#
# This file is part of Plinth.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

"""
Plinth module for configuring timezone, hostname etc.
"""

import cherrypy
from django import forms
from django.core import validators
from gettext import gettext as _
try:
    import simplejson as json
except ImportError:
    import json
import os
import socket

import actions
import cfg
from modules.auth import require
from plugin_mount import PagePlugin
import util


def get_hostname():
    """Return the hostname"""
    return socket.gethostname()


class TrimmedCharField(forms.CharField):
    """Trim the contents of a CharField"""
    def clean(self, value):
        """Clean and validate the field value"""
        if value:
            value = value.strip()

        return super(TrimmedCharField, self).clean(value)


class ConfigurationForm(forms.Form):
    """Main system configuration form"""
    time_zone = forms.ChoiceField(
        label=_('Time Zone'),
        help_text=_('Set your timezone to get accurate timestamps. \
This information will be used to set your systemwide timezone'))

    # We're more conservative than RFC 952 and RFC 1123
    hostname = TrimmedCharField(
        label=_('Hostname'),
        help_text=_('Your hostname is the local name by which other machines \
on your LAN can reach you. It must be alphanumeric, start with an alphabet \
and must not be greater than 63 characters in length.'),
        validators=[
            validators.RegexValidator(r'^[a-zA-Z][a-zA-Z0-9]{,62}$',
                                      _('Invalid hostname'))])

    def __init__(self, *args, **kwargs):
        # pylint: disable-msg=E1101, W0233
        forms.Form.__init__(self, *args, **kwargs)

        self.fields['time_zone'].choices = [(zone, zone)
                                            for zone in self.get_time_zones()]

    @staticmethod
    def get_time_zones():
        """Return list of available time zones"""
        # XXX: Get rid of a custom file and read the values from /usr
        module_file = __file__
        if module_file.endswith(".pyc"):
            module_file = module_file[:-1]

        module_dir = os.path.dirname(os.path.realpath(module_file))
        time_zones_file = os.path.join(module_dir, 'time_zones')
        return json.loads(util.slurp(time_zones_file))


class Configuration(PagePlugin):
    """System configuration page"""
    def __init__(self, *args, **kwargs):
        del args  # Unused
        del kwargs  # Unused

        self.register_page('sys.config')

        self.menu = cfg.html_root.sys.menu.add_item(_('Configure'), 'icon-cog',
                                                    '/sys/config', 10)

    @cherrypy.expose
    @require()
    def index(self, **kwargs):
        """Serve the configuration form"""
        status = self.get_status()

        form = None
        messages = []

        if kwargs and cfg.users.expert():
            form = ConfigurationForm(kwargs, prefix='configuration')
            # pylint: disable-msg=E1101
            if form.is_valid():
                self._apply_changes(status, form.cleaned_data, messages)
                status = self.get_status()
                form = ConfigurationForm(initial=status,
                                         prefix='configuration')
        else:
            form = ConfigurationForm(initial=status, prefix='configuration')

        return util.render_template(template='config',
                                    title=_('General Configuration'),
                                    form=form, messages=messages)

    @staticmethod
    def get_status():
        """Return the current status"""
        return {'hostname': get_hostname(),
                'time_zone': util.slurp('/etc/timezone').rstrip()}

    @staticmethod
    def _apply_changes(old_status, new_status, messages):
        """Apply the form changes"""
        if old_status['hostname'] != new_status['hostname']:
            set_hostname(new_status['hostname'])
            messages.append(('success', _('Hostname set')))
        else:
            messages.append(('info', _('Hostname is unchanged')))

        if old_status['time_zone'] != new_status['time_zone']:
            output, error = actions.superuser_run('timezone-change',
                                                  [new_status['time_zone']])
            del output  # Unused
            if error:
                messages.append(('error',
                                 _('Error setting time zone - %s') % error))
            else:
                messages.append(('success', _('Time zone set')))
        else:
            messages.append(('info', _('Time zone is unchanged')))


def set_hostname(hostname):
    """Sets machine hostname to hostname"""
    # Hostname should be ASCII. If it's unicode but passed our
    # valid_hostname check, convert to ASCII.
    hostname = str(hostname)

    cfg.log.info("Changing hostname to '%s'" % hostname)
    try:
        actions.superuser_run("xmpp-pre-hostname-change")
        actions.superuser_run("hostname-change", hostname)
        actions.superuser_run("xmpp-hostname-change", hostname, async=True)
        # don't persist/cache change unless it was saved successfuly
        sys_store = util.filedict_con(cfg.store_file, 'sys')
        sys_store['hostname'] = hostname
    except OSError as exception:
        raise cherrypy.HTTPError(500,
                                 'Updating hostname failed: %s' % exception)