<?php

namespace Kirby\Session;

/**
 * @package   Kirby Session
 * @author    Lukas Bestle <lukas@getkirby.com>
 * @link      https://getkirby.com
 * @copyright Bastian Allgeier
 * @license   https://opensource.org/licenses/MIT
 */
abstract class SessionStore
{
    /**
     * Creates a new session ID with the given expiry time
     *
     * Needs to make sure that the session does not already exist
     * and needs to reserve it by locking it exclusively.
     *
     * @param int $expiryTime Timestamp
     * @return string Randomly generated session ID (without timestamp)
     */
    abstract public function createId(int $expiryTime): string;

    /**
     * Checks if the given session exists
     *
     * @param int $expiryTime Timestamp
     * @param string $id Session ID
     * @return bool true:  session exists,
     *              false: session doesn't exist
     */
    abstract public function exists(int $expiryTime, string $id): bool;

    /**
     * Locks the given session exclusively
     *
     * Needs to throw an Exception on error.
     *
     * @param int $expiryTime Timestamp
     * @param string $id Session ID
     * @return void
     */
    abstract public function lock(int $expiryTime, string $id);

    /**
     * Removes all locks on the given session
     *
     * Needs to throw an Exception on error.
     *
     * @param int $expiryTime Timestamp
     * @param string $id Session ID
     * @return void
     */
    abstract public function unlock(int $expiryTime, string $id);

    /**
     * Returns the stored session data of the given session
     *
     * Needs to throw an Exception on error.
     *
     * @param int $expiryTime Timestamp
     * @param string $id Session ID
     * @return string
     */
    abstract public function get(int $expiryTime, string $id): string;

    /**
     * Stores data to the given session
     *
     * Needs to make sure that the session exists.
     * Needs to throw an Exception on error.
     *
     * @param int $expiryTime Timestamp
     * @param string $id Session ID
     * @param string $data Session data to write
     * @return void
     */
    abstract public function set(int $expiryTime, string $id, string $data);

    /**
     * Deletes the given session
     *
     * Needs to throw an Exception on error.
     *
     * @param int $expiryTime Timestamp
     * @param string $id Session ID
     * @return void
     */
    abstract public function destroy(int $expiryTime, string $id);

    /**
     * Deletes all expired sessions
     *
     * Needs to throw an Exception on error.
     *
     * @return void
     */
    abstract public function collectGarbage();

    /**
     * Securely generates a random session ID
     *
     * @return string Random hex string with 20 bytes
     */
    protected static function generateId(): string
    {
        return bin2hex(random_bytes(10));
    }
}