Merge "Clean up time zone handling in MtpUtils::parseDateTime."

#include <stdio.h>

#include <time.h>

#include <../private/bionic_time.h> /* TODO: switch this code to icu4c! */

#include "MtpUtils.h"

namespace android {

DD replaced by the day (01-31), T is a constant character 'T' delimiting time from date,

hh is replaced by the hour (00-23), mm is replaced by the minute (00-59), and ss by the

second (00-59). The ".s" is optional, and represents tenths of a second.

This is followed by a UTC offset given as "[+-]zzzz" or the literal "Z", meaning UTC.

*/

bool parseDateTime(const char* dateTime, time_t& outSeconds) {

    int year, month, day, hour, minute, second;

    struct tm tm;

    if (sscanf(dateTime, "%04d%02d%02dT%02d%02d%02d",

               &year, &month, &day, &hour, &minute, &second) != 6)

        return false;

    const char* tail = dateTime + 15;

    // skip optional tenth of second

    if (tail[0] == '.' && tail[1])

        tail += 2;

    //FIXME - support +/-hhmm

    bool useUTC = (tail[0] == 'Z');

    const char* tail = dateTime + 15;

    if (tail[0] == '.' && tail[1]) tail += 2;

    // hack to compute timezone

    time_t dummy;

    localtime_r(&dummy, &tm);

    // FIXME: "Z" means UTC, but non-"Z" doesn't mean local time.

    // It might be that you're in Asia/Seoul on vacation and your Android

    // device has noticed this via the network, but your camera was set to

    // America/Los_Angeles once when you bought it and doesn't know where

    // it is right now, so the camera says "20160106T081700-0800" but we

    // just ignore the "-0800" and assume local time which is actually "+0900".

    // I think to support this (without switching to Java or using icu4c)

    // you'd want to always use timegm(3) and then manually add/subtract

    // the UTC offset parsed from the string (taking care of wrapping).

    // mktime(3) ignores the tm_gmtoff field, so you can't let it do the work.

    bool useUTC = (tail[0] == 'Z');

    struct tm tm = {};

    tm.tm_sec = second;

    tm.tm_min = minute;

    tm.tm_hour = hour;

    tm.tm_mday = day;

    tm.tm_mon = month - 1;  // mktime uses months in 0 - 11 range

    tm.tm_year = year - 1900;

    tm.tm_wday = 0;

    tm.tm_isdst = -1;

    if (useUTC)

        outSeconds = mktime(&tm);

    else

        outSeconds = mktime_tz(&tm, tm.tm_zone);

    outSeconds = useUTC ? timegm(&tm) : mktime(&tm);

    return true;

}