# UGE / L2 / Intro to relational databases / Python project prototype
# Author: Pacien TRAN-GIRARD
# Licence: EUPL-1.2

from fastapi import APIRouter, Depends, Request, Form, status

from passlib.context import CryptContext
import re

from embrace.exceptions import IntegrityError
from psycopg2.errors import UniqueViolation

from app_sessions import UserSession
from app_database import db_transaction


# Password hashing context.
# Handles proper salting and migration automatically.
password_ctx = CryptContext(schemes=['bcrypt'], deprecated='auto')

username_pattern = re.compile(r'^[a-zA-Z0-9-_]{4,16}$')

router = APIRouter()


@router.get('/')
def homepage(
    session: UserSession=Depends(UserSession),
):
    if session.is_logged_in():
        return 'Welcome!'

    return 'Homepage here.'


@router.post('/account/register')
def account_register(
    session: UserSession=Depends(UserSession),
    username: str=Form(...),
    password: str=Form(...),
):
    try:
        if username_pattern.match(username) is None:
            return 'error: Invalid username format.'

        if not 4 <= len(password) <= 32:
            return 'error: Invalid password length.'

        hash = password_ctx.hash(password)
        with db_transaction() as tx:
            user = tx.create_account(username=username, password_hash=hash)

        session.login(user.id)
        return 'Account succesfully created. Welcome!'

    except IntegrityError as exception:
        if isinstance(exception.__cause__, UniqueViolation):
            return 'error: This username is already taken.'
        else:
            raise exception


@router.post('/account/login')
def session_login(
    session: UserSession=Depends(UserSession),
    username: str=Form(...),
    password: str=Form(...),
):
    with db_transaction() as tx:
        user = tx.fetch_account_username(username=username)

    if user is not None and password_ctx.verify(password, user.password_hash):
        session.login(user.id)
        return 'Welcome back!'
    else:
        return 'error: Invalid credentials.'


@router.post('/account/logout')
def session_logout(
    session: UserSession=Depends(UserSession),
):
    if session.is_logged_in():
        session.logout()
        return 'You have been successfully logged out.'

    return 'Nothing to do'