#!/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 = 5


class AlreadyMountedError(Exception):
    pass


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='Enryption 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')

    # SSH mount actions
    mount = subparsers.add_parser('mount', help='mount an ssh filesystem')
    mount.add_argument('--mountpoint', help='Local mountpoint', required=True)
    umount = subparsers.add_parser('umount',
                                   help='unmount an ssh filesystem')
    umount.add_argument('--mountpoint', help='Mountpoint to unmount',
                        required=True)
    is_mounted = subparsers.add_parser('is-mounted',
                                       help='Check whether an sshfs is mouned')
    is_mounted.add_argument('--mountpoint', help='Mountpoint to check',
                            required=True)

    for cmd in [info, init, list_repo, create_archive, delete_archive,
                export_tar, get_archive_apps, mount, setup]:
        cmd.add_argument('--path', help='Repository or Archive path',
                         required=False)  # TODO: set required to True!
        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)

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

    subparsers.required = True
    return parser.parse_args()


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

        init(arguments.path, 'none', env=env)


def init(path, encryption, env=None):
    """Initialize a local or remote borg repository"""
    # TODO: verify that the repository does not exist?
    # TODO: does remote borg also create folders if they don't exist?
    if encryption != 'none' and 'BORG_PASSPHRASE' not in env:
        raise ValueError('No encryption passphrase provided')
    cmd = ['borg', 'init', '--encryption', encryption, path]
    run(cmd, env=env)


def get_env(arguments):
    """Create encryption and ssh kwargs out of given arguments"""
    env = dict(os.environ, BORG_RELOCATED_REPO_ACCESS_IS_OK='yes')
    if arguments.encryption_passphrase:
        env['BORG_PASSPHRASE'] = arguments.encryption_passphrase
    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'
    return env


def get_sshfs_env(arguments):
    """Create encryption and ssh kwargs out of given arguments"""
    env = dict(os.environ, BORG_RELOCATED_REPO_ACCESS_IS_OK='yes')
    if arguments.encryption_passphrase:
        env['BORG_PASSPHRASE'] = arguments.encryption_passphrase
    if arguments.ssh_keyfile:
        env['SSHKEY'] = arguments.ssh_keyfile
    else:
        password = read_password()
        if password:
            env['SSHPASS'] = password
    return env


def subcommand_init(arguments):
    env = get_env(arguments)
    init(arguments.path, arguments.encryption, env=env)


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


def subcommand_mount(arguments):
    """Show repository information."""
    try:
        validate_mountpoint(arguments.mountpoint)
    except AlreadyMountedError:
        return

    env = get_env(arguments)
    remote_path = arguments.path
    kwargs = {}
    # the shell would expand ~/ to the local home directory
    remote_path = remote_path.replace('~/', '').replace('~', '')
    cmd = ['sshfs', remote_path, arguments.mountpoint, '-o',
           'UserKnownHostsFile=/dev/null', '-o',
           'StrictHostKeyChecking=no']
    timeout = None
    if 'SSHPASS' in env:
        cmd += ['-o', 'password_stdin']
        kwargs['input'] = env['SSHPASS'].encode()
    elif 'SSHKEY' in env:
        cmd += ['-o', 'IdentityFile=$SSHKEY']
        timeout = TIMEOUT
    else:
        raise ValueError('mount requires either SSHPASS or SSHKEY in env')
    subprocess.run(cmd, check=True, env=env, timeout=timeout, **kwargs)


def subcommand_umount(arguments):
    """Show repository information."""
    run(['umount', arguments.mountpoint])


def validate_mountpoint(mountpoint):
    """Check that the folder is empty, and create it if it doesn't exist"""
    if os.path.exists(mountpoint):
        if _is_mounted(mountpoint):
            raise AlreadyMountedError('Mountpoint %s already mounted' %
                                      mountpoint)
        if os.listdir(mountpoint) or not os.path.isdir(mountpoint):
            raise ValueError('Mountpoint %s is not an empty directory' %
                             mountpoint)
    else:
        os.makedirs(mountpoint)


def _is_mounted(mountpoint):
    """Return boolean whether a local directory is a mountpoint."""
    cmd = ['mountpoint', '-q', mountpoint]
    # mountpoint exits with status non-zero if it didn't find a mountpoint
    try:
        subprocess.run(cmd, check=True)
        return True
    except subprocess.CalledProcessError:
        return False


def subcommand_is_mounted(arguments):
    print(json.dumps(_is_mounted(arguments.mountpoint)))


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


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


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


def _extract(archive_path, destination, locations=None):
    """Extract archive contents."""
    prev_dir = os.getcwd()
    env = dict(os.environ, LANG='C.UTF-8')
    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."""
    env = get_env(arguments)
    run(['borg', 'export-tar', arguments.path, '-'],
        env=env)


def _read_archive_file(archive, filepath):
    """Read the content of a file inside an archive"""
    arguments = ['borg', 'extract', archive, filepath, '--stdout']
    return subprocess.check_output(arguments).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)
        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 type(manifest) is list:
        apps = manifest
    elif type(manifest) is 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 t:
        filenames = t.getnames()
        for name in filenames:
            if 'var/lib/plinth/backups-manifests/' in name \
               and name.endswith('.json'):
                manifest_data = t.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."""
    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)


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 ''
    else:
        return ''.join(sys.stdin)


def run(cmd, env=None, check=True):
    """Wrap the command with ssh password or keyfile authentication"""
    # If the remote server asks for a password but no password is
    # provided, we get stuck at asking the password.
    timeout = None
    if env and 'BORG_RSH' in env and 'SSHPASS' not in env:
        timeout = TIMEOUT
    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()