#include "cache.h"
#include "string-list.h"

/*
 * versioncmp(): copied from string/strverscmp.c in glibc commit
 * ee9247c38a8def24a59eb5cfb7196a98bef8cfdc, reformatted to Git coding
 * style. The implementation is under LGPL-2.1 and Git relicenses it
 * to GPLv2.
 */

/*
 * states: S_N: normal, S_I: comparing integral part, S_F: comparing
 * fractionnal parts, S_Z: idem but with leading Zeroes only
 */
#define  S_N    0x0
#define  S_I    0x3
#define  S_F    0x6
#define  S_Z    0x9

/* result_type: CMP: return diff; LEN: compare using len_diff/diff */
#define  CMP    2
#define  LEN    3

static const struct string_list *prereleases;
static int initialized;

struct suffix_match {
        int conf_pos;
        int start;
        int len;
};

static void find_better_matching_suffix(const char *tagname, const char *suffix,
                                        int suffix_len, int start, int conf_pos,
                                        struct suffix_match *match)
{
        /*
         * A better match either starts earlier or starts at the same offset
         * but is longer.
         */
        int end = match->len < suffix_len ? match->start : match->start-1;
        int i;
        for (i = start; i <= end; i++)
                if (starts_with(tagname + i, suffix)) {
                        match->conf_pos = conf_pos;
                        match->start = i;
                        match->len = suffix_len;
                        break;
                }
}

/*
 * off is the offset of the first different character in the two strings
 * s1 and s2. If either s1 or s2 contains a prerelease suffix containing
 * that offset or a suffix ends right before that offset, then that
 * string will be forced to be on top.
 *
 * If both s1 and s2 contain a (different) suffix around that position,
 * their order is determined by the order of those two suffixes in the
 * configuration.
 * If any of the strings contains more than one different suffixes around
 * that position, then that string is sorted according to the contained
 * suffix which starts at the earliest offset in that string.
 * If more than one different contained suffixes start at that earliest
 * offset, then that string is sorted according to the longest of those
 * suffixes.
 *
 * Return non-zero if *diff contains the return value for versioncmp()
 */
static int swap_prereleases(const char *s1,
                            const char *s2,
                            int off,
                            int *diff)
{
        int i;
        struct suffix_match match1 = { -1, off, -1 };
        struct suffix_match match2 = { -1, off, -1 };

        for (i = 0; i < prereleases->nr; i++) {
                const char *suffix = prereleases->items[i].string;
                int start, suffix_len = strlen(suffix);
                if (suffix_len < off)
                        start = off - suffix_len;
                else
                        start = 0;
                find_better_matching_suffix(s1, suffix, suffix_len, start,
                                            i, &match1);
                find_better_matching_suffix(s2, suffix, suffix_len, start,
                                            i, &match2);
        }
        if (match1.conf_pos == -1 && match2.conf_pos == -1)
                return 0;
        if (match1.conf_pos == match2.conf_pos)
                /* Found the same suffix in both, e.g. "-rc" in "v1.0-rcX"
                 * and "v1.0-rcY": the caller should decide based on "X"
                 * and "Y". */
                return 0;

        if (match1.conf_pos >= 0 && match2.conf_pos >= 0)
                *diff = match1.conf_pos - match2.conf_pos;
        else if (match1.conf_pos >= 0)
                *diff = -1;
        else /* if (match2.conf_pos >= 0) */
                *diff = 1;
        return 1;
}

/*
 * Compare S1 and S2 as strings holding indices/version numbers,
 * returning less than, equal to or greater than zero if S1 is less
 * than, equal to or greater than S2 (for more info, see the texinfo
 * doc).
 */

int versioncmp(const char *s1, const char *s2)
{
        const unsigned char *p1 = (const unsigned char *) s1;
        const unsigned char *p2 = (const unsigned char *) s2;
        unsigned char c1, c2;
        int state, diff;

        /*
         * Symbol(s)    0       [1-9]   others
         * Transition   (10) 0  (01) d  (00) x
         */
        static const uint8_t next_state[] = {
                /* state    x    d    0  */
                /* S_N */  S_N, S_I, S_Z,
                /* S_I */  S_N, S_I, S_I,
                /* S_F */  S_N, S_F, S_F,
                /* S_Z */  S_N, S_F, S_Z
        };

        static const int8_t result_type[] = {
                /* state   x/x  x/d  x/0  d/x  d/d  d/0  0/x  0/d  0/0  */

                /* S_N */  CMP, CMP, CMP, CMP, LEN, CMP, CMP, CMP, CMP,
                /* S_I */  CMP, -1,  -1,  +1,  LEN, LEN, +1,  LEN, LEN,
                /* S_F */  CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
                /* S_Z */  CMP, +1,  +1,  -1,  CMP, CMP, -1,  CMP, CMP
        };

        if (p1 == p2)
                return 0;

        c1 = *p1++;
        c2 = *p2++;
        /* Hint: '0' is a digit too.  */
        state = S_N + ((c1 == '0') + (isdigit (c1) != 0));

        while ((diff = c1 - c2) == 0) {
                if (c1 == '\0')
                        return diff;

                state = next_state[state];
                c1 = *p1++;
                c2 = *p2++;
                state += (c1 == '0') + (isdigit (c1) != 0);
        }

        if (!initialized) {
                const struct string_list *deprecated_prereleases;
                initialized = 1;
                prereleases = git_config_get_value_multi("versionsort.suffix");
                deprecated_prereleases = git_config_get_value_multi("versionsort.prereleasesuffix");
                if (prereleases) {
                        if (deprecated_prereleases)
                                warning("ignoring versionsort.prereleasesuffix because versionsort.suffix is set");
                } else
                        prereleases = deprecated_prereleases;
        }
        if (prereleases && swap_prereleases(s1, s2, (const char *) p1 - s1 - 1,
                                            &diff))
                return diff;

        state = result_type[state * 3 + (((c2 == '0') + (isdigit (c2) != 0)))];

        switch (state) {
        case CMP:
                return diff;

        case LEN:
                while (isdigit (*p1++))
                        if (!isdigit (*p2++))
                                return 1;

                return isdigit (*p2) ? -1 : diff;

        default:
                return state;
        }
}