<?php

namespace alveolata\session;

// require_once(DIR_ALVEOLATA . '/definitions.php');


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
class struct_subject_memory {
	
	/**
	 * @var string
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public $id;
	
	
	/**
	 * @var integar
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public $timestamp;
	
	
	/**
	 * @var map<string,string>
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public $data;
	
	
	/**
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public function __construct(
		string $id,
		int $timestamp = -1,
		array $data = []
	)
	{
		if ($timestamp < 0) $timestamp = time();
		$this->id = $id;
		$this->timestamp = $timestamp;
		$this->data = $data;
	}
	
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
class _state_memory {
	
	/**
	 * @var map<string,struct_subject_memory>
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public static $pool = [];
	
	
	/**
	 * @var int
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public static $time_to_live_in_seconds = 3600; // ~1h
	
}


/**
 * @throw \Exception if timed out
 * @author Christian Fraß <frass@greenscale.de>
 */
function _memory_ttlcheck(
	struct_subject_memory $subject
) : void
{
	$now = time();
	if (($subject->timestamp + _state_memory::$time_to_live_in_seconds) < $now) {
		throw (new \Exception('session timed out'));
	}
}


/**
 * @param struct_subject_memory $subject
 * @param string $key
 * @throw \Exception if no such key
 * @author Christian Fraß <frass@greenscale.de>
 */
function _memory_keycheck(
	struct_subject_memory $subject,
	string $key
) : void
{
	if (! array_key_exists($key, $subject->data)) {
		$message = sprintf('no key "%s"', $key);
		throw (new \Exception($message));
	}
}


/**
 * @param struct_subject_memory $subject
 * @author Christian Fraß <frass@greenscale.de>
 */
function _memory_update(
	struct_subject_memory $subject
) : void
{
	$subject->timestamp = time();
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function memory_begin(
) : struct_subject_memory
{
	$id = hash('sha256', strval(time()));
	$subject = (new struct_subject_memory($id));
	_state_memory::$pool[$id] = $subject;
	return $subject;
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function memory_get(
	string $id
) : struct_subject_memory
{
	if (! array_key_exists($id, _state_memory::$pool)) {
		$message = sprintf('no session "%s"', $id);
		throw (new \Exception($message));
	}
	else {
		$subject = _state_memory::$pool[$id];
		_memory_ttlcheck($subject);
		return $subject;
	}
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function memory_id(
	struct_subject_memory $subject
) : string
{
	return $subject->id;
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function memory_read(
	struct_subject_memory $subject,
	string $key
) : string
{
	_memory_ttlcheck($subject);
	_memory_keycheck($subject, $key);
	$value = $subject->data[$key];
	_memory_update($subject);
	return $value;
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function memory_write(
	struct_subject_memory $subject,
	string $key,
	string $value
) : void
{
	_memory_ttlcheck($subject);
	$subject->data[$key] = $value;
	_memory_update($subject);
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function memory_remove(
	struct_subject_memory $subject,
	string $key
) : void
{
	_memory_ttlcheck($subject);
	_memory_keycheck($subject, $key);
	unset($subject->data[$key]);
	_memory_update($subject);
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 * @todo check for existence and ttl
 */
function memory_end(
	struct_subject_memory $subject
) : void
{
	$subject->id = 0;
	$subject->timestamp = 0;
	$subject->data = [];
	unset(_state_memory::$pool[$subject->id]);
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
class implementation_memory implements interface_session {
	
	/**
	 * @var struct_subject_memory 
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	private $subject;
	
	
	/**
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	private function __construct(struct_subject_memory $subject) {$this->subject = $subject;}
	
	
	/**
	 * implementations
	 * 
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public static function begin() : interface_session {return (new implementation_memory(memory_begin()));}
	public static function get(string $id) : interface_session {return (new implementation_memory(memory_get($id)));}
	public function id() : string {return memory_id($this->subject);}
	public function read(string $key) : string {return memory_read($this->subject, $key);}
	public function write(string $key, string $value) : void {memory_write($this->subject, $key, $value);}
	public function remove(string $key) : void {memory_remove($this->subject, $key);}
	public function end() : void {memory_end($this->subject);}
	
}

 ?>