"""/backup: the backup settings, the last run and the local archives, and a run now."""

import configparser
import shutil

import vpnrouter
import vpnrouter_backup
from vpnrouter_status import run


def backup_settings(settings):
    """The backup section as /backup shows it: its settings but pbs_password, with pbs_password_set."""
    return {**{option: value for option, value in settings.items() if option != 'pbs_password'},
            'pbs_password_set': bool(settings['pbs_password'])}


def rclone_remotes():
    """The names of the remotes of vpnrouter_backup.RCLONE_CONFIG; [] when it cannot be read, as when it is encrypted."""
    parser = configparser.ConfigParser(interpolation=None)
    try:
        parser.read(vpnrouter_backup.RCLONE_CONFIG, encoding='utf-8')
    except (OSError, configparser.Error):
        return []
    return parser.sections()


def backup(method, path, body):
    """Answer a /backup request: the HTTP status and the JSON document.

      GET  /backup      {"settings", "state", "archives", "next", "client", "rclone"}: the backup section without
                        pbs_password, with pbs_password_set; the last run (vpnrouter_backup.state), null before the
                        first; the local archives of this host, newest first, [{name, time, size}], [] with the pbs
                        target; the next run of the timer as systemd shows it, null while backups are disabled;
                        whether proxmox-backup-client is installed; and {"installed", "config", "remotes"} of rclone
      PUT  /backup      change any of the settings of the backup section; an empty or absent pbs_password keeps the
                        current secret
      POST /backup/run  start a backup now, without waiting for it; 409 while one runs

    A change is made as /site-to-site makes one, and applied by restarting vpn-router-setup without waiting for it.
    """
    if body == 'invalid' or (body is not None and not isinstance(body, dict)):
        return 400, {'error': 'the body must be a JSON object'}
    body = body or {}
    if (method, path) == ('POST', '/backup/run'):
        if vpnrouter_backup.running():
            return 409, {'error': 'a backup is running'}
        result = run('systemctl', 'start', '--no-block', vpnrouter_backup.UNIT)
        if result is None or result.returncode != 0:
            return 500, {'error': f'the backup cannot be started: {result.stderr.strip() if result else "no systemctl"}'}
        return 202, {'started': True}
    if (method, path) not in (('GET', '/backup'), ('PUT', '/backup')):
        return 404, {'error': f'no route {method} {path}'}
    try:
        if method == 'GET':
            settings = vpnrouter.load_config()['backup']
            timer = run('systemctl', 'show', '-p', 'NextElapseUSecRealtime', '--value', vpnrouter_backup.TIMER)
            next_run = timer.stdout.strip() if timer and timer.returncode == 0 else ''
            return 200, {
                'settings': backup_settings(settings),
                'state': vpnrouter_backup.state() or None,
                'archives': vpnrouter_backup.archives(settings['path']) if settings['target'] == 'local' else [],
                'next': next_run if settings['enabled'] and next_run not in ('', 'n/a') else None,
                'client': vpnrouter_backup.PBS_CLIENT.exists(),
                'rclone': {'installed': shutil.which('rclone') is not None,
                           'config': vpnrouter_backup.RCLONE_CONFIG.is_file(), 'remotes': rclone_remotes()},
            }
        settings = {option: body[option] for option in vpnrouter.SCHEMA['backup'] if option in body}
        if not settings.get('pbs_password'):
            settings.pop('pbs_password', None)
        with vpnrouter.config_lock():
            data = vpnrouter.read_settings()
            current = data.get('backup')
            data['backup'] = {**(current if isinstance(current, dict) else {}), **settings}
            cfg = vpnrouter.with_defaults(data)
            vpnrouter.validate(cfg)
            vpnrouter.save_config(data)
    except vpnrouter.ConfigError as exc:
        return 400, {'error': str(exc)}
    except OSError as exc:
        return 500, {'error': f'the configuration cannot be written: {exc}'}
    except SystemExit as exc:
        return 500, {'error': str(exc.code)}
    run('systemctl', 'restart', '--no-block', 'vpn-router-setup.service')
    return 200, {'settings': backup_settings(cfg['backup'])}