pac-proxy-url.py

import ctypes
import ctypes.wintypes


class WinhttpAutoproxyOptions(ctypes.Structure):
    _fields_ = [
        ("dwFlags", ctypes.wintypes.DWORD),
        ("dwAutoDetectFlags", ctypes.wintypes.DWORD),
        ("u", ctypes.wintypes.LPCWSTR),
        ("r", ctypes.c_void_p),
        ("d", ctypes.wintypes.DWORD),
        ("fAutoLogonIfChallenged", ctypes.wintypes.BOOL),
    ]


class WinhttpProxyInfo(ctypes.Structure):
    _fields_ = [
        ("dwAccessType", ctypes.wintypes.DWORD),
        ("lpszProxy", ctypes.wintypes.LPWSTR),
        ("lpszProxyBypass", ctypes.wintypes.LPWSTR),
    ]


def proxy_for(url: str) -> str:
    h = w.WinHttpOpen("py", 1, None, None, 0)
    winhttp_autoproxy_options = WinhttpAutoproxyOptions(
        1, 3, None, None, 0, True
    )  # AUTO_DETECT | DHCP+DNS
    winhttp_proxy_info = WinhttpProxyInfo()
    ok = w.WinHttpGetProxyForUrl(
        h,
        url,
        ctypes.byref(winhttp_autoproxy_options),
        ctypes.byref(winhttp_proxy_info),
    )
    w.WinHttpCloseHandle(h)
    if ok and winhttp_proxy_info.lpszProxy:
        return winhttp_proxy_info.lpszProxy

    return "DIRECT"


if __name__ == "__main__":
    import sys

    w = ctypes.WinDLL("winhttp", use_last_error=True)
    w.WinHttpOpen.restype = ctypes.wintypes.HANDLE

    w.WinHttpGetProxyForUrl.argtypes = (
        ctypes.wintypes.HANDLE,  # hSession
        ctypes.wintypes.LPCWSTR,  # lpcwszUrl
        ctypes.POINTER(WinhttpAutoproxyOptions),  # pAutoProxyOptions
        ctypes.POINTER(WinhttpProxyInfo),  # pProxyInfo
    )
    w.WinHttpGetProxyForUrl.restype = ctypes.wintypes.BOOL

    w.WinHttpCloseHandle.argtypes = (ctypes.wintypes.HANDLE,)
    w.WinHttpCloseHandle.restype = ctypes.wintypes.BOOL

    print(proxy_for(sys.argv[1]))