# -*- coding: utf-8 -*-
"""
    billiard._win
    ~~~~~~~~~~~~~

    Windows utilities to terminate process groups.

"""
from __future__ import absolute_import

import os

# psutil is painfully slow in win32. So to avoid adding big
# dependencies like pywin32 a ctypes based solution is preferred

# Code based on the winappdbg project http://winappdbg.sourceforge.net/
# (BSD License)
from ctypes import (
    byref, sizeof, windll,
    Structure, WinError, POINTER,
    c_size_t, c_char, c_void_p,
)
from ctypes.wintypes import DWORD, LONG

ERROR_NO_MORE_FILES = 18
INVALID_HANDLE_VALUE = c_void_p(-1).value


class PROCESSENTRY32(Structure):
    _fields_ = [
        ('dwSize',              DWORD),
        ('cntUsage',            DWORD),
        ('th32ProcessID',       DWORD),
        ('th32DefaultHeapID',   c_size_t),
        ('th32ModuleID',        DWORD),
        ('cntThreads',          DWORD),
        ('th32ParentProcessID', DWORD),
        ('pcPriClassBase',      LONG),
        ('dwFlags',             DWORD),
        ('szExeFile',           c_char * 260),
    ]
LPPROCESSENTRY32 = POINTER(PROCESSENTRY32)


def CreateToolhelp32Snapshot(dwFlags=2, th32ProcessID=0):
    hSnapshot = windll.kernel32.CreateToolhelp32Snapshot(dwFlags,
                                                         th32ProcessID)
    if hSnapshot == INVALID_HANDLE_VALUE:
        raise WinError()
    return hSnapshot


def Process32First(hSnapshot, pe=None):
    return _Process32n(windll.kernel32.Process32First, hSnapshot, pe)


def Process32Next(hSnapshot, pe=None):
    return _Process32n(windll.kernel32.Process32Next, hSnapshot, pe)


def _Process32n(fun, hSnapshot, pe=None):
    if pe is None:
        pe = PROCESSENTRY32()
    pe.dwSize = sizeof(PROCESSENTRY32)
    success = fun(hSnapshot, byref(pe))
    if not success:
        if windll.kernel32.GetLastError() == ERROR_NO_MORE_FILES:
            return
        raise WinError()
    return pe


def get_all_processes_pids():
    """Return a dictionary with all processes pids as keys and their
       parents as value. Ignore processes with no parents.
    """
    h = CreateToolhelp32Snapshot()
    parents = {}
    pe = Process32First(h)
    while pe:
        if pe.th32ParentProcessID:
            parents[pe.th32ProcessID] = pe.th32ParentProcessID
        pe = Process32Next(h, pe)

    return parents


def get_processtree_pids(pid, include_parent=True):
    """Return a list with all the pids of a process tree"""
    parents = get_all_processes_pids()
    all_pids = parents.keys()
    pids = set([pid])
    while 1:
        pids_new = pids.copy()

        for _pid in all_pids:
            if parents[_pid] in pids:
                pids_new.add(_pid)

        if pids_new == pids:
            break

        pids = pids_new.copy()

    if not include_parent:
        pids.remove(pid)

    return list(pids)


def kill_processtree(pid, signum):
    """Kill a process and all its descendants"""
    family_pids = get_processtree_pids(pid)

    for _pid in family_pids:
        os.kill(_pid, signum)
