<?php

namespace alveolata\session;

// require_once(DIR_ALVEOLATA . '/definitions.php');
require_once(DIR_ALVEOLATA . '/session/interface.php');
require_once(DIR_ALVEOLATA . '/json/functions.php');
require_once(DIR_ALVEOLATA . '/file/functions.php');


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
class _state_file
{
	
	/**
	 * @var string
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public static $directory = '/tmp/sessions';
	
	
	/**
	 * @var int
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public static $time_to_live_in_seconds = 3600;
	
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
class struct_subject_file {
	
	/**
	 * @var string
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public $id;
	
	
	/**
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public function __construct(
		string $id
	)
	{
		$this->id = $id;
	}
	
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function file_set_directory(
	string $directory
) : void
{
	_state_file::$directory = $directory;
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
function file_set_time_to_live_in_seconds(
	int $time_to_live_in_seconds
) : void
{
	_state_file::$time_to_live_in_seconds = $time_to_live_in_seconds;
}


/**
 * @param string $id
 * @return string
 * @author Christian Fraß <frass@greenscale.de>
 */
function _file_get_path(
	string $id
) : string
{
	return \alveolata\string\coin(
		'{{directory}}/{{id}}.json',
		[
			'directory' => _state_file::$directory,
			'id' => $id,
		]
	);
}


/**
 * @param struct_subject_file $subject
 * @return map<string,string>
 * @author Christian Fraß <frass@greenscale.de>
 */
function _file_get_data(
	struct_subject_file $subject
) : array
{
	$path = _file_get_path($subject->id);
	try {
		$content = \alveolata\file\read($path);
		$data = \alveolata\json\decode($content);
	}
	catch (\Exception $exception) {
		$data = null;
	}
	if ($data === null) {
		throw (new \Exception('session does not exist'));
	}
	else {
		$now = time();
		if (($data['timestamp'] + _state_file::$time_to_live_in_seconds) < $now) {
			throw (new \Exception('session timed out'));
		}
		else {
			return $data['data'];
		}
	}
}


/**
 * @return struct_subject_file
 * @author Christian Fraß <frass@greenscale.de>
 */
function file_begin(
) : struct_subject_file
{
	$id = hash('sha256', strval(time()));
	$subject = (new struct_subject_file($id));
	$path = _file_get_path($id);
	$data = [
		'timestamp' => time(),
		'data' => [],
	];
	$content = \alveolata\json\encode($data);
	\alveolata\file\write($path, $content, true);
	return $subject;
}


/**
 * @param string $id
 * @return struct_subject_file
 * @author Christian Fraß <frass@greenscale.de>
 */
function file_get(
	string $id
) : struct_subject_file
{
	$subject = (new struct_subject_file($id));
	return $subject;
}


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


/**
 * @param struct_subject_file $subject
 * @return string
 * @author Christian Fraß <frass@greenscale.de>
 */
function file_read(
	struct_subject_file $subject,
	string $key
) : string
{
	$data = _file_get_data($subject);
	return $data[$key];
}


/**
 * @param struct_subject_file $subject
 * @param string $key
 * @return string $value
 * @author Christian Fraß <frass@greenscale.de>
 */
function file_write(
	struct_subject_file $subject,
	string $key,
	string $value
) : void
{
	$data = _file_get_data($subject);
	$data['timestamp'] = time();
	$data['data'][$key] = $value;
	$content = \alveolata\json\encode($data);
	$path = _file_get_path($subject->id);
	\alveolata\file\write($path, $content, true);
}


/**
 * @param struct_subject_file $subject
 * @author Christian Fraß <frass@greenscale.de>
 */
function file_end(
	struct_subject_file $subject
) : void
{
	$path = _file_get_path($subject->id);
	\alveolata\file\remove($path);
}


/**
 * @author Christian Fraß <frass@greenscale.de>
 */
class implementation_file implements interface_session {
	
	/**
	 * @var struct_subject_file 
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	private $subject;
	
	
	/**
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	private function __construct(struct_subject_file $subject) {$this->subject = $subject;}
	
	
	/**
	 * implementations
	 * 
	 * @author Christian Fraß <frass@greenscale.de>
	 */
	public static function begin() : interface_session {return (new implementation_file(file_begin()));}
	public static function get(string $id) : interface_session {return (new implementation_file(file_get($id)));}
	public function id() : string {return file_id($this->subject);}
	public function read(string $key) : string {return file_read($this->subject, $key);}
	public function write(string $key, string $value) : void {file_write($this->subject, $key, $value);}
	public function remove(string $key) : void {file_remove($this->subject, $key);}
	public function end() : void {file_end($this->subject);}
	
}

 ?>