#include <stdlib.h>
#include <langinfo.h>
#include <time.h>
#include <ctype.h>
#include <stddef.h>
#include <string.h>
#include <strings.h>
#include "time_impl.h"

char *strptime(const char *restrict s, const char *restrict f, struct tm *restrict tm)
{
        int i, w, neg, adj, min, range, *dest, dummy;
        const char *ex;
        size_t len;
        int want_century = 0, century = 0, relyear = 0;
        while (*f) {
                if (*f != '%') {
                        if (isspace(*f)) for (; *s && isspace(*s); s++);
                        else if (*s != *f) return 0;
                        else s++;
                        f++;
                        continue;
                }
                f++;
                if (*f == '+') f++;
                if (isdigit(*f)) {
                        char *new_f;
                        w=strtoul(f, &new_f, 10);
                        f = new_f;
                } else {
                        w=-1;
                }
                adj=0;
                switch (*f++) {
                case 'a': case 'A':
                        dest = &tm->tm_wday;
                        // Haiku defines this constants the opposite way musl/Glibc does (first the full
                        // version, then the abbreviated version). This results in strptime failing to
                        // match the patterns. Keep this to make musl's strptime Haiku-compatible.
#ifdef __HAIKU__
                        min = DAY_1;
#else
                        min = ABDAY_1;
#endif
                        range = 7;
                        goto symbolic_range;
                case 'b': case 'B': case 'h':
                        dest = &tm->tm_mon;
#ifdef __HAIKU__        // To make musl's strptime Haiku-compatible
                        min = MON_1;
#else
                        min = ABMON_1;
#endif
                        range = 12;
                        goto symbolic_range;
                case 'c':
                        s = strptime(s, nl_langinfo(D_T_FMT), tm);
                        if (!s) return 0;
                        break;
                case 'C':
                        dest = &century;
                        if (w<0) w=2;
                        want_century |= 2;
                        goto numeric_digits;
                case 'd': case 'e':
                        dest = &tm->tm_mday;
                        min = 1;
                        range = 31;
                        goto numeric_range;
                case 'D':
                        s = strptime(s, "%m/%d/%y", tm);
                        if (!s) return 0;
                        break;
                case 'F':
                        /* Use temp buffer to implement the odd requirement
                         * that entire field be width-limited but the year
                         * subfield not itself be limited. */
                        i = 0;
                        {
                        char tmp[20];
                        if (*s == '-' || *s == '+') tmp[i++] = *s++;
                        while (*s=='0' && isdigit(s[1])) s++;
                        for (; *s && i<(size_t)w && i+1<sizeof tmp; i++) {
                                tmp[i] = *s++;
                        }
                        tmp[i] = 0;
                        {
                        char *p = strptime(tmp, "%12Y-%m-%d", tm);
                        if (!p) return 0;
                        s -= tmp+i-p;
                        }
                        }
                        break;
                case 'H':
                        dest = &tm->tm_hour;
                        min = 0;
                        range = 24;
                        goto numeric_range;
                case 'I':
                        dest = &tm->tm_hour;
                        min = 1;
                        range = 12;
                        goto numeric_range;
                case 'j':
                        dest = &tm->tm_yday;
                        min = 1;
                        range = 366;
                        adj = 1;
                        goto numeric_range;
                case 'm':
                        dest = &tm->tm_mon;
                        min = 1;
                        range = 12;
                        adj = 1;
                        goto numeric_range;
                case 'M':
                        dest = &tm->tm_min;
                        min = 0;
                        range = 60;
                        goto numeric_range;
                case 'n': case 't':
                        for (; *s && isspace(*s); s++);
                        break;
                case 'p':
                        ex = nl_langinfo(AM_STR);
                        len = strlen(ex);
                        if (!strncasecmp(s, ex, len)) {
                                tm->tm_hour %= 12;
                                s += len;
                                break;
                        }
                        ex = nl_langinfo(PM_STR);
                        len = strlen(ex);
                        if (!strncasecmp(s, ex, len)) {
                                tm->tm_hour %= 12;
                                tm->tm_hour += 12;
                                s += len;
                                break;
                        }
                        return 0;
                case 'r':
                        s = strptime(s, nl_langinfo(T_FMT_AMPM), tm);
                        if (!s) return 0;
                        break;
                case 'R':
                        s = strptime(s, "%H:%M", tm);
                        if (!s) return 0;
                        break;
                case 's':
                        /* Parse only. Effect on tm is unspecified
                         * and presently no effect is implemented.. */
                        if (*s == '-') s++;
                        if (!isdigit(*s)) return 0;
                        while (isdigit(*s)) s++;
                        break;
                case 'S':
                        dest = &tm->tm_sec;
                        min = 0;
                        range = 61;
                        goto numeric_range;
                case 'T':
                        s = strptime(s, "%H:%M:%S", tm);
                        if (!s) return 0;
                        break;
                case 'U':
                case 'W':
                        /* Throw away result of %U, %V, %W, %g, and %G. Effect
                         * is unspecified and there is no clear right choice. */
                        dest = &dummy;
                        min = 0;
                        range = 54;
                        goto numeric_range;
                case 'V':
                        dest = &dummy;
                        min = 1;
                        range = 53;
                        goto numeric_range;
                case 'g':
                        dest = &dummy;
                        w = 2;
                        goto numeric_digits;
                case 'G':
                        dest = &dummy;
                        if (w<0) w=4;
                        goto numeric_digits;
                case 'u':
                        dest = &tm->tm_wday;
                        min = 1;
                        range = 7;
                        goto numeric_range;
                case 'w':
                        dest = &tm->tm_wday;
                        min = 0;
                        range = 7;
                        goto numeric_range;
                case 'x':
                        s = strptime(s, nl_langinfo(D_FMT), tm);
                        if (!s) return 0;
                        break;
                case 'X':
                        s = strptime(s, nl_langinfo(T_FMT), tm);
                        if (!s) return 0;
                        break;
                case 'y':
                        dest = &relyear;
                        w = 2;
                        want_century |= 1;
                        goto numeric_digits;
                case 'Y':
                        dest = &tm->tm_year;
                        if (w<0) w=4;
                        adj = 1900;
                        want_century = 0;
                        goto numeric_digits;
                case 'z':
                        if (*s == '+') neg = 0;
                        else if (*s == '-') neg = 1;
                        else return 0;
                        for (i=0; i<4; i++) if (!isdigit(s[1+i])) return 0;
                        tm->__tm_gmtoff = (s[1]-'0')*36000+(s[2]-'0')*3600
                                + (s[3]-'0')*600 + (s[4]-'0')*60;
                        if (neg) tm->__tm_gmtoff = -tm->__tm_gmtoff;
                        s += 5;
                        break;
                case 'Z':
                        if (!strncmp(s, tzname[0], len = strlen(tzname[0]))) {
                                tm->tm_isdst = 0;
                                s += len;
                        } else if (!strncmp(s, tzname[1], len=strlen(tzname[1]))) {
                                tm->tm_isdst = 1;
                                s += len;
                        } else {
                                /* FIXME: is this supposed to be an error? */
                                while ((*s|32)-'a' <= 'z'-'a') s++;
                        }
                        break;
                case '%':
                        if (*s++ != '%') return 0;
                        break;
                default:
                        return 0;
                numeric_range:
                        if (!isdigit(*s)) return 0;
                        *dest = 0;
                        for (i=1; i<=min+range && isdigit(*s); i*=10)
                                *dest = *dest * 10 + *s++ - '0';
                        if (*dest - min >= (unsigned)range) return 0;
                        *dest -= adj;
                        switch((char *)dest - (char *)tm) {
                        case offsetof(struct tm, tm_yday):
                                ;
                        }
                        goto update;
                numeric_digits:
                        neg = 0;
                        if (*s == '+') s++;
                        else if (*s == '-') neg=1, s++;
                        if (!isdigit(*s)) return 0;
                        for (*dest=i=0; i<w && isdigit(*s); i++)
                                *dest = *dest * 10 + *s++ - '0';
                        if (neg) *dest = -*dest;
                        *dest -= adj;
                        goto update;
                symbolic_range:
#ifdef __HAIKU__        // To make musl's strptime Haiku-compatible
                        for (i=0; i<=2*range-1; i++) {
#else
                        for (i=2*range-1; i>=0; i--) {
#endif
                                ex = nl_langinfo(min+i);
                                len = strlen(ex);
                                if (strncasecmp(s, ex, len)) continue;
                                s += len;
                                *dest = i % range;
                                break;
                        }
                        if (i<0) return 0;
                        goto update;
                update:
                        //FIXME
                        ;
                }
        }
        if (want_century) {
                tm->tm_year = relyear;
                if (want_century & 2) tm->tm_year += century * 100 - 1900;
                else if (tm->tm_year <= 68) tm->tm_year += 100;
        }
        return (char *)s;
}