/*
 * The authors of this software are Rob Pike and Ken Thompson.
 *              Copyright (c) 2002 by Lucent Technologies.
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 */

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

#include "utf.h"

namespace kuzu {
namespace regex {

enum {
    Bit1 = 7,
    Bitx = 6,
    Bit2 = 5,
    Bit3 = 4,
    Bit4 = 3,
    Bit5 = 2,

    T1 = ((1 << (Bit1 + 1)) - 1) ^ 0xFF, /* 0000 0000 */
    Tx = ((1 << (Bitx + 1)) - 1) ^ 0xFF, /* 1000 0000 */
    T2 = ((1 << (Bit2 + 1)) - 1) ^ 0xFF, /* 1100 0000 */
    T3 = ((1 << (Bit3 + 1)) - 1) ^ 0xFF, /* 1110 0000 */
    T4 = ((1 << (Bit4 + 1)) - 1) ^ 0xFF, /* 1111 0000 */
    T5 = ((1 << (Bit5 + 1)) - 1) ^ 0xFF, /* 1111 1000 */

    Rune1 = (1 << (Bit1 + 0 * Bitx)) - 1, /* 0000 0000 0111 1111 */
    Rune2 = (1 << (Bit2 + 1 * Bitx)) - 1, /* 0000 0111 1111 1111 */
    Rune3 = (1 << (Bit3 + 2 * Bitx)) - 1, /* 1111 1111 1111 1111 */
    Rune4 = (1 << (Bit4 + 3 * Bitx)) - 1,
    /* 0001 1111 1111 1111 1111 1111 */

    Maskx = (1 << Bitx) - 1, /* 0011 1111 */
    Testx = Maskx ^ 0xFF,    /* 1100 0000 */

    Bad = Runeerror,
};

int chartorune(Rune* rune, const char* str) {
    int c, c1, c2, c3;
    long l;

    /*
     * one character sequence
     *	00000-0007F => T1
     */
    c = *(unsigned char*)str;
    if (c < Tx) {
        *rune = c;
        return 1;
    }

    /*
     * two character sequence
     *	0080-07FF => T2 Tx
     */
    c1 = *(unsigned char*)(str + 1) ^ Tx;
    if (c1 & Testx)
        goto bad;
    if (c < T3) {
        if (c < T2)
            goto bad;
        l = ((c << Bitx) | c1) & Rune2;
        if (l <= Rune1)
            goto bad;
        *rune = l;
        return 2;
    }

    /*
     * three character sequence
     *	0800-FFFF => T3 Tx Tx
     */
    c2 = *(unsigned char*)(str + 2) ^ Tx;
    if (c2 & Testx)
        goto bad;
    if (c < T4) {
        l = ((((c << Bitx) | c1) << Bitx) | c2) & Rune3;
        if (l <= Rune2)
            goto bad;
        *rune = l;
        return 3;
    }

    /*
     * four character sequence (21-bit value)
     *	10000-1FFFFF => T4 Tx Tx Tx
     */
    c3 = *(unsigned char*)(str + 3) ^ Tx;
    if (c3 & Testx)
        goto bad;
    if (c < T5) {
        l = ((((((c << Bitx) | c1) << Bitx) | c2) << Bitx) | c3) & Rune4;
        if (l <= Rune3)
            goto bad;
        *rune = l;
        return 4;
    }

    /*
     * Support for 5-byte or longer UTF-8 would go here, but
     * since we don't have that, we'll just fall through to bad.
     */

    /*
     * bad decoding
     */
bad:
    *rune = Bad;
    return 1;
}

int runetochar(char* str, const Rune* rune) {
    /* Runes are signed, so convert to unsigned for range check. */
    unsigned long c;

    /*
     * one character sequence
     *	00000-0007F => 00-7F
     */
    c = *rune;
    if (c <= Rune1) {
        str[0] = static_cast<char>(c);
        return 1;
    }

    /*
     * two character sequence
     *	0080-07FF => T2 Tx
     */
    if (c <= Rune2) {
        str[0] = T2 | static_cast<char>(c >> 1 * Bitx);
        str[1] = Tx | (c & Maskx);
        return 2;
    }

    /*
     * If the Rune is out of range, convert it to the error rune.
     * Do this test here because the error rune encodes to three bytes.
     * Doing it earlier would duplicate work, since an out of range
     * Rune wouldn't have fit in one or two bytes.
     */
    if (c > Runemax)
        c = Runeerror;

    /*
     * three character sequence
     *	0800-FFFF => T3 Tx Tx
     */
    if (c <= Rune3) {
        str[0] = T3 | static_cast<char>(c >> 2 * Bitx);
        str[1] = Tx | ((c >> 1 * Bitx) & Maskx);
        str[2] = Tx | (c & Maskx);
        return 3;
    }

    /*
     * four character sequence (21-bit value)
     *     10000-1FFFFF => T4 Tx Tx Tx
     */
    str[0] = T4 | static_cast<char>(c >> 3 * Bitx);
    str[1] = Tx | ((c >> 2 * Bitx) & Maskx);
    str[2] = Tx | ((c >> 1 * Bitx) & Maskx);
    str[3] = Tx | (c & Maskx);
    return 4;
}

int runelen(Rune rune) {
    char str[10];

    return runetochar(str, &rune);
}

int fullrune(const char* str, int n) {
    if (n > 0) {
        int c = *(unsigned char*)str;
        if (c < Tx)
            return 1;
        if (n > 1) {
            if (c < T3)
                return 1;
            if (n > 2) {
                if (c < T4 || n > 3)
                    return 1;
            }
        }
    }
    return 0;
}

int utflen(const char* s) {
    int c;
    long n;
    Rune rune;

    n = 0;
    for (;;) {
        c = *(unsigned char*)s;
        if (c < Runeself) {
            if (c == 0)
                return n;
            s++;
        } else
            s += chartorune(&rune, s);
        n++;
    }
    return 0;
}

char* utfrune(const char* s, Rune c) {
    long c1;
    Rune r;
    int n;

    if (c < Runesync) /* not part of utf sequence */
        return strchr((char*)s, c);

    for (;;) {
        c1 = *(unsigned char*)s;
        if (c1 < Runeself) { /* one byte rune */
            if (c1 == 0)
                return 0;
            if (c1 == c)
                return (char*)s;
            s++;
            continue;
        }
        n = chartorune(&r, s);
        if (r == c)
            return (char*)s;
        s += n;
    }
    return 0;
}
} // namespace regex
} // namespace kuzu
