#!/usr/bin/python3
# SPDX-License-Identifier: MIT
'''
Simple clipboard storing anything from stdin in a file or outputing from
the file to stdout. Direction is determined from pipe redirection.

Examples:

Store something to clipboard:
    echo abc | clip

Output clipboard content to console:
    clip

Use content:
    clip > file
    clip | command
'''


import contextlib
import functools
import getpass
import os
import sys


class Error(Exception): pass
class SecurityError(Error): pass


@contextlib.contextmanager
def secure_opendir(dirname):
    os.makedirs(dirname, mode=0o700, exist_ok=True)
    dfd = os.open(dirname, os.O_RDONLY | os.O_DIRECTORY)
    try:
        dir_stat = os.stat(dfd)
        if (dir_stat.st_uid != os.getuid() or dir_stat.st_mode & 0o777 != 0o700):
            raise SecurityError('Wrong directory permissions/owner')
        yield dfd
    finally:
        os.close(dfd)


@contextlib.contextmanager
def secure_open(*l, **kw):
    with secure_opendir(os.path.dirname(l[0])) as dfd:
        _opener = functools.partial(os.open, dir_fd=dfd)
        with open(*l, **kw, opener=_opener) as ffd:
            yield ffd


if __name__ == '__main__':
    os.umask(0o077)
    clipboard_filepath = '/dev/shm/%s-clipboard/content' % getpass.getuser()
    if(sys.stdin.isatty()):
        # Should write clipboard contents out to stdout
        try:
            with secure_open(clipboard_filepath, 'rb') as fo:
                sys.stdout.buffer.write(fo.read())
        except FileNotFoundError:
            # equivalent to an empty file
            pass
    elif(sys.stdout.isatty()):
        # Should save stdin to clipboard
        with secure_open(clipboard_filepath, 'wb') as fo:
            fo.write(sys.stdin.buffer.read())