# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4; encoding:utf-8 -*-
#
# Copyright 2020 Jose L. Domingo Lopez <github@24x7linux.com>
#
# This file is part of duplicity.
#
# Duplicity is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2 of the License, or (at your
# option) any later version.
#
# Duplicity 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
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with duplicity; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA


import os
import re
import subprocess

import duplicity.backend
from duplicity.errors import BackendException


class Megav2Backend(duplicity.backend.Backend):
    """ Backend for MEGA.nz cloud storage, only one that works for accounts created since Nov. 2018
         See https://github.com/megous/megatools/issues/411 for more details

         This MEGA backend resorts to official tools (MEGAcmd) as available at https://mega.nz/cmd
         MEGAcmd works through a single binary called "mega-cmd", which talks to a backend server
         "mega-cmd-server", which keeps state (for example, persisting a session). Multiple "mega-*"
         shell wrappers (ie. "mega-ls") exist as the user interface to "mega-cmd" and MEGA API
         The full MEGAcmd User Guide can be found in the software's GitHub page below :
         https://github.com/meganz/MEGAcmd/blob/master/UserGuide.md """

    def __init__(self, parsed_url):
        duplicity.backend.Backend.__init__(self, parsed_url)

        # Sanity check : ensure all the necessary "MEGAcmd" binaries exist
        self._check_binary_exists('mega-login')
        self._check_binary_exists('mega-logout')
        self._check_binary_exists('mega-cmd')
        self._check_binary_exists('mega-cmd-server')
        self._check_binary_exists('mega-ls')
        self._check_binary_exists('mega-mkdir')
        self._check_binary_exists('mega-get')
        self._check_binary_exists('mega-put')
        self._check_binary_exists('mega-rm')

        # "MEGAcmd" does not use a config file, however it is handy to keep one (with the old ".megarc" format) to
        # securely store the username and password
        self._hostname = parsed_url.hostname
        if parsed_url.password is None:
            self._megarc = f"{os.getenv('HOME')}/.megav2rc"
            try:
                conf_file = open(self._megarc, "r")
            except Exception as e:
                raise BackendException(f"No password provided in URL and MEGA configuration file for "
                                       f"duplicity does not exist as '{self._megarc}'")

            myvars = {}
            for line in conf_file:
                name, var = line.partition("=")[::2]
                myvars[name.strip()] = str(var.strip())
            conf_file.close()
            self._username = myvars["Username"]
            self._password = myvars["Password"]

        else:
            self._username = parsed_url.username
            self._password = self.get_password()

        # Remote folder ("MEGAcmd" no longer shows "Root/" at the top of the hierarchy)
        self._folder = f"/{parsed_url.path[1:]}"

        # Only create the remote folder if it doesn't exist yet
        self.mega_login()
        cmd = ['mega-ls', self._folder]
        try:
            self.subprocess_popen(cmd)
        except Exception as e:
            self._makedir(self._folder)

    def _check_binary_exists(self, cmd):
        """Checks that a specified command exists in the running user command path"""

        try:
            # Ignore the output, as we only need the return code
            subprocess.check_output(['which', cmd])
        except Exception as e:
            raise BackendException(f"Command '{cmd}' not found, make sure 'MEGAcmd' tools (https://mega.nz/cmd) "
                                   f"is properly installed and in the running user command path")

    def _makedir(self, path):
        """Creates a remote directory (recursively if necessary)"""

        self.mega_login()
        cmd = ['mega-mkdir', '-p', path]
        try:
            self.subprocess_popen(cmd)
        except Exception as e:
            error_str = str(e)
            if "Folder already exists" in error_str:
                raise BackendException(f"Folder '{path}' could not be created on MEGA because it already exists. "
                                       f"Use another path or remove the folder in MEGA manually")
            else:
                raise BackendException(f"Folder '{path}' could not be created, reason : '{e}'")

    def _put(self, source_path, remote_filename):
        """Uploads file to the specified remote folder (tries to delete it first to make
            sure the new one can be uploaded)"""

        try:
            self.delete(remote_filename.decode())
        except Exception:
            pass
        self.upload(local_file=source_path.get_canonical().decode(), remote_file=remote_filename.decode())

    def _get(self, remote_filename, local_path):
        """Downloads file from the specified remote path"""

        self.download(remote_file=remote_filename.decode(), local_file=local_path.name.decode())

    def _list(self):
        """Lists files in the specified remote path"""

        return self.folder_contents(files_only=True)

    def _delete(self, filename):
        """Deletes file from the specified remote path"""

        self.delete(remote_file=filename.decode())

    def _close(self):
        """Function called when backend is done being used"""

        cmd = ['mega-logout']
        self.subprocess_popen(cmd)

    def mega_login(self):
        """Helper function to call from each method interacting with MEGA to make
            sure a session already exists or one is created to start with"""

        # Abort if command doesn't return in a reasonable time (somehow "mega-session" sometimes
        # doesn't return), and create session if one doesn't exist yet
        try:
            subprocess.check_output('mega-session', timeout=30)
        except subprocess.TimeoutExpired:
            raise BackendException("Timed out while trying to determine if a MEGA session exists")
        except Exception as e:
            cmd = ['mega-login', self._username, self._password]
            try:
                subprocess.check_output(cmd, stderr=subprocess.DEVNULL)
            except Exception as e:
                raise BackendException(f"Could not log in to MEGA, error : '{e}'")

    def folder_contents(self, files_only=False):
        """Lists contents of a remote MEGA path, optionally ignoring subdirectories"""

        cmd = ['mega-ls', '-l', self._folder]

        self.mega_login()
        files = subprocess.check_output(cmd)
        files = files.decode().split('\n')

        # Optionally ignore directories
        if files_only:
            files = [f.split()[5] for f in files if re.search('^-', f)]

        return files

    def download(self, remote_file, local_file):
        """Downloads a file from a remote MEGA path"""

        cmd = ['mega-get', f"{self._folder}/{remote_file}", local_file]
        self.mega_login()
        self.subprocess_popen(cmd)

    def upload(self, local_file, remote_file):
        """Uploads a file to a remote MEGA path"""

        cmd = ['mega-put', local_file, f"{self._folder}/{remote_file}"]
        self.mega_login()
        try:
            self.subprocess_popen(cmd)
        except Exception as e:
            error_str = str(e)
            if "Reached storage quota" in error_str:
                raise BackendException(f"MEGA account over quota, could not write file : '{remote_file}'. "
                                       f"Upgrade your storage at https://mega.nz/pro or remove some data.")
            else:
                raise BackendException(f"Failed writing file '{remote_file}' to MEGA, reason : '{e}'")

    def delete(self, remote_file):
        """Deletes a file from a remote MEGA path"""

        cmd = ['mega-rm', '-f', f"{self._folder}/{remote_file}"]
        self.mega_login()
        self.subprocess_popen(cmd)


duplicity.backend.register_backend('megav2', Megav2Backend)
duplicity.backend.uses_netloc.extend(['megav2'])
