# SPDX-License-Identifier: AGPL-3.0-or-later
"""
FreedomBox app for using Let's Encrypt.
"""

import json
import logging
import pathlib

from django.utils.translation import ugettext_lazy as _

from plinth import actions
from plinth import app as app_module
from plinth import cfg, menu
from plinth.errors import ActionError
from plinth.modules import names
from plinth.modules.apache.components import diagnose_url
from plinth.modules.backups.components import BackupRestore
from plinth.modules.names.components import DomainType
from plinth.signals import domain_added, domain_removed, post_module_loading
from plinth.utils import format_lazy

from . import components, manifest

version = 3

is_essential = True

depends = ['names']

managed_packages = ['certbot']

_description = [
    format_lazy(
        _('A digital certificate allows users of a web service to verify the '
          'identity of the service and to securely communicate with it. '
          '{box_name} can automatically obtain and setup digital '
          'certificates for each available domain.  It does so by proving '
          'itself to be the owner of a domain to Let\'s Encrypt, a '
          'certificate authority (CA).'), box_name=_(cfg.box_name)),
    _('Let\'s Encrypt is a free, automated, and open certificate '
      'authority, run for the public\'s benefit by the Internet Security '
      'Research Group (ISRG).  Please read and agree with the '
      '<a href="https://letsencrypt.org/repository/">Let\'s Encrypt '
      'Subscriber Agreement</a> before using this service.')
]

LIVE_DIRECTORY = '/etc/letsencrypt/live/'
CERTIFICATE_CHECK_DELAY = 120
logger = logging.getLogger(__name__)

app = None


class LetsEncryptApp(app_module.App):
    """FreedomBox app for Let's Encrypt."""

    app_id = 'letsencrypt'

    def __init__(self):
        """Create components for the app."""
        super().__init__()
        info = app_module.Info(app_id=self.app_id, version=version,
                               is_essential=is_essential, depends=depends,
                               name=_('Let\'s Encrypt'), icon='fa-lock',
                               short_description=_('Certificates'),
                               description=_description,
                               manual_page='LetsEncrypt',
                               donation_url='https://letsencrypt.org/donate/')
        self.add(info)

        menu_item = menu.Menu('menu-letsencrypt', info.name,
                              info.short_description, info.icon,
                              'letsencrypt:index', parent_url_name='system')
        self.add(menu_item)

        backup_restore = BackupRestore('backup-restore-letsencrypt',
                                       **manifest.backup)
        self.add(backup_restore)

        domain_added.connect(on_domain_added)
        domain_removed.connect(on_domain_removed)

        post_module_loading.connect(_certificate_handle_modified)

    def diagnose(self):
        """Run diagnostics and return the results."""
        results = super().diagnose()

        for domain in names.components.DomainName.list():
            if domain.domain_type.can_have_certificate:
                results.append(diagnose_url('https://' + domain.name))

        return results


def setup(helper, old_version=None):
    """Install and configure the module."""
    helper.install(managed_packages)
    actions.superuser_run(
        'letsencrypt',
        ['setup', '--old-version', str(old_version)])


def certificate_obtain(domain):
    """Obtain a certificate for a domain and notify handlers."""
    actions.superuser_run('letsencrypt', ['obtain', '--domain', domain])
    components.on_certificate_event('obtained', [domain], None)


def certificate_reobtain(domain):
    """Re-obtain a certificate for a domain and notify handlers.

    Don't trigger an obtained event. Re-obtaining a certificate also leads to a
    renewal (deploy) event from Let's Encrypt. Further, this event is not sent
    when obtaining the certificate for the first time. There is no easy way to
    distinguish if a renewal event is trigger because of obtain or because of
    re-obtain. Hence, handle re-obtain differently from obtain and don't
    trigger obtain event (LE will trigger a renewal event).

    """
    actions.superuser_run('letsencrypt', ['obtain', '--domain', domain])


def certificate_revoke(domain):
    """Revoke a certificate for a domain and notify handlers."""
    actions.superuser_run('letsencrypt', ['revoke', '--domain', domain])
    components.on_certificate_event('revoked', [domain], None)


def certificate_delete(domain):
    """Delete a certificate for a domain and notify handlers."""
    actions.superuser_run('letsencrypt', ['delete', '--domain', domain])
    components.on_certificate_event('deleted', [domain], None)


def on_domain_added(sender, domain_type='', name='', description='',
                    services=None, **kwargs):
    """Obtain a certificate for the new domain"""
    if not DomainType.get(domain_type).can_have_certificate:
        return False

    # Check if a cert if already available
    for domain_name, domain_status in get_status()['domains'].items():
        if domain_name == name and domain_status and \
           domain_status['certificate_available'] and \
           domain_status['validity'] == 'valid':
            return False

    try:
        if name:
            logger.info('Obtaining certificate for %s', name)
            certificate_obtain(name)
        return True
    except ActionError:
        return False


def on_domain_removed(sender, domain_type, name='', **kwargs):
    """Revoke Let's Encrypt certificate for the removed domain"""
    if not DomainType.get(domain_type).can_have_certificate:
        return False

    try:
        if name:
            logger.info('Revoking certificate for %s', name)
            certificate_revoke(name)
        return True
    except ActionError as exception:
        logger.warning('Failed to revoke certificate for %s: %s', name,
                       exception.args[2])
        return False


def get_status():
    """Get the current settings."""
    status = actions.superuser_run('letsencrypt', ['get-status'])
    status = json.loads(status)

    for domain in names.components.DomainName.list():
        if domain.domain_type.can_have_certificate:
            status['domains'].setdefault(domain.name, {})

    return status


def _certificate_handle_modified(**kwargs):
    """Generate events for certificates that got modified during downtime.

    This runs as a synchronous method soon after initializing the apps. After
    this is done, remaining initialization happens.

    This method is a wrapper over the read method to catch and print
    exceptions.

    """
    logger.info('Checking if any Let\'s Encrypt certificates got renewed.')
    try:
        _certificate_handle_modified_internal()
    except Exception:
        logger.exception('Error triggering certificate events.')


def _certificate_handle_modified_internal():
    """Generate events for certificates that got modified during downtime."""
    status = get_status()
    for domain, domain_status in status['domains'].items():
        if not domain_status:
            continue

        lineage = domain_status['lineage']
        modified_time = domain_status['modified_time']
        if certificate_get_last_seen_modified_time(lineage) < modified_time:
            logger.info('Certificate for %s got renewed offline.', domain)
            components.on_certificate_event_sync('renewed', domain, lineage)
        else:
            logger.info('Certificate for %s is already the latest known.',
                        domain)


def certificate_get_last_seen_modified_time(lineage):
    """Return the last seen expiry date of a certificate."""
    from plinth import kvstore
    info = kvstore.get_default('letsencrypt_certificate_info', '{}')
    info = json.loads(info)
    try:
        return info[str(lineage)]['last_seen_modified_time']
    except KeyError:
        return 0


def certificate_set_last_seen_modified_time(lineage):
    """Write to store a certificate's last seen expiry date."""
    lineage = pathlib.Path(lineage)
    output = actions.superuser_run(
        'letsencrypt', ['get-modified-time', '--domain', lineage.name])
    modified_time = int(output)

    from plinth import kvstore
    info = kvstore.get_default('letsencrypt_certificate_info', '{}')
    info = json.loads(info)

    certificate_info = info.setdefault(str(lineage), {})
    certificate_info['last_seen_modified_time'] = modified_time

    kvstore.set('letsencrypt_certificate_info', json.dumps(info))