"""passlib.ifc - abstract interfaces used by Passlib"""
#=============================================================================
# imports
#=============================================================================
# core
import logging; log = logging.getLogger(__name__)
import sys
# site
# pkg
# local
__all__ = [
    "PasswordHash",
]

#=============================================================================
# 2.5-3.2 compatibility helpers
#=============================================================================
if sys.version_info >= (2,6):
    from abc import ABCMeta, abstractmethod, abstractproperty
else:
    # create stub for python 2.5
    ABCMeta = type
    def abstractmethod(func):
        return func
#    def abstractproperty():
#        return None

def create_with_metaclass(meta):
    """class decorator that re-creates class using metaclass"""
    # have to do things this way since abc not present in py25,
    # and py2/py3 have different ways of doing metaclasses.
    def builder(cls):
        if meta is type(cls):
            return cls
        return meta(cls.__name__, cls.__bases__, cls.__dict__.copy())
    return builder

#=============================================================================
# PasswordHash interface
#=============================================================================
class PasswordHash(object):
    """This class describes an abstract interface which all password hashes
    in Passlib adhere to. Under Python 2.6 and up, this is an actual
    Abstract Base Class built using the :mod:`!abc` module.

    See the Passlib docs for full documentation.
    """
    #===================================================================
    # class attributes
    #===================================================================

    #---------------------------------------------------------------
    # general information
    #---------------------------------------------------------------
    ##name
    ##setting_kwds
    ##context_kwds

    #---------------------------------------------------------------
    # salt information -- if 'salt' in setting_kwds
    #---------------------------------------------------------------
    ##min_salt_size
    ##max_salt_size
    ##default_salt_size
    ##salt_chars
    ##default_salt_chars

    #---------------------------------------------------------------
    # rounds information -- if 'rounds' in setting_kwds
    #---------------------------------------------------------------
    ##min_rounds
    ##max_rounds
    ##default_rounds
    ##rounds_cost

    #---------------------------------------------------------------
    # encoding info -- if 'encoding' in context_kwds
    #---------------------------------------------------------------
    ##default_encoding

    #===================================================================
    # primary methods
    #===================================================================
    @classmethod
    @abstractmethod
    def encrypt(cls, secret, **setting_and_context_kwds): # pragma: no cover -- abstract method
        """encrypt secret, returning resulting hash"""
        raise NotImplementedError("must be implemented by subclass")

    @classmethod
    @abstractmethod
    def verify(cls, secret, hash, **context_kwds): # pragma: no cover -- abstract method
        """verify secret against hash, returns True/False"""
        raise NotImplementedError("must be implemented by subclass")

    #===================================================================
    # additional methods
    #===================================================================
    @classmethod
    @abstractmethod
    def identify(cls, hash): # pragma: no cover -- abstract method
        """check if hash belongs to this scheme, returns True/False"""
        raise NotImplementedError("must be implemented by subclass")

    @classmethod
    @abstractmethod
    def genconfig(cls, **setting_kwds): # pragma: no cover -- abstract method
        """compile settings into a configuration string for genhash()"""
        raise NotImplementedError("must be implemented by subclass")

    @classmethod
    @abstractmethod
    def genhash(cls, secret, config, **context_kwds): # pragma: no cover -- abstract method
        """generated hash for secret, using settings from config/hash string"""
        raise NotImplementedError("must be implemented by subclass")

    #===================================================================
    # undocumented methods / attributes
    #===================================================================
    # the following entry points are used internally by passlib,
    # and aren't documented as part of the exposed interface.
    # they are subject to change between releases,
    # but are documented here so there's a list of them *somewhere*.

    #---------------------------------------------------------------
    # checksum information - defined for many hashes
    #---------------------------------------------------------------
    ## checksum_chars
    ## checksum_size

    #---------------------------------------------------------------
    # CryptContext flags
    #---------------------------------------------------------------

    # hack for bsdi_crypt: if True, causes CryptContext to only generate
    # odd rounds values. assumed False if not defined.
    ## _avoid_even_rounds = False

    ##@classmethod
    ##def _bind_needs_update(cls, **setting_kwds):
    ##    """return helper to detect hashes that need updating.
    ##
    ##    if this method is defined, the CryptContext constructor
    ##    will invoke it with the settings specified for the context.
    ##    this method should return either ``None``, or a callable
    ##    with the signature ``needs_update(hash,secret)->bool``.
    ##
    ##    this ``needs_update`` function should return True if the hash
    ##    should be re-encrypted, whether due to internal
    ##    issues or the specified settings.
    ##
    ##    CryptContext will automatically take care of deprecating
    ##    hashes with insufficient rounds for classes which define fromstring()
    ##    and a rounds attribute - though the requirements for this last
    ##    part may change at some point.
    ##    """

    #---------------------------------------------------------------
    # experimental methods
    #---------------------------------------------------------------

    ##@classmethod
    ##def normhash(cls, hash):
    ##    """helper to clean up non-canonic instances of hash.
    ##    currently only provided by bcrypt() to fix an historical passlib issue.
    ##    """

    # experimental helper to parse hash into components.
    ##@classmethod
    ##def parsehash(cls, hash, checksum=True, sanitize=False):
    ##    """helper to parse hash into components, returns dict"""

    # experiment helper to estimate bitsize of different hashes,
    # implement for GenericHandler, but may be currently be off for some hashes.
    # want to expand this into a way to programmatically compare
    # "strengths" of different hashes and hash algorithms.
    # still needs to have some factor for estimate relative cost per round,
    # ala in the style of the scrypt whitepaper.
    ##@classmethod
    ##def bitsize(cls, **kwds):
    ##    """returns dict mapping component -> bits contributed.
    ##    components currently include checksum, salt, rounds.
    ##    """

    #===================================================================
    # eoc
    #===================================================================

PasswordHash = create_with_metaclass(ABCMeta)(PasswordHash)

#=============================================================================
# eof
#=============================================================================