import warnings

from OpenSSL import SSL
from twisted.internet._sslverify import _setAcceptableProtocols
from twisted.internet.ssl import optionsForClientTLS, CertificateOptions, platformTrust, AcceptableCiphers
from twisted.web.client import BrowserLikePolicyForHTTPS
from twisted.web.iweb import IPolicyForHTTPS
from zope.interface.declarations import implementer
from zope.interface.verify import verifyObject

from scrapy.core.downloader.tls import DEFAULT_CIPHERS, openssl_methods, ScrapyClientTLSOptions
from scrapy.utils.misc import create_instance, load_object


@implementer(IPolicyForHTTPS)
class ScrapyClientContextFactory(BrowserLikePolicyForHTTPS):
    """
    Non-peer-certificate verifying HTTPS context factory

    Default OpenSSL method is TLS_METHOD (also called SSLv23_METHOD)
    which allows TLS protocol negotiation

    'A TLS/SSL connection established with [this method] may
     understand the SSLv3, TLSv1, TLSv1.1 and TLSv1.2 protocols.'
    """

    def __init__(self, method=SSL.SSLv23_METHOD, tls_verbose_logging=False, tls_ciphers=None, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._ssl_method = method
        self.tls_verbose_logging = tls_verbose_logging
        if tls_ciphers:
            self.tls_ciphers = AcceptableCiphers.fromOpenSSLCipherString(tls_ciphers)
        else:
            self.tls_ciphers = DEFAULT_CIPHERS

    @classmethod
    def from_settings(cls, settings, method=SSL.SSLv23_METHOD, *args, **kwargs):
        tls_verbose_logging = settings.getbool('DOWNLOADER_CLIENT_TLS_VERBOSE_LOGGING')
        tls_ciphers = settings['DOWNLOADER_CLIENT_TLS_CIPHERS']
        return cls(method=method, tls_verbose_logging=tls_verbose_logging, tls_ciphers=tls_ciphers, *args, **kwargs)

    def getCertificateOptions(self):
        # setting verify=True will require you to provide CAs
        # to verify against; in other words: it's not that simple

        # backward-compatible SSL/TLS method:
        #
        # * this will respect `method` attribute in often recommended
        #   `ScrapyClientContextFactory` subclass
        #   (https://github.com/scrapy/scrapy/issues/1429#issuecomment-131782133)
        #
        # * getattr() for `_ssl_method` attribute for context factories
        #   not calling super().__init__
        return CertificateOptions(
            verify=False,
            method=getattr(self, 'method', getattr(self, '_ssl_method', None)),
            fixBrokenPeers=True,
            acceptableCiphers=self.tls_ciphers,
        )

    # kept for old-style HTTP/1.0 downloader context twisted calls,
    # e.g. connectSSL()
    def getContext(self, hostname=None, port=None):
        return self.getCertificateOptions().getContext()

    def creatorForNetloc(self, hostname, port):
        return ScrapyClientTLSOptions(hostname.decode("ascii"), self.getContext(),
                                      verbose_logging=self.tls_verbose_logging)


@implementer(IPolicyForHTTPS)
class BrowserLikeContextFactory(ScrapyClientContextFactory):
    """
    Twisted-recommended context factory for web clients.

    Quoting the documentation of the :class:`~twisted.web.client.Agent` class:

        The default is to use a
        :class:`~twisted.web.client.BrowserLikePolicyForHTTPS`, so unless you
        have special requirements you can leave this as-is.

    :meth:`creatorForNetloc` is the same as
    :class:`~twisted.web.client.BrowserLikePolicyForHTTPS` except this context
    factory allows setting the TLS/SSL method to use.

    The default OpenSSL method is ``TLS_METHOD`` (also called
    ``SSLv23_METHOD``) which allows TLS protocol negotiation.
    """

    def creatorForNetloc(self, hostname, port):
        # trustRoot set to platformTrust() will use the platform's root CAs.
        #
        # This means that a website like https://www.cacert.org will be rejected
        # by default, since CAcert.org CA certificate is seldom shipped.
        return optionsForClientTLS(
            hostname=hostname.decode("ascii"),
            trustRoot=platformTrust(),
            extraCertificateOptions={'method': self._ssl_method},
        )


@implementer(IPolicyForHTTPS)
class AcceptableProtocolsContextFactory:
    """Context factory to used to override the acceptable protocols
    to set up the [OpenSSL.SSL.Context] for doing NPN and/or ALPN
    negotiation.
    """

    def __init__(self, context_factory, acceptable_protocols):
        verifyObject(IPolicyForHTTPS, context_factory)
        self._wrapped_context_factory = context_factory
        self._acceptable_protocols = acceptable_protocols

    def creatorForNetloc(self, hostname, port):
        options = self._wrapped_context_factory.creatorForNetloc(hostname, port)
        _setAcceptableProtocols(options._ctx, self._acceptable_protocols)
        return options


def load_context_factory_from_settings(settings, crawler):
    ssl_method = openssl_methods[settings.get('DOWNLOADER_CLIENT_TLS_METHOD')]
    context_factory_cls = load_object(settings['DOWNLOADER_CLIENTCONTEXTFACTORY'])
    # try method-aware context factory
    try:
        context_factory = create_instance(
            objcls=context_factory_cls,
            settings=settings,
            crawler=crawler,
            method=ssl_method,
        )
    except TypeError:
        # use context factory defaults
        context_factory = create_instance(
            objcls=context_factory_cls,
            settings=settings,
            crawler=crawler,
        )
        msg = """
            '%s' does not accept `method` argument (type OpenSSL.SSL method,\
            e.g. OpenSSL.SSL.SSLv23_METHOD) and/or `tls_verbose_logging` argument and/or `tls_ciphers` argument.\
            Please upgrade your context factory class to handle them or ignore them.""" % (
            settings['DOWNLOADER_CLIENTCONTEXTFACTORY'],)
        warnings.warn(msg)

    return context_factory
