#!/usr/bin/python3
# -*- mode: python -*-
#
# This file is part of FreedomBox.
#
# 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/>.
#
"""
Wrapper to handle backups using borg-backups.
"""

import argparse
import json
import os
import subprocess
import sys
import tarfile

from plinth.modules.backups import MANIFESTS_FOLDER

TIMEOUT = 30


def parse_arguments():
    """Return parsed command line arguments as dictionary."""
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')

    setup = subparsers.add_parser(
        'setup', help='Create repository if it does not already exist')

    init = subparsers.add_parser('init', help='Initialize a repository')
    init.add_argument('--encryption', help='Encryption of the repository',
                      required=True)

    info = subparsers.add_parser('info', help='Show repository information')

    list_repo = subparsers.add_parser('list-repo',
                                      help='List repository contents')

    create_archive = subparsers.add_parser('create-archive',
                                           help='Create archive')
    create_archive.add_argument('--paths', help='Paths to include in archive',
                                nargs='+')

    delete_archive = subparsers.add_parser('delete-archive',
                                           help='Delete archive')

    export_help = 'Export archive contents as tar on stdout'
    export_tar = subparsers.add_parser('export-tar', help=export_help)

    get_archive_apps = subparsers.add_parser(
        'get-archive-apps', help='Get list of apps included in archive')

    restore_archive = subparsers.add_parser(
        'restore-archive', help='Restore files from an archive')
    restore_archive.add_argument('--destination', help='Destination',
                                 required=True)

    for cmd in [
            info, init, list_repo, create_archive, delete_archive, export_tar,
            get_archive_apps, restore_archive, setup
    ]:
        cmd.add_argument('--path', help='Repository or Archive path',
                         required=False)
        cmd.add_argument('--ssh-keyfile', help='Path of private ssh key',
                         default=None)
        cmd.add_argument('--encryption-passphrase',
                         help='Encryption passphrase', default=None)

    get_exported_archive_apps = subparsers.add_parser(
        'get-exported-archive-apps',
        help='Get list of apps included in exported archive file')
    get_exported_archive_apps.add_argument('--path', help='Tarball file path',
                                           required=True)

    restore_exported_archive = subparsers.add_parser(
        'restore-exported-archive',
        help='Restore files from an exported archive')
    restore_exported_archive.add_argument('--path', help='Tarball file path',
                                          required=True)

    subparsers.required = True
    return parser.parse_args()


def subcommand_setup(arguments):
    """Create repository if it does not already exist."""
    try:
        run(['borg', 'info', arguments.path], arguments=arguments, check=True)
    except subprocess.CalledProcessError:
        path = os.path.dirname(arguments.path)
        if not os.path.exists(path):
            os.makedirs(path)

        init_repository(arguments, encryption='none')


def init_repository(arguments, encryption):
    """Initialize a local or remote borg repository"""
    if encryption != 'none':
        if not hasattr(arguments, 'encryption_passphrase') or not \
           arguments.encryption_passphrase:
            raise ValueError('No encryption passphrase provided')

    cmd = ['borg', 'init', '--encryption', encryption, arguments.path]
    run(cmd, arguments=arguments)


def subcommand_init(arguments):
    """Initialize the borg repository."""
    init_repository(arguments, encryption=arguments.encryption)


def subcommand_info(arguments):
    """Show repository information."""
    run(['borg', 'info', '--json', arguments.path], arguments=arguments)


def subcommand_list_repo(arguments):
    """List repository contents."""
    run(['borg', 'list', '--json', arguments.path], arguments=arguments)


def subcommand_create_archive(arguments):
    """Create archive."""
    paths = filter(os.path.exists, arguments.paths)
    run(['borg', 'create', '--json', arguments.path] + list(paths),
        arguments=arguments)


def subcommand_delete_archive(arguments):
    """Delete archive."""
    run(['borg', 'delete', arguments.path], arguments)


def _extract(archive_path, destination, locations=None, env=None):
    """Extract archive contents."""
    if not env:
        env = dict(os.environ)
    env['LANG'] = 'C.UTF-8'

    prev_dir = os.getcwd()
    borg_call = ['borg', 'extract', archive_path]
    # do not extract any files when we get an empty locations list
    if locations is not None:
        borg_call.extend(locations)
    try:
        os.chdir(os.path.expanduser(destination))
        # TODO: with python 3.7 use subprocess.run with the 'capture_output'
        # argument
        process = subprocess.run(borg_call, env=env, stdout=subprocess.PIPE,
                                 stderr=subprocess.PIPE)
        if process.returncode != 0:
            error = process.stderr.decode()
            # Don't fail on the borg error when no files were matched
            if "never matched" not in error:
                raise subprocess.CalledProcessError(process.returncode,
                                                    process.args)
    finally:
        os.chdir(prev_dir)


def subcommand_export_tar(arguments):
    """Export archive contents as tar stream on stdout."""
    run(['borg', 'export-tar', arguments.path, '-', '--tar-filter=gzip'],
        arguments=arguments)


def _read_archive_file(archive, filepath, env=None):
    """Read the content of a file inside an archive"""
    arguments = ['borg', 'extract', archive, filepath, '--stdout']
    return subprocess.check_output(arguments, env=env).decode()


def subcommand_get_archive_apps(arguments):
    """Get list of apps included in archive."""
    env = get_env(arguments)
    manifest_folder = os.path.relpath(MANIFESTS_FOLDER, '/')
    borg_call = [
        'borg', 'list', arguments.path, manifest_folder, '--format',
        '{path}{NEWLINE}'
    ]
    timeout = None
    if 'BORG_RSH' in env and 'SSHPASS' not in env:
        timeout = TIMEOUT
    try:
        manifest_path = subprocess.check_output(borg_call, env=env,
                                                timeout=timeout).decode()\
                                                .strip()
    except subprocess.CalledProcessError:
        sys.exit(1)

    manifest = None
    if manifest_path:
        manifest_data = _read_archive_file(arguments.path, manifest_path,
                                           env=env)
        manifest = json.loads(manifest_data)
    if manifest:
        for app in _get_apps_of_manifest(manifest):
            print(app['name'])


def _get_apps_of_manifest(manifest):
    """
    Get apps of a manifest.
    Supports both dict format as well as list format of plinth <=0.42
    """
    if isinstance(manifest, list):
        apps = manifest
    elif isinstance(manifest, dict) and 'apps' in manifest:
        apps = manifest['apps']
    else:
        raise RuntimeError('Unknown manifest format')

    return apps


def subcommand_get_exported_archive_apps(arguments):
    """Get list of apps included in an exported archive file."""
    manifest = None
    with tarfile.open(arguments.path) as tar_handle:
        filenames = tar_handle.getnames()
        for name in filenames:
            if 'var/lib/plinth/backups-manifests/' in name \
               and name.endswith('.json'):
                manifest_data = tar_handle.extractfile(name).read()
                manifest = json.loads(manifest_data)
                break

    if manifest:
        for app in _get_apps_of_manifest(manifest):
            print(app['name'])


def subcommand_restore_archive(arguments):
    """Restore files from an archive."""
    env = get_env(arguments)
    locations_data = ''.join(sys.stdin)
    _locations = json.loads(locations_data)
    locations = _locations['directories'] + _locations['files']
    locations = [os.path.relpath(location, '/') for location in locations]
    _extract(arguments.path, arguments.destination, locations=locations,
             env=env)


def subcommand_restore_exported_archive(arguments):
    """Restore files from an exported archive."""
    locations_data = ''.join(sys.stdin)
    locations = json.loads(locations_data)

    with tarfile.open(arguments.path) as tar_handle:
        for member in tar_handle.getmembers():
            path = '/' + member.name
            if path in locations['files']:
                tar_handle.extract(member, '/')
            else:
                for directory in locations['directories']:
                    if path.startswith(directory):
                        tar_handle.extract(member, '/')
                        break


def read_password():
    """Read the password from stdin."""
    if sys.stdin.isatty():
        return ''

    return ''.join(sys.stdin)


def get_env(arguments, use_credentials=False):
    """Create encryption and ssh kwargs out of given arguments"""
    env = dict(os.environ, BORG_RELOCATED_REPO_ACCESS_IS_OK='yes')
    # always provide BORG_PASSPHRASE (also if empty) so borg does not get stuck
    # while asking for a passphrase.
    passphrase = arguments.encryption_passphrase or ''
    env['BORG_PASSPHRASE'] = passphrase
    if use_credentials:
        if arguments.ssh_keyfile:
            env['BORG_RSH'] = 'ssh -i %s' % arguments.ssh_keyfile
        else:
            password = read_password()
            if password:
                env['SSHPASS'] = password
                env['BORG_RSH'] = 'sshpass -e ssh -o StrictHostKeyChecking=no'
            else:
                raise ValueError('could not find credentials')

    return env


def run(cmd, arguments, check=True):
    """Wrap the command with ssh password or keyfile authentication"""
    # Set a timeout to not get stuck if the remote server asks for a password.
    timeout = None
    use_credentials = False
    if '@' in arguments.path:
        timeout = TIMEOUT
        use_credentials = True

    env = get_env(arguments, use_credentials=use_credentials)
    subprocess.run(cmd, check=check, env=env, timeout=timeout)


def main():
    """Parse arguments and perform all duties."""
    arguments = parse_arguments()

    subcommand = arguments.subcommand.replace('-', '_')
    subcommand_method = globals()['subcommand_' + subcommand]
    subcommand_method(arguments)


if __name__ == '__main__':
    main()