/*
 * Copyright (c) Contributors to the Open 3D Engine Project.
 * For complete copyright and license terms please see the LICENSE at the root of this distribution.
 *
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 */

#include <AzCore/std/string/alphanum.h>

//#define ALPHANUM_LOCALE
#ifdef ALPHANUM_LOCALE
#   include <cctype>
#endif

namespace AZStd
{
    /*
    The Alphanum Algorithm is an improved sorting algorithm for strings
    containing numbers.  Instead of sorting numbers in ASCII order like a
    standard sort, this algorithm sorts numbers in numeric order.

    The Alphanum Algorithm is discussed at http://www.DaveKoelle.com

    This implementation is Copyright (c) 2008 Dirk Jagdmann <doj@cubic.org>.
    It is a cleanroom implementation of the algorithm and not derived by
    other's works. In contrast to the versions written by Dave Koelle this
    source code is distributed with the libpng/zlib license.

    This software is provided 'as-is', without any express or implied
    warranty. In no event will the authors be held liable for any damages
    arising from the use of this software.

    Permission is granted to anyone to use this software for any purpose,
    including commercial applications, and to alter it and redistribute it
    freely, subject to the following restrictions:

        1. The origin of this software must not be misrepresented; you
           must not claim that you wrote the original software. If you use
           this software in a product, an acknowledgment in the product
           documentation would be appreciated but is not required.

        2. Altered source versions must be plainly marked as such, and
           must not be misrepresented as being the original software.

        3. This notice may not be removed or altered from any source
           distribution. */

    /* $Header: /code/doj/alphanum.hpp,v 1.3 2008/01/28 23:06:47 doj Exp $ */

    // TODO: make comparison with hexadecimal numbers. Extend the alphanum_comp() function by traits to choose between decimal and hexadecimal.
    namespace Internal
    {
        // if you want to honour the locale settings for detecting digit
        // characters, you should define ALPHANUM_LOCALE
#ifdef ALPHANUM_LOCALE
        /** wrapper function for ::isdigit() */
        AZ_FORCE_INLINE bool alphanum_isdigit(int c)
        {
            return isdigit(c);
        }
#else
        /** this function does not consider the current locale and only
        works with ASCII digits.
        @return true if c is a digit character
        */
        AZ_FORCE_INLINE bool alphanum_isdigit(const char c)
        {
            return c >= '0' && c <= '9';
        }
#endif

        /**
           compare l and r with strcmp() semantics, but using
           the "Alphanum Algorithm". This function is designed to read
           through the l and r strings only one time, for
           maximum performance. It does not allocate memory for
           substrings. It can either use the C-library functions isdigit()
           and atoi() to honour your locale settings, when recognizing
           digit characters when you "#define ALPHANUM_LOCALE=1" or use
           it's own digit character handling which only works with ASCII
           digit characters, but provides better performance.

           @param l NULL-terminated C-style string
           @param r NULL-terminated C-style string
           @return negative if l<r, 0 if l equals r, positive if l>r
         */
        int alphanum_impl(const char* l, const char* r)
        {
            enum mode_t
            {
                STRING, NUMBER
            } mode = STRING;
            while (*l && *r)
            {
                if (mode == STRING)
                {
                    char l_char, r_char;
                    while ((l_char = *l) != 0 && (r_char = *r) != 0)
                    {
                        // check if this are digit characters
                        const bool l_digit = alphanum_isdigit(l_char), r_digit = alphanum_isdigit(r_char);
                        // if both characters are digits, we continue in NUMBER mode
                        if (l_digit && r_digit)
                        {
                            mode = NUMBER;
                            break;
                        }

                        // if only the left character is a digit, we have a result
                        if (l_digit)
                        {
                            return -1;
                        }
                        // if only the right character is a digit, we have a result
                        if (r_digit)
                        {
                            return +1;
                        }
                        // compute the difference of both characters
                        const int diff = l_char - r_char;
                        // if they differ we have a result
                        if (diff != 0)
                        {
                            return diff;
                        }
                        // otherwise process the next characters
                        ++l;
                        ++r;
                    }
                }
                else // mode==NUMBER
                {
    #ifdef ALPHANUM_LOCALE
                    // get the left number
                    char* end;
                    unsigned long l_int = strtoul(l, &end, 0);
                    l = end;

                    // get the right number
                    unsigned long r_int = strtoul(r, &end, 0);
                    r = end;
    #else
                    // get the left number
                    unsigned long l_int = 0;
                    while (*l && alphanum_isdigit(*l))
                    {
                        // TODO: this can overflow
                        l_int = l_int * 10 + *l - '0';
                        ++l;
                    }

                    // get the right number
                    unsigned long r_int = 0;
                    while (*r && alphanum_isdigit(*r))
                    {
                        // TODO: this can overflow
                        r_int = r_int * 10 + *r - '0';
                        ++r;
                    }
    #endif

                    // if the difference is not equal to zero, we have a comparison result
                    const long diff = l_int - r_int;
                    if (diff != 0)
                    {
                        return static_cast<int>(diff);
                    }

                    // otherwise we process the next substring in STRING mode
                    mode = STRING;
                }
            }

            if (*r)
            {
                return -1;
            }
            if (*l)
            {
                return +1;
            }
            return 0;
        }
    } // namespace Internal
} // namespace AZStd
