def create_user():
"""
Create a new user if not exists.
:return: Flask `Response` object with added JSON representation of `User` and
`Content-Type: application/json` HTTP header.
"""
user_data = request.get_json() or {}
if any(field not in user_data for field in ('username', 'password')):
return bad_request('Username and password are mandatory fields')
if User.query.filter_by(username=user_data['username']).first():
return bad_request(
'The user is already exist, please use a different username')
user = User()
user.from_dict(user_data, new_user=True)
db.session.add(user)
db.session.commit()
response = jsonify(user.to_dict())
response.status_code = 201
response.headers['Location'] = url_for('api.get_user', id_=user.id_)
return response
