from django.shortcuts import render
from django.http import JsonResponse

from profiles.models import User

import string
import random
import hashlib
import datetime


MIN_USERNAME_LEN = 5
MAX_USERNAME_LEN = 30
MIN_PASSWORD_LEN = 6
MAX_PASSWORD_LEN = 30
TOKEN_LEN = 20
SATL_LEN = 20

SECRET_SALT = "20randomnyhsimwolow)"
ALPHABET = ''.join([string.ascii_letters, string.digits])


def generate_str(len):
    res = []
    for i in range(len):
        res.append(random.choice(ALPHABET))
    return ''.join(res)


def check_auth(username, token):
    count = User.objects.filter(
            username__iexact = username,
            token = token,
            token_time__gte = datetime.datetime.now() - datetime.timedelta(days = 1)
    ).count()

    return (count == 1) and (len(token) == TOKEN_LEN)


def user_exists(username):
    count_username = User.objects.filter(username__iexact = username).count()
    if count_username == 0:
        return False
    elif count_username == 1:
        return True

    # ошибка: существуют пользователи с одинаковым username
    return False


def register(request):
    if ('username' not in request.GET) or ('password' not in request.GET) or ('email' not in request.GET):
        return JsonResponse({'result':'error', 'error':'input error'})

    username = request.GET['username']
    password = request.GET['password']
    email = request.GET['email']

    if len(username) < MIN_USERNAME_LEN or len(username) > MAX_USERNAME_LEN:
        return JsonResponse({'result':'error', 'error':'invalid username length'})

    if len(password) < MIN_PASSWORD_LEN or len(password) > MAX_PASSWORD_LEN:
        return JsonResponse({'result':'error', 'error':'invalid password length'})

    count_email = User.objects.filter(email__iexact = email).count()
    if count_email > 0:
        return JsonResponse({'result':'error', 'error':'email is already used'})

    if user_exists(username):
        return JsonResponse({'result':'error', 'error':'username is already used'})

    private_salt = generate_str(SATL_LEN)
    password_hash = hashlib.sha512((password + private_salt + SECRET_SALT).encode()).hexdigest()

    new_user = User(username = username, password_hash = password_hash,
                    token = '', email = email, private_salt = private_salt)
    new_user.save()

    return JsonResponse({'result':'success'})

...