<?php
/**
 * Magic session class.
 * This class is intended to extend the $_SESSION magic variable by providing an API hook
 * to plug in other values.
 *
 * Primarily this is intended to provide a way of supplying "logged in user"
 * details without touching the session (which can cause problems when
 * accessed server side).
 *
 * If a value is present in the session then that value is returned, otherwise
 * a plugin hook 'session:get', '$var' is called, where $var is the variable
 * being requested.
 *
 * Setting values will store variables in the session in the normal way.
 *
 * LIMITATIONS: You can not access multidimensional arrays
 *
 * @package    Elgg.Core
 * @subpackage Sessions
 */
class ElggSession implements ArrayAccess {
	/** Local cache of trigger retrieved variables */
	private static $__localcache;

	/**
	 * Test if property is set either as an attribute or metadata.
	 *
	 * @param string $key The name of the attribute or metadata.
	 *
	 * @return bool
	 */
	function __isset($key) {
		return $this->offsetExists($key);
	}

	/**
	 * Set a value, go straight to session.
	 *
	 * @param string $key   Name
	 * @param mixed  $value Value
	 *
	 * @return void
	 */
	function offsetSet($key, $value) {
		$_SESSION[$key] = $value;
	}

	/**
	 * Get a variable from either the session, or if its not in the session
	 * attempt to get it from an api call.
	 *
	 * @see ArrayAccess::offsetGet()
	 *
	 * @param mixed $key Name
	 *
	 * @return mixed
	 */
	function offsetGet($key) {
		if (!ElggSession::$__localcache) {
			ElggSession::$__localcache = array();
		}

		if (isset($_SESSION[$key])) {
			return $_SESSION[$key];
		}

		if (isset(ElggSession::$__localcache[$key])) {
			return ElggSession::$__localcache[$key];
		}

		$value = NULL;
		$value = elgg_trigger_plugin_hook('session:get', $key, NULL, $value);

		ElggSession::$__localcache[$key] = $value;

		return ElggSession::$__localcache[$key];
	}

	/**
	 * Unset a value from the cache and the session.
	 *
	 * @see ArrayAccess::offsetUnset()
	 *
	 * @param mixed $key Name
	 *
	 * @return void
	 */
	function offsetUnset($key) {
		unset(ElggSession::$__localcache[$key]);
		unset($_SESSION[$key]);
	}

	/**
	 * Return whether the value is set in either the session or the cache.
	 *
	 * @see ArrayAccess::offsetExists()
	 *
	 * @param int $offset Offset
	 *
	 * @return bool
	 */
	function offsetExists($offset) {
		if (isset(ElggSession::$__localcache[$offset])) {
			return true;
		}

		if (isset($_SESSION[$offset])) {
			return true;
		}

		if ($this->offsetGet($offset)) {
			return true;
		}

		return false;
	}


	/**
	 * Alias to ::offsetGet()
	 *
	 * @param string $key Name
	 *
	 * @return mixed
	 */
	function get($key) {
		return $this->offsetGet($key);
	}

	/**
	 * Alias to ::offsetSet()
	 *
	 * @param string $key   Name
	 * @param mixed  $value Value
	 *
	 * @return void
	 */
	function set($key, $value) {
		$this->offsetSet($key, $value);
	}

	/**
	 * Alias to offsetUnset()
	 *
	 * @param string $key Name
	 *
	 * @return void
	 */
	function del($key) {
		$this->offsetUnset($key);
	}
}