JetEngine Add to Calendar Button for Advanced Date (Google & Apple)

/**
 * BoostMyCroco: Add to Calendar buttons for JetEngine Advanced Date fields.
 * Shortcode: [bmc_add_to_calendar] outputs a Google Calendar link and an .ics download.
 */

// 1. Settings: change these to match your site.
function bmc_atc_config() {
	return array(
		'post_types'      => array( 'events' ), // Post type slug(s) that use the Advanced Date field.
		'start_key'       => 'event_date',      // Advanced Date field name (meta key with start timestamps).
		'end_key'         => 'event_date__end_date', // JetEngine stores end timestamps as {field}__end_date. Empty = none.
		'location_key'    => 'event_location',  // Text field with an address or meeting URL. Empty = none.
		'default_minutes' => 60,                // Length used when a timed event has no end.
	);
}

// 2. Collect numeric timestamps from meta values (single row, multiple rows or arrays).
function bmc_atc_timestamps( $values ) {
	$out = array();
	foreach ( (array) $values as $value ) {
		if ( is_array( $value ) ) {
			$out = array_merge( $out, bmc_atc_timestamps( $value ) );
		} elseif ( is_numeric( $value ) && (int) $value > 0 ) {
			$out[] = (int) $value;
		}
	}
	$out = array_values( array_unique( $out ) );
	sort( $out );
	return $out;
}

// 3. Build the list of occurrences for a post.
function bmc_atc_get_occurrences( $post_id ) {
	$cfg    = bmc_atc_config();
	$starts = bmc_atc_timestamps( get_post_meta( $post_id, $cfg['start_key'], false ) );
	if ( empty( $starts ) ) {
		return array();
	}

	$ends   = $cfg['end_key'] ? bmc_atc_timestamps( get_post_meta( $post_id, $cfg['end_key'], false ) ) : array();
	$paired = count( $ends ) === count( $starts );

	// Fallback length: first start/end pair (rule-based recurrence offsets every end the same way).
	$first_length = ( $ends && $ends[0] >= $starts[0] ) ? $ends[0] - $starts[0] : null;

	$occurrences = array();
	foreach ( $starts as $i => $start ) {
		$duration = $first_length;

		// One end per start: each date keeps its own end (needed for manually entered dates).
		if ( $paired && $ends[ $i ] >= $start ) {
			$duration = $ends[ $i ] - $start;
		}

		// Values are site-local wall-clock time, so 00:00 here means midnight on the site.
		$all_day = ( '00:00' === gmdate( 'H:i', $start ) ) && ( null === $duration || 0 === $duration % DAY_IN_SECONDS );

		if ( $all_day ) {
			$length = (int) $duration;
		} else {
			$length = $duration ? $duration : (int) $cfg['default_minutes'] * MINUTE_IN_SECONDS;
		}

		$occurrences[] = array(
			'start'   => $start,
			'end'     => $start + $length,
			'all_day' => $all_day,
		);
	}
	return $occurrences;
}

// 4. Read a site-local wall-clock timestamp as a date in the site time zone.
function bmc_atc_local( $timestamp ) {
	return new DateTimeImmutable( gmdate( 'Y-m-d H:i:s', $timestamp ), wp_timezone() );
}

// 5. Format one occurrence: UTC for timed events, plain dates for all-day events.
function bmc_atc_format( $occ ) {
	if ( $occ['all_day'] ) {
		return array(
			'all_day' => true,
			'start'   => gmdate( 'Ymd', $occ['start'] ),
			'end'     => gmdate( 'Ymd', $occ['end'] + DAY_IN_SECONDS ), // All-day end date is exclusive.
		);
	}

	$utc = new DateTimeZone( 'UTC' );
	return array(
		'all_day' => false,
		'start'   => bmc_atc_local( $occ['start'] )->setTimezone( $utc )->format( 'Ymd\THis\Z' ),
		'end'     => bmc_atc_local( $occ['end'] )->setTimezone( $utc )->format( 'Ymd\THis\Z' ),
	);
}

// 6. Next occurrence that has not ended yet, or the last one if all are past.
function bmc_atc_pick_next( $occurrences ) {
	foreach ( $occurrences as $occ ) {
		$end = $occ['all_day'] ? $occ['end'] + DAY_IN_SECONDS : $occ['end'];
		if ( bmc_atc_local( $end )->getTimestamp() >= time() ) {
			return $occ;
		}
	}
	return end( $occurrences );
}

// 7. Title, summary, URL and location shared by both buttons.
function bmc_atc_event_data( $post_id ) {
	$cfg     = bmc_atc_config();
	$title   = wp_strip_all_tags( html_entity_decode( get_the_title( $post_id ), ENT_QUOTES, 'UTF-8' ) );
	$excerpt = html_entity_decode( (string) get_post_field( 'post_excerpt', $post_id ), ENT_QUOTES, 'UTF-8' );

	$location = '';
	if ( $cfg['location_key'] ) {
		$raw      = get_post_meta( $post_id, $cfg['location_key'], true );
		$location = is_scalar( $raw ) ? sanitize_text_field( (string) $raw ) : '';
	}

	return array(
		'title'    => $title,
		'summary'  => trim( wp_trim_words( $excerpt, 40, '...' ) ),
		'url'      => get_permalink( $post_id ),
		'location' => $location,
	);
}

// 8. Description text. Google gets a one-line version because esc_url() strips line breaks.
function bmc_atc_details( $data, $separator ) {
	return implode( $separator, array_filter( array( $data['summary'], $data['url'] ) ) );
}

// 9. Shortcode: [bmc_add_to_calendar id="" series="no" google_label="" ics_label=""]
add_shortcode( 'bmc_add_to_calendar', 'bmc_atc_shortcode' );
function bmc_atc_shortcode( $atts ) {
	$atts = shortcode_atts(
		array(
			'id'           => 0,
			'series'       => 'no',
			'google_label' => 'Add to Google Calendar',
			'ics_label'    => 'Add to Apple Calendar',
		),
		$atts,
		'bmc_add_to_calendar'
	);

	$cfg     = bmc_atc_config();
	$post_id = absint( $atts['id'] ) ? absint( $atts['id'] ) : get_the_ID();
	if ( ! $post_id || ! in_array( get_post_type( $post_id ), $cfg['post_types'], true ) ) {
		return '';
	}

	$occurrences = bmc_atc_get_occurrences( $post_id );
	if ( empty( $occurrences ) ) {
		return '';
	}

	$data  = bmc_atc_event_data( $post_id );
	$times = bmc_atc_format( bmc_atc_pick_next( $occurrences ) );

	$google_args = array(
		'action'  => 'TEMPLATE',
		'text'    => $data['title'],
		'dates'   => $times['start'] . '/' . $times['end'],
		'details' => bmc_atc_details( $data, ' | ' ),
	);
	if ( $data['location'] ) {
		$google_args['location'] = $data['location'];
	}
	$google = 'https://calendar.google.com/calendar/render?' . http_build_query( $google_args, '', '&', PHP_QUERY_RFC3986 );

	$ics_args = array( 'bmc_ics' => 1 );
	if ( 'yes' === $atts['series'] ) {
		$ics_args['series'] = 'all';
	}
	$ics = add_query_arg( $ics_args, get_permalink( $post_id ) );

	return sprintf(
		'<div class="bmc-atc"><a class="bmc-atc__google" href="%1$s" target="_blank" rel="noopener nofollow">%2$s</a> <a class="bmc-atc__ics" href="%3$s" rel="nofollow">%4$s</a></div>',
		esc_url( $google ),
		esc_html( $atts['google_label'] ),
		esc_url( $ics ),
		esc_html( $atts['ics_label'] )
	);
}

// 10. iCalendar text escaping and line folding.
function bmc_atc_ics_text( $text ) {
	$text = str_replace( '\\', '\\\\', $text );
	$text = str_replace( array( ';', ',' ), array( '\;', '\,' ), $text );
	return str_replace( array( "\r\n", "\r", "\n" ), '\n', $text );
}

function bmc_atc_fold( $line ) {
	if ( ! function_exists( 'mb_strcut' ) ) {
		return $line;
	}
	$out   = '';
	$limit = 75;
	while ( strlen( $line ) > $limit ) {
		$chunk = mb_strcut( $line, 0, $limit, 'UTF-8' );
		$out  .= $chunk . "\r\n ";
		$line  = substr( $line, strlen( $chunk ) );
		$limit = 74;
	}
	return $out . $line;
}

// 11. Serve the .ics file: /your-event/?bmc_ics=1 (add &series=all for every stored date).
add_action( 'template_redirect', 'bmc_atc_serve_ics' );
function bmc_atc_serve_ics() {
	if ( ! isset( $_GET['bmc_ics'] ) ) {
		return;
	}

	$cfg = bmc_atc_config();
	if ( ! is_singular( $cfg['post_types'] ) ) {
		return;
	}

	$post = get_queried_object();
	if ( ! ( $post instanceof WP_Post ) || 'publish' !== $post->post_status || post_password_required( $post ) ) {
		return;
	}

	$occurrences = bmc_atc_get_occurrences( $post->ID );
	if ( empty( $occurrences ) ) {
		return;
	}

	$series = isset( $_GET['series'] ) ? sanitize_key( wp_unslash( $_GET['series'] ) ) : '';
	if ( 'all' !== $series ) {
		$occurrences = array( bmc_atc_pick_next( $occurrences ) );
	}

	$data  = bmc_atc_event_data( $post->ID );
	$host  = wp_parse_url( home_url(), PHP_URL_HOST );
	$stamp = gmdate( 'Ymd\THis\Z' );

	$lines = array(
		'BEGIN:VCALENDAR',
		'VERSION:2.0',
		'PRODID:-//BoostMyCroco//Add to Calendar//EN',
		'CALSCALE:GREGORIAN',
		'METHOD:PUBLISH',
	);

	foreach ( $occurrences as $occ ) {
		$times   = bmc_atc_format( $occ );
		$lines[] = 'BEGIN:VEVENT';
		$lines[] = 'UID:' . $post->ID . '-' . $occ['start'] . '@' . $host;
		$lines[] = 'DTSTAMP:' . $stamp;
		if ( $times['all_day'] ) {
			$lines[] = 'DTSTART;VALUE=DATE:' . $times['start'];
			$lines[] = 'DTEND;VALUE=DATE:' . $times['end'];
		} else {
			$lines[] = 'DTSTART:' . $times['start'];
			$lines[] = 'DTEND:' . $times['end'];
		}
		$lines[] = 'SUMMARY:' . bmc_atc_ics_text( $data['title'] );
		$lines[] = 'DESCRIPTION:' . bmc_atc_ics_text( bmc_atc_details( $data, "\n\n" ) );
		if ( $data['location'] ) {
			$lines[] = 'LOCATION:' . bmc_atc_ics_text( $data['location'] );
		}
		$lines[] = 'URL:' . esc_url_raw( $data['url'] );
		$lines[] = 'END:VEVENT';
	}
	$lines[] = 'END:VCALENDAR';

	$filename = sanitize_file_name( $post->post_name ? $post->post_name : 'event' ) . '.ics';

	nocache_headers();
	header( 'Content-Type: text/calendar; charset=utf-8' );
	header( 'Content-Disposition: attachment; filename="' . $filename . '"' );
	echo implode( "\r\n", array_map( 'bmc_atc_fold', $lines ) ) . "\r\n"; // phpcs:ignore WordPress.Security.EscapeOutput -- iCalendar body, values escaped above.
	exit;
}