def get_by_id(id):
    return db.select('users', where='id=$id')[0]

def get_by_username(username):
    return db.select('users', where='username=$username')[0]

def get_by_email(email):
    return db.select('users', where='email=$email')[0]

def is_email_available(email):
    return not db.select('users', vars = dict(email=email), what = 'count(id) as c', where = 'email = $email')[0].c

def is_correct_password(username, password):
    userdata = user.get_user_by_username(username)
    hashed = userdate['password']
    return bcrypt.hashpw(password, hashed) == hashed

def create(username, password, email, **kw):
    hashed = bcrypt.hashpw(password, bcrypt.gensalt())
    db.insert('users', username=username, password=hashed, email=email, **kw)

def delete(id):
    db.delete('users', where='id=$id')

login_form = form.Form(
    form.Textbox('username'),
    form.Password('password'),
    form.Button('Login'),
    validators = [
        form.Validator('Incorrect username / password combination.', lambda i: user.is_correct_password(i.username, i.password))
    ]
)

class login:
    def GET(SELF):
        # do $:form.render() in the template
        form = login_form()
        return render.login(form)

    def POST(SELF):
        form = login_form()
        username, password = web.input().username, web.input().password
        if not form.validates():
            return render.login(form)
        else:
            session.logged_in = 1
            session.username = username
            #redirect user back where they came from or to index
            referer = web.ctx.env.get('HTTP_REFERER', '/')
            raise web.seeother(referer)