<?php declare(strict_types=1);

namespace MyPrayerJournal\Domain;

use DateInterval;
use JsonSerializable;

/**
 * The recurrence for a prayer request
 */
class Recurrence implements JsonSerializable
{
    /**
     * @param RecurrencePeriod $period The recurrence period
     * @param int|null $interval How many of the periods will pass before the request is visible again
     */
    public function __construct(public RecurrencePeriod $period, public ?int $interval = null) { }

    /**
     * Get the date/time interval for this recurrence
     *
     * @return DateInterval The interval matching the recurrence
     */
    public function interval(): DateInterval
    {
        $period = match ($this->period) {
            RecurrencePeriod::Immediate => 'T0S',
            RecurrencePeriod::Hours     => "T{$this->interval}H",
            RecurrencePeriod::Days      => "{$this->interval}D",
            RecurrencePeriod::Weeks     => ($this->interval * 7) . 'D'
        };
        return new DateInterval("P$period");
    }

    public function jsonSerialize(): mixed
    {
        $values = ['period' => $this->period->value];
        if (isset($this->interval)) $values['interval'] = $this->interval;
        return $values;
    }
}