from datetime import datetime
from hashlib import md5
from werkzeug.security import generate_password_hash, check_password_hash
from flask_login import UserMixin
from app import db, login


@login.user_loader
def load_user(id):
    return User.query.get(int(id))


followers = db.Table(
    "followers",
    db.Column("follower_id", db.Integer, db.ForeignKey("user.id")),
    db.Column("followed_id", db.Integer, db.ForeignKey("user.id")),
)


class User(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), index=True, unique=True)
    email = db.Column(db.String(120), index=True, unique=True)
    password_hash = db.Column(db.String(128))
    posts = db.relationship("Post", backref="author", lazy="dynamic")
    about_me = db.Column(db.String(140))
    last_seen = db.Column(db.DateTime, default=datetime.utcnow)
    followed = db.relationship(
        "User",
        secondary=followers,
        primaryjoin=(followers.c.follower_id == id),
        secondaryjoin=(followers.c.followed_id == id),
        backref=db.backref("followers", lazy="dynamic"),
        lazy="dynamic",
    )

    def __repr__(self):
        return "<User {}>".format(self.username)

    def set_password(self, password):
        self.password_hash = generate_password_hash(password)

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

    def avatar(self, size):
        digest = md5(self.email.lower().encode("utf-8")).hexdigest()
        return "https://www.gravatar.com/avatar/{}?d=identicon&s={}".format(
            digest, size
        )

    def follow(self, user):
        if not self.is_following(user):
            self.followed.append(user)

    def unfollow(self, user):
        if self.is_following(user):
            self.followed.remove(user)

    def is_following(self, user):
        return (
            self.followed.filter(followers.c.followed_id == user.id).count()
            > 0
        )

    def followed_posts(self):
        followed = Post.query.join(
            followers, (followers.c.followed_id == Post.user_id)
        ).filter(followers.c.follower_id == self.id)
        own = Post.query.filter_by(user_id=self.id)
        return followed.union(own).order_by(Post.timestamp.desc())


class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    body = db.Column(db.String(140))
    timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
    user_id = db.Column(db.Integer, db.ForeignKey("user.id"))

    def __repr__(self):
        return "<Post {}>".format(self.body)