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


followers = db.Table(
    'followers',
    db.Column('follower_id', db.Integer, db.ForeignKey('user.id'),
              primary_key=True),
    db.Column('followed_id', db.Integer, db.ForeignKey('user.id'),
              primary_key=True)
)


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', back_populates='author', lazy='dynamic')
    about_me = db.Column(db.String(140))
    last_seen = db.Column(db.DateTime, default=datetime.utcnow)
    following = db.relationship(
        'User', secondary=followers,
        primaryjoin=(followers.c.follower_id == id),
        secondaryjoin=(followers.c.followed_id == id),
        lazy='dynamic', back_populates='followers')
    followers = db.relationship(
        'User', secondary=followers,
        primaryjoin=(followers.c.followed_id == id),
        secondaryjoin=(followers.c.follower_id == id),
        lazy='dynamic', back_populates='following')

    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 f'https://www.gravatar.com/avatar/{digest}?d=identicon&s={size}'

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

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

    def is_following(self, user):
        return user in self.following

    def following_posts(self):
        following = 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 following.union(own).order_by(Post.timestamp.desc())


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


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'), index=True)
    author = db.relationship('User', back_populates='posts')

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