text: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  from . import db
  from werkzeug.security import generate_password_hash, check_password_hash
  from flask_login import UserMixin, AnonymousUserMixin
  from . import login_manager
  from itsdangerous import TimedJSONWebSignatureSerializer as Serializer
  from flask import current_app, request, url_for
  from datetime import datetime
  import hashlib
  from markdown import markdown
  import bleach
  from app.exceptions import ValidationError
  
  
  class Permission:
      FOLLOW = 0x01
      COMMIT = 0x02
      WRITE_ARTICLES = 0x04
      MODERATE_COMMENTS = 0x08
      ADMINISTER = 0x80
  
  
  class Role(db.Model):
      __tablename__ = 'roles'
      id = db.Column(db.Integer, primary_key=True)
      name = db.Column(db.String(64), unique=True)
      default = db.Column(db.Boolean, default=False, index=True)
      permissions = db.Column(db.Integer)
      users = db.relationship('User', backref='role', lazy='dynamic')
  
      @staticmethod
      def insert_roles():
          roles = {
              'User': (Permission.FOLLOW |
                       Permission.COMMIT |
                       Permission.WRITE_ARTICLES, True),
              'Moderator': (Permission.FOLLOW |
                            Permission.COMMIT |
                            Permission.WRITE_ARTICLES |
                            Permission.MODERATE_COMMENTS, False),
              'Administrator': (0xff, False)
          }
          for r in roles:
              role = Role.query.filter_by(name=r).first()
              if not role:
                  role = Role(name=r)
              role.default = roles[r][1]
              role.permissions = roles[r][0]
              db.session.add(role)
          db.session.commit()
  
      def __repr__(self):
          return '<Role %r>' % self.name
  
  
  class Follow(db.Model):
      __tablename__ = 'follows'
      follower_id = db.Column(db.Integer, db.ForeignKey('users.id'), primary_key=True)
      followed_id = db.Column(db.Integer, db.ForeignKey('users.id'), primary_key=True)
      timestamp = db.Column(db.DateTime, default=datetime.utcnow)
  
  
  class User(UserMixin, db.Model):
  
      def __init__(self, **kwargs):
          super(User, self).__init__(**kwargs)
          if self.role is None:
              if self.email == current_app.config['FLASKY_ADMIN']:
                  self.role = Role.query.filter_by(permissions=0xff).first()
              else:
                  self.role = Role.query.filter_by(default=True).first()
  
          if self.email is not None and self.avatar_hash is None:
              self.avatar_hash = hashlib.md5(self.email.encode('utf-8')).hexdigest()
          self.follow(self)
  
      __tablename__ = 'users'
      id = db.Column(db.Integer, primary_key=True)
      username = db.Column(db.String(64), unique=True, index=True)
      role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
      password_hash = db.Column(db.String(128))
      email = db.Column(db.String(64), unique=True, index=True)
      confirm = db.Column(db.Boolean, default=False)
  
      name = db.Column(db.String(64))
      location = db.Column(db.String(64))
      about_me = db.Column(db.Text())
      member_since = db.Column(db.DateTime(), default=datetime.utcnow)
      last_seen = db.Column(db.DateTime(), default=datetime.utcnow)
     
      avatar_hash = db.Column(db.String(32))
  
      posts = db.relationship('Post', backref='author', lazy='dynamic')
  
      comments = db.relationship('Comment', backref='author', lazy='dynamic')
  
      followed = db.relationship('Follow',
              foreign_keys=[Follow.follower_id],
              backref=db.backref('follower', lazy='joined'),
              lazy='dynamic',
              cascade='all, delete-orphan')
      followers = db.relationship('Follow',
              foreign_keys=[Follow.followed_id],
              backref=db.backref('followed', lazy='joined'),
              lazy='dynamic',
              cascade='all, delete-orphan')
  
      @staticmethod
      def add_self_follows():
          for user in User.query.all():
              if not user.is_following(user):
                  user.follow(user)
                  db.session.add(user)
                  db.session.commit()
  
      def ping(self):
          self.last_seen = datetime.utcnow()
          db.session.add(self)
  
      @property
      def password(self):
          raise AttributeError('password is not a readable attribute')
  
      @password.setter
      def password(self, password):
          self.password_hash = generate_password_hash(password)
  
      def verify_password(self, password):
          return check_password_hash(self.password_hash, password)
  
      def generate_token(self, expiration=3600):
          s = Serializer(current_app.config['SECRET_KEY'], expires_in=expiration)
          return s.dumps({'confirm': self.id})
  
      def confirm_token(self, token):
          s = Serializer(current_app.config['SECRET_KEY'])
          try:
              data = s.loads(token)
          except:
              return False
          if data.get('confirm') != self.id:
              return False
          self.confirm = True
          db.session.add(self)
          return True
  
      def can(self, permissions):
          return self.role is not None and \
              (self.role.permissions & permissions) == permissions
  
      def is_administrator(self):
          return self.can(Permission.ADMINISTER)
  
      def gravatar(self, size=100, default='identicon', rating='g'):
          if request.is_secure:
              url = 'https://secure.gravatar.com/avatar'
          else:
              url = 'http://www.gravatar.com/avatar'
          hash = self.avatar_hash or hashlib.md5(self.email.encode('utf-8')).hexdigest()
          return '{url}/{hash}?s={size}&d={default}&r={rating}'.format(url=url, hash=hash, size=size, default=default, rating=rating)
  
      def change_email(self, new_email):
  
          self.email = new_email
          self.avatar_hash = hashlib.md5(self.email.encode('utf-8')).hexdigest()
          db.session.add(self)
          return True
  
      @staticmethod
      def generate_fake(count=100):
          from sqlalchemy.exc import IntegrityError
          from random import seed
          import forgery_py
  
          seed()
          for i in range(count):
              try:
                  u = User(email=forgery_py.internet.email_address(),
                          username=forgery_py.internet.user_name(),
                          password=forgery_py.lorem_ipsum.word(),
                          confirm=True,
                          name=forgery_py.name.full_name(),
                          location=forgery_py.address.city(),
                          about_me=forgery_py.lorem_ipsum.sentence(),
                          member_since=forgery_py.date.date(True))
                  db.session.add(u)
                  db.session.commit()
              except IntegrityError:
                  db.session.rollback()
  
  
      def follow(self, user):
          if not self.is_following(user):
              f = Follow(follower=self, followed=user)
              db.session.add(f)
  
      def unfollow(self, user):
          f = self.followed.filter_by(followed_id=user.id).first()
          if f:
              db.session.delete(f)
  
      def is_following(self, user):
          return self.followed.filter_by(followed_id=user.id).first()
  
      def is_followed_by(self, user):
          return self.followers.filter_by(follower_id=user.id).first()
  
      @property
      def followed_posts(self):
         return Post.query.join(Follow, Post.author_id == Follow.followed_id).filter(Follow.follower_id == self.id)
  
      @staticmethod 
      def add_self_follows():
          for user in User.query.all():
              if not user.is_following(user):
                  user.follow(user)
                  db.session.add(user)
                  db.session.commit()
  
      def generate_auth_token(self, expiration):
          s = Serializer(current_app.config['SECRET_KEY'], expires_in=expiration)
          return s.dumps({'id': self.id})
  
      @staticmethod
      def verify_auth_token(token):
          s = Serializer(current_app.config['SECRET_KEY'])
          try:
              data = s.loads(token)
          except:
              return None
          return User.query.get(data['id'])
  
      def to_json(self):
  
          json_user = {
                  'url': url_for('api.get_user', id=self.id, _external=True),
                  'username': self.username,
                  'member_since': self.member_since,
                  'last_seen': self.last_seen,
                  'posts': url_for('api.get_user_posts', id=self.id, _external=True),
                  'followed_posts': url_for('api.get_user_followed_posts', id=self.id, _external=True),
                  'post_count': self.posts.count()
                  }
          return json_user
  
      def __repr__(self):
          return '<User %r>' % self.username
  
  
  class Post(db.Model):
      __tablename__ = "posts"
      id = db.Column(db.Integer, primary_key=True)
      body = db.Column(db.Text)
      timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
      author_id = db.Column(db.Integer, db.ForeignKey('users.id'))
      body_html = db.Column(db.Text)
  
      comments = db.relationship('Comment', backref='post', lazy='dynamic')
  
      @staticmethod
      def generate_fake(count=100):
          from random import seed, randint
          import forgery_py
  
          seed()
          user_count = User.query.count()
          for i in range(count):
              u = User.query.offset(randint(0, user_count-1)).first()
              p = Post(body=forgery_py.lorem_ipsum.sentences(randint(1, 3)),
                      timestamp=forgery_py.date.date(True),
                      author=u)
              db.session.add(p)
              db.session.commit()
  
      @staticmethod
      def on_change_body(target, value, oldvalue, initiator):
          allowed_tags = ['a', 'abbr', 'acronym', 'b', 'blockquote', 'code',
                  'em', 'i', 'li', 'ol', 'pre', 'strong', 'ul',
                  'h1', 'h2', 'h3', 'p']
          target.body_html = bleach.linkify(bleach.clean(markdown(value, output_format='html'), tags=allowed_tags, strip=True))
  
      def to_json(self):
          
          json_post = {
                  'url': url_for('api.get_post', id=self.id, _external=True),
                  'body': self.body,
                  'body_html': self.body_html,
                  'timestamp': self.timestamp,
                  'author': url_for('api.get_user', id=self.author_id, _external=True),
                  'comments': url_for('api.get_post_comments', id=self.id, _external=True),
                  'comments_count': self.comments.count()
                  }
          return json_post
  
      @staticmethod
      def from_json(json_post):
          body = json_post.get('body')
          if body is None or body == '':
              raise ValidationError('post does not have a body')
          return Post(body=body)
  
  
  
  db.event.listen(Post.body, 'set', Post.on_change_body)
  
  class Comment(db.Model):
      __tablename__ = 'comments'
      id = db.Column(db.Integer, primary_key=True)
      body = db.Column(db.Text)
      body_html = db.Column(db.Text)
      disabled = db.Column(db.Boolean)
      timestamp = db.Column(db.DateTime, default=datetime.utcnow)
  
      author_id = db.Column(db.Integer, db.ForeignKey('users.id'))
  
      post_id = db.Column(db.Integer, db.ForeignKey('posts.id'))
  
      @staticmethod
      def on_changed_body(target, value, oldvalue, initiator):
          allowed_tags = ['a', 'abbr', 'acronym', 'b', 'code', 'em', 'i', 
                  'strong']
          target.body_html = bleach.linkify(bleach.clean(markdown(value, output_format='html'), tags=allowed_tags, strip=True))
  
      def to_json(self):
          json_comment = {
                  'url': url_for('api.get_comment', id=self.id, _external=True),
                  'body': self.body,
                  'body_html': self.body_html,
                  'timestamp': self.timestamp,
                  'author_url': url_for('api.get_user', id=self.author.id, _external=True),
                  'post_url': url_for('api.get_post', id=self.post.id, _external=True)
                  }
          return json_comment
  
      @staticmethod
      def from_json(json_comment):
          body = json_comment.get('body')
          if body == None or body == '':
              raise ValidationError('comment does not have a body')
          return Comment(body)
  
  db.event.listen(Comment.body, 'set', Comment.on_changed_body)
  
  
  class AnonymousUser(AnonymousUserMixin):
  
      def can(self, permissions):
          return False
  
      def is_administrator(self):
          return False
  
  login_manager.anonymous_user = AnonymousUser
  
  
  @login_manager.user_loader
  def load_user(user_id):
      return User.query.get(int(user_id))
  