import enum
import collections


@enum.unique
class Mechanisms(enum.Enum):
    """Enumeration for representing possible mechanisms."""

    @classmethod
    def as_string(cls, mech):
        return {
            cls.plain: "PLAIN",
            cls.ecdsa_nist256p_challenge: "ECDSA-NIST256P-CHALLENGE",
            cls.scram_sha_256: "SCRAM-SHA-256",
        }[mech]

    plain = 1
    ecdsa_nist256p_challenge = 2
    scram_sha_256 = 3


Authentication = collections.namedtuple(
    "Authentication", "mechanisms username password ecdsa_key"
)
Authentication.__new__.__defaults__ = ([Mechanisms.plain], None, None, None)