#!/usr/bin/env python3

# Copyright 2018 Jay Kamat <jaygkamat@gmail.com>
#
# This file is part of qutebrowser.
#
# qutebrowser 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.
#
# qutebrowser 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 qutebrowser.  If not, see <http://www.gnu.org/licenses/>.

"""This userscript allows for insertion of usernames and passwords from keepass
databases using pykeepass. Since it is a userscript, it must be run from
qutebrowser.

A sample invocation of this script is:

:spawn --userscript qute-keepass -p ~/KeePassFiles/MainDatabase.kdbx

And a sample binding

:bind --mode=insert <ctrl-i> spawn --userscript qute-keepass -p ~/KeePassFiles/MainDatabase.kdbx

-p or --path is a required argument.

--keyfile-path allows you to specify a keepass keyfile. If you only use a
keyfile, also add --no-password as well. Specifying --no-password without
--keyfile-path will lead to an error.

login information is inserted using :insert-text and :fake-key <Tab>, which
means you must have a cursor in position before initiating this userscript. If
you do not do this, you will get 'element not editable' errors.

If keepass takes a while to open the DB, you might want to consider reducing
the number of transform rounds in your database settings.

Dependencies: pykeepass (in python3), PyQt5. Without pykeepass, you will get an
exit code of 100.

********************!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!******************

WARNING: The login details are viewable as plaintext in qutebrowser's debug log
(qute://log) and could be compromised if you decide to submit a crash report!

********************!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!******************

"""

# pylint: disable=bad-builtin

import argparse
import enum
import functools
import os
import shlex
import subprocess
import sys

from PyQt5.QtCore import QUrl
from PyQt5.QtWidgets import QApplication, QInputDialog, QLineEdit

try:
    import pykeepass
except ImportError as e:
    print("pykeepass not found: {}".format(str(e)), file=sys.stderr)

    # Since this is a common error, try to print it to the FIFO if we can.
    if 'QUTE_FIFO' in os.environ:
        with open(os.environ['QUTE_FIFO'], 'w') as fifo:
            fifo.write('message-error "pykeepass failed to be imported."\n')
            fifo.flush()
    sys.exit(100)

argument_parser = argparse.ArgumentParser(
    description="Fill passwords using keepass.",
    formatter_class=argparse.RawDescriptionHelpFormatter,
    epilog=__doc__)
argument_parser.add_argument('url', nargs='?', default=os.getenv('QUTE_URL'))
argument_parser.add_argument('--path', '-p', required=True,
                             help='Path to the keepass db.')
argument_parser.add_argument('--keyfile-path', '-k', default=None,
                             help='Path to a keepass keyfile')
argument_parser.add_argument(
    '--no-password', action='store_true',
    help='Supply if no password is required to unlock this database. '
    'Only allowed with --keyfile-path')
argument_parser.add_argument(
    '--dmenu-invocation', '-d', default='dmenu',
    help='Invocation used to execute a dmenu-provider')
argument_parser.add_argument(
    '--dmenu-format', '-f', default='{title}: {username}',
    help='Format string for keys to display in dmenu.'
    ' Must generate a unique string.')
argument_parser.add_argument(
    '--no-insert-mode', '-n', dest='insert_mode', action='store_false',
    help="Don't automatically enter insert mode")
argument_parser.add_argument(
    '--io-encoding', '-i', default='UTF-8',
    help='Encoding used to communicate with subprocesses')
group = argument_parser.add_mutually_exclusive_group()
group.add_argument('--username-fill-only', '-e',
                   action='store_true', help='Only insert username')
group.add_argument('--password-fill-only', '-w',
                   action='store_true', help='Only insert password')

CMD_DELAY = 50


class ExitCodes(enum.IntEnum):
    """Stores various exit codes groups to use."""
    SUCCESS = 0
    FAILURE = 1
    # 1 is automatically used if Python throws an exception
    NO_CANDIDATES = 2
    USER_QUIT = 3
    DB_OPEN_FAIL = 4

    INTERNAL_ERROR = 10


def qute_command(command):
    with open(os.environ['QUTE_FIFO'], 'w') as fifo:
        fifo.write(command + '\n')
        fifo.flush()


def stderr(to_print):
    """Extra functionality to echo out errors to qb ui."""
    print(to_print, file=sys.stderr)
    qute_command('message-error "{}"'.format(to_print))


def dmenu(items, invocation, encoding):
    """Runs dmenu with given arguments."""
    command = shlex.split(invocation)
    process = subprocess.run(command, input='\n'.join(items).encode(encoding),
                             stdout=subprocess.PIPE)
    return process.stdout.decode(encoding).strip()


def get_password():
    """Get a keepass db password from user."""
    _app = QApplication(sys.argv)
    text, ok = QInputDialog.getText(
        None, "KeePass DB Password",
        "Please enter your KeePass Master Password",
        QLineEdit.Password)
    if not ok:
        stderr('Password Prompt Rejected.')
        sys.exit(ExitCodes.USER_QUIT)
    return text


def find_candidates(args, host):
    """Finds candidates that match host"""
    file_path = os.path.expanduser(args.path)

    # TODO find a way to keep the db open, so we don't open (and query
    # password) it every time

    pw = None
    if not args.no_password:
        pw = get_password()

    kf = args.keyfile_path
    if kf:
        kf = os.path.expanduser(kf)

    try:
        kp = pykeepass.PyKeePass(file_path, password=pw, keyfile=kf)
    except Exception as e:
        stderr("There was an error opening the DB: {}".format(str(e)))

    return kp.find_entries(url="{}{}{}".format(".*", host, ".*"), regex=True)


def candidate_to_str(args, candidate):
    """Turns candidate into a human readable string for dmenu"""
    return args.dmenu_format.format(title=candidate.title,
                                    url=candidate.url,
                                    username=candidate.username,
                                    path=candidate.path,
                                    uuid=candidate.uuid)


def candidate_to_secret(candidate):
    """Turns candidate into a generic (user, password) tuple"""
    return (candidate.username, candidate.password)


def run(args):
    """Runs qute-keepass"""
    if not args.url:
        argument_parser.print_help()
        return ExitCodes.FAILURE

    url_host = QUrl(args.url).host()

    if not url_host:
        stderr('{} was not parsed as a valid URL!'.format(args.url))
        return ExitCodes.INTERNAL_ERROR

    # Find candidates matching the host of the given URL
    candidates = find_candidates(args, url_host)
    if not candidates:
        stderr('No candidates for URL {!r} found!'.format(args.url))
        return ExitCodes.NO_CANDIDATES

    # Create a map so we can get turn the resulting string from dmenu back into
    # a candidate
    candidates_strs = list(map(functools.partial(candidate_to_str, args),
                               candidates))
    candidates_map = dict(zip(candidates_strs, candidates))

    if len(candidates) == 1:
        selection = candidates.pop()
    else:
        selection = dmenu(candidates_strs,
                          args.dmenu_invocation,
                          args.io_encoding)

        if selection not in candidates_map:
            stderr("'{}' was not a valid entry!").format(selection)
            return ExitCodes.USER_QUIT

        selection = candidates_map[selection]

    username, password = candidate_to_secret(selection)

    insert_mode = ';; enter-mode insert' if args.insert_mode else ''
    if args.username_fill_only:
        qute_command('insert-text {}{}'.format(username, insert_mode))
    elif args.password_fill_only:
        qute_command('insert-text {}{}'.format(password, insert_mode))
    else:
        # Enter username and password using insert-key and fake-key <Tab>
        # (which supports more passwords than fake-key only), then switch back
        # into insert-mode, so the form can be directly submitted by hitting
        # enter afterwards. It dosen't matter when we go into insert mode, but
        # the other commands need to be be executed sequentially, so we add
        # delays with later.
        qute_command('insert-text {} ;;'
                     'later {} fake-key <Tab> ;;'
                     'later {} insert-text {}{}'
                     .format(username, CMD_DELAY,
                             CMD_DELAY * 2, password, insert_mode))

    return ExitCodes.SUCCESS


if __name__ == '__main__':
    arguments = argument_parser.parse_args()
    sys.exit(run(arguments))
