# Copyright (C) 2024–present  Loren Eteval & contributors <loren.eteval@proton.me>
#
# This file is part of Furious.
#
# 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 <https://www.gnu.org/licenses/>.

"""Provide process utilities for app main process."""

from __future__ import annotations

from Furious.Frozenlib import *
from Furious.Interface import *

from typing import Callable

import os
import sys
import time
import signal
import logging
import datetime
import operator
import functools
import traceback
import multiprocessing

__all__ = ['AppMainProcess']

logger = logging.getLogger(__name__)

if PLATFORM == 'Windows':
    ProcessContext = multiprocessing
else:
    ProcessContext = multiprocessing.get_context('spawn')


class AppMainProcess(ProcessContext.Process):
    """Represent app main process."""

    ShutdownTimeout = 10.0
    ShutdownPollInterval = 0.1
    KillJoinTimeout = 3.0

    def __init__(self, func: Callable[[], ApplicationRunner], **kwargs):
        """Initialize the AppMainProcess."""
        super().__init__(**kwargs)

        self.startupTime = str(datetime.datetime.now()).replace(':', '')
        self.logFileName = f'{self.startupTime}.log'

        # Shared scalars need neither a manager process nor a response from the
        # child's potentially blocked event loop during shutdown.
        self.fileWritten = ProcessContext.Value('b', False, lock=False)
        self._shutdownDeadline = ProcessContext.Value('d', 0.0, lock=False)
        self._shutdownExitCode = ProcessContext.Value('i', 0, lock=False)

        self.func = func
        self.application = None
        self.forcedExit = False

    def beginShutdown(self, exitcode=None):
        """Publish the semantic result and arm one deadline before cleanup starts."""
        if exitcode is not None:
            self._shutdownExitCode.value = int(exitcode)

        if not self._shutdownDeadline.value:
            self._shutdownDeadline.value = time.monotonic() + self.ShutdownTimeout

    def waitForExit(self):
        """Join this child, forcing exit once its shutdown grace period expires."""
        while self.is_alive():
            deadline = self._shutdownDeadline.value

            if deadline and time.monotonic() >= deadline:
                exitcode = self._shutdownExitCode.value

                self.forcedExit = True

                logger.warning('application shutdown timed out; forcing process exit')

                # terminate() is SIGTERM on POSIX, which this child handles by
                # requesting graceful shutdown again. kill() cannot be caught.
                self.kill()
                self.join(self.KillJoinTimeout)

                if self.is_alive():
                    raise RuntimeError('application process survived forced shutdown')

                return exitcode

            self.join(self.ShutdownPollInterval)

        self.join(0)
        return self.exitcode

    def exceptHook(self, exceptionType, exceptionValue, tb, *, raiseSystemExit=False):
        """Handle except hook for the app main process."""
        if logger.level < logging.CRITICAL:
            traceback.print_exception(exceptionType, exceptionValue, tb)

        if isinstance(exceptionValue, AssertionError):
            exitcode = ApplicationRunner.ExitCode.AssertionError.value
        else:
            exitcode = ApplicationRunner.ExitCode.UnknownException.value

        self.beginShutdown(exitcode)

        logger.error(f'stopped with exitcode {exitcode}')

        self.saveCrashLog(exceptionType, exceptionValue, tb)

        if not raiseSystemExit and APP() is not None:
            APP().exit(exitcode)
        else:
            sys.exit(exitcode)

    def saveCrashLog(self, exceptionType, exceptionValue, tb):
        """Save crash log."""
        try:
            os.mkdir(CRASH_LOG_DIR)
        except FileExistsError:
            # Directory already exists

            pass
        except Exception:
            # Any non-exit exceptions

            return

        try:
            stackLog = functools.reduce(
                operator.add,
                traceback.format_exception(exceptionType, exceptionValue, tb),
            )

            logManager = getattr(APP(), 'logManager', None)

            crashLog = (
                f'{logManager.plainText()}\n{stackLog}'
                if logManager is not None
                else f'{stackLog}'
            )

            with open(CRASH_LOG_DIR / self.logFileName, 'w', encoding='utf-8') as file:
                file.write(crashLog)

            self.fileWritten.value = True
        except Exception:
            # Any non-exit exceptions

            pass

    def handler(self, signum, frame):
        """Handle r."""
        self.beginShutdown()

        logger.info(f'received signal {signal.Signals(signum).name}. Exit application')

        if self.application is None:
            sys.exit(ApplicationRunner.ExitCode.ExitSuccess.value)

        self.application.exit()

    def run(self):
        """Run the app main process task."""
        sys.excepthook = self.exceptHook

        try:
            self.application = self.func()

            shutdownRequested = getattr(self.application, 'shutdownRequested', None)

            if shutdownRequested is not None:
                shutdownRequested.connect(self.beginShutdown)

            for sig in [signal.SIGTERM, signal.SIGINT]:
                signal.signal(sig, self.handler)

            exitcode = self.application.run()

            self.beginShutdown(exitcode)

            sys.exit(exitcode)
        except SystemExit as ex:
            self.beginShutdown(
                ex.code if isinstance(ex.code, int) else (0 if ex.code is None else 1)
            )

            raise
        except Exception:
            # Any non-exit exceptions

            # Multiprocessing catches escaping failures before sys.excepthook.
            # The factory/run frame has ended, so no Qt loop can honor exit().
            self.exceptHook(*sys.exc_info(), raiseSystemExit=True)