models.py

from app import db
from hashlib import md5

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(db.Model):
    id = db.Column(db.Integer, primary_key = True)
    nickname = db.Column(db.String(64), index=True, unique = True)
    password = db.Column(db.String(120), index=True)
    email = db.Column(db.String(120), index = True)
    about_me = db.Column(db.String(140))
    last_seen = db.Column(db.DateTime)

    posts = db.relationship('Post', backref='author', lazy='dynamic')
    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')

    is_authenticated = True
    is_active = True
    is_anonymous = False
    
    def get_id(self):
        try:
            return unicode(self.id)
        except NameError:
            return str(self.id)
    
    def avatar(self, size):
        return 'http://www.gravatar.com/avatar/' + md5(self.email.encode("utf-8")).hexdigest() + '?d=mm&s=' + str(size)

    # be used to debug
    def __repr__(self):
        return '<User %r>' % (self.nickname)
    
    @staticmethod
    def make_unique_nickname(nickname):
        if User.query.filter_by(nickname = nickname).first() == None:
            return nickname
        version = 2
        while True:
            new_nickname = nickname + str(version)
            if User.query.filter_by(nickname = new_nickname).first() == None:
                break
            version += 1
        return new_nickname

    def follow(self, user):
        if not self.is_following(user):
            self.followed.append(user)
            return self
    def unfollow(self, user):
        if self.is_following(user):
            self.followed.remove(user)
            return self
    def is_following(self, user):
        return self.followed.filter(followers.c.followed_id == user.id).count() > 0

    def followed_posts(self):
        return Post.query.join(followers, 
        (followers.c.followed_id == Post.user_id)).filter(followers.c.follower_id == self.id).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)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))

    def __repr__(self):
        return '<Post %r>' % (self.body)