import jwt
from uuid import uuid4
from flask_mongoengine import Document, DoesNotExist
from mongoengine import StringField, BooleanField, DateField, DateTimeField, EmailField
from flask_login import UserMixin
from time import time
from werkzeug.security import generate_password_hash, check_password_hash


_JWT_ALGO = 'HSA256'


class JWTTokenExpiredException(Exception):
    pass


class UserAlreadyVerified(Exception):
    pass


class CurrentEmailNotVerified(Exception):
    pass


class User(UserMixin, Document):
    user_name = StringField(required=True, unique=True)
    pass_hash = StringField(required=True)
    email = EmailField(required=True, unique=True)
    first_name = StringField(required=True)
    last_name = StringField(required=True)
    join_date = DateField(required=False)
    last_login = DateTimeField(required=False)
    email_verified = BooleanField(default=False)

    def set_password(self, password):
        self.pass_hash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.pass_hash, password)

    def update_email(self, new_email):
        if not self.email_verified:
            raise CurrentEmailNotVerified()

        self.email_verified = False
        self.email = new_email

    def get_activation_token(self, expire_secs=1200, secret_key=None):
        payload = {
            'exp': time() + expire_secs,
            'activate': self.user_name
        }

        return jwt.encode(payload, secret_key, algorithm=_JWT_ALGO)

    @staticmethod
    def from_activation_token(token, secret_key=None):
        try:
            jwt_data = jwt.decode(token, secret_key, algorithms=_JWT_ALGO)
            user_name = jwt_data['activate']
        except jwt.ExpiredSignatureError:
            raise JWTTokenExpiredException('The JWT token has expired!')
        user = User.objects(user_name=user_name).first()
        if not user:
            raise DoesNotExist('The given user does not exist')
        elif user.email_verified:
            raise UserAlreadyVerified('The given user has already verified their email')
        user.email_verified = True

    def get_password_reset_token(self, expire_secs=600, secret_key=None):
        payload = {
            'exp': time() + expire_secs,
            'reset_password': self.user_name,
            'jti': str(uuid4())
        }
        return jwt.encode(payload, secret_key, algorithm=_JWT_ALGO)

    @staticmethod
    def from_password_reset_token(token, secret_key=None):
        try:
            jwt_data = jwt.decode(token, secret_key, algorithms=_JWT_ALGO)
            user_name = jwt_data['reset_password']
        except jwt.ExpiredSignatureError:
            raise JWTTokenExpiredException('The JWT token has expired')
        return User.objects(user_name=user_name).first()