// Arduino Timezone Library Copyright (C) 2018 by Jack Christensen and
// licensed under GNU GPL v3.0, https://www.gnu.org/licenses/gpl.html
//
// Arduino Timezone Library example sketch.
// Sketch to verify operation of Timezone library.
// Jack Christensen 14Nov2018

#include <Timezone.h>   // https://github.com/JChristensen/Timezone
#include <TimeLib.h>    // https://github.com/PaulStoffregen/Time

// New Zealand Time Zone
TimeChangeRule nzSTD = {"NZST", First, Sun, Apr, 3, 720};   // UTC + 12 hours
TimeChangeRule nzDST = {"NZDT", Last, Sun, Sep, 2, 780};    // UTC + 13 hours
Timezone nz(nzDST, nzSTD);

// US Eastern Time Zone (New York, Detroit)
TimeChangeRule etDST = {"EDT", Second, Sun, Mar, 2, -240};  // Daylight time = UTC - 4 hours
TimeChangeRule etSTD = {"EST", First, Sun, Nov, 2, -300};   // Standard time = UTC - 5 hours
Timezone et(etDST, etSTD);

void setup()
{
    Serial.begin(115200);

    // New Zealand
    printTimes( 1,  4, 2018, nzSTD.hour, nzDST.offset, nz); // day, month, year, hour, offset, tz
    printTimes(30,  9, 2018, nzDST.hour, nzSTD.offset, nz);
    printTimes( 7,  4, 2019, nzSTD.hour, nzDST.offset, nz);
    printTimes(29,  9, 2019, nzDST.hour, nzSTD.offset, nz);
    printTimes( 5,  4, 2020, nzSTD.hour, nzDST.offset, nz);
    printTimes(27,  9, 2020, nzDST.hour, nzSTD.offset, nz);

    // US Eastern
    printTimes(11,  3, 2018, etDST.hour, etSTD.offset, et); // day, month, year, hour, offset, tz
    printTimes( 4, 11, 2018, etSTD.hour, etDST.offset, et);
    printTimes(10,  3, 2019, etDST.hour, etSTD.offset, et);
    printTimes( 3, 11, 2019, etSTD.hour, etDST.offset, et);
    printTimes( 8,  3, 2020, etDST.hour, etSTD.offset, et);
    printTimes( 1, 11, 2020, etSTD.hour, etDST.offset, et);
}

void loop() {}

// print corresponding UTC and local times "n" seconds before and after the time change.
// h is the hour to change the clock using the *current* time (i.e. before the change).
// offset is the utc offset in minutes for the time *after* the change.
void printTimes(uint8_t d, uint8_t m, int y, uint8_t h, int offset, Timezone tz)
{
    const time_t n(3);      // number of times to print before and after the time change
    tmElements_t tm;
    tm.Hour = h;
    tm.Minute = 0;
    tm.Second = 0;
    tm.Day = d;
    tm.Month = m;
    tm.Year = y - 1970;     // offset from 1970
    time_t utc = makeTime(tm) - offset * SECS_PER_MIN - n;

    Serial.print(F("\n-------- "));
    Serial.print(monthShortStr(m));
    Serial.print('-');
    Serial.print(y);
    Serial.print(F(" time change --------\n"));

    for (uint16_t i=0; i<n*2; i++)
    {
        TimeChangeRule *tcr;    // pointer to the time change rule, use to get TZ abbrev
        time_t local = tz.toLocal(utc, &tcr);
        printDateTime(utc, "UTC = ");
        printDateTime(local, tcr -> abbrev);
        Serial.println();
        ++utc;
    }
}

// format and print a time_t value, with a time zone appended.
void printDateTime(time_t t, const char *tz)
{
    char buf[32];
    char m[4];    // temporary storage for month string (DateStrings.cpp uses shared buffer)
    strcpy(m, monthShortStr(month(t)));
    sprintf(buf, "%.2d:%.2d:%.2d %s %.2d %s %d %s",
        hour(t), minute(t), second(t), dayShortStr(weekday(t)), day(t), m, year(t), tz);
    Serial.print(buf);
}