"""
    Slixmpp: The Slick XMPP Library
    Copyright (C) 2017 Emmanuel Gil Peyrot
    This file is part of Slixmpp.

    See the file LICENSE for copying permission.
"""

from base64 import b64encode
import hashlib
import logging

from slixmpp.plugins import BasePlugin
from slixmpp.plugins.xep_0300 import stanza, Hash


log = logging.getLogger(__name__)


class XEP_0300(BasePlugin):

    name = 'xep_0300'
    description = 'XEP-0300: Use of Cryptographic Hash Functions in XMPP'
    dependencies = {'xep_0030'}
    stanza = stanza
    default_config = {
        'block_size': 1024 * 1024,  # One MiB
        'preferded': 'sha-256',
        'enable_sha-1': False,
        'enable_sha-256': True,
        'enable_sha-512': True,
        'enable_sha3-256': True,
        'enable_sha3-512': True,
        'enable_BLAKE2b256': True,
        'enable_BLAKE2b512': True,
    }

    _hashlib_function = {
        'sha-1': hashlib.sha1,
        'sha-256': hashlib.sha256,
        'sha-512': hashlib.sha512,
        'sha3-256': lambda: hashlib.sha3_256(),
        'sha3-512': lambda: hashlib.sha3_512(),
        'BLAKE2b256': lambda: hashlib.blake2b(digest_size=32),
        'BLAKE2b512': lambda: hashlib.blake2b(digest_size=64),
    }

    def plugin_init(self):
        namespace = 'urn:xmpp:hash-function-text-names:%s'
        self.enabled_hashes = []
        for algo in self._hashlib_function:
            if getattr(self, 'enable_' + algo, False):
                # XXX: this is a hack for Python 3.5 or below, which
                # don’t support sha3 or blake2b…
                try:
                    self._hashlib_function[algo]()
                except AttributeError:
                    log.warn('Algorithm %s unavailable, disabling.', algo)
                else:
                    self.enabled_hashes.append(namespace % algo)

    def session_bind(self, jid):
        self.xmpp['xep_0030'].add_feature(Hash.namespace)

        for namespace in self.enabled_hashes:
            self.xmpp['xep_0030'].add_feature(namespace)

    def plugin_end(self):
        for namespace in self.enabled_hashes:
            self.xmpp['xep_0030'].del_feature(namespace)

        self.xmpp['xep_0030'].del_feature(feature=Hash.namespace)

    def compute_hash(self, filename, function=None):
        if function is None:
            function = self.preferred
        h = self._hashlib_function[function]()
        with open(filename, 'rb') as f:
            while True:
                block = f.read(self.block_size)
                if not block:
                    break
                h.update(block)
        hash_elem = Hash()
        hash_elem['algo'] = function
        hash_elem['value'] = b64encode(h.digest())
        return hash_elem
