//========================================================================
//
// DateInfo.cc
//
// Copyright (C) 2008, 2018, 2019 Albert Astals Cid <aacid@kde.org>
// Copyright (C) 2009 Carlos Garcia Campos <carlosgc@gnome.org>
// Copyright (C) 2015 André Guerreiro <aguerreiro1985@gmail.com>
// Copyright (C) 2015 André Esser <bepandre@hotmail.com>
// Copyright (C) 2016, 2018 Adrian Johnson <ajohnson@redneon.com>
// Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, <info@kdab.com>. Work sponsored by Technische Universität Dresden
//
// To see a description of the changes please see the Changelog file that
// came with your tarball or type make ChangeLog if you are building from git
//
//========================================================================

//========================================================================
//
// Based on code from pdfinfo.cc
//
// Copyright 1998-2003 Glyph & Cog, LLC
//
//========================================================================

#include <config.h>

#include "glibc.h"
#include "DateInfo.h"

#include <cstdio>
#include <cstring>

/* See PDF Reference 1.3, Section 3.8.2 for PDF Date representation */
bool parseDateString(const char *dateString, int *year, int *month, int *day, int *hour, int *minute, int *second, char *tz, int *tzHour, int *tzMinute)
{
    if (dateString == nullptr)
        return false;
    if (strlen(dateString) < 2)
        return false;

    if (dateString[0] == 'D' && dateString[1] == ':')
        dateString += 2;

    *month = 1;
    *day = 1;
    *hour = 0;
    *minute = 0;
    *second = 0;
    *tz = 0x00;
    *tzHour = 0;
    *tzMinute = 0;

    if (sscanf(dateString, "%4d%2d%2d%2d%2d%2d%c%2d%*c%2d", year, month, day, hour, minute, second, tz, tzHour, tzMinute) > 0) {
        /* Workaround for y2k bug in Distiller 3 stolen from gpdf, hoping that it won't
         * be used after y2.2k */
        if (*year < 1930 && strlen(dateString) > 14) {
            int century, years_since_1900;
            if (sscanf(dateString, "%2d%3d%2d%2d%2d%2d%2d", &century, &years_since_1900, month, day, hour, minute, second) == 7) {
                *year = century * 100 + years_since_1900;
            } else {
                return false;
            }
        }

        if (*year <= 0)
            return false;

        return true;
    }

    return false;
}

GooString *timeToDateString(const time_t *timeA)
{
    const time_t timet = timeA ? *timeA : time(nullptr);

    struct tm localtime_tm;
    localtime_r(&timet, &localtime_tm);

    char buf[50];
    strftime(buf, sizeof(buf), "D:%Y%m%d%H%M%S", &localtime_tm);
    GooString *dateString = new GooString(buf);

    // strftime "%z" does not work on windows (it prints zone name, not offset)
    // calculate time zone offset by comparing local and gmtime time_t value for same
    // time.
    const time_t timeg = timegm(&localtime_tm);
    const time_t offset = difftime(timeg, timet); // find time zone offset in seconds
    if (offset > 0) {
        dateString->appendf("+{0:02d}'{1:02d}'", offset / 3600, (offset % 3600) / 60);
    } else if (offset < 0) {
        dateString->appendf("-{0:02d}'{1:02d}'", -offset / 3600, (-offset % 3600) / 60);
    } else {
        dateString->append("Z");
    }

    return dateString;
}

// Convert PDF date string to time. Returns -1 if conversion fails.
time_t dateStringToTime(const GooString *dateString)
{
    int year, mon, day, hour, min, sec, tz_hour, tz_minute;
    char tz;
    struct tm tm;
    time_t time;

    if (!parseDateString(dateString->c_str(), &year, &mon, &day, &hour, &min, &sec, &tz, &tz_hour, &tz_minute))
        return -1;

    tm.tm_year = year - 1900;
    tm.tm_mon = mon - 1;
    tm.tm_mday = day;
    tm.tm_hour = hour;
    tm.tm_min = min;
    tm.tm_sec = sec;
    tm.tm_wday = -1;
    tm.tm_yday = -1;
    tm.tm_isdst = -1; /* 0 = DST off, 1 = DST on, -1 = don't know */

    /* compute tm_wday and tm_yday and check date */
    time = timegm(&tm);
    if (time == (time_t)-1)
        return time;

    time_t offset = (tz_hour * 60 + tz_minute) * 60;
    if (tz == '-')
        offset *= -1;
    time -= offset;

    return time;
}