<?php
/**
 * Hours during which nothing may be sent.
 *
 * @package Rahkar\WP
 */

declare( strict_types = 1 );

namespace Rahkar\WP\Notifications;

use DateTimeImmutable;

defined( 'ABSPATH' ) || exit;

/**
 * A nightly window in which the shop does not text its customers.
 *
 * ## What it does, and what it must never do
 *
 * It **defers**, it does not drop. A message that falls due at two in the
 * morning goes out when the window opens, not never. Dropping would make the
 * setting quietly destructive: a shop that set quiet hours to protect its
 * customers' sleep would find it had silently cancelled every invitation that
 * happened to come due overnight, and nothing anywhere would say so.
 *
 * ## Local time, not UTC
 *
 * The queue stores everything in UTC, as it should. But a shop owner typing
 * "23:00" means eleven at night in Tehran, and every calculation here is
 * therefore done in the site's own timezone through `wp_timezone()`. Comparing
 * an hour typed by a human against a UTC clock is the bug this class exists to
 * avoid making three times over in three modules.
 *
 * ## Windows that cross midnight
 *
 * The useful window is the one that wraps — 22:00 to 09:00 — so that case is
 * the normal one here rather than an afterthought. A window whose ends are
 * equal is treated as no window at all: "from 09:00 to 09:00" is far more
 * likely to be a half-finished setting than a request for silence all day, and
 * guessing the other way would take a shop's messages offline entirely.
 *
 * Born in the add-on beside the review invitation; moved here in 0.27.0 so
 * {@see SendPolicy} can hold one window for every module, free or paid.
 */
final class QuietHours {

	/**
	 * How long until sending is allowed again.
	 *
	 * Zero means now. Anything else is the number of seconds to wait, which is
	 * exactly what the queue's delay argument wants.
	 *
	 * @param int    $now  Timestamp to judge, normally `time()`.
	 * @param string $from Window start as `HH:MM` in the site's timezone.
	 * @param string $to   Window end as `HH:MM` in the site's timezone.
	 */
	public static function secondsUntilOpen( int $now, string $from, string $to ): int {
		$start = self::minutes( $from );
		$end   = self::minutes( $to );

		if ( null === $start || null === $end || $start === $end ) {
			return 0;
		}

		$local   = ( new DateTimeImmutable( '@' . $now ) )->setTimezone( wp_timezone() );
		$current = ( (int) $local->format( 'G' ) * 60 ) + (int) $local->format( 'i' );

		$quiet = $start < $end
			? ( $current >= $start && $current < $end )
			: ( $current >= $start || $current < $end );

		if ( ! $quiet ) {
			return 0;
		}

		// Built as a date rather than by adding minutes, so a timezone whose
		// offset changes between now and the morning lands on the wall-clock time
		// the shop asked for rather than a fixed number of seconds later.
		$opens = $local->setTime( intdiv( $end, 60 ), $end % 60, 0 );

		if ( $opens <= $local ) {
			$opens = $opens->modify( '+1 day' );
		}

		return max( 1, $opens->getTimestamp() - $now );
	}

	/**
	 * Is this moment inside the window?
	 *
	 * @param int    $now  Timestamp to judge.
	 * @param string $from Window start as `HH:MM`.
	 * @param string $to   Window end as `HH:MM`.
	 */
	public static function isQuiet( int $now, string $from, string $to ): bool {
		return self::secondsUntilOpen( $now, $from, $to ) > 0;
	}

	/**
	 * `HH:MM` as minutes past midnight, or null when it is not a time.
	 *
	 * @param string $value Stored setting.
	 */
	private static function minutes( string $value ): ?int {
		if ( 1 !== preg_match( '/^([01][0-9]|2[0-3]):([0-5][0-9])$/', trim( $value ), $parts ) ) {
			return null;
		}

		return ( (int) $parts[1] * 60 ) + (int) $parts[2];
	}
}