from base64 import b64decode, b64encode
from hashlib import pbkdf2_hmac, md5


def password_is_correct(password_plain, password_db):
    """Returns true if a plain text password corresponds to the hash of the password as stored in the MediaWiki db.

    :param password_plain: plain text password as string, e.g. 'abc'
    :param password_db: complete password line as string as stored in the database,
        e.g. ':pbkdf2:sha256:10000:128:EXgVGhc2mAs710feKvkiaw==:J5fYth9pg/R2d0F8bSsYfTR8SBpTBNIcdv/DgJ0tOPC' +
             '1rtajl2Dr0RLqOozLb8O0XpDhtv4a3JJd/M0b58WebfNWAcdJBJI9nNeC0EYYD7OCYZGVAaRhiYtK4m53KZBBL6x/k2j4' +
             'RjHPT1NmgV8Fr1DPqBNOlOHxUIh5z5oslM4='
    """
    if not password_db.startswith(':'):
        raise ValueError("Password entry in the database does have an unexpected format (does not start with ':').")
    pwd_parts = password_db[1:].split(':')
    pwd_type = pwd_parts[0]
    if pwd_type == 'B':
        # legacy
        # example: password_db == ':B:d25b2886:41e46c952790b1b442aac4f24f7ea7a8'
        # pwd_parts == ['B', 'd25b2886', '41e46c952790b1b442aac4f24f7ea7a8']
        if len(pwd_parts) != 3:
            raise ValueError("Password entry in the database does have an unexpected format (too few ':').")
        salt, pwd_md5 = tuple(pwd_parts[1:3])  # salt = 'd25b2886'; pwd_md5 = '41e46c952790b1b442aac4f24f7ea7a8'
        # log.info("user: '%s'; md5 of salt+' '+entered_pwd: '%s'; md5-part of DB-pwd: %s"
        # % (username, md5(salt + '-' + md5(password)), pwd_md5))
        salt_and_plain = salt + '-' + md5(password_plain.encode()).hexdigest()
        return md5(salt_and_plain.encode()).hexdigest() == pwd_md5
    elif pwd_type == 'pbkdf2':
        if len(pwd_parts) != 6:
            raise ValueError("Password entry in the database does have an unexpected format (too few ':').")
        _, algorithm, rounds, num_bit, salt, pwd_hash = pwd_parts
        salt = b64decode(salt)
        hashcode = pbkdf2_hmac(algorithm, password_plain.encode(), salt, int(rounds), int(num_bit))
        hashcode = b64encode(hashcode).decode()
        return hashcode == pwd_hash
    else:
        raise ValueError("Unknown password type")