<?php
/**
 * ICal (.ics) formatting, shared by the shop's calendar link and the customer's "Add to calendar".
 */

defined( 'ABSPATH' ) || exit;

/**
 * Escape text for iCal.
 */
function dayslot_ical_text( $text ) {
	$text = wp_strip_all_tags( html_entity_decode( (string) $text, ENT_QUOTES, 'UTF-8' ) );
	return str_replace( array( '\\', ';', ',', "\r\n", "\r", "\n" ), array( '\\\\', '\;', '\,', '\n', '\n', '\n' ), $text );
}

/**
 * Fold a content line to max 75 octets (RFC 5545), UTF-8 safe.
 */
function dayslot_ical_fold( $line ) {
	$out    = '';
	$first  = true;
	$length = strlen( $line );
	while ( $length > ( $first ? 75 : 74 ) ) {
		$chunk  = mb_strcut( $line, 0, $first ? 75 : 74, 'UTF-8' );
		$out   .= ( $first ? '' : ' ' ) . $chunk . "\r\n";
		$line   = substr( $line, strlen( $chunk ) );
		$length = strlen( $line );
		$first  = false;
	}
	return $out . ( $first ? '' : ' ' ) . $line . "\r\n";
}

/**
 * DTSTART/DTEND lines for a date + slot. A window ending before it starts (night) ends the next day.
 */
function dayslot_ical_times( $date, $slot, $variant_id = '' ) {
	$range = dayslot_slot_range( $slot );
	$day   = dayslot_parse_date( $date );
	if ( $range && $variant_id && dayslot_night_next_day( dayslot_variant( $variant_id ), $slot ) ) {
		$day  = $day->modify( '+1 day' );
		$date = $day->format( 'Y-m-d' );
	}
	if ( ! $range || ! $day ) {
		return array(
			'DTSTART;VALUE=DATE:' . $day->format( 'Ymd' ),
			'DTEND;VALUE=DATE:' . $day->modify( '+1 day' )->format( 'Ymd' ),
		);
	}
	$utc  = new DateTimeZone( 'UTC' );
	$from = DateTimeImmutable::createFromFormat( 'Y-m-d H:i', $date . ' ' . $range[0], wp_timezone() );
	$to   = DateTimeImmutable::createFromFormat( 'Y-m-d H:i', $date . ' ' . $range[1], wp_timezone() );
	if ( $to <= $from ) {
		$to = $to->modify( '+1 day' );
	}
	return array(
		'DTSTART:' . $from->setTimezone( $utc )->format( 'Ymd\THis\Z' ),
		'DTEND:' . $to->setTimezone( $utc )->format( 'Ymd\THis\Z' ),
	);
}