#include <wchar.h>
#include <string.h>
#include <stdarg.h>



struct putchdata {
    wchar_t *buffer;
    size_t maxlen, count;
};

static void reverse(char *str, size_t len) {
    if (len > 1) {
        char *start = str;
        char *end = str + len - 1;
        char tmp;

        while (start < end) {
            tmp = *end;
            *end-- = *start;
            *start++ = tmp;
        }
    }
}

static size_t itoa(unsigned num, char *dst, unsigned base, int issigned, int addplus, int uppercase) {
    int a = uppercase ? 'A' : 'a';
    int negative = 0;
    char *d = dst;
    size_t len;

    if (num == 0) {
        *d = '0';
        return 1;
    }

    if (issigned && (int)num < 0 && base == 10) {
        negative = 1;
        num = -num;
    }

    while (num > 0) {
        unsigned rem = num % base;
        num /= base;
        *d++ = (rem > 9) ? (rem - 10 + a) : (rem + '0');
    }

    if (negative)
        *d++ = '-';
    else if (addplus)
        *d++ = '+';

    len = d - dst;
    reverse(dst, len);

    return len;
}

static size_t lltoa(unsigned long long num, char *dst, unsigned base, int issigned, int addplus, int uppercase) {
    int a = uppercase ? 'A' : 'a';
    int negative = 0;
    char *d = dst;
    size_t len;

    if (num == 0) {
        *d = '0';
        return 1;
    }

    if (issigned && (signed long long)num < 0 && base == 10) {
        negative = 1;
        num = -num;
    }

    while (num > 0) {
        unsigned rem = num % base;
        num /= base;
        *d++ = (rem > 9) ? (rem - 10 + a) : (rem + '0');
    }

    if (negative)
        *d++ = '-';
    else if (addplus)
        *d++ = '+';

    len = d - dst;
    reverse(dst, len);

    return len;
}

static void putchproc(wchar_t ch, struct putchdata *pcd) {
    size_t index = pcd->count;

    if (ch != '\0')
        pcd->count++;

    if (pcd->count > pcd->maxlen)
        return;

    if (pcd->count == pcd->maxlen) {
        pcd->buffer[index] =  '\0';
        return;
    }

    pcd->buffer[index] = ch;
}

#define PUTCH(ch) putchproc((ch), &pcd)

int vswprintf(wchar_t *buffer, size_t maxlen, const wchar_t *fmt, va_list ap) {
    struct putchdata pcd;
    wchar_t ch;
    const wchar_t *src;
    char tmp[128];
    const char *hsrc;

    pcd.buffer = buffer;
    pcd.maxlen = maxlen;
    pcd.count = 0;

    while ((ch = *fmt++) != '\0') {
        if (ch == '%') {
            int left = 0;
            int addplus = 0;
            int alternate = 0;
            int padzeros = 0;
            size_t width = 0;
            size_t limit = 0;
            int longlong = 0;
            int half = 0;
            size_t len, i;
            int uppercase;
            void *ptr;
            const wchar_t *start = fmt;

            if ((ch = *fmt++) == '\0')
                goto out;

            for (;;) {
                if (ch == '-')
                    left = 1;
                else if (ch == '+')
                    addplus = 1;
                else if (ch == '#')
                    alternate = 1;
                else if (ch == '0')
                    padzeros = 1;
                else
                    break;

                if ((ch = *fmt++) == '\0')
                    goto out;
            }

            while (ch >= '0' && ch <= '9') {
                width = 10 * width + (ch - '0');

                if ((ch = *fmt++) == '\0')
                    goto out;
            }

            if (ch == '.') {
                if ((ch = *fmt++) == '\0')
                    goto out;

                if (ch == '*') {
                    limit = va_arg(ap, size_t);

                    if ((ch = *fmt++) == '\0')
                        goto out;
                } else {
                    while (ch >= '0' && ch <= '9') {
                        limit = 10 * limit + (ch - '0');

                        if ((ch = *fmt++) == '\0')
                            goto out;
                    }
                }
            }

            if (ch == 'L') {
                longlong = 1;

                if ((ch = *fmt++) == '\0')
                    goto out;
            } else if (ch == 'l') {
                if ((ch = *fmt++) == '\0')
                    goto out;

                if (ch == 'l') {
                    longlong = 1;

                    if ((ch = *fmt++) == '\0')
                        goto out;
                }
            } else if (ch == 'h') {
                half = 1;

                if ((ch = *fmt++) == '\0')
                    goto out;
            }

            switch (ch) {
                default:
                    fmt = start;
                    /* Fall through */
                case '%':
                    PUTCH('%');
                    break;
                case 'C':
                case 'c':
                    PUTCH(va_arg(ap, wchar_t));
                    break;
                case 'D':
                case 'd':
                    uppercase = (ch == 'D');
                    if (longlong)
                        len = lltoa(va_arg(ap, long long), tmp, 10, 1, addplus, uppercase);
                    else
                        len = itoa(va_arg(ap, int), tmp, 10, 1, addplus, uppercase);

                    hsrc = tmp;

                    if (width > len)
                        width -= len;
                    else
                        width = 0;

                    if (left == 0) {
                        for (i = 0; i < width; i++) PUTCH(padzeros ? '0' : ' ');
                    }

                    for (i = 0; i < len; i++) PUTCH(hsrc[i]);

                    if (left != 0) {
                        for (i = 0; i < width; i++) PUTCH(' ');
                    }
                    break;

                case 'U':
                case 'u':
                    uppercase = (ch == 'U');
                    if (longlong)
                        len = lltoa(va_arg(ap, unsigned long long), tmp, 10, 0, addplus, uppercase);
                    else
                        len = itoa(va_arg(ap, unsigned int), tmp, 10, 0, addplus, uppercase);

                    hsrc = tmp;

                    if (width > len)
                        width -= len;
                    else
                        width = 0;

                    if (left == 0) {
                        for (i = 0; i < width; i++) PUTCH(padzeros ? '0' : ' ');
                    }

                    for (i = 0; i < len; i++) PUTCH(hsrc[i]);

                    if (left != 0) {
                        for (i = 0; i < width; i++) PUTCH(' ');
                    }
                    break;
                case 'X':
                case 'x':
                    uppercase = (ch == 'X');
                    if (longlong)
                        len = lltoa(va_arg(ap, unsigned long long), tmp, 16, 0, addplus, uppercase);
                    else
                        len = itoa(va_arg(ap, unsigned int), tmp, 16, 0, addplus, uppercase);

                    hsrc = tmp;

                    if (width > len)
                        width -= len;
                    else
                        width = 0;

                    if (left == 0) {
                        for (i = 0; i < width; i++) PUTCH(padzeros ? '0' : ' ');
                    }

                    for (i = 0; i < len; i++) PUTCH(hsrc[i]);

                    if (left != 0) {
                        for (i = 0; i < width; i++) PUTCH(' ');
                    }
                    break;
                case 'P':
                case 'p':
                    uppercase = (ch == 'P');
                    ptr = va_arg(ap, void *);
                    len = itoa((unsigned)ptr, tmp, 16, 0, 0, uppercase);

                    hsrc = tmp;
                    width = 8;

                    if (width > len)
                        width -= len;
                    else
                        width = 0;

                    if (alternate && ptr != NULL) {
                        PUTCH('0');
                        PUTCH('x');
                    }

                    for (i = 0; i < width; i++) PUTCH('0');

                    for (i = 0; i < len; i++) PUTCH(hsrc[i]);
                    break;

                case 'F':
                case 'f':
                    uppercase = (ch == 'D');
                    len = ftoa  /*???*/




                case 'S':
                case 's':
                    if (half) {
                        hsrc = va_arg(ap, const char *);
                        if (hsrc == NULL)
                            hsrc = "(null)";

                        len = strlen(hsrc);

                        if (limit > 0 && len > limit)
                            len = limit;

                        if (width > len)
                            width -= len;
                        else
                            width = 0;

                        if (left == 0) {
                            for (i = 0; i < width; i++) PUTCH(' ');
                        }

                        for (i = 0; i < len; i++) PUTCH(hsrc[i]);

                        if (left != 0) {
                            for (i = 0; i < width; i++) PUTCH(' ');
                        }
                    } else {
                        src = va_arg(ap, const wchar_t *);
                        if (src == NULL)
                            src = L"(null)";

                        len = wcslen(src);

                        if (limit > 0 && len > limit)
                            len = limit;

                        if (width > len)
                            width -= len;
                        else
                            width = 0;

                        if (left == 0) {
                            for (i = 0; i < width; i++) PUTCH(' ');
                        }

                        for (i = 0; i < len; i++) PUTCH(src[i]);

                        if (left != 0) {
                            for (i = 0; i < width; i++) PUTCH(' ');
                        }
                    }
                    break;
            }
        } else {
            PUTCH(ch);
        }
    }

out:

    PUTCH('\0');

    return pcd.count;
}

int swprintf(wchar_t *buffer, size_t maxlen, const wchar_t *fmt, ...) {
    va_list ap;
    int wc;

    va_start(ap, fmt);
    wc = vswprintf(buffer, maxlen, fmt, ap);
    va_end(ap);

    return wc;
}