import os
import msvcrt
import ctypes
from ctypes import wintypes

kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)

KEY_EVENT = 0x0001

class KEY_EVENT_RECORD(ctypes.Structure):
    class UCHAR(ctypes.Union):
        _fields_ = (('UnicodeChar', wintypes.WCHAR),
                    ('AsciiChar',   wintypes.CHAR))
    _fields_ = (('bKeyDown',          wintypes.BOOL),
                ('wRepeatCount',      wintypes.WORD),
                ('wVirtualKeyCode',   wintypes.WORD),
                ('wVirtualScanCode',  wintypes.WORD),
                ('uChar',             UCHAR),
                ('dwControlKeyState', wintypes.DWORD))

class INPUT_RECORD(ctypes.Structure):
    class EVENT(ctypes.Union):
        _fields_ = (('KeyEvent', KEY_EVENT_RECORD),)
    _fields_ = (('EventType', wintypes.WORD),
                ('Event',     EVENT))

PINPUT_RECORD = ctypes.POINTER(INPUT_RECORD)

def _check_zero(result, func, args):
    if not result:
        raise ctypes.WinError(ctypes.get_last_error())
    return args

kernel32.WriteConsoleInputW.errcheck = _check_zero
kernel32.WriteConsoleInputW.argtypes = (
    wintypes.HANDLE,  # _In_  hConsoleInput
    PINPUT_RECORD,    # _In_  lpBuffer
    wintypes.DWORD,   # _In_  nLength
    wintypes.LPDWORD) # _Out_ lpNumberOfEventsWritten

def write_console_input(s):
    length = len(s) + sum(1 for c in s if ord(c) > 65535)
    recs = (INPUT_RECORD * length)()
    i = 0
    for char in s:
        if ord(char) > 65535:
            b = char.encode('utf-16le')
            char = [b[:2].decode('utf-16le', 'surrogatepass'),
                    b[2:].decode('utf-16le', 'surrogatepass')]
        for c in char:
            recs[i].EventType = KEY_EVENT
            recs[i].Event.KeyEvent.bKeyDown = True
            recs[i].Event.KeyEvent.wRepeatCount = 1
            recs[i].Event.KeyEvent.uChar.UnicodeChar = c
            i = i + 1
    fd = os.open('CONIN$', os.O_RDWR | os.O_BINARY)
    hInput = msvcrt.get_osfhandle(fd)
    total = 0
    precs = ctypes.byref(recs[0])
    n = wintypes.DWORD()
    try:
        # This loop is probably unnecessary, since the input buffer
        # expands dynamically to allow writing any number of records. 
        while True:
            kernel32.WriteConsoleInputW(hInput, precs, len(recs) - total,
                                        ctypes.byref(n))
            total += n.value
            if total >= len(recs):
                break
            precs = ctypes.byref(recs[total])
    finally:
        os.close(fd)
    return total

if __name__ == '__main__':
    import sys
    test_input = 'test input: U00010000\r\n'
    n = write_console_input(test_input)
    assert n == len(test_input)
    line = sys.stdin.buffer.readline()
    read_input = line.decode(sys.stdin.encoding, sys.stdin.errors)
    assert read_input == test_input

    # WideCharToMultiByte requires valid UTF, so thelone surrogate
    # gets replaced by U+FFFD. Generally the Windows wide-character
    # API allows lone surrogates, so this should probably be fixed.
    # Doing that is easier said than done.
    test_input = 'test input: \udc00\r\n'
    n = write_console_input(test_input)
    assert n == len(test_input)
    line = sys.stdin.buffer.readline()
    read_input = line.decode(sys.stdin.encoding, sys.stdin.errors)
    assert read_input[-3] == '\ufffd'