Helper functions for compiling date and ical outputs with event calendar

get-event-add-to-calendar.php

<?php
/**
 * Get the "Add to Calendar" button output, used with addevent.com service.
 * 
 * @see https://www.addevent.com/buttons/add-to-calendar
 * 
 * @uses event_is_multiday()
 * @uses wp_trim_characters()
 * 
 * @param int $post_id
 * @param array $args
 * 
 * @return string|boolean $output The add event output. False on failure.
 */
function get_event_add_to_calendar( $post_id, $args = array() ) {
	
	// Bail if the post id is invalid
	if( ! absint( $post_id ) )
		return false;
	
	// Get the meta
	$all_day_event = esc_attr( get_post_meta( $post_id, 'event_all_day', true ) );
	$event_start = intval( get_post_meta( $post_id, 'event_start', true ) );
	$event_end = intval( get_post_meta( $post_id, 'event_end', true ) );
	$desciption = wp_kses_post( get_post_meta( $post_id, 'event_description', true ) );
	
	// Verify the start and end times are good to go
	if( !is_timestamp( $event_start ) || !is_timestamp( $event_end ) )
		return false;
	
	// Parse the arguments
	$defaults = array(
		'host'		=> '',
		'host_email'	=> '',
		'location'	=> '',
	);
	$args = wp_parse_args( $args, $defaults );
	$date_format = 'd/m/Y';
	$time_format = 'h:i A';
	
	// If it's an all day event or if there are issues with the event end meta
	if( 'on' == $all_day_event ) {
		// Multiple day event
		if( event_is_multiday( $post_id ) ) {
			$output_start = date( $date_format . ' ' . $time_format, $event_start );
			$output_end = date( $date_format . ' ' . $time_format, $event_end );
			
		// Single day event
		} else {
			$output_start = date( $date_format . ' ', $event_start ) . ' 12:01 AM';
			$output_end = date( $date_format . ' ', $event_start ) . ' 23:59 PM';
		}
	
	// Not an all-day event
	} else {
		$output_start = date( $date_format . ' ' . $time_format, $event_start );
		$output_end = date( $date_format . ' ' . $time_format, $event_end );
	}
	
	// Mandatory: Start and end times
	$output = '<span class="start">' . $output_start . '</span>';
	$output .= '<span class="end">' . $output_end . '</span>';
	
	// Mandatory: Event Title
	$output .= '<span class="title">' . get_the_title( $post_id ) . '</span>';
	
	// Mandatory: date format
	$output .= '<span class="date_format">MM/DD/YYYY</span>';
	
	// Mandatory: Timezone
	$output .= '<span class="timezone">' . esc_attr( get_option( 'timezone_string' ) ) . '</span>';
	
	// Optional Information
	
	// Description
	$output .= !empty( $desciption ) ? '<span class="description">' . wp_trim_characters( wp_strip_all_tags( $desciption ), 500 ) . '</span>' : '';
	
	// host information
	$output .= !empty( $args['host'] ) ? '<span class="organizer">' . esc_attr( $args['host'] ) . '</span>' : '';
	$output .= !empty( $args['host_email'] ) ? '<span class="organizer_email">' . esc_attr( $args['host_email'] ) . '</span>' : '';
		
	// Event Location
	$output .= !empty( $args['location'] ) ? '<span class="location">' . esc_attr( $args['location'] ) . '</span>' : '';
	
	// All day event
	$output .= ( 'on' == $all_day_event ) ? '<span class="all_day_event ">true</span>' : '<span class="all_day_event">false</span>';
	
	return '<div title="Add to Calendar" class="addevetatc">Add to Calendar' . $output . '</div>';
}

/**
 * Trims a string of words to a specified number of characters, gracefully stopping at white spaces.
 * Also strips HTML tags, to prevent breaking in the middle of a tag.
 * 
 * @link http://bavotasan.com/2012/trim-characters-using-php/
 *
 * @param	string $text  The string of words to be trimmed.
 * @param	int $length  Maximum number of characters; defaults to 45.
 * @param	string $append  String to append to end, when trimmed; defaults to ellipsis.
 *
 * @return	String of words trimmed at specified character length.
 *
 * @author c.bavota
 */
 if( !function_exists( 'wp_trim_characters' ) ) {
	function wp_trim_characters( $text, $length = 45, $append = '&hellip;' ) {
	
		$length = (int) $length;
		$text = trim( strip_tags( $text ) );
	
		if ( strlen( $text ) > $length ) {
			$text = substr( $text, 0, $length + 1 );
			$words = preg_split( "/[\s]|&nbsp;/", $text, -1, PREG_SPLIT_NO_EMPTY );
			preg_match( "/[\s]|&nbsp;/", $text, $lastchar, 0, $length );
			if ( empty( $lastchar ) )
				array_pop( $words );
	
			$text = implode( ' ', $words ) . $append;
		}
	
		return $text;
	}
 }

get-event-date.php

<?php

/**
 * Get the event details for the ical.
 * 
 * @uses event_is_multiday()
 * @uses is_timestamp()
 * 
 * @param int $post_id
 * @param array $args
 * 
 * @return string $date The date output or empty string.
 */
function get_event_date( $post_id, $args = array() ) {
	
	// Bail if the post id isn't valid
	if( ! absint( $post_id ) )
		return '';
	
 	// Get the post meta.
 	$all_day_event = esc_attr( get_post_meta( $post_id, 'event_all_day', true ) );
 	$event_start = intval( get_post_meta( $post_id, 'event_start', true ) );
 	$event_end = intval( get_post_meta( $post_id, 'event_end', true ) );
	
 	// Bail if these aren't valid
 	if( ! is_timestamp( $event_start ) || ! is_timestamp( $event_end ) )
 		return '';
 	
	// Parse the arguments
	$defaults = array(
 		'date_format' 	=> 'M j, Y',
 		'time_format'	=> 'g:i A',
 		'wrap'		=> 'div', // the html element wrapping the dates
 		'date_wrap'	=> 'span' // the html element wrapping each individual date (start and end)
 	);
 	$args = wp_parse_args( $args, $defaults );
 	
 	// Setup variables
 	$date_format = esc_attr( $args['date_format'] );
 	$time_format = esc_attr( $args['time_format'] );
 	$wrap = empty( $args['wrap'] ) ? 'div' : esc_attr( $args['wrap'] );
 	$date_wrap = empty( $args['date_wrap'] ) ? 'span' : esc_attr( $args['date_wrap'] );
	$multiday = event_is_multiday( $post_id );
	$all_day = ( 'on' == $all_day_event ) ? true : false; // setup for CMB2, which gives checkboxes an 'on' value
 	$print_date_format = $all_day ? $date_format : $date_format . ' ' . $time_format;
	
 	// Build the dates
 	$start = date( $print_date_format, $event_start );
 	$end = ( $multiday ) ? date( $print_date_format, $event_end ) : date( $time_format, $event_end );
 	$iso_start = date( 'c', $event_start );
 	$iso_end = date( 'c', $event_end );
	
 	// Add the values to the output
	$date = !empty( $start ) ? "<{$date_wrap} class=\"start-date\" itemprop=\"startDate\" content=\"{$iso_start}\">{$start}</{$date_wrap}>" : '';

	// only show the end date/time if it's not an all day event, or if it's a multiday event (which could also be an all day event)
	if( ! $all_day || $multiday )
		$date .= empty( $end ) ?: " - <{$date_wrap} class=\"end-date\" itemprop=\"endDate\" content=\"{$iso_end}\">{$end}</{$date_wrap}>"; 

	// If we have an output, wrap it up
	return empty( $date ) ?: "<{$wrap} class=\"event-date\">{$date}</{$wrap}>";
}

/**
 * Determine if the event occurs over multiple days.
 * 
 * @uses is_timestamp()
 * 
 * @param int $post_id
 * 
 * @return boolean
 */
function event_is_multiday( $post_id ) {
	$start = intval( get_post_meta( $post_id, 'event_start', true ) );
	$end = intval( get_post_meta( $post_id, 'event_end', true ) );
	
	if( is_timestamp( $start ) && is_timestamp( $end ) && date( 'Ymd', $start ) < date( 'Ymd', $end ) ) {
		return true;
	}
	
	return false;
}

/**
 * Checks if a string is a valid timestamp.
 *
 * @link https://gist.github.com/sepehr/6351385
 * 
 * @param  string $timestamp Timestamp to validate.
 * 
 * @return bool
 */
function is_timestamp( $timestamp ) {
	$check = ( is_int( $timestamp ) OR is_float( $timestamp ) )
		? $timestamp
		: (string) (int) $timestamp;
	return  ( $check === $timestamp )
        	AND ( (int) $timestamp <=  PHP_INT_MAX)
        	AND ( (int) $timestamp >= ~PHP_INT_MAX);
}