#!/usr/bin/env python3
from __future__ import print_function, absolute_import, division

import errno
import logging
import math
import os
import signal
import stat
import subprocess
from dataclasses import dataclass
from functools import reduce
from itertools import groupby
from operator import itemgetter
from time import time, mktime, time_ns
from typing import Sequence, Iterator, Union

from dateutil import parser as dateparser
from fuse import FUSE, Operations, LoggingMixIn, FuseOSError


@dataclass
class Entry:
    name: str
    parent: 'Directory | None'
    expiration: float

    @property
    def path(self) -> str:
        if self.parent is None:
            return self.name
        else:
            return f'{self.parent.path}/{self.name}'.lstrip('/')


@dataclass
class Directory(Entry, dict[str, Entry]):
    def __iter__(self) -> Iterator[str]:
        return iter(self.children)

    def __len__(self) -> int:
        return len(self.children)

    def __getitem__(self, name: str) -> Union[Entry, None]:
        if name in list(self.children.keys()):
            return self.children[name]
        else:
            return None

    children: dict[str, Entry]


@dataclass
class File(Entry):
    content: Union[str, None]
    mod_time: Union[int, None]
    loaded: bool = False

    @property
    def size(self):
        return len(self.content)


def parse_history_line(line: str) -> int:
    return int(mktime(dateparser.parse(''.join(line.split('-')[2:5]).strip()).timetuple()))


def get_gopass_data(cmd: Sequence[str]) -> Union[str, None]:
    my_env: dict[str, str] = os.environ.copy()
    process: subprocess.Popen = subprocess.Popen(cmd, stdout=subprocess.PIPE, env=my_env, stdin=subprocess.PIPE)
    stdout, stderr = process.communicate()
    exit_code: int = process.wait()
    if exit_code == 0:
        return stdout.decode('utf-8')
    else:
        return None


def get_secret(entry: File) -> Union[str, None]:
    cmd: Sequence[str] = ['gopass', 'show', '-f', entry.path]
    data: Union[str, None] = get_gopass_data(cmd)
    return data


def get_file_history(file: File) -> Union[list[str], None]:
    cmd: Sequence[str] = ['gopass', 'history', file.path]
    data: Union[str, None] = get_gopass_data(cmd)
    if data is None:
        return None
    else:
        return [s for s in data.split('\n') if len(s) > 0]


def get_secrets(path: str) -> Union[list[str], None]:
    cmd: Sequence[str] = ['gopass', 'list', '--flat', '--strip-prefix', path, path]
    data: Union[str, None] = get_gopass_data(cmd)
    if data is None:
        return None
    else:
        return data.split()


class GopassFilesystem(LoggingMixIn, Operations):
    logger: logging
    refresh_interval: int
    root: Directory
    user_id: int
    group_id: int
    use_ns: bool = True

    def __init__(self, refresh_interval: int):
        self.logger = logging.getLogger()
        self.refresh_interval = refresh_interval
        self.user_id = os.getuid()
        self.group_id = os.getgid()
        self.root = Directory('', None, 0, {})
        self.refresh(self.root)

    # noinspection PyUnusedLocal
    def reload(self, signum: int, frame) -> None:
        self.refresh_item(self.root)

    def refresh_item(self, entry: Entry) -> None:
        if isinstance(entry, Directory):
            entry.children = self.get_directory(entry.path, entry).children
        elif isinstance(entry, File):
            entry.loaded = False
            entry.content = None
        entry.expiration = time() + self.refresh_interval

    def refresh(self, entry: Entry) -> None:
        if time() > entry.expiration:
            self.refresh_item(entry)
        elif isinstance(entry, Directory):
            if len(entry.children) == 0:
                self.refresh_item(entry)
        entry.expiration = time() + self.refresh_interval
        if entry.parent is not None:
            self.refresh(entry.parent)

    def get_directory(self, path: str, parent: Union[Directory, None]) -> Directory:
        secrets: Union[Sequence[str], None] = get_secrets(path)
        children: dict[str, Entry]
        if secrets is None:
            children = dict()
        else:
            children = self.convert_to_directory_tree(parent, secrets)

        return Directory(path.split('/')[-1] if parent is not None else '', parent, time() + self.refresh_interval,
                         children)

    def convert_to_directory_tree(self, parent: Directory, entries: Union[Sequence[str], Sequence[Sequence[str]]]) -> \
            dict[str, Entry]:
        now: float = time()
        if isinstance(entries[0], list):
            paths: Sequence[Sequence[str]] = entries
        else:
            paths: Sequence[Sequence[str]] = [s.split('/') for s in entries]
        grouped_paths: groupby[str, Sequence[str]] = groupby(paths, key=itemgetter(0))

        tree: dict[str, Entry] = dict()

        name: str
        children: Sequence[Sequence[str]]
        for name, children in grouped_paths:
            children: Sequence[Sequence[str]] = [s[1:] for s in children]
            if len(children[0]) > 0:
                new_directory: Directory = Directory(name, parent, now + self.refresh_interval, {})
                new_directory.children = self.convert_to_directory_tree(new_directory, children)
                tree[name] = new_directory
            else:
                tree[name] = File(name, parent, math.inf, None, None)

        return tree

    def get_entry(self, path: str) -> Union[Entry, None]:
        if path == '/':
            return self.root
        path = path.lstrip('/')
        path_parts: Sequence[str] = path.split('/')
        if path_parts[0] not in list(self.root.children.keys()):
            return None
        entry: Entry = reduce((lambda e, p: e[p] if e[p] is not None else e), path_parts, self.root)

        if entry.name != path_parts[-1]:
            return None
        else:
            return entry

    def load_file(self, file: File) -> None:
        if not file.loaded:
            secret: Union[str, None] = get_secret(file)
            if secret is None:
                raise FuseOSError(errno.EIO)
            file.content = secret
            history: Union[Sequence[str], None] = get_file_history(file)
            if history is None:
                raise FuseOSError(errno.EIO)
            file.mod_time = parse_history_line(history[0]) * (10 ** 9)
            file.loaded = True
            file.expiration = time() + self.refresh_interval

    def getattr(self, path: str, fh: int = None) -> dict[str, int]:
        now: int = time_ns()
        st: dict[str, int] = dict(st_atime=now, st_mode=0, st_uid=self.user_id, st_gid=self.group_id)

        if path == '/':
            st['st_mode'] = stat.S_IFDIR | 0o755
            st['st_nlink'] = 2
        else:
            entry: Union[Entry, None] = self.get_entry(path)
            if isinstance(entry, File):
                st['st_mode'] = stat.S_IFREG | 0o400
                st['st_nlink'] = 1
                self.load_file(entry)
                st['st_size'] = len(entry.content)
                st['st_ctime'] = entry.mod_time
                st['st_mtime'] = entry.mod_time
            elif isinstance(entry, Directory):
                st['st_mode'] = stat.S_IFDIR | 0o500
                st['st_nlink'] = len([d for d in entry.children if isinstance(d, Directory)])
                st['st_ctime'] = now
                st['st_mtime'] = now
            else:
                raise FuseOSError(errno.ENOENT)

        return st

    def read(self, path: str, size: int, offset: int, fh: int) -> bytes:
        entry: Union[Entry, None] = self.get_entry(path)
        if isinstance(entry, File):
            self.load_file(entry)
            return ('%s\n' % entry.content).encode('utf-8')
        elif isinstance(entry, Directory):
            raise FuseOSError(errno.EISDIR)
        elif entry is None:
            raise FuseOSError(errno.ENOENT)

    def readdir(self, path: str, fh: int) -> list[str]:
        entry: Union[Entry, None] = self.get_entry(path)
        if isinstance(entry, Directory):
            return ['.', '..'] + list(entry.children.keys())
        if isinstance(entry, File):
            raise FuseOSError(errno.ENOTDIR)
        elif entry is None:
            raise FuseOSError(errno.ENOENT)

    def access(self, path: str, amode: int) -> None:
        entry: Union[Entry, None] = self.get_entry(path)
        if entry is None:
            raise FuseOSError(errno.ENOENT)
        else:
            self.refresh(entry)

    def open(self, path: str, flags: int) -> int:
        entry: Union[Entry, None] = self.get_entry(path)
        if entry is None:
            raise FuseOSError(errno.ENOENT)
        else:
            access_mode: int = os.O_RDONLY | os.O_WRONLY | os.O_RDWR | os.O_APPEND | os.O_CREAT
            if (flags & access_mode) != os.O_RDONLY:
                raise FuseOSError(errno.EROFS)
            else:
                return 0


if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser()
    parser.add_argument('--mount', required=True, type=str)
    parser.add_argument('--refresh-interval', required=False, default=60, type=int)
    parser.add_argument('--foreground', required=False, action='store_true')
    args = parser.parse_args()

    logging.basicConfig(level=logging.INFO)

    gfs = GopassFilesystem(args.refresh_interval)

    signal.signal(signal.SIGUSR1, gfs.reload)

    fuse = FUSE(
        gfs,
        args.mount,
        foreground=args.foreground,
        nothreads=True,
        allow_other=False)