<?php
// This script grabs the events from zwift.com/events and makes them available in ical form so you can use them in your calendar
// Disclaimer: This is  script created for myself to use in my calendar, and is NOT supported by or related to Zwift in any way

class zwift_ics{

    private $url = "http://zwift.com/json/events";
    private $cachefile = "cache.txt";
    private $cachetime = "600";
    private $output = FALSE;


    function run(){
        header('Content-type: text/calendar; charset=utf-8');
        header('Content-Disposition: attachment; filename=zwift_events.ics');

        // Try to get the data from cache
        $this->output = $this->get_cache();

        // No data, query zwift
        if($this->output === FALSE){
            $data = $this->get_data_from_zwift();
            if($data !== FALSE){
                $this->create_output($data);
            }else{
                throw new Exception("Sorry, I wasn't able to grab the latest data from Zwift");
            }
            $this->set_cache($this->output);
        }

        // Print everything and exit
        exit($this->output);
    }

    function create_output($data){
        $data = json_decode($data);
        if(!is_array($data)){
            throw new Exception("Retrieved data incorrect");
        }
        $this->output = $this->header();

        foreach($data as $id => $event){
            $this->output .= $this->event($event);
        }

        $this->output .= $this->footer();

        return $this->output;
    }

    function get_cache(){
        if(!file_exists($this->cachefile)){
            file_put_contents($this->cachefile, "");
        }
        $cache = file_get_contents($this->cachefile);

        // If the file is empty
        if(strlen($cache) < 100){
            return FALSE;
        }

        // if it is modified longer than given time ago
        if((filemtime($this->cachefile) + $this->cachetime) < time()){
            return FALSE;
        }

        return $cache;
    }

    function set_cache($data){
        file_put_contents($this->cachefile, $data);
    }

    function get_data_from_zwift(){
        return file_get_contents($this->url);
    }


    function dateToCal($timestamp) {
        return date('Ymd\THis\Z', $timestamp);
    }

    function escapeString($string) {
        $string = str_replace("\n", "\\n", $string);
        return preg_replace('/([\,;])/','\\\$1', $string);
    }

    function header(){
        return "BEGIN:VCALENDAR\n" .
                "VERSION:2.0\n" .
                "METHOD:PUBLISH\n" .
                "PRODID:-//onlinephpfunctions.com//zwift 1.0//EN\n";
    }

    function event($event){
        return "BEGIN:VEVENT" .
        "\nDESCRIPTION:" . $this->escapeString($event->description) .
                "\nDTEND:" . $this->dateToCal($event->start + $event->durationInSeconds) .
                "\nDTSTAMP:" . $this->dateToCal($event->start) .
                "\nDTSTART:" . $this->dateToCal($event->start) .
                "\nSEQUENCE:0" .
                "\nLOCATION:" . $this->escapeString($event->route) .
                "\nSUMMARY:" . $this->escapeString($event->name) . // Go to Zwift.com/events for full details"  // . $this->escapeString($event->description) . "
                "\nUID:" . uniqid() .
                "\nEND:VEVENT\n";
    }

    function  footer(){
        return "\nEND:VCALENDAR\n";
    }

}

$zwift_events = new zwift_ics();
$zwift_events->run();