import logging
import ssl
import platform
import time
import os

from gnutls import crypto
import netifaces
import ping
import requests

from leap import __branding as BRANDING
from leap import certs
from leap.base import constants as baseconstants
from leap.base import providers
from leap.eip import config as eipconfig
from leap.eip import constants as eipconstants
from leap.eip import exceptions as eipexceptions
from leap.eip import specs as eipspecs
from leap.util.fileutil import mkdir_p

logger = logging.getLogger(name=__name__)

"""
ProviderCertChecker
-------------------
Checks on certificates. To be moved to base.
docs TBD

EIPConfigChecker
----------
It is used from the eip conductor (a instance of EIPConnection that is
managed from the QtApp), running `run_all` method before trying to call
`connect` or any other of the state-changing methods.

It checks that the needed files are provided or can be discovered over the
net. Much of these tests are not specific to EIP module, and can be splitted
into base.tests to be invoked by the base leap init routines.
However, I'm testing them alltogether for the sake of having the whole unit
reachable and testable as a whole.

"""


def get_ca_cert():
    ca_file = BRANDING.get('provider_ca_file')
    if ca_file:
        return certs.where(ca_file)


class ProviderCertChecker(object):
    """
    Several checks needed for getting
    client certs and checking tls connection
    with provider.
    """
    def __init__(self, fetcher=requests):
        self.fetcher = fetcher
        self.cacert = get_ca_cert()

    def run_all(self, checker=None, skip_download=False, skip_verify=False):
        if not checker:
            checker = self

        do_verify = not skip_verify
        logger.debug('do_verify: %s', do_verify)
        # For MVS+
        # checker.download_ca_cert()
        # checker.download_ca_signature()
        # checker.get_ca_signatures()
        # checker.is_there_trust_path()

        # For MVS
        checker.is_there_provider_ca()

        # XXX FAKE IT!!!
        checker.is_https_working(verify=do_verify)
        checker.check_new_cert_needed(verify=do_verify)

    def download_ca_cert(self):
        # MVS+
        raise NotImplementedError

    def download_ca_signature(self):
        # MVS+
        raise NotImplementedError

    def get_ca_signatures(self):
        # MVS+
        raise NotImplementedError

    def is_there_trust_path(self):
        # MVS+
        raise NotImplementedError

    def is_there_provider_ca(self):
        from leap import certs
        logger.debug('do we have provider_ca?')
        cacert_path = BRANDING.get('provider_ca_file', None)
        if not cacert_path:
            logger.debug('False')
            return False
        self.cacert = certs.where(cacert_path)
        logger.debug('True')
        return True

    def is_https_working(self, uri=None, verify=True):
        if uri is None:
            uri = self._get_root_uri()
        # XXX raise InsecureURI or something better
        assert uri.startswith('https')
        if verify is True and self.cacert is not None:
            logger.debug('verify cert: %s', self.cacert)
            verify = self.cacert
        logger.debug('is https working?')
        logger.debug('uri: %s (verify:%s)', uri, verify)
        try:
            self.fetcher.get(uri, verify=verify)
        except requests.exceptions.SSLError as exc:
            logger.warning('False! CERT VERIFICATION FAILED! '
                           '(this should be CRITICAL)')
            logger.warning('SSLError: %s', exc.message)
            # XXX RAISE! See #638
            #raise eipexceptions.EIPBadCertError
        # XXX get requests.exceptions.ConnectionError Errno 110
        # Connection timed out, and raise ours.
        else:
            logger.debug('True')
            return True

    def check_new_cert_needed(self, skip_download=False, verify=True):
        logger.debug('is new cert needed?')
        if not self.is_cert_valid(do_raise=False):
            logger.debug('True')
            self.download_new_client_cert(
                skip_download=skip_download,
                verify=verify)
            return True
        logger.debug('False')
        return False

    def download_new_client_cert(self, uri=None, verify=True,
                                 skip_download=False):
        logger.debug('download new client cert')
        if skip_download:
            return True
        if uri is None:
            uri = self._get_client_cert_uri()
        # XXX raise InsecureURI or something better
        assert uri.startswith('https')
        if verify is True and self.cacert is not None:
            verify = self.cacert
        try:
            # XXX FIXME!!!!
            # verify=verify
            # Workaround for #638. return to verification
            # when That's done!!!
            req = self.fetcher.get(uri, verify=False)
            req.raise_for_status()
        except requests.exceptions.SSLError:
            logger.warning('SSLError while fetching cert. '
                           'Look below for stack trace.')
            # XXX raise better exception
            raise
        try:
            pemfile_content = req.content
            self.is_valid_pemfile(pemfile_content)
            cert_path = self._get_client_cert_path()
            self.write_cert(pemfile_content, to=cert_path)
        except:
            logger.warning('Error while validating cert')
            raise
        return True

    def is_cert_valid(self, cert_path=None, do_raise=True):
        exists = lambda: self.is_certificate_exists()
        valid_pemfile = lambda: self.is_valid_pemfile()
        not_expired = lambda: self.is_cert_not_expired()

        valid = exists() and valid_pemfile() and not_expired()
        if not valid:
            if do_raise:
                raise Exception('missing cert')
            else:
                return False
        return True

    def is_certificate_exists(self, certfile=None):
        if certfile is None:
            certfile = self._get_client_cert_path()
        return os.path.isfile(certfile)

    def is_cert_not_expired(self, certfile=None, now=time.gmtime):
        if certfile is None:
            certfile = self._get_client_cert_path()
        with open(certfile) as cf:
            cert_s = cf.read()
        cert = crypto.X509Certificate(cert_s)
        return cert.activation_time < now() < cert.expiration_time

    def is_valid_pemfile(self, cert_s=None):
        """
        checks that the passed string
        is a valid pem certificate
        @param cert_s: string containing pem content
        @type cert_s: string
        @rtype: bool
        """
        if cert_s is None:
            certfile = self._get_client_cert_path()
            with open(certfile) as cf:
                cert_s = cf.read()
        try:
            # XXX get a real cert validation
            # so far this is only checking begin/end
            # delimiters :)
            # XXX use gnutls for get proper
            # validation.
            # crypto.X509Certificate(cert_s)
            sep = "-" * 5 + "BEGIN CERTIFICATE" + "-" * 5
            # we might have private key and cert in the same file
            certparts = cert_s.split(sep)
            if len(certparts) > 1:
                cert_s = sep + certparts[1]
            ssl.PEM_cert_to_DER_cert(cert_s)
        except:
            # XXX raise proper exception
            raise
        return True

    def _get_root_uri(self):
        return u"https://%s/" % baseconstants.DEFAULT_PROVIDER

    def _get_client_cert_uri(self):
        # XXX get the whole thing from constants
        return "https://%s/1/cert" % (baseconstants.DEFAULT_PROVIDER)

    def _get_client_cert_path(self):
        # MVS+ : get provider path
        return eipspecs.client_cert_path()

    def write_cert(self, pemfile_content, to=None):
        folder, filename = os.path.split(to)
        if not os.path.isdir(folder):
            mkdir_p(folder)
        with open(to, 'w') as cert_f:
            cert_f.write(pemfile_content)


class EIPConfigChecker(object):
    """
    Several checks needed
    to ensure a EIPConnection
    can be sucessfully established.
    use run_all to run all checks.
    """

    def __init__(self, fetcher=requests):
        # we do not want to accept too many
        # argument on init.
        # we want tests
        # to be explicitely run.
        self.fetcher = fetcher

        self.eipconfig = eipconfig.EIPConfig()
        self.defaultprovider = providers.LeapProviderDefinition()
        self.eipserviceconfig = eipconfig.EIPServiceConfig()

    def run_all(self, checker=None, skip_download=False):
        """
        runs all checks in a row.
        will raise if some error encountered.
        catching those exceptions is not
        our responsibility at this moment
        """
        if not checker:
            checker = self

        # let's call all tests
        # needed for a sane eip session.

        # TODO: get rid of check_default.
        # check_complete should
        # be enough. but here to make early tests easier.
        checker.check_default_eipconfig()

        checker.check_is_there_default_provider()
        checker.fetch_definition(skip_download=skip_download)
        checker.fetch_eip_service_config(skip_download=skip_download)
        checker.check_complete_eip_config()
        #checker.ping_gateway()

    # public checks

    def check_default_eipconfig(self):
        """
        checks if default eipconfig exists,
        and dumps a default file if not
        """
        # XXX ONLY a transient check
        # because some old function still checks
        # for eip config at the beginning.

        # it *really* does not make sense to
        # dump it right now, we can get an in-memory
        # config object and dump it to disk in a
        # later moment
        logger.debug('checking default eip config')
        if not self._is_there_default_eipconfig():
            self._dump_default_eipconfig()

    def check_is_there_default_provider(self, config=None):
        """
        raises EIPMissingDefaultProvider if no
        default provider found on eip config.
        This is catched by ui and runs FirstRunWizard (MVS+)
        """
        if config is None:
            config = self.eipconfig.get_config()
        logger.debug('checking default provider')
        provider = config.get('provider', None)
        if provider is None:
            raise eipexceptions.EIPMissingDefaultProvider
        # XXX raise also if malformed ProviderDefinition?
        return True

    def fetch_definition(self, skip_download=False,
                         config=None, uri=None):
        """
        fetches a definition file from server
        """
        # TODO:
        # - Implement diff
        # - overwrite only if different.
        #   (attend to serial field different, for instance)

        logger.debug('fetching definition')

        if skip_download:
            logger.debug('(fetching def skipped)')
            return True
        if config is None:
            config = self.defaultprovider.get_config()
        if uri is None:
            domain = config.get('provider', None)
            uri = self._get_provider_definition_uri(domain=domain)

        # FIXME! Pass ca path verify!!!
        self.defaultprovider.load(
            from_uri=uri,
            fetcher=self.fetcher,
            verify=False)
        self.defaultprovider.save()

    def fetch_eip_service_config(self, skip_download=False,
                                 config=None, uri=None):
        if skip_download:
            return True
        if config is None:
            config = self.eipserviceconfig.get_config()
        if uri is None:
            domain = config.get('provider', None)
            uri = self._get_eip_service_uri(domain=domain)

        self.eipserviceconfig.load(from_uri=uri, fetcher=self.fetcher)
        self.eipserviceconfig.save()

    def check_complete_eip_config(self, config=None):
        # TODO check for gateway
        if config is None:
            config = self.eipconfig.get_config()
        try:
            'trying assertions'
            assert 'provider' in config
            assert config['provider'] is not None
            # XXX assert there is gateway !!
        except AssertionError:
            raise eipexceptions.EIPConfigurationError

        # XXX TODO:
        # We should WRITE eip config if missing or
        # incomplete at this point
        #self.eipconfig.save()

    #
    # private helpers
    #

    def _is_there_default_eipconfig(self):
        return self.eipconfig.exists()

    def _dump_default_eipconfig(self):
        self.eipconfig.save()

    def _get_provider_definition_uri(self, domain=None, path=None):
        if domain is None:
            domain = baseconstants.DEFAULT_PROVIDER
        if path is None:
            path = baseconstants.DEFINITION_EXPECTED_PATH
        uri = u"https://%s/%s" % (domain, path)
        logger.debug('getting provider definition from %s' % uri)
        return uri

    def _get_eip_service_uri(self, domain=None, path=None):
        if domain is None:
            domain = baseconstants.DEFAULT_PROVIDER
        if path is None:
            path = eipconstants.EIP_SERVICE_EXPECTED_PATH
        uri = "https://%s/%s" % (domain, path)
        logger.debug('getting eip service file from %s', uri)
        return uri