<?php

/**
 * Class ParameterConfirmationToken
 *
 * When you need to use a dangerous GET parameter that needs to be set before core/Core.php is
 * established, this class takes care of allowing some other code of confirming the parameter,
 * by generating a one-time-use token & redirecting with that token included in the redirected URL
 *
 * WARNING: This class is experimental and designed specifically for use pre-startup in main.php
 * It will likely be heavily refactored before the release of 3.2
 */
class ParameterConfirmationToken {
	protected $parameterName = null;
	protected $parameter = null;
	protected $token = null;

	protected function pathForToken($token) {
		return TEMP_FOLDER.'/token_'.preg_replace('/[^a-z0-9]+/', '', $token);
	}

	protected function genToken() {
		// Generate a new random token (as random as possible)
		require_once(dirname(dirname(dirname(__FILE__))).'/security/RandomGenerator.php');
		$rg = new RandomGenerator();
		$token = $rg->randomToken('md5');

		// Store a file in the session save path (safer than /tmp, as open_basedir might limit that)
		file_put_contents($this->pathForToken($token), $token);

		return $token;
	}

	protected function checkToken($token) {
		$file = $this->pathForToken($token);
		$content = null;

		if (file_exists($file)) {
			$content = file_get_contents($file);
			unlink($file);
		}

		return $content == $token;
	}

	public function __construct($parameterName) {
		// Store the parameter name
		$this->parameterName = $parameterName;
		// Store the parameter value
		$this->parameter = isset($_GET[$parameterName]) ? $_GET[$parameterName] : null;
		// Store the token
		$this->token = isset($_GET[$parameterName.'token']) ? $_GET[$parameterName.'token'] : null;

		// If a token was provided, but isn't valid, ignore it
		if ($this->token && (!$this->checkToken($this->token))) $this->token = null;
	}
	
	/**
	 * Get the name of this token
	 * 
	 * @return string
	 */
	public function getName() {
		return $this->parameterName;
	}

	/**
	 * Is the parameter requested?
	 * 
	 * @return bool
	 */
	public function parameterProvided() {
		return $this->parameter !== null;
	}

	/**
	 * Is the necessary token provided for this parameter?
	 * 
	 * @return bool
	 */
	public function tokenProvided() {
		return $this->token !== null;
	}
	
	/**
	 * Is this parameter requested without a valid token?
	 * 
	 * @return bool True if the parameter is given without a valid token
	 */
	public function reloadRequired() {
		return $this->parameterProvided() && !$this->tokenProvided();
	}
	
	/**
	 * Suppress the current parameter by unsetting it from $_GET
	 */
	public function suppress() {
		unset($_GET[$this->parameterName]);
	}

	public function params() {
		return array(
			$this->parameterName => $this->parameter,
			$this->parameterName.'token' => $this->genToken()
		);
	}

	/** What to use instead of BASE_URL. Must not contain protocol or host. @var string */
	static public $alternateBaseURL = null;

	protected function currentAbsoluteURL() {
		global $url;

		// Are we http or https? Replicates Director::is_https() without its dependencies/
		$proto = 'http';
		if(
			TRUSTED_PROXY
			&& isset($_SERVER['HTTP_X_FORWARDED_PROTO'])
			&& strtolower($_SERVER['HTTP_X_FORWARDED_PROTO']) == 'https'
		) { 
			// Convention for (non-standard) proxy signaling a HTTPS forward,
			// see https://en.wikipedia.org/wiki/List_of_HTTP_header_fields
			$proto = 'https';
		} else if(
			TRUSTED_PROXY
			&& isset($_SERVER['HTTP_X_FORWARDED_PROTOCOL'])
			&& strtolower($_SERVER['HTTP_X_FORWARDED_PROTOCOL']) == 'https'
		) { 
			// Less conventional proxy header
			$proto = 'https';
		} else if(
			isset($_SERVER['HTTP_FRONT_END_HTTPS'])
			&& strtolower($_SERVER['HTTP_FRONT_END_HTTPS']) == 'on'
		) { 
			// Microsoft proxy convention: https://support.microsoft.com/?kbID=307347
			$proto = 'https';
		} else if((!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off')) {
			$proto = 'https';
		} else if(isset($_SERVER['SSL'])) {
			$proto = 'https';
		}

		if((!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off')) $proto = 'https';
		if(isset($_SERVER['SSL'])) $proto = 'https';

		$parts = array_filter(array(
			// What's our host
			$_SERVER['HTTP_HOST'],
			// SilverStripe base
			self::$alternateBaseURL !== null ? self::$alternateBaseURL : BASE_URL,
			// And URL
			$url
		));

		// Join together with protocol into our current absolute URL, avoiding duplicated "/" characters
		return "$proto://" . preg_replace('#/{2,}#', '/', implode('/', $parts));
	}

	public function reloadWithToken() {
		$location = $this->currentAbsoluteURL();

		// What's our GET params (ensuring they include the original parameter + a new token)
		$params = array_merge($_GET, $this->params());
		unset($params['url']);

		if ($params) $location .= '?'.http_build_query($params);

		// And redirect
		if (headers_sent()) {
			echo "
<script>location.href='$location';</script>
<noscript><meta http-equiv='refresh' content='0; url=$location'></noscript>
You are being redirected. If you are not redirected soon, <a href='$location'>click here to continue the flush</a>
";
		}
		else header('location: '.$location, true, 302);
		die;
	}
	
	/**
	 * Given a list of token names, suppress all tokens that have not been validated, and 
	 * return the non-validated token with the highest priority
	 * 
	 * @param type $keys List of token keys in ascending priority (low to high)
	 * @return ParameterConfirmationToken The token container for the unvalidated $key given with the highest priority
	 */
	public static function prepare_tokens($keys) {
		$target = null;
		foreach($keys as $key) {
			$token = new ParameterConfirmationToken($key);
			// Validate this token
			if($token->reloadRequired()) {
				$token->suppress();
				$target = $token;
			}
		}
		return $target;
	}
}