defaults = {
    'openssh': {
        'allowed_users': {
            # Usernames for backup clients always start with 'c-'
            'c-*',
        },
    },
}

@metadata_reactor.provides(
    'backup-server/clients',
)
def get_my_clients(metadata):
    my_clients = {}

    for rnode in repo.nodes:
        if not rnode.has_bundle('backup-client') or rnode.metadata.get('backups/exclude_from_backups', False):
            continue

        my_clients[rnode.name] = {
            'user': rnode.metadata.get('backup-client/user-name'),
        }

    return {
        'backup-server': {
            'clients': my_clients,
        },
    }


@metadata_reactor.provides(
    'backup-server/zfs-base',
    'dm-crypt/encrypted-devices',
    'zfs/pools',
)
def zfs_pool(metadata):
    if not metadata.get('backup-server/encrypted-devices', {}):
        return {}

    crypt_devices = {}
    pool_devices = set()
    unlock_actions = set()

    for number, (device, passphrase) in enumerate(sorted(metadata.get('backup-server/encrypted-devices', {}).items())):
        crypt_devices[device] = {
            'dm-name': f'backup{number}',
            'passphrase': passphrase,
        }
        pool_devices.add(f'/dev/mapper/backup{number}')
        unlock_actions.add(f'action:dm-crypt_open_backup{number}')

    pool_opts = {
        'devices': pool_devices,
    }

    if len(pool_devices) > 2:
        pool_opts['type'] = 'raidz'
    elif len(pool_devices) > 1:
        pool_opts['type'] = 'mirror'

    return {
        'backup-server': {
            'zfs-base': 'backups',
        },
        'dm-crypt': {
            'encrypted-devices': crypt_devices,
        },
        'zfs': {
            'pools': {
                'backups': {
                    'when_creating': {
                        'config': [
                            pool_opts,
                        ],
                    },
                    'needs': unlock_actions,
                    # That's a bit hacky. We do it this way to auto-import
                    # the pool after decrypting the devices. Otherwise
                    # the pool wouldn't exist, which leads to bundlewrap
                    # trying to re-create the pool.
                    # Also, -N to not auto-mount anything.
                    'unless': 'zpool import -N backups',
                },
            },
        }
    }



@metadata_reactor.provides(
    'zfs/datasets',
    'zfs/snapshots/retain_per_dataset',
)
def zfs_datasets_and_snapshots(metadata):
    zfs_datasets = {}
    zfs_retains = {}
    retain_defaults = {
        'weekly': 4,
        'monthly': 6,
    }

    for client in metadata.get('backup-server/clients', {}).keys():
        dataset = '{}/{}'.format(metadata.get('backup-server/zfs-base'), client)

        zfs_datasets[dataset] = {
            'mountpoint': '/srv/backups/{}'.format(client),
            'compression': 'on',
        }

        zfs_retains[dataset] = retain_defaults.copy()

    return {
        'zfs': {
            'datasets': zfs_datasets,
            'snapshots': {
                'retain_per_dataset': zfs_retains,
            },
        },
    }