<?php
include 'apikey.php';

if (empty($apikey)) {
    die("missing api key");
}
$context = stream_context_create([
    "http" => [
        "method" => "GET",
        "header" => "X-API-Key: $apikey\r\n"
    ]
]);

$from = gmdate("Y-m-d\TH:i:s\Z", strtotime("now + 1 day"));
$to   = gmdate("Y-m-d\TH:i:s\Z", strtotime("now + 8 days"));

$schedule = json_decode(
    file_get_contents(
        "https://radio.tildeverse.org/api/station/1/streamers/schedule?start=$from&end=$to",
        false,
        $context
    ),
    true
);

usort($schedule, function ($a, $b) {
    return $a["start"] <=> $b["start"];
});

function formatdate($date) {
    return gmdate("Ymd\THis\Z", strtotime($date));
}

header("Content-Type: text/calendar");

// ICS generation. Here be dragons.
// I created the file using a Python script and reverse-engineered it to figure this out.

// Header.
echo "BEGIN:VCALENDAR".PHP_EOL;
echo "VERSION:2.0".PHP_EOL;
echo "PRODID:tilderadio schedule".PHP_EOL;

foreach ($schedule as $event) {
	// The VEVENT structure's pretty easy to generate, especially since we're already in UTC.
	echo "BEGIN:VEVENT".PHP_EOL;
	// First, the event start and end.
	echo "DTEND:".formatdate($event["end"]).PHP_EOL;
	echo "DTSTART:".formatdate($event["start"]).PHP_EOL;
	// Next, the event title, or "summary" as the spec calls it.
	echo "SUMMARY:DJ ".$event["title"].PHP_EOL;
	// Finally, a unique ID for this event.
	// To make absolutely certain we don't repeat the same event ID, I decided to use a SHA256 hash of the event structure.
	echo "UID:";
	echo hash("sha256",json_encode($event));
	echo "@tilderadio.org".PHP_EOL;
	// Finally, close the VEVENT structure.
	echo "END:VEVENT".PHP_EOL;
	// Next event?
}

// Finally, close out the VCALENDAR structure.
echo "END:VCALENDAR".PHP_EOL;

?>