Add documentation for ALARM component

[markuspoerschke]

[JorisDebonnet]

Any hint you can give already? When I try:

$event->addAlarm(
	new Alarm(
		new Alarm\DisplayAction('Reminder: this task is scheduled now.'),
		new Alarm\RelativeTrigger(new \DateInterval('PT1M'))
	)
);

Then the output is:

BEGIN:VALARM
ACTION:DISPLAY
DESCRIPTION:Reminder: this task is scheduled now.
TRIGGER:PT1M
END:VALARM

But that doesn't do anything in any of the calendar apps I have tested. Also, I notice in online examples that the trigger usually starts with a - sign (to indicate "before" rather than "after" the DTSTART, I assume), but I cannot create a negative DateInterval, so not sure how to implement that here.

[markuspoerschke]

@JorisDebonnet Here you can find a working example

<?php

use Eluceo\iCal\Domain\Entity\Calendar;

require_once __DIR__ . '/../vendor/autoload.php';

$event = new \Eluceo\iCal\Domain\Entity\Event();
$event->setSummary('Alarm Test');
$event->setOccurrence(
    new \Eluceo\iCal\Domain\ValueObject\TimeSpan(
        new \Eluceo\iCal\Domain\ValueObject\DateTime(new DateTimeImmutable('2021-04-25 17:30:00'), true),
        new \Eluceo\iCal\Domain\ValueObject\DateTime(new DateTimeImmutable('2021-04-25 17:45:00'), true),
    )
);

$alarmInterval = new DateInterval('PT1M');
$alarmInterval->invert = 1;
$event->addAlarm(
    new \Eluceo\iCal\Domain\ValueObject\Alarm(new \Eluceo\iCal\Domain\ValueObject\Alarm\AudioAction(),
        new \Eluceo\iCal\Domain\ValueObject\Alarm\RelativeTrigger($alarmInterval)
    )
);

// 2. Create Calendar domain entity.
$calendar = new Calendar([$event]);

echo (new \Eluceo\iCal\Presentation\Factory\CalendarFactory())->createCalendar($calendar);

The clue is indeed to make the date interval negative.

There are the following ways in PHP to make DateTimeInterval negative:

$alarmInterval = new DateInterval('PT1M');
$alarmInterval->invert = 1;

or

$alarmInterval = DateInterval::createFromDateString('1 minute ago');