<?php

namespace RobThree\Auth\Providers\Time;

use DateTime;

/**
 * Takes the time from any webserver by doing a HEAD request on the specified URL and extracting the 'Date:' header
 */
class HttpTimeProvider implements ITimeProvider {
	/** @var string */
	public $url;

	/** @var string */
	public $expectedtimeformat;

	/** @var array */
	public $options;

	/**
	 * @param string $url
	 * @param string $expectedtimeformat
	 * @param array $options
	 */
	public function __construct(
		$url = "https://google.com",
		$expectedtimeformat = "D, d M Y H:i:s O+",
		array $options = null,
	) {
		$this->url = $url;
		$this->expectedtimeformat = $expectedtimeformat;
		if ($options === null) {
			$options = [
				"http" => [
					"method" => "HEAD",
					"follow_location" => false,
					"ignore_errors" => true,
					"max_redirects" => 0,
					"request_fulluri" => true,
					"header" => [
						"Connection: close",
						"User-agent: TwoFactorAuth HttpTimeProvider (https://github.com/RobThree/TwoFactorAuth)",
						"Cache-Control: no-cache",
					],
				],
			];
		}
		$this->options = $options;
	}

	/**
	 * {@inheritdoc}
	 */
	public function getTime() {
		try {
			$context = stream_context_create($this->options);
			$fd = fopen($this->url, "rb", false, $context);
			$headers = stream_get_meta_data($fd);
			fclose($fd);

			foreach ($headers["wrapper_data"] as $h) {
				if (strcasecmp(substr($h, 0, 5), "Date:") === 0) {
					return DateTime::createFromFormat(
						$this->expectedtimeformat,
						trim(substr($h, 5)),
					)->getTimestamp();
				}
			}
			throw new \Exception('Invalid or no "Date:" header found');
		} catch (\Exception $ex) {
			throw new TimeException(
				sprintf("Unable to retrieve time from %s (%s)", $this->url, $ex->getMessage()),
			);
		}
	}
}