)
    category_id = Column(Integer, ForeignKey("quiz_categories.id", ondelete="SET NULL"), nullable=True)
    title = Column(String, nullable=False)
    questions_count = Column(Integer, default=0)
    time_limit_minutes = Column(Integer, nullable=True)  # null = no limit
    mode = Column(String, default="timed")  # timed, learning
    skipped_questions = Column(Text, nullable=True)  # JSON list of skipped question texts
    created_at = Column(DateTime, default=datetime.utcnow)
    deleted_at = Column(DateTime, nullable=True)   # soft delete — null = active
    is_published = Column(Integer, default=1)      # 1 = visible to users, 0 = hidden (admin only)
    is_shared = Column(Integer, default=0)         # 0=private, 1=shared (visible to other users)
    # A repetition is practice, not a new measurement. You have already seen
    # these questions and their answers, so getting them right the second time
    # says nothing about whether you knew them — it cannot raise a percentage
    # that is meant to mean "how much of this do you know".
    is_repetition = Column(Integer, default=0, index=True)
    max_attempts = Column(Integer, nullable=True)  # null = unlimited
    questions_per_attempt = Column(Integer, nullable=True)  # null = all; set = random subset from pool
    share_token = Column(String(64), unique=True, nullable=True)  # public /share/{token} link when set
    # bank | upload | ai | sample | plan.
    # "plan" marks a quiz that exists to back a study-plan block. It is still a
    # real quiz — it just is not something the learner picks off a list.
    origin = Column(String(20), default="bank")

    section = relationship("Section", back_populates="quizzes")
    user = relationship("User", back_populates="quizzes")
    category = relationship("QuizCategory", back_populates="quizzes", foreign_keys=[category_id])
    questions = relationship(
        "Question",
        secondary="quiz_question_links",
        primaryjoin="Quiz.id == foreign(QuizQuestionLink.quiz_id)",
        secondaryjoin="Question.id == foreign(QuizQuestionLink.question_id)",
        order_by="QuizQuestionLink.position",
        viewonly=True,  # mutations handled explicitly via QuizQuestionLink
    )
    attempts = relationship("QuizAttempt", back_populates="quiz", cascade="all, delete-orphan")