/*
 * Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Assertions.h>
#include <AK/StringBuilder.h>
#include <AK/Types.h>
#include <bits/stdio_file_implementation.h>
#include <errno.h>
#include <stdio.h>
#include <wchar.h>

static_assert(AssertSize<wchar_t, sizeof(u32)>());

extern "C" {

wint_t fgetwc(FILE* stream)
{
    VERIFY(stream);
    Array<u8, 4> underlying;
    auto underlying_bytes = underlying.span();
    size_t encoded_length = 0;
    size_t bytes_read = 0;
    do {
        size_t nread = fread(underlying_bytes.offset_pointer(bytes_read), 1, 1, stream);
        if (nread != 1) {
            errno = EILSEQ;
            return WEOF;
        }
        ++bytes_read;
        if (bytes_read == 1) {
            if (underlying[0] >> 7 == 0) {
                encoded_length = 1;
            } else if (underlying[0] >> 5 == 6) {
                encoded_length = 2;
            } else if (underlying[0] >> 4 == 0xe) {
                encoded_length = 3;
            } else if (underlying[0] >> 3 == 0x1e) {
                encoded_length = 4;
            } else {
                errno = EILSEQ;
                return WEOF;
            }
        }
    } while (bytes_read < encoded_length);

    wchar_t code_point;
    auto read_bytes = mbrtowc(&code_point, bit_cast<char const*>(underlying.data()), encoded_length, nullptr);
    VERIFY(read_bytes == encoded_length);
    return code_point;
}

wint_t getwc(FILE* stream)
{
    return fgetwc(stream);
}

wint_t getwchar()
{
    return getwc(stdin);
}
}