#!/usr/bin/env python3

"""A simple utility to unpickle some code, run it, and pickle the
results.
"""

import logging
import os
import signal
import threading
import sys
import time

import cloudpickle  # type: ignore
import psutil  # type: ignore

import argparse_utils
import bootstrap
import config
from thread_utils import background_thread


logger = logging.getLogger(__file__)

cfg = config.add_commandline_args(
    f"Remote Worker ({__file__})",
    "Helper to run pickled code remotely and return results",
)
cfg.add_argument(
    '--code_file',
    type=str,
    required=True,
    metavar='FILENAME',
    help='The location of the bundle of code to execute.',
)
cfg.add_argument(
    '--result_file',
    type=str,
    required=True,
    metavar='FILENAME',
    help='The location where we should write the computation results.',
)
cfg.add_argument(
    '--watch_for_cancel',
    action=argparse_utils.ActionNoYes,
    default=True,
    help='Should we watch for the cancellation of our parent ssh process?',
)


@background_thread
def watch_for_cancel(terminate_event: threading.Event) -> None:
    logger.debug('Starting up background thread...')
    p = psutil.Process(os.getpid())
    while True:
        saw_sshd = False
        ancestors = p.parents()
        for ancestor in ancestors:
            name = ancestor.name()
            pid = ancestor.pid
            logger.debug(f'Ancestor process {name} (pid={pid})')
            if 'ssh' in name.lower():
                saw_sshd = True
                break
        if not saw_sshd:
            logger.error(
                'Did not see sshd in our ancestors list?!  Committing suicide.'
            )
            os.system('pstree')
            os.kill(os.getpid(), signal.SIGTERM)
            time.sleep(5.0)
            os.kill(os.getpid(), signal.SIGKILL)
            sys.exit(-1)
        if terminate_event.is_set():
            return
        time.sleep(1.0)


@bootstrap.initialize
def main() -> None:
    in_file = config.config['code_file']
    out_file = config.config['result_file']

    stop_thread = None
    if config.config['watch_for_cancel']:
        (thread, stop_thread) = watch_for_cancel()

    logger.debug(f'Reading {in_file}.')
    try:
        with open(in_file, 'rb') as rb:
            serialized = rb.read()
    except Exception as e:
        logger.exception(e)
        logger.critical(f'Problem reading {in_file}.  Aborting.')
        stop_thread.set()
        sys.exit(-1)

    logger.debug(f'Deserializing {in_file}.')
    try:
        fun, args, kwargs = cloudpickle.loads(serialized)
    except Exception as e:
        logger.exception(e)
        logger.critical(f'Problem deserializing {in_file}.  Aborting.')
        stop_thread.set()
        sys.exit(-1)

    logger.debug('Invoking user code...')
    start = time.time()
    ret = fun(*args, **kwargs)
    end = time.time()
    logger.debug(f'User code took {end - start:.1f}s')

    logger.debug('Serializing results')
    try:
        serialized = cloudpickle.dumps(ret)
    except Exception as e:
        logger.exception(e)
        logger.critical(f'Could not serialize result ({type(ret)}).  Aborting.')
        stop_thread.set()
        sys.exit(-1)

    logger.debug(f'Writing {out_file}.')
    try:
        with open(out_file, 'wb') as wb:
            wb.write(serialized)
    except Exception as e:
        logger.exception(e)
        logger.critical(f'Error writing {out_file}.  Aborting.')
        stop_thread.set()
        sys.exit(-1)

    if stop_thread is not None:
        stop_thread.set()
        thread.join()


if __name__ == '__main__':
    main()