# 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 fastapi.responses import RedirectResponse, HTMLResponse

from passlib.context import CryptContext
import re

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

from app_sessions import UserSession, FlashMessageQueue
from app_database import db_transaction
from app_templating import TemplateRenderer


# 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}$')

to_homepage = RedirectResponse('/', status_code=status.HTTP_303_SEE_OTHER)
to_wallet = RedirectResponse('/wallet', status_code=status.HTTP_303_SEE_OTHER)

router = APIRouter()


@router.get('/', response_class=HTMLResponse)
def homepage(
    session: UserSession=Depends(UserSession),
    render: TemplateRenderer=Depends(TemplateRenderer),
):
    if session.is_logged_in():
        return to_wallet

    return render('homepage.html.jinja')


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

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

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

        session.login(user.id)
        messages.add('success', 'Account succesfully created. Welcome!')
        return to_wallet

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


@router.post('/account/login')
def session_login(
    session: UserSession=Depends(UserSession),
    messages: FlashMessageQueue=Depends(FlashMessageQueue),
    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)
        messages.add('info', 'Welcome back!')
        return to_wallet
    else:
        messages.add('error', 'Invalid credentials.')
        return to_homepage


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

    return to_homepage