# Copyright (C) 2000-2014 Bastian Kleineidam
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
Handle https links.
"""
import time
import threading
from . import _ConnectionPlugin
from .. import strformat, LinkCheckerError
from ..decorators import synchronized

_lock = threading.Lock()

# configuration option names
sslcertwarndays = "sslcertwarndays"


class SslCertificateCheck(_ConnectionPlugin):
    """Check SSL certificate expiration date. Only internal https: links
    will be checked. A domain will only be checked once to avoid duplicate
    warnings.
    The expiration warning time can be configured with the sslcertwarndays
    option."""

    def __init__(self, config):
        """Initialize clamav configuration."""
        super().__init__(config)
        self.warn_ssl_cert_secs_valid = (
            config[sslcertwarndays] * strformat.SECONDS_PER_DAY
        )
        # do not check hosts multiple times
        self.checked_hosts = set()

    def applies_to(self, url_data):
        """Check validity, scheme, extern and url_connection."""
        return (
            url_data.valid
            and url_data.scheme == 'https'
            and not url_data.extern[0]
            and url_data.url_connection is not None
        )

    @synchronized(_lock)
    def check(self, url_data):
        """Run all SSL certificate checks that have not yet been done.
        OpenSSL already checked the SSL notBefore and notAfter dates.
        """
        host = url_data.urlparts[1]
        if host in self.checked_hosts:
            return
        self.checked_hosts.add(host)
        cert = url_data.ssl_cert
        config = url_data.aggregate.config
        if cert and 'notAfter' in cert:
            self.check_ssl_valid_date(url_data, cert)
        elif config['sslverify']:
            msg = _('certificate did not include "notAfter" information')
            url_data.add_warning(msg)
        else:
            msg = _('SSL verification is disabled; enable the sslverify option')
            url_data.add_warning(msg)

    def check_ssl_valid_date(self, url_data, cert):
        """Check if the certificate is still valid, or if configured check
        if it's at least a number of days valid.
        """
        import ssl

        try:
            notAfter = ssl.cert_time_to_seconds(cert['notAfter'])
        except ValueError as msg:
            msg = _('Invalid SSL certficate "notAfter" value %r') % cert['notAfter']
            url_data.add_warning(msg)
            return
        curTime = time.time()
        # Calculate seconds until certifcate expires. Can be negative if
        # the certificate is already expired.
        secondsValid = notAfter - curTime
        args = dict(expire=cert['notAfter'])
        if secondsValid < 0:
            msg = _('SSL certficate is expired on %(expire)s.')
            url_data.add_warning(msg % args)
        else:
            args['valid'] = strformat.strduration_long(secondsValid)
            if secondsValid < self.warn_ssl_cert_secs_valid:
                msg = _(
                    'SSL certificate expires on %(expire)s and is only %(valid)s valid.'
                )
                url_data.add_warning(msg % args)
            else:
                msg = _('SSL certificate expires on %(expire)s and is %(valid)s valid.')
                url_data.add_info(msg % args)

    @classmethod
    def read_config(cls, configparser):
        """Read configuration file options."""
        config = dict()
        section = cls.__name__
        option = sslcertwarndays
        if configparser.has_option(section, option):
            num = configparser.getint(section, option)
            if num > 0:
                config[option] = num
            else:
                msg = _("invalid value for %s: %d must not be less than %d") % (
                    option,
                    num,
                    0,
                )
                raise LinkCheckerError(msg)
        else:
            # set the default
            config[option] = 30
        return config
