###############################################################################
# Extra reducers for Windows system and connections objects
#
# author: Thomas Moreau and Olivier Grisel
#
# adapted from multiprocessing/reduction.py (17/02/2017)
#  * Add adapted reduction for LokyProcesses and socket/PipeConnection
#
import os
import socket
import _winapi
from multiprocessing.connection import PipeConnection
from multiprocessing.reduction import _reduce_socket

from .reduction import register


class DupHandle:
    def __init__(self, handle, access, pid=None):
        # duplicate handle for process with given pid
        if pid is None:
            pid = os.getpid()
        proc = _winapi.OpenProcess(_winapi.PROCESS_DUP_HANDLE, False, pid)
        try:
            self._handle = _winapi.DuplicateHandle(
                _winapi.GetCurrentProcess(),
                handle, proc, access, False, 0)
        finally:
            _winapi.CloseHandle(proc)
        self._access = access
        self._pid = pid

    def detach(self):
        # retrieve handle from process which currently owns it
        if self._pid == os.getpid():
            return self._handle
        proc = _winapi.OpenProcess(_winapi.PROCESS_DUP_HANDLE, False,
                                   self._pid)
        try:
            return _winapi.DuplicateHandle(
                proc, self._handle, _winapi.GetCurrentProcess(),
                self._access, False, _winapi.DUPLICATE_CLOSE_SOURCE)
        finally:
            _winapi.CloseHandle(proc)


def rebuild_pipe_connection(dh, readable, writable):
    handle = dh.detach()
    return PipeConnection(handle, readable, writable)


def reduce_pipe_connection(conn):
    access = ((_winapi.FILE_GENERIC_READ if conn.readable else 0) |
              (_winapi.FILE_GENERIC_WRITE if conn.writable else 0))
    dh = DupHandle(conn.fileno(), access)
    return rebuild_pipe_connection, (dh, conn.readable, conn.writable)


register(PipeConnection, reduce_pipe_connection)
register(socket.socket, _reduce_socket)