import hashlib
import random
from collections import OrderedDict
from szurubooru import config, db, errors
from szurubooru.func import util


RANK_MAP = OrderedDict([
    (db.User.RANK_ANONYMOUS, 'anonymous'),
    (db.User.RANK_RESTRICTED, 'restricted'),
    (db.User.RANK_REGULAR, 'regular'),
    (db.User.RANK_POWER, 'power'),
    (db.User.RANK_MODERATOR, 'moderator'),
    (db.User.RANK_ADMINISTRATOR, 'administrator'),
    (db.User.RANK_NOBODY, 'nobody'),
])


def get_password_hash(salt, password):
    ''' Retrieve new-style password hash. '''
    digest = hashlib.sha256()
    digest.update(config.config['secret'].encode('utf8'))
    digest.update(salt.encode('utf8'))
    digest.update(password.encode('utf8'))
    return digest.hexdigest()


def get_legacy_password_hash(salt, password):
    ''' Retrieve old-style password hash. '''
    digest = hashlib.sha1()
    digest.update(b'1A2/$_4xVa')
    digest.update(salt.encode('utf8'))
    digest.update(password.encode('utf8'))
    return digest.hexdigest()


def create_password():
    alphabet = {
        'c': list('bcdfghijklmnpqrstvwxyz'),
        'v': list('aeiou'),
        'n': list('0123456789'),
    }
    pattern = 'cvcvnncvcv'
    return ''.join(random.choice(alphabet[l]) for l in list(pattern))


def is_valid_password(user, password):
    assert user
    salt, valid_hash = user.password_salt, user.password_hash
    possible_hashes = [
        get_password_hash(salt, password),
        get_legacy_password_hash(salt, password)
    ]
    return valid_hash in possible_hashes


def has_privilege(user, privilege_name):
    assert user
    all_ranks = list(RANK_MAP.keys())
    assert privilege_name in config.config['privileges']
    assert user.rank in all_ranks
    minimal_rank = util.flip(RANK_MAP)[
        config.config['privileges'][privilege_name]]
    good_ranks = all_ranks[all_ranks.index(minimal_rank):]
    return user.rank in good_ranks


def verify_privilege(user, privilege_name):
    assert user
    if not has_privilege(user, privilege_name):
        raise errors.AuthError('Insufficient privileges to do this.')


def generate_authentication_token(user):
    ''' Generate nonguessable challenge (e.g. links in password reminder). '''
    assert user
    digest = hashlib.md5()
    digest.update(config.config['secret'].encode('utf8'))
    digest.update(user.password_salt.encode('utf8'))
    return digest.hexdigest()