"""Process boundary for the patched DSView GUI (host protocol 1, Windows).

The host owns only its child process/window. Qt 5, Python and libusb remain
inside DSView; they must never be loaded into the hosting application's Qt.
"""
from contextlib import contextmanager
import ctypes
import os
from pathlib import Path
import sys


def resolve_runtime(bundled, executable=None, frozen=None):
    """A dsview folder beside the GUI EXE overrides its bundled runtime."""
    frozen = getattr(sys, 'frozen', False) if frozen is None else frozen
    if frozen:
        external = Path(executable or sys.executable).resolve().parent / 'dsview'
        if external.exists():
            # An incomplete external install should be reported, not silently
            # replaced with an older bundled component.
            return external
    return Path(bundled)


def child_environment(runtime, stylesheet, capture_directory, environment=None):
    """Remove Python/Qt/PyInstaller overrides before starting the private runtime."""
    env = dict(os.environ if environment is None else environment)
    for key in list(env):
        if key.upper().startswith(('PYTHON', 'QT_', 'QML', 'PYSIDE', '_PYI', '_MEIPASS')):
            env.pop(key)
    windows = Path(env.get('SystemRoot', r'C:\Windows'))
    env['PATH'] = os.pathsep.join(map(str, (Path(runtime), windows / 'System32', windows)))
    env['DSVIEW_HOST_STYLE'] = str(stylesheet)
    env['DSVIEW_CAPTURE_DIR'] = str(capture_directory)
    env['PYTHONDONTWRITEBYTECODE'] = '1'
    return env


def ready_window(line):
    """Only accept the versioned child's explicit ready message."""
    fields = line.strip().split()
    if len(fields) == 2 and fields[0] == 'DSVIEW_READY':
        try:
            value = int(fields[1])
            return value if value > 0 else None
        except ValueError:
            pass
    return None


def window_api():
    from ctypes import wintypes
    api = ctypes.WinDLL('user32', use_last_error=True)
    api.GetWindowThreadProcessId.argtypes = [wintypes.HWND, ctypes.POINTER(wintypes.DWORD)]
    api.GetWindowThreadProcessId.restype = wintypes.DWORD
    api.GetParent.argtypes = [wintypes.HWND]
    api.GetParent.restype = wintypes.HWND
    return api


def owns_window(window, pid, parent=None):
    if sys.platform != 'win32' or not window or not pid:
        return False
    from ctypes import wintypes
    api = window_api()
    owner = wintypes.DWORD()
    api.GetWindowThreadProcessId(window, ctypes.byref(owner))
    return owner.value == pid and (parent is None or api.GetParent(window) == parent)


@contextmanager
def independent_dll_directory():
    """Do not inherit PyInstaller's Qt DLL search directory into DSView."""
    if sys.platform != 'win32' or not getattr(sys, 'frozen', False):
        yield
        return
    api = ctypes.WinDLL('kernel32', use_last_error=True)
    api.GetDllDirectoryW.argtypes = [ctypes.c_uint32, ctypes.c_wchar_p]
    api.SetDllDirectoryW.argtypes = [ctypes.c_wchar_p]
    buffer = ctypes.create_unicode_buffer(32768)
    api.GetDllDirectoryW(len(buffer), buffer)
    if not api.SetDllDirectoryW(None):
        raise ctypes.WinError(ctypes.get_last_error())
    try:
        yield
    finally:
        api.SetDllDirectoryW(buffer.value or None)