calibre-web/cps/helper.py

# -*- coding: utf-8 -*-

#  This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)
#    Copyright (C) 2012-2019 cervinko, idalin, SiphonSquirrel, ouzklcn, akushsky,
#                            OzzieIsaacs, bodybybuddha, jkrehm, matthazinski, janeczku
#
#  This program 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 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 General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program. If not, see <http://www.gnu.org/licenses/>.

from __future__ import division, print_function, unicode_literals
import sys
import os
import io
import mimetypes
import re
import shutil
import time
import unicodedata
from datetime import datetime, timedelta
from tempfile import gettempdir

import requests
from babel.dates import format_datetime
from babel.units import format_unit
from flask import send_from_directory, make_response, redirect, abort, url_for
from flask_babel import gettext as _
from flask_login import current_user
from sqlalchemy.sql.expression import true, false, and_, text, func
from werkzeug.datastructures import Headers
from werkzeug.security import generate_password_hash

try:
    from urllib.parse import quote
except ImportError:
    from urllib import quote

try:
    import unidecode
    use_unidecode = True
except ImportError:
    use_unidecode = False

from . import calibre_db
from .tasks.convert import TaskConvert
from . import logger, config, get_locale, db, ub
from . import gdriveutils as gd
from .constants import STATIC_DIR as _STATIC_DIR
from .subproc_wrapper import process_wait
from .services.worker import WorkerThread, STAT_WAITING, STAT_FAIL, STAT_STARTED, STAT_FINISH_SUCCESS
from .tasks.mail import TaskEmail

log = logger.create()

try:
    from wand.image import Image
    from wand.exceptions import MissingDelegateError
    use_IM = True
except (ImportError, RuntimeError) as e:
    log.debug('Cannot import Image, generating covers from non jpg files will not work: %s', e)
    use_IM = False
    MissingDelegateError = BaseException


# Convert existing book entry to new format
def convert_book_format(book_id, calibrepath, old_book_format, new_book_format, user_id, kindle_mail=None):
    book = calibre_db.get_book(book_id)
    data = calibre_db.get_book_format(book.id, old_book_format)
    file_path = os.path.join(calibrepath, book.path, data.name)
    if not data:
        error_message = _(u"%(format)s format not found for book id: %(book)d", format=old_book_format, book=book_id)
        log.error("convert_book_format: %s", error_message)
        return error_message
    if config.config_use_google_drive:
        if not gd.getFileFromEbooksFolder(book.path, data.name + "." + old_book_format.lower()):
            error_message = _(u"%(format)s not found on Google Drive: %(fn)s",
                              format=old_book_format, fn=data.name + "." + old_book_format.lower())
            return error_message
    else:
        if not os.path.exists(file_path + "." + old_book_format.lower()):
            error_message = _(u"%(format)s not found: %(fn)s",
                              format=old_book_format, fn=data.name + "." + old_book_format.lower())
            return error_message
    # read settings and append converter task to queue
    if kindle_mail:
        settings = config.get_mail_settings()
        settings['subject'] = _('Send to Kindle')  # pretranslate Subject for e-mail
        settings['body'] = _(u'This e-mail has been sent via Calibre-Web.')
    else:
        settings = dict()
    txt = (u"%s -> %s: %s" % (
           old_book_format,
           new_book_format,
           "<a href=\"" + url_for('web.show_book', book_id=book.id) + "\">" + book.title + "</a>"))
    settings['old_book_format'] = old_book_format
    settings['new_book_format'] = new_book_format
    WorkerThread.add(user_id, TaskConvert(file_path, book.id, txt, settings, kindle_mail, user_id))
    return None


def send_test_mail(kindle_mail, user_name):
    WorkerThread.add(user_name, TaskEmail(_(u'Calibre-Web test e-mail'), None, None,
                     config.get_mail_settings(), kindle_mail, _(u"Test e-mail"),
                                          _(u'This e-mail has been sent via Calibre-Web.')))
    return


# Send registration email or password reset email, depending on parameter resend (False means welcome email)
def send_registration_mail(e_mail, user_name, default_password, resend=False):
    txt = "Hello %s!\r\n" % user_name
    if not resend:
        txt += "Your new account at Calibre-Web has been created. Thanks for joining us!\r\n"
    txt += "Please log in to your account using the following informations:\r\n"
    txt += "User name: %s\r\n" % user_name
    txt += "Password: %s\r\n" % default_password
    txt += "Don't forget to change your password after first login.\r\n"
    txt += "Sincerely\r\n\r\n"
    txt += "Your Calibre-Web team"
    WorkerThread.add(None, TaskEmail(
        subject=_(u'Get Started with Calibre-Web'),
        filepath=None,
        attachment=None,
        settings=config.get_mail_settings(),
        recipient=e_mail,
        taskMessage=_(u"Registration e-mail for user: %(name)s", name=user_name),
        text=txt
    ))
    return


def check_send_to_kindle_with_converter(formats):
    bookformats = list()
    if 'EPUB' in formats and 'MOBI' not in formats:
        bookformats.append({'format': 'Mobi',
                            'convert': 1,
                            'text': _('Convert %(orig)s to %(format)s and send to Kindle',
                                      orig='Epub',
                                      format='Mobi')})
    if 'AZW3' in formats and not 'MOBI' in formats:
        bookformats.append({'format': 'Mobi',
                            'convert': 2,
                            'text': _('Convert %(orig)s to %(format)s and send to Kindle',
                                      orig='Azw3',
                                      format='Mobi')})
    return bookformats


def check_send_to_kindle(entry):
    """
        returns all available book formats for sending to Kindle
    """
    formats = list()
    bookformats = list()
    if len(entry.data):
        for ele in iter(entry.data):
            if ele.uncompressed_size < config.mail_size:
                formats.append(ele.format)
        if 'MOBI' in formats:
            bookformats.append({'format': 'Mobi',
                                'convert': 0,
                                'text': _('Send %(format)s to Kindle', format='Mobi')})
        if 'PDF' in formats:
            bookformats.append({'format': 'Pdf',
                                'convert': 0,
                                'text': _('Send %(format)s to Kindle', format='Pdf')})
        if 'AZW' in formats:
            bookformats.append({'format': 'Azw',
                                'convert': 0,
                                'text': _('Send %(format)s to Kindle', format='Azw')})
        if config.config_converterpath:
            bookformats.extend(check_send_to_kindle_with_converter(formats))
        return bookformats
    else:
        log.error(u'Cannot find book entry %d', entry.id)
        return None


# Check if a reader is existing for any of the book formats, if not, return empty list, otherwise return
# list with supported formats
def check_read_formats(entry):
    EXTENSIONS_READER = {'TXT', 'PDF', 'EPUB', 'CBZ', 'CBT', 'CBR', 'DJVU'}
    bookformats = list()
    if len(entry.data):
        for ele in iter(entry.data):
            if ele.format.upper() in EXTENSIONS_READER:
                bookformats.append(ele.format.lower())
    return bookformats


# Files are processed in the following order/priority:
# 1: If Mobi file is existing, it's directly send to kindle email,
# 2: If Epub file is existing, it's converted and send to kindle email,
# 3: If Pdf file is existing, it's directly send to kindle email
def send_mail(book_id, book_format, convert, kindle_mail, calibrepath, user_id):
    """Send email with attachments"""
    book = calibre_db.get_book(book_id)

    if convert == 1:
        # returns None if success, otherwise errormessage
        return convert_book_format(book_id, calibrepath, u'epub', book_format.lower(), user_id, kindle_mail)
    if convert == 2:
        # returns None if success, otherwise errormessage
        return convert_book_format(book_id, calibrepath, u'azw3', book_format.lower(), user_id, kindle_mail)

    for entry in iter(book.data):
        if entry.format.upper() == book_format.upper():
            converted_file_name = entry.name + '.' + book_format.lower()
            WorkerThread.add(user_id, TaskEmail(_(u"Send to Kindle"), book.path, converted_file_name,
                             config.get_mail_settings(), kindle_mail,
                             _(u"E-mail: %(book)s", book=book.title), _(u'This e-mail has been sent via Calibre-Web.')))
            return
    return _(u"The requested file could not be read. Maybe wrong permissions?")


def get_valid_filename(value, replace_whitespace=True):
    """
    Returns the given string converted to a string that can be used for a clean
    filename. Limits num characters to 128 max.
    """
    if value[-1:] == u'.':
        value = value[:-1]+u'_'
    value = value.replace("/", "_").replace(":", "_").strip('\0')
    if use_unidecode:
        value = (unidecode.unidecode(value))
    else:
        value = value.replace(u'§', u'SS')
        value = value.replace(u'ß', u'ss')
        value = unicodedata.normalize('NFKD', value)
        re_slugify = re.compile(r'[\W\s-]', re.UNICODE)
        if isinstance(value, str):  # Python3 str, Python2 unicode
            value = re_slugify.sub('', value)
        else:
            value = unicode(re_slugify.sub('', value))
    if replace_whitespace:
        #  *+:\"/<>? are replaced by _
        value = re.sub(r'[*+:\\\"/<>?]+', u'_', value, flags=re.U)
        # pipe has to be replaced with comma
        value = re.sub(r'[|]+', u',', value, flags=re.U)
    value = value[:128].strip()
    if not value:
        raise ValueError("Filename cannot be empty")
    if sys.version_info.major == 3:
        return value
    else:
        return value.decode('utf-8')


def split_authors(values):
    authors_list = []
    for value in values:
        authors = re.split('[&;]', value)
        for author in authors:
            commas = author.count(',')
            if commas == 1:
                author_split = author.split(',')
                authors_list.append(author_split[1].strip() + ' ' + author_split[0].strip())
            elif commas > 1:
                authors_list.extend([x.strip() for x in author.split(',')])
            else:
                authors_list.append(author.strip())
    return authors_list


def get_sorted_author(value):
    try:
        if ',' not in value:
            regexes = [r"^(JR|SR)\.?$", r"^I{1,3}\.?$", r"^IV\.?$"]
            combined = "(" + ")|(".join(regexes) + ")"
            value = value.split(" ")
            if re.match(combined, value[-1].upper()):
                if len(value) > 1:
                    value2 = value[-2] + ", " + " ".join(value[:-2]) + " " + value[-1]
                else:
                    value2 = value[0]
            elif len(value) == 1:
                value2 = value[0]
            else:
                value2 = value[-1] + ", " + " ".join(value[:-1])
        else:
            value2 = value
    except Exception as ex:
        log.error("Sorting author %s failed: %s", value, ex)
        if isinstance(list, value2):
            value2 = value[0]
        else:
            value2 = value
    return value2


# Deletes a book fro the local filestorage, returns True if deleting is successfull, otherwise false
def delete_book_file(book, calibrepath, book_format=None):
    # check that path is 2 elements deep, check that target path has no subfolders
    if book.path.count('/') == 1:
        path = os.path.join(calibrepath, book.path)
        if book_format:
            for file in os.listdir(path):
                if file.upper().endswith("."+book_format):
                    os.remove(os.path.join(path, file))
            return True, None
        else:
            if os.path.isdir(path):
                try:
                    for root, folders, files in os.walk(path):
                        for f in files:
                            os.unlink(os.path.join(root, f))
                        if len(folders):
                            log.warning("Deleting book {} failed, path {} has subfolders: {}".format(book.id,
                                        book.path, folders))
                            return True, _("Deleting bookfolder for book %(id)s failed, path has subfolders: %(path)s",
                                           id=book.id,
                                           path=book.path)
                    shutil.rmtree(path)
                except (IOError, OSError) as e:
                    log.error("Deleting book %s failed: %s", book.id, e)
                    return False, _("Deleting book %(id)s failed: %(message)s", id=book.id, message=e)
                authorpath = os.path.join(calibrepath, os.path.split(book.path)[0])
                if not os.listdir(authorpath):
                    try:
                        shutil.rmtree(authorpath)
                    except (IOError, OSError) as e:
                        log.error("Deleting authorpath for book %s failed: %s", book.id, e)
                return True, None

    log.error("Deleting book %s from database only, book path in database not valid: %s",
              book.id, book.path)
    return True, _("Deleting book %(id)s from database only, book path in database not valid: %(path)s",
                   id=book.id,
                   path=book.path)


# Moves files in file storage during author/title rename, or from temp dir to file storage
def update_dir_structure_file(book_id, calibrepath, first_author, orignal_filepath, db_filename):
    # get book database entry from id, if original path overwrite source with original_filepath
    localbook = calibre_db.get_book(book_id)
    if orignal_filepath:
        path = orignal_filepath
    else:
        path = os.path.join(calibrepath, localbook.path)

    # Create (current) authordir and titledir from database
    authordir = localbook.path.split('/')[0]
    titledir = localbook.path.split('/')[1]

    # Create new_authordir from parameter or from database
    # Create new titledir from database and add id
    if first_author:
        new_authordir = get_valid_filename(first_author)
    else:
        new_authordir = get_valid_filename(localbook.authors[0].name)
    new_titledir = get_valid_filename(localbook.title) + " (" + str(book_id) + ")"

    if titledir != new_titledir or authordir != new_authordir or orignal_filepath:
        new_path = os.path.join(calibrepath, new_authordir, new_titledir)
        new_name = get_valid_filename(localbook.title) + ' - ' + get_valid_filename(new_authordir)
        try:
            if orignal_filepath:
                if not os.path.isdir(new_path):
                    os.makedirs(new_path)
                shutil.move(os.path.normcase(path), os.path.normcase(os.path.join(new_path, db_filename)))
                log.debug("Moving title: %s to %s/%s", path, new_path, new_name)
                # Check new path is not valid path
            else:
                if not os.path.exists(new_path):
                    # move original path to new path
                    log.debug("Moving title: %s to %s", path, new_path)
                    shutil.move(os.path.normcase(path), os.path.normcase(new_path))
                else: # path is valid copy only files to new location (merge)
                    log.info("Moving title: %s into existing: %s", path, new_path)
                    # Take all files and subfolder from old path (strange command)
                    for dir_name, __, file_list in os.walk(path):
                        for file in file_list:
                            shutil.move(os.path.normcase(os.path.join(dir_name, file)),
                                            os.path.normcase(os.path.join(new_path + dir_name[len(path):], file)))
                            # os.unlink(os.path.normcase(os.path.join(dir_name, file)))
            # change location in database to new author/title path
            localbook.path = os.path.join(new_authordir, new_titledir).replace('\\','/')
        except (OSError) as ex:
            log.error("Rename title from: %s to %s: %s", path, new_path, ex)
            log.debug(ex, exc_info=True)
            return _("Rename title from: '%(src)s' to '%(dest)s' failed with error: %(error)s",
                     src=path, dest=new_path, error=str(ex))

        # Rename all files from old names to new names
        try:
            for file_format in localbook.data:
                shutil.move(os.path.normcase(
                    os.path.join(new_path, file_format.name + '.' + file_format.format.lower())),
                    os.path.normcase(os.path.join(new_path, new_name + '.' + file_format.format.lower())))
                file_format.name = new_name
            if not orignal_filepath and len(os.listdir(os.path.dirname(path))) == 0:
                shutil.rmtree(os.path.dirname(path))
        except (OSError) as ex:
            log.error("Rename file in path %s to %s: %s", new_path, new_name, ex)
            log.debug(ex, exc_info=True)
            return _("Rename file in path '%(src)s' to '%(dest)s' failed with error: %(error)s",
                     src=new_path, dest=new_name, error=str(ex))
    return False

def update_dir_structure_gdrive(book_id, first_author):
    error = False
    book = calibre_db.get_book(book_id)
    path = book.path

    authordir = book.path.split('/')[0]
    if first_author:
        new_authordir = get_valid_filename(first_author)
    else:
        new_authordir = get_valid_filename(book.authors[0].name)
    titledir = book.path.split('/')[1]
    new_titledir = get_valid_filename(book.title) + u" (" + str(book_id) + u")"

    if titledir != new_titledir:
        gFile = gd.getFileFromEbooksFolder(os.path.dirname(book.path), titledir)
        if gFile:
            gFile['title'] = new_titledir
            gFile.Upload()
            book.path = book.path.split('/')[0] + u'/' + new_titledir
            path = book.path
            gd.updateDatabaseOnEdit(gFile['id'], book.path)     # only child folder affected
        else:
            error = _(u'File %(file)s not found on Google Drive', file=book.path)  # file not found

    if authordir != new_authordir:
        gFile = gd.getFileFromEbooksFolder(os.path.dirname(book.path), new_titledir)
        if gFile:
            gd.moveGdriveFolderRemote(gFile, new_authordir)
            book.path = new_authordir + u'/' + book.path.split('/')[1]
            path = book.path
            gd.updateDatabaseOnEdit(gFile['id'], book.path)
        else:
            error = _(u'File %(file)s not found on Google Drive', file=authordir)  # file not found
    # Rename all files from old names to new names

    if authordir != new_authordir or titledir != new_titledir:
        new_name = get_valid_filename(book.title) + u' - ' + get_valid_filename(new_authordir)
        for file_format in book.data:
            gFile = gd.getFileFromEbooksFolder(path, file_format.name + u'.' + file_format.format.lower())
            if not gFile:
                error = _(u'File %(file)s not found on Google Drive', file=file_format.name)  # file not found
                break
            gd.moveGdriveFileRemote(gFile, new_name + u'.' + file_format.format.lower())
            file_format.name = new_name
    return error


def delete_book_gdrive(book, book_format):
    error = None
    if book_format:
        name = ''
        for entry in book.data:
            if entry.format.upper() == book_format:
                name = entry.name + '.' + book_format
        gFile = gd.getFileFromEbooksFolder(book.path, name)
    else:
        gFile = gd.getFileFromEbooksFolder(os.path.dirname(book.path), book.path.split('/')[1])
    if gFile:
        gd.deleteDatabaseEntry(gFile['id'])
        gFile.Trash()
    else:
        error = _(u'Book path %(path)s not found on Google Drive', path=book.path)  # file not found

    return error is None, error


def reset_password(user_id):
    existing_user = ub.session.query(ub.User).filter(ub.User.id == user_id).first()
    if not existing_user:
        return 0, None
    if not config.get_mail_server_configured():
        return 2, None
    try:
        password = generate_random_password()
        existing_user.password = generate_password_hash(password)
        ub.session.commit()
        send_registration_mail(existing_user.email, existing_user.name, password, True)
        return 1, existing_user.name
    except Exception:
        ub.session.rollback()
        return 0, None


def generate_random_password():
    s = "abcdefghijklmnopqrstuvwxyz01234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%&*()?"
    passlen = 8
    if sys.version_info < (3, 0):
        return "".join(s[ord(c) % len(s)] for c in os.urandom(passlen))
    else:
        return "".join(s[c % len(s)] for c in os.urandom(passlen))


def uniq(inpt):
    output = []
    inpt = [ " ".join(inp.split()) for inp in inpt]
    for x in inpt:
        if x not in output:
            output.append(x)
    return output

def check_email(email):
    email = valid_email(email)
    if ub.session.query(ub.User).filter(func.lower(ub.User.email) == email.lower()).first():
        log.error(u"Found an existing account for this e-mail address")
        raise Exception(_(u"Found an existing account for this e-mail address"))
    return email


def check_username(username):
    username = username.strip()
    if ub.session.query(ub.User).filter(func.lower(ub.User.name) == username.lower()).scalar():
        log.error(u"This username is already taken")
        raise Exception (_(u"This username is already taken"))
    return username


def valid_email(email):
    email = email.strip()
    # Regex according to https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/email#validation
    if not re.search(r"^[\w.!#$%&'*+\\/=?^_`{|}~-]+@[\w](?:[\w-]{0,61}[\w])?(?:\.[\w](?:[\w-]{0,61}[\w])?)*$",
                     email):
        log.error(u"Invalid e-mail address format")
        raise Exception(_(u"Invalid e-mail address format"))
    return email

# ################################# External interface #################################


def update_dir_stucture(book_id, calibrepath, first_author=None, orignal_filepath=None, db_filename=None):
    if config.config_use_google_drive:
        return update_dir_structure_gdrive(book_id, first_author)
    else:
        return update_dir_structure_file(book_id, calibrepath, first_author, orignal_filepath, db_filename)


def delete_book(book, calibrepath, book_format):
    if config.config_use_google_drive:
        return delete_book_gdrive(book, book_format)
    else:
        return delete_book_file(book, calibrepath, book_format)


def get_cover_on_failure(use_generic_cover):
    if use_generic_cover:
        return send_from_directory(_STATIC_DIR, "generic_cover.jpg")
    else:
        return None


def get_book_cover(book_id):
    book = calibre_db.get_filtered_book(book_id, allow_show_archived=True)
    return get_book_cover_internal(book, use_generic_cover_on_failure=True)


def get_book_cover_with_uuid(book_uuid,
                             use_generic_cover_on_failure=True):
    book = calibre_db.get_book_by_uuid(book_uuid)
    return get_book_cover_internal(book, use_generic_cover_on_failure)


def get_book_cover_internal(book, use_generic_cover_on_failure):
    if book and book.has_cover:
        if config.config_use_google_drive:
            try:
                if not gd.is_gdrive_ready():
                    return get_cover_on_failure(use_generic_cover_on_failure)
                path = gd.get_cover_via_gdrive(book.path)
                if path:
                    return redirect(path)
                else:
                    log.error('%s/cover.jpg not found on Google Drive', book.path)
                    return get_cover_on_failure(use_generic_cover_on_failure)
            except Exception as ex:
                log.debug_or_exception(ex)
                return get_cover_on_failure(use_generic_cover_on_failure)
        else:
            cover_file_path = os.path.join(config.config_calibre_dir, book.path)
            if os.path.isfile(os.path.join(cover_file_path, "cover.jpg")):
                return send_from_directory(cover_file_path, "cover.jpg")
            else:
                return get_cover_on_failure(use_generic_cover_on_failure)
    else:
        return get_cover_on_failure(use_generic_cover_on_failure)


# saves book cover from url
def save_cover_from_url(url, book_path):
    try:
        img = requests.get(url, timeout=(10, 200))      # ToDo: Error Handling
        img.raise_for_status()
        return save_cover(img, book_path)
    except (requests.exceptions.HTTPError,
            requests.exceptions.ConnectionError,
            requests.exceptions.Timeout) as ex:
        log.info(u'Cover Download Error %s', ex)
        return False, _("Error Downloading Cover")
    except MissingDelegateError as ex:
        log.info(u'File Format Error %s', ex)
        return False, _("Cover Format Error")


def save_cover_from_filestorage(filepath, saved_filename, img):
    # check if file path exists, otherwise create it, copy file to calibre path and delete temp file
    if not os.path.exists(filepath):
        try:
            os.makedirs(filepath)
        except OSError:
            log.error(u"Failed to create path for cover")
            return False, _(u"Failed to create path for cover")
    try:
        # upload of jgp file without wand
        if isinstance(img, requests.Response):
            with open(os.path.join(filepath, saved_filename), 'wb') as f:
                f.write(img.content)
        else:
            if hasattr(img, "metadata"):
                # upload of jpg/png... via url
                img.save(filename=os.path.join(filepath, saved_filename))
                img.close()
            else:
                # upload of jpg/png... from hdd
                img.save(os.path.join(filepath, saved_filename))
    except (IOError, OSError):
        log.error(u"Cover-file is not a valid image file, or could not be stored")
        return False, _(u"Cover-file is not a valid image file, or could not be stored")
    return True, None


# saves book cover to gdrive or locally
def save_cover(img, book_path):
    content_type = img.headers.get('content-type')

    if use_IM:
        if content_type not in ('image/jpeg', 'image/png', 'image/webp', 'image/bmp'):
            log.error("Only jpg/jpeg/png/webp/bmp files are supported as coverfile")
            return False, _("Only jpg/jpeg/png/webp/bmp files are supported as coverfile")
        # convert to jpg because calibre only supports jpg
        if content_type != 'image/jpg':
            if hasattr(img, 'stream'):
                imgc = Image(blob=img.stream)
            else:
                imgc = Image(blob=io.BytesIO(img.content))
            imgc.format = 'jpeg'
            imgc.transform_colorspace("rgb")
            img = imgc
    else:
        if content_type not in 'image/jpeg':
            log.error("Only jpg/jpeg files are supported as coverfile")
            return False, _("Only jpg/jpeg files are supported as coverfile")

    if config.config_use_google_drive:
        tmp_dir = os.path.join(gettempdir(), 'calibre_web')

        if not os.path.isdir(tmp_dir):
            os.mkdir(tmp_dir)
        ret, message = save_cover_from_filestorage(tmp_dir, "uploaded_cover.jpg", img)
        if ret is True:
            gd.uploadFileToEbooksFolder(os.path.join(book_path, 'cover.jpg').replace("\\","/"),
                                        os.path.join(tmp_dir, "uploaded_cover.jpg"))
            log.info("Cover is saved on Google Drive")
            return True, None
        else:
            return False, message
    else:
        return save_cover_from_filestorage(os.path.join(config.config_calibre_dir, book_path), "cover.jpg", img)


def do_download_file(book, book_format, client, data, headers):
    if config.config_use_google_drive:
        startTime = time.time()
        df = gd.getFileFromEbooksFolder(book.path, data.name + "." + book_format)
        log.debug('%s', time.time() - startTime)
        if df:
            return gd.do_gdrive_download(df, headers)
        else:
            abort(404)
    else:
        filename = os.path.join(config.config_calibre_dir, book.path)
        if not os.path.isfile(os.path.join(filename, data.name + "." + book_format)):
            # ToDo: improve error handling
            log.error('File not found: %s', os.path.join(filename, data.name + "." + book_format))

        if client == "kobo" and book_format == "kepub":
            headers["Content-Disposition"] = headers["Content-Disposition"].replace(".kepub", ".kepub.epub")

        response = make_response(send_from_directory(filename, data.name + "." + book_format))
        # ToDo Check headers parameter
        for element in headers:
            response.headers[element[0]] = element[1]
        log.info('Downloading file: {}'.format(os.path.join(filename, data.name + "." + book_format)))
        return response

##################################


def check_unrar(unrarLocation):
    if not unrarLocation:
        return

    if not os.path.exists(unrarLocation):
        return _('Unrar binary file not found')

    try:
        if sys.version_info < (3, 0):
            unrarLocation = unrarLocation.encode(sys.getfilesystemencoding())
        unrarLocation = [unrarLocation]
        value = process_wait(unrarLocation, pattern='UNRAR (.*) freeware')
        if value:
            version = value.group(1)
            log.debug("unrar version %s", version)

    except (OSError, UnicodeDecodeError) as err:
        log.debug_or_exception(err)
        return _('Error excecuting UnRar')


def json_serial(obj):
    """JSON serializer for objects not serializable by default json code"""

    if isinstance(obj, datetime):
        return obj.isoformat()
    if isinstance(obj, timedelta):
        return {
            '__type__': 'timedelta',
            'days': obj.days,
            'seconds': obj.seconds,
            'microseconds': obj.microseconds,
        }
    raise TypeError("Type %s not serializable" % type(obj))


# helper function for displaying the runtime of tasks
def format_runtime(runtime):
    retVal = ""
    if runtime.days:
        retVal = format_unit(runtime.days, 'duration-day', length="long", locale=get_locale()) + ', '
    mins, seconds = divmod(runtime.seconds, 60)
    hours, minutes = divmod(mins, 60)
    # ToDo: locale.number_symbols._data['timeSeparator'] -> localize time separator ?
    if hours:
        retVal += '{:d}:{:02d}:{:02d}s'.format(hours, minutes, seconds)
    elif minutes:
        retVal += '{:2d}:{:02d}s'.format(minutes, seconds)
    else:
        retVal += '{:2d}s'.format(seconds)
    return retVal


# helper function to apply localize status information in tasklist entries
def render_task_status(tasklist):
    renderedtasklist = list()
    for __, user, __, task in tasklist:
        if user == current_user.name or current_user.role_admin():
            ret = {}
            if task.start_time:
                ret['starttime'] = format_datetime(task.start_time, format='short', locale=get_locale())
                ret['runtime'] = format_runtime(task.runtime)

            # localize the task status
            if isinstance(task.stat, int):
                if task.stat == STAT_WAITING:
                    ret['status'] = _(u'Waiting')
                elif task.stat == STAT_FAIL:
                    ret['status'] = _(u'Failed')
                elif task.stat == STAT_STARTED:
                    ret['status'] = _(u'Started')
                elif task.stat == STAT_FINISH_SUCCESS:
                    ret['status'] = _(u'Finished')
                else:
                    ret['status'] = _(u'Unknown Status')

            ret['taskMessage'] = "{}: {}".format(_(task.name), task.message)
            ret['progress'] = "{} %".format(int(task.progress * 100))
            ret['user'] = user
            renderedtasklist.append(ret)

    return renderedtasklist


def tags_filters():
    negtags_list = current_user.list_denied_tags()
    postags_list = current_user.list_allowed_tags()
    neg_content_tags_filter = false() if negtags_list == [''] else db.Tags.name.in_(negtags_list)
    pos_content_tags_filter = true() if postags_list == [''] else db.Tags.name.in_(postags_list)
    return and_(pos_content_tags_filter, ~neg_content_tags_filter)


# checks if domain is in database (including wildcards)
# example SELECT * FROM @TABLE WHERE  'abcdefg' LIKE Name;
# from https://code.luasoftware.com/tutorials/flask/execute-raw-sql-in-flask-sqlalchemy/
# in all calls the email address is checked for validity
def check_valid_domain(domain_text):
    sql = "SELECT * FROM registration WHERE (:domain LIKE domain and allow = 1);"
    result = ub.session.query(ub.Registration).from_statement(text(sql)).params(domain=domain_text).all()
    if not len(result):
        return False
    sql = "SELECT * FROM registration WHERE (:domain LIKE domain and allow = 0);"
    result = ub.session.query(ub.Registration).from_statement(text(sql)).params(domain=domain_text).all()
    return not len(result)


def get_cc_columns(filter_config_custom_read=False):
    tmpcc = calibre_db.session.query(db.Custom_Columns)\
        .filter(db.Custom_Columns.datatype.notin_(db.cc_exceptions)).all()
    cc = []
    r = None
    if config.config_columns_to_ignore:
        r = re.compile(config.config_columns_to_ignore)

    for col in tmpcc:
        if filter_config_custom_read and config.config_read_column and config.config_read_column == col.id:
            continue
        if r and r.match(col.name):
            continue
        cc.append(col)

    return cc


def get_download_link(book_id, book_format, client):
    book_format = book_format.split(".")[0]
    book = calibre_db.get_filtered_book(book_id)
    if book:
        data1 = calibre_db.get_book_format(book.id, book_format.upper())
    else:
        log.error("Book id {} not found for downloading".format(book_id))
        abort(404)
    if data1:
        # collect downloaded books only for registered user and not for anonymous user
        if current_user.is_authenticated:
            ub.update_download(book_id, int(current_user.id))
        file_name = book.title
        if len(book.authors) > 0:
            file_name = book.authors[0].name + '_' + file_name
        file_name = get_valid_filename(file_name)
        headers = Headers()
        headers["Content-Type"] = mimetypes.types_map.get('.' + book_format, "application/octet-stream")
        headers["Content-Disposition"] = "attachment; filename=%s.%s; filename*=UTF-8''%s.%s" % (
            quote(file_name.encode('utf-8')), book_format, quote(file_name.encode('utf-8')), book_format)
        return do_download_file(book, book_format, client, data1, headers)
    else:
        abort(404)