/*
 * This code is taken from the RPM package manager.
 *
 * RPM is Copyright (c) 1998 by Red Hat Software, Inc.,
 * and may be distributed under the terms of the GPL and LGPL.
 * See http://rpm.org/gitweb?p=rpm.git;a=blob_plain;f=COPYING;hb=HEAD
 *
 * The code should follow upstream as closely as possible.
 * See http://rpm.org/gitweb?p=rpm.git;a=blob_plain;f=lib/rpmvercmp.c;hb=HEAD
 *
 * Currently the only difference as a policy is that upstream uses C99
 * features and pkg-config does not require a C99 compiler yet.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <string.h>
#include <ctype.h>
#include <stdlib.h>

/* macros to help code look more like upstream */
#define rstreq(a, b)    (strcmp(a, b) == 0)
#define risalnum(c)     isalnum((char)(c))
#define risdigit(c)     isdigit((char)(c))
#define risalpha(c)     isalpha((char)(c))

int rmpvercmp_impl(const char *a, const char *b, char *buf1, char *buf2);

/* compare alpha and numeric segments of two versions */
/* return 1: a is newer than b */
/*        0: a and b are the same version */
/*       -1: b is newer than a */
int rpmvercmp(const char * a, const char * b)
{
    /* easy comparison to see if versions are identical */
    if (rstreq(a, b)) return 0;

    char *buf1 = malloc(strlen(a) + 1);
    char *buf2 = malloc(strlen(b) + 1);

    if (!buf1 || !buf2) return 0; // arbitrary

    int r = rmpvercmp_impl(a, b, buf1, buf2);

    free(buf1);
    free(buf2);

    return r;
}

int rmpvercmp_impl(const char *a, const char *b, char *str1, char *str2) {
    char oldch1, oldch2;
    char * one, * two;
    int rc;
    int isnum;

    strcpy(str1, a);
    strcpy(str2, b);

    one = str1;
    two = str2;

    /* loop through each version segment of str1 and str2 and compare them */
    while (*one && *two) {
        while (*one && !risalnum(*one)) one++;
        while (*two && !risalnum(*two)) two++;

        /* If we ran to the end of either, we are finished with the loop */
        if (!(*one && *two)) break;

        str1 = one;
        str2 = two;

        /* grab first completely alpha or completely numeric segment */
        /* leave one and two pointing to the start of the alpha or numeric */
        /* segment and walk str1 and str2 to end of segment */
        if (risdigit(*str1)) {
            while (*str1 && risdigit(*str1)) str1++;
            while (*str2 && risdigit(*str2)) str2++;
            isnum = 1;
        } else {
            while (*str1 && risalpha(*str1)) str1++;
            while (*str2 && risalpha(*str2)) str2++;
            isnum = 0;
        }

        /* save character at the end of the alpha or numeric segment */
        /* so that they can be restored after the comparison */
        oldch1 = *str1;
        *str1 = '\0';
        oldch2 = *str2;
        *str2 = '\0';

        /* this cannot happen, as we previously tested to make sure that */
        /* the first string has a non-null segment */
        if (one == str1) return -1;     /* arbitrary */

        /* take care of the case where the two version segments are */
        /* different types: one numeric, the other alpha (i.e. empty) */
        /* numeric segments are always newer than alpha segments */
        /* XXX See patch #60884 (and details) from bugzilla #50977. */
        if (two == str2) return (isnum ? 1 : -1);

        if (isnum) {
            /* this used to be done by converting the digit segments */
            /* to ints using atoi() - it's changed because long  */
            /* digit segments can overflow an int - this should fix that. */

            /* throw away any leading zeros - it's a number, right? */
            while (*one == '0') one++;
            while (*two == '0') two++;

            /* whichever number has more digits wins */
            if (strlen(one) > strlen(two)) return 1;
            if (strlen(two) > strlen(one)) return -1;
        }

        /* strcmp will return which one is greater - even if the two */
        /* segments are alpha or if they are numeric.  don't return  */
        /* if they are equal because there might be more segments to */
        /* compare */
        rc = strcmp(one, two);
        if (rc) return (rc < 1 ? -1 : 1);

        /* restore character that was replaced by null above */
        *str1 = oldch1;
        one = str1;
        *str2 = oldch2;
        two = str2;
    }

    /* this catches the case where all numeric and alpha segments have */
    /* compared identically but the segment separating characters were */
    /* different */
    if ((!*one) && (!*two)) return 0;

    /* whichever version still has characters left over wins */
    if (!*one) return -1; else return 1;
}
