/* SPDX-License-Identifier: LGPL-2.1-or-later */

#ifndef SD_BOOT
#include <ctype.h>

#include "macro.h"
#endif
#include "string-util-fundamental.h"

sd_char *startswith(const sd_char *s, const sd_char *prefix) {
        size_t l;

        assert(s);
        assert(prefix);

        l = strlen(prefix);
        if (!strneq(s, prefix, l))
                return NULL;

        return (sd_char*) s + l;
}

#ifndef SD_BOOT
sd_char *startswith_no_case(const sd_char *s, const sd_char *prefix) {
        size_t l;

        assert(s);
        assert(prefix);

        l = strlen(prefix);
        if (!strncaseeq(s, prefix, l))
                return NULL;

        return (sd_char*) s + l;
}
#endif

sd_char* endswith(const sd_char *s, const sd_char *postfix) {
        size_t sl, pl;

        assert(s);
        assert(postfix);

        sl = strlen(s);
        pl = strlen(postfix);

        if (pl == 0)
                return (sd_char*) s + sl;

        if (sl < pl)
                return NULL;

        if (strcmp(s + sl - pl, postfix) != 0)
                return NULL;

        return (sd_char*) s + sl - pl;
}

sd_char* endswith_no_case(const sd_char *s, const sd_char *postfix) {
        size_t sl, pl;

        assert(s);
        assert(postfix);

        sl = strlen(s);
        pl = strlen(postfix);

        if (pl == 0)
                return (sd_char*) s + sl;

        if (sl < pl)
                return NULL;

        if (strcasecmp(s + sl - pl, postfix) != 0)
                return NULL;

        return (sd_char*) s + sl - pl;
}

#ifdef SD_BOOT
static sd_bool isdigit(sd_char a) {
        return a >= '0' && a <= '9';
}
#endif

static sd_bool is_alpha(sd_char a) {
        /* Locale independent version of isalpha(). */
        return (a >= 'a' && a <= 'z') || (a >= 'A' && a <= 'Z');
}

static sd_bool is_valid_version_char(sd_char a) {
        return isdigit(a) || is_alpha(a) || IN_SET(a, '~', '-', '^', '.');
}

sd_int strverscmp_improved(const sd_char *a, const sd_char *b) {

        /* This is based on RPM's rpmvercmp(). But this explicitly handles '-' and '.', as we usually
         * want to directly compare strings which contain both version and release; e.g.
         * '247.2-3.1.fc33.x86_64' or '5.11.0-0.rc5.20210128git76c057c84d28.137.fc34'.
         * Unlike rpmvercmp(), this distiguishes e.g. 123a and 123.a, and 123a is newer.
         *
         * This splits the input strings into segments. Each segment is numeric or alpha, and may be
         * prefixed with the following:
         *  '~' : used for pre-releases, a segment prefixed with this is the oldest,
         *  '-' : used for the separator between version and release,
         *  '^' : used for patched releases, a segment with this is newer than one with '-'.
         *  '.' : used for point releases.
         * Note, no prefix segment is the newest. All non-supported characters are dropped, and
         * handled as a separator of segments, e.g., 123_a is equivalent to 123a.
         *
         * By using this, version strings can be sorted like following:
         *  (older) 122.1
         *     ^    123~rc1-1
         *     |    123
         *     |    123-a
         *     |    123-a.1
         *     |    123-1
         *     |    123-1.1
         *     |    123^post1
         *     |    123.a-1
         *     |    123.1-1
         *     v    123a-1
         *  (newer) 124-1
         */

        if (isempty(a) || isempty(b))
                return strcmp_ptr(a, b);

        for (;;) {
                const sd_char *aa, *bb;
                sd_int r;

                /* Drop leading invalid characters. */
                while (*a != '\0' && !is_valid_version_char(*a))
                        a++;
                while (*b != '\0' && !is_valid_version_char(*b))
                        b++;

                /* Handle '~'. Used for pre-releases, e.g. 123~rc1, or 4.5~alpha1 */
                if (*a == '~' || *b == '~') {
                        /* The string prefixed with '~' is older. */
                        r = CMP(*a != '~', *b != '~');
                        if (r != 0)
                                return r;

                        /* Now both strings are prefixed with '~'. Compare remaining strings. */
                        a++;
                        b++;
                }

                /* If at least one string reaches the end, then longer is newer.
                 * Note that except for '~' prefixed segments, a string has more segments is newer.
                 * So, this check must be after the '~' check. */
                if (*a == '\0' || *b == '\0')
                        return CMP(*a, *b);

                /* Handle '-', which separates version and release, e.g 123.4-3.1.fc33.x86_64 */
                if (*a == '-' || *b == '-') {
                        /* The string prefixed with '-' is older (e.g., 123-9 vs 123.1-1) */
                        r = CMP(*a != '-', *b != '-');
                        if (r != 0)
                                return r;

                        a++;
                        b++;
                }

                /* Handle '^'. Used for patched release. */
                if (*a == '^' || *b == '^') {
                        r = CMP(*a != '^', *b != '^');
                        if (r != 0)
                                return r;

                        a++;
                        b++;
                }

                /* Handle '.'. Used for point releases. */
                if (*a == '.' || *b == '.') {
                        r = CMP(*a != '.', *b != '.');
                        if (r != 0)
                                return r;

                        a++;
                        b++;
                }

                if (isdigit(*a) || isdigit(*b)) {
                        /* Skip leading '0', to make 00123 equivalent to 123. */
                        while (*a == '0')
                                a++;
                        while (*b == '0')
                                b++;

                        /* Find the leading numeric segments. One may be an empty string. So,
                         * numeric segments are always newer than alpha segments. */
                        for (aa = a; isdigit(*aa); aa++)
                                ;
                        for (bb = b; isdigit(*bb); bb++)
                                ;

                        /* To compare numeric segments without parsing their values, first compare the
                         * lengths of the segments. Eg. 12345 vs 123, longer is newer. */
                        r = CMP(aa - a, bb - b);
                        if (r != 0)
                                return r;

                        /* Then, compare them as strings. */
                        r = strncmp(a, b, aa - a);
                        if (r != 0)
                                return r;
                } else {
                        /* Find the leading non-numeric segments. */
                        for (aa = a; is_alpha(*aa); aa++)
                                ;
                        for (bb = b; is_alpha(*bb); bb++)
                                ;

                        /* Note that the segments are usually not NUL-terminated. */
                        r = strncmp(a, b, MIN(aa - a, bb - b));
                        if (r != 0)
                                return r;

                        /* Longer is newer, e.g. abc vs abcde. */
                        r = CMP(aa - a, bb - b);
                        if (r != 0)
                                return r;
                }

                /* The current segments are equivalent. Let's compare the next one. */
                a = aa;
                b = bb;
        }
}
