from datetime import datetime

from sqlalchemy import Column, ForeignKey, Integer, String, DateTime, Boolean
from sqlalchemy.orm import relationship
from sqlalchemy.sql import false as sa_false

from app.database import Base
from app.models.exam import Exam  # noqa — users.active_exam_id FK needs the table in metadata.


class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True, index=True)
    email = Column(String, unique=True, index=True, nullable=False)
    # Null where there is no password at all. Somebody who arrived through
    # single sign-on, or who only ever signs in with a code, has never chosen
    # one — and storing a random string they can never guess made that
    # indistinguishable from having one, so Settings asked them for a current
    # password before it would let them set their first.
    hashed_password = Column(String, nullable=True)
    name = Column(String, nullable=False)
    role = Column(String, default="user")  # admin, moderator, user
    # Which exam the learner is studying for; scopes the bank they see.
    active_exam_id = Column(Integer, ForeignKey("exams.id", ondelete="SET NULL"), nullable=True)
    is_unthrottled = Column(Integer, default=0)  # 1 = exempt from rate limits
    reminders_disabled = Column(Boolean, default=False, nullable=False, server_default=sa_false())
    # Which voice reads a question aloud. A setting, not a decision to retake at
    # the top of every session — it used to be a dropdown in the player, beside
    # the question, where it was the only control on screen that had nothing to
    # do with answering. Null means whichever voice an administrator marked
    # default, so a learner who never opens Settings still gets a working one.
    tts_voice = Column(String, nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)

    # passive_deletes leaves the child rows to the database, which already
    # knows what to do with every one of them — the foreign keys are CASCADE or
    # SET NULL. Without it SQLAlchemy insists on emptying each relationship
    # itself first, by writing NULL into columns that are NOT NULL, and
    # deleting a user failed with a constraint violation from a table nobody
    # was looking at.
    documents = relationship("PDFDocument", back_populates="user", passive_deletes=True)
    quizzes = relationship("Quiz", back_populates="user", passive_deletes=True)
    attempts = relationship("QuizAttempt", back_populates="user", passive_deletes=True)
    favorites = relationship("Favorite", back_populates="user",
                             cascade="all, delete-orphan", passive_deletes=True)
    note = relationship("UserNote", back_populates="user", cascade="all, delete-orphan",
                        uselist=False, passive_deletes=True)

    @property
    def is_admin(self):
        return self.role == "admin"

    @property
    def is_moderator(self):
        return self.role in ("admin", "moderator")