#
# Module providing the `Process` class which emulates `threading.Thread`
#
# multiprocessing/process.py
#
# Copyright (c) 2006-2008, R Oudkerk
# Licensed to PSF under a Contributor Agreement.
#
#
# Imports
#

import os
import sys
import signal
import itertools
import logging
import threading
from _weakrefset import WeakSet

from multiprocessing import process as _mproc

try:
    ORIGINAL_DIR = os.path.abspath(os.getcwd())
except OSError:
    ORIGINAL_DIR = None

__all__ = ['BaseProcess', 'Process', 'current_process', 'active_children']

#
# Public functions
#


def current_process():
    '''
    Return process object representing the current process
    '''
    return _current_process


def _set_current_process(process):
    global _current_process
    _current_process = _mproc._current_process = process


def _cleanup():
    # check for processes which have finished
    for p in list(_children):
        if p._popen.poll() is not None:
            _children.discard(p)


def _maybe_flush(f):
    try:
        f.flush()
    except (AttributeError, EnvironmentError, NotImplementedError):
        pass


def active_children(_cleanup=_cleanup):
    '''
    Return list of process objects corresponding to live child processes
    '''
    try:
        _cleanup()
    except TypeError:
        # called after gc collect so _cleanup does not exist anymore
        return []
    return list(_children)


class BaseProcess:
    '''
    Process objects represent activity that is run in a separate process

    The class is analogous to `threading.Thread`
    '''

    def _Popen(self):
        raise NotImplementedError()

    def __init__(self, group=None, target=None, name=None,
                 args=(), kwargs={}, daemon=None, **_kw):
        assert group is None, 'group argument must be None for now'
        count = next(_process_counter)
        self._identity = _current_process._identity + (count, )
        self._config = _current_process._config.copy()
        self._parent_pid = os.getpid()
        self._popen = None
        self._closed = False
        self._target = target
        self._args = tuple(args)
        self._kwargs = dict(kwargs)
        self._name = (
            name or type(self).__name__ + '-' +
            ':'.join(str(i) for i in self._identity)
        )
        if daemon is not None:
            self.daemon = daemon
        if _dangling is not None:
            _dangling.add(self)
        
        self._controlled_termination = False

    def _check_closed(self):
        if self._closed:
            raise ValueError("process object is closed")

    def run(self):
        '''
        Method to be run in sub-process; can be overridden in sub-class
        '''
        if self._target:
            self._target(*self._args, **self._kwargs)

    def start(self):
        '''
        Start child process
        '''
        self._check_closed()
        assert self._popen is None, 'cannot start a process twice'
        assert self._parent_pid == os.getpid(), \
            'can only start a process object created by current process'
        _cleanup()
        self._popen = self._Popen(self)
        self._sentinel = self._popen.sentinel
        _children.add(self)

    def close(self):
        '''
        Close the Process object and release the resources it holds.

        It is an error to call this method while the child is still running.
        Other methods and properties then raise ValueError.
        '''
        if self._popen is not None:
            # poll() also reports None when the child was already reaped by
            # someone else (ECHILD, e.g. a SIGCHLD handler calling
            # waitpid(-1)), so such a process can never be closed; this is
            # the same in multiprocessing.
            if self._popen.poll() is None:
                raise ValueError(
                    "Cannot close a process while it is still running. "
                    "You should first call join() or terminate().")
            self._popen.close()
            self._popen = None
            del self._sentinel
            _children.discard(self)
        self._closed = True

    def terminate(self):
        '''
        Terminate process; sends SIGTERM signal or uses TerminateProcess()
        '''
        self._check_closed()
        self._popen.terminate()
        
    def terminate_controlled(self):
        self._controlled_termination = True
        self.terminate()

    def join(self, timeout=None):
        '''
        Wait until child process terminates
        '''
        self._check_closed()
        assert self._parent_pid == os.getpid(), 'can only join a child process'
        assert self._popen is not None, 'can only join a started process'
        res = self._popen.wait(timeout)
        if res is not None:
            _children.discard(self)
            # only release the sentinel: callers still read exitcode after join
            self._popen.close()

    def is_alive(self):
        '''
        Return whether process is alive
        '''
        self._check_closed()
        if self is _current_process:
            return True
        assert self._parent_pid == os.getpid(), 'can only test a child process'
        if self._popen is None:
            return False
        self._popen.poll()
        return self._popen.returncode is None

    def _is_alive(self):
        if self._popen is None:
            return False
        return self._popen.poll() is None

    @property
    def name(self):
        return self._name

    @name.setter
    def name(self, name):   # noqa
        assert isinstance(name, str), 'name must be a string'
        self._name = name

    @property
    def daemon(self):
        '''
        Return whether process is a daemon
        '''
        return self._config.get('daemon', False)

    @daemon.setter  # noqa
    def daemon(self, daemonic):
        '''
        Set whether process is a daemon
        '''
        assert self._popen is None, 'process has already started'
        self._config['daemon'] = daemonic

    @property
    def authkey(self):
        return self._config['authkey']

    @authkey.setter  # noqa
    def authkey(self, authkey):
        '''
        Set authorization key of process
        '''
        self._config['authkey'] = AuthenticationString(authkey)

    @property
    def exitcode(self):
        '''
        Return exit code of process or `None` if it has yet to stop
        '''
        self._check_closed()
        if self._popen is None:
            return self._popen
        return self._popen.poll()

    @property
    def ident(self):
        '''
        Return identifier (PID) of process or `None` if it has yet to start
        '''
        self._check_closed()
        if self is _current_process:
            return os.getpid()
        else:
            return self._popen and self._popen.pid

    pid = ident

    @property
    def sentinel(self):
        '''
        Return a file descriptor (Unix) or handle (Windows) suitable for
        waiting for process termination.
        '''
        self._check_closed()
        try:
            return self._sentinel
        except AttributeError:
            raise ValueError("process not started")

    @property
    def _counter(self):
        # compat for 2.7
        return _process_counter

    @property
    def _children(self):
        # compat for 2.7
        return _children

    @property
    def _authkey(self):
        # compat for 2.7
        return self.authkey

    @property
    def _daemonic(self):
        # compat for 2.7
        return self.daemon

    @property
    def _tempdir(self):
        # compat for 2.7
        return self._config.get('tempdir')

    def __repr__(self):
        if self is _current_process:
            status = 'started'
        elif self._closed:
            status = 'closed'
        elif self._parent_pid != os.getpid():
            status = 'unknown'
        elif self._popen is None:
            status = 'initial'
        else:
            if self._popen.poll() is not None:
                status = self.exitcode
            else:
                status = 'started'

        if type(status) is int:
            if status == 0:
                status = 'stopped'
            else:
                status = 'stopped[%s]' % _exitcode_to_name.get(status, status)

        return '<%s(%s, %s%s)>' % (type(self).__name__, self._name,
                                   status, self.daemon and ' daemon' or '')

    ##

    def _bootstrap(self):
        from . import util, context
        global _current_process, _process_counter, _children

        try:
            if self._start_method is not None:
                context._force_start_method(self._start_method)
            _process_counter = itertools.count(1)
            _children = set()
            if sys.stdin is not None:
                try:
                    sys.stdin.close()
                    sys.stdin = open(os.devnull)
                except (EnvironmentError, OSError, ValueError):
                    pass
            old_process = _current_process
            _set_current_process(self)

            # Re-init logging system.
            # Workaround for https://bugs.python.org/issue6721/#msg140215
            # Python logging module uses RLock() objects which are broken
            # after fork. This can result in a deadlock (Celery Issue #496).
            loggerDict = logging.Logger.manager.loggerDict
            logger_names = list(loggerDict.keys())
            logger_names.append(None)  # for root logger
            for name in logger_names:
                if not name or not isinstance(loggerDict[name],
                                              logging.PlaceHolder):
                    for handler in logging.getLogger(name).handlers:
                        handler.createLock()
            logging._lock = threading.RLock()

            try:
                util._finalizer_registry.clear()
                util._run_after_forkers()
            finally:
                # delay finalization of the old process object until after
                # _run_after_forkers() is executed
                del old_process
            util.info('child process %s calling self.run()', self.pid)
            try:
                self.run()
                exitcode = 0
            finally:
                util._exit_function()
        except SystemExit as exc:
            if not exc.args:
                exitcode = 1
            elif isinstance(exc.args[0], int):
                exitcode = exc.args[0]
            else:
                sys.stderr.write(str(exc.args[0]) + '\n')
                _maybe_flush(sys.stderr)
                exitcode = 0 if isinstance(exc.args[0], str) else 1
        except:
            exitcode = 1
            if not util.error('Process %s', self.name, exc_info=True):
                import traceback
                sys.stderr.write('Process %s:\n' % self.name)
                traceback.print_exc()
        finally:
            util.info('process %s exiting with exitcode %d',
                      self.pid, exitcode)
            _maybe_flush(sys.stdout)
            _maybe_flush(sys.stderr)

        return exitcode

#
# We subclass bytes to avoid accidental transmission of auth keys over network
#


class AuthenticationString(bytes):

    def __reduce__(self):
        from .context import get_spawning_popen

        if get_spawning_popen() is None:
            raise TypeError(
                'Pickling an AuthenticationString object is '
                'disallowed for security reasons')
        return AuthenticationString, (bytes(self),)

#
# Create object representing the main process
#


class _MainProcess(BaseProcess):

    def __init__(self):
        self._identity = ()
        self._name = 'MainProcess'
        self._parent_pid = None
        self._popen = None
        self._closed = False
        self._config = {'authkey': AuthenticationString(os.urandom(32)),
                        'semprefix': '/mp'}

_current_process = _MainProcess()
_process_counter = itertools.count(1)
_children = set()
del _MainProcess


Process = BaseProcess

#
# Give names to some return codes
#

_exitcode_to_name = {}

for name, signum in signal.__dict__.items():
    if name[:3] == 'SIG' and '_' not in name:
        _exitcode_to_name[-signum] = name

# For debug and leak testing
_dangling = WeakSet()