from app import db
import sqlalchemy as sa
from flask_login import UserMixin
from datetime import datetime
from werkzeug.security import generate_password_hash, check_password_hash


enrollment = db.Table(
    "enrollment",
    sa.Column("user_id", sa.ForeignKey("user.id"), primary_key=True),
    sa.Column("course_id", sa.ForeignKey("course.id"), primary_key=True),
)


class User(UserMixin, db.Model):
    id = sa.Column(sa.Integer, primary_key=True)
    username = sa.Column(sa.String(64), index=True, unique=True)
    role = sa.Column(sa.String(32), index=True)
    email = sa.Column(sa.String(120), index=True, unique=True)
    password_hash = sa.Column(sa.String(128))
    last_seen = sa.Column(sa.DateTime, default=datetime.utcnow)
    token = sa.Column(sa.String(32), index=True, unique=True)
    enrolled_courses = db.relationship(
        "Course",
        secondary=enrollment,
        backref=db.backref("students", lazy="dynamic"),
        lazy="dynamic",
    )

    def __repr__(self) -> str:
        return f"<User {self.username}>"

    def set_password(self, password) -> None:
        self.password_hash = generate_password_hash(password)

    def check_password(self, password) -> bool:
        return check_password_hash(self.password_hash, password)

    def is_enrolled(self, c) -> bool:
        return self.enrolled_courses.filter(enrollment.c.course_id == c.id).count() > 0

    def enroll(self, c) -> bool:
        if not self.is_enrolled(c):
            self.enrolled_courses.append(c)
            return True
        return False

    def to_dict(self) -> dict:
        return {
            "id": self.id,
            "username": self.username,
            "email": self.email,
        }

    def from_dict(self, data, new_user=False) -> None:
        for field in ["role", "username", "email"]:
            if field in data:
                setattr(self, field, data[field])
        if new_user and "password" in data:
            self.set_password(data["password"])


class Course(db.Model):
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String(128), index=True)
    description = sa.Column(sa.Text, index=True)
    instructor = sa.Column(sa.ForeignKey(User.id), index=True)
    created_at = sa.Column(sa.DateTime)

    def __repr__(self) -> str:
        return f"<Course {self.name}>"

    def from_dict(self, data) -> None:
        for field in ["name", "description", "instructor"]:
            if field in data:
                setattr(self, field, data[field])

        if not self.created_at:
            self.created_at = datetime.now()

    def to_dict(self) -> dict:
        d = {}
        for f in ["id", "name", "description", "instructor", "created_at"]:
            d[f] = getattr(self, f)
        return d