TEC - iCal export of this year's events

ical-export-events-custom.php

<?php
/**
	* Description:	This snippet will enable you to have an iCal export of all this year's events
	* when using this url:
	* http://example.com/events/?ical=1&tribe_display=custom
	*
	* Formats you can use:
	* Simple: exports events of this year, i.e. Jan 1st to Dec 31 of current year 
	* http://example.com/events/?ical=1&tribe_display=custom
	*
	* If no end date is defined then events until the end of the current year will be exported
	* I.e. from Feb 2, 2017 until end of current year
	* http://example.com/events/?ical=1&tribe_display=custom&start_date=2017-02-10
	*
	* If no start date is defined, then events starting from Jan 1 of current year will be exported
	* I.e. from Jan 1 of current year until July 31, 2018
	* http://example.com/events/?ical=1&tribe_display=custom&end_date=2018-07-31
	*
	* Define start and end date
	* I.e. from July 1, 2017 until June 30, 2018
	* http://example.com/events/?ical=1&tribe_display=custom&start_date=2017-07-01&end_date=2018-06-30
	*
	* Define start year: events from January 1 of that year will be exported
	* I.e. from Jan 1, current year until Dec 31, 2019
	* http://example.com/events/?ical=1&tribe_display=custom&start_date=2019
	*
	* Define end year: events until December 31 of that year will be exported
	* I.e. from Jan 1, current year until Dec 31, 2019
	* http://example.com/events/?ical=1&tribe_display=custom&end_date=2019
	*
	* Paste the code in your (child) theme's functions.php file
	* 
	* Required plugins:  The Events Calendar
	* Last updated:      2017-11-28
	* Author:            Brook Harding, Andras Guseo
*/
add_action( 'pre_get_posts', 'filter_ical_query' );

function filter_ical_query( $query ) {
	
	if ( ! isset( $_GET['ical'] ) || ! isset( $query->tribe_is_event_query ) || ! $query->tribe_is_event_query ) return;
	
	$tribe_display	= $_GET[ 'tribe_display' ];
	$start_date	= isset( $_GET[ 'start_date' ] ) ? $_GET[ 'start_date' ] : "" ;
	$end_date	= isset( $_GET[ 'end_date' ] )   ? $_GET[ 'end_date' ]   : "";
	
	if( $tribe_display === 'custom' ) {
		
		// Check if there is a start_date set
		if( isset( $start_date ) && !empty( $start_date ) ) {
			// Full date
			if ( validateDate( $start_date, 'Y-m-d' ) ) {
				$start_of_year = $start_date;
			}
			// Only year, then from beggining of that year
			elseif ( validateDate( $start_date, 'Y' ) ) {
				$start_of_year = $start_date . '-01-01';
			}
			// If set to anything else then fall back to this year's beginning
			else {
				$start_of_year = date( 'Y' ) . '-01-01';
			}
		}
		// If not, fall back to this year's beginning
		else {
			$start_of_year = date( 'Y' ) . '-01-01';
		}
		
		// Check if there is an end_date set
		if( isset( $end_date ) && !empty( $end_date ) ) {
			// Full date
			if( validateDate( $end_date, 'Y-m-d' ) ) {
				$end_of_year = $end_date;
			}
			// only year, then end of that year (Max. 3 years ahead)
			elseif( validateDate( $end_date, 'Y' ) && date( 'Y' ) <= $end_date && $end_date <= date('Y') + 3 ) {
				$end_of_year = $end_date . '-12-31';
			}
		}
		// If there is no end date but there was a start year defined, then till the end of that year
		elseif( validateDate( $start_date, 'Y' ) ) {
			$end_of_year = $start_date . '-12-31';
		}
		// If no end date defined, fall back to this year's end
		else {
			$end_of_year = date( 'Y' ) . '-12-31';
		}
		
		$query->set( 'eventDisplay', 'custom' );
		$query->set( 'start_date', $start_of_year );
		$query->set( 'end_date', $end_of_year );
		$query->set( 'posts_per_page', - 1 );
	}
}

function validateDate($date, $format = 'Y-m-d H:i:s')
{
	$d = DateTime::createFromFormat($format, $date);
	return $d && $d->format($format) == $date;
}