from ctypes import (
    POINTER,
    WINFUNCTYPE,
    Structure,
    WinDLL,
    byref,
    c_char_p,
    c_void_p,
    cast,
    create_string_buffer,
    memmove,
    windll,
)

try:
    from ctypes import wintypes
except ValueError:
    # see http://bugs.python.org/issue16396
    raise ImportError("wintypes")

# Crypto API ctypes bindings


class DATA_BLOB(Structure):
    _fields_ = [('cbData', wintypes.DWORD), ('pbData', POINTER(wintypes.BYTE))]


class CRYPTPROTECT_PROMPTSTRUCT(Structure):
    _fields_ = [
        ('cbSize', wintypes.DWORD),
        ('dwPromptFlags', wintypes.DWORD),
        ('hwndApp', wintypes.HWND),
        ('szPrompt', POINTER(wintypes.WCHAR)),
    ]


# Flags for CRYPTPROTECT_PROMPTSTRUCT

CRYPTPROTECT_PROMPT_ON_UNPROTECT = 1
CRYPTPROTECT_PROMPT_ON_PROTECT = 2

# Flags for CryptProtectData/CryptUnprotectData

CRYPTPROTECT_UI_FORBIDDEN = 0x01
CRYPTPROTECT_LOCAL_MACHINE = 0x04
CRYPTPROTECT_CRED_SYNC = 0x08
CRYPTPROTECT_AUDIT = 0x10
CRYPTPROTECT_NO_RECOVERY = 0x20
CRYPTPROTECT_VERIFY_PROTECTION = 0x40
CRYPTPROTECT_CRED_REGENERATE = 0x80

# Crypto API Functions

_dll = WinDLL('CRYPT32.DLL')

CryptProtectData = WINFUNCTYPE(
    wintypes.BOOL,
    POINTER(DATA_BLOB),
    POINTER(wintypes.WCHAR),
    POINTER(DATA_BLOB),
    c_void_p,
    POINTER(CRYPTPROTECT_PROMPTSTRUCT),
    wintypes.DWORD,
    POINTER(DATA_BLOB),
)(('CryptProtectData', _dll))

CryptUnprotectData = WINFUNCTYPE(
    wintypes.BOOL,
    POINTER(DATA_BLOB),
    POINTER(wintypes.WCHAR),
    POINTER(DATA_BLOB),
    c_void_p,
    POINTER(CRYPTPROTECT_PROMPTSTRUCT),
    wintypes.DWORD,
    POINTER(DATA_BLOB),
)(('CryptUnprotectData', _dll))

# Functions


def encrypt(data, non_interactive=0):
    blobin = DATA_BLOB(
        cbData=len(data), pbData=cast(c_char_p(data), POINTER(wintypes.BYTE))
    )
    blobout = DATA_BLOB()

    if not CryptProtectData(
        byref(blobin),
        'python-keyring-lib.win32crypto',
        None,
        None,
        None,
        CRYPTPROTECT_UI_FORBIDDEN,
        byref(blobout),
    ):
        raise OSError("Can't encrypt")

    encrypted = create_string_buffer(blobout.cbData)
    memmove(encrypted, blobout.pbData, blobout.cbData)
    windll.kernel32.LocalFree(blobout.pbData)
    return encrypted.raw


def decrypt(encrypted, non_interactive=0):
    blobin = DATA_BLOB(
        cbData=len(encrypted), pbData=cast(c_char_p(encrypted), POINTER(wintypes.BYTE))
    )
    blobout = DATA_BLOB()

    if not CryptUnprotectData(
        byref(blobin),
        'python-keyring-lib.win32crypto',
        None,
        None,
        None,
        CRYPTPROTECT_UI_FORBIDDEN,
        byref(blobout),
    ):
        raise OSError("Can't decrypt")

    data = create_string_buffer(blobout.cbData)
    memmove(data, blobout.pbData, blobout.cbData)
    windll.kernel32.LocalFree(blobout.pbData)
    return data.raw
