<?php

declare(strict_types=1);

require_once __DIR__ . '/db.php';

use App\Database\Database;

class MySqlSessionHandler implements SessionHandlerInterface
{
    private ?PDO $connection = null;
    private bool $ipMismatch = false;

    public function open(string $savePath, string $sessionName): bool
    {
        try {
            $database = new Database();
            $this->connection = $database->getConnection();

            return true;
        } catch (Throwable $exception) {
            return false;
        }
    }

    public function close(): bool
    {
        $this->connection = null;
        return true;
    }

    public function read(string $id): string
    {
        if ($this->connection === null) {
            if (!$this->open('', '')) {
                return '';
            }
        }

        $statement = $this->connection->prepare(
            'SELECT data, ip_address
             FROM sessions
             WHERE id = :id'
        );
        $statement->bindValue(':id', $id, PDO::PARAM_STR);
        $statement->execute();

        $row = $statement->fetch(PDO::FETCH_ASSOC);

        if ($row === false) {
            return '';
        }

        $currentIp = $_SERVER['REMOTE_ADDR'] ?? '';

        if (!empty($row['ip_address']) && $row['ip_address'] !== $currentIp) {
            $this->ipMismatch = true;
            return '';
        }

        $this->updateAccessAndIp($id, $currentIp);

        return (string) $row['data'];
    }

    public function write(string $id, string $data): bool
    {
        if ($this->connection === null) {
            if (!$this->open('', '')) {
                return false;
            }
        }

        $currentIp = $_SERVER['REMOTE_ADDR'] ?? '';
        $access = time();
        $userId = isset($_SESSION['user_id']) ? (int) $_SESSION['user_id'] : null;
        $createdAt = date('Y-m-d H:i:s');

        $statement = $this->connection->prepare(
            'INSERT INTO sessions (id, access, data, user_id, ip_address, created_at)
             VALUES (:id, :access, :data, :user_id, :ip_address, :created_at)
             ON DUPLICATE KEY UPDATE
                 access = VALUES(access),
                 data = VALUES(data),
                 user_id = VALUES(user_id),
                 ip_address = VALUES(ip_address)'
        );
        $statement->bindValue(':id', $id, PDO::PARAM_STR);
        $statement->bindValue(':access', $access, PDO::PARAM_INT);
        $statement->bindValue(':data', $data, PDO::PARAM_STR);

        if ($userId === null) {
            $statement->bindValue(':user_id', null, PDO::PARAM_NULL);
        } else {
            $statement->bindValue(':user_id', $userId, PDO::PARAM_INT);
        }

        $statement->bindValue(':ip_address', $currentIp, PDO::PARAM_STR);
        $statement->bindValue(':created_at', $createdAt, PDO::PARAM_STR);

        try {
            return $statement->execute();
        } catch (Throwable $e) {
            return false;
        }
    }

    public function destroy(string $id): bool
    {
        if ($this->connection === null) {
            return false;
        }

        $statement = $this->connection->prepare(
            'DELETE FROM sessions WHERE id = :id'
        );
        $statement->bindValue(':id', $id, PDO::PARAM_STR);

        return $statement->execute();
    }

    public function gc(int $maxLifetime): int|false
    {
        if ($this->connection === null) {
            return false;
        }

        $statement = $this->connection->prepare(
            'DELETE FROM sessions WHERE access < :time'
        );
        $statement->bindValue(':time', time() - $maxLifetime, PDO::PARAM_INT);

        return $statement->execute();
    }

    public function validateIp(string $id): bool
    {
        if ($this->connection === null) {
            return true;
        }

        $statement = $this->connection->prepare(
            'SELECT ip_address FROM sessions WHERE id = :id'
        );
        $statement->bindValue(':id', $id, PDO::PARAM_STR);
        $statement->execute();

        $row = $statement->fetch(PDO::FETCH_ASSOC);
        $currentIp = $_SERVER['REMOTE_ADDR'] ?? '';

        return empty($row['ip_address']) || $row['ip_address'] === $currentIp;
    }

    public function hasIpMismatch(): bool
    {
        return $this->ipMismatch;
    }

    private function updateAccessAndIp(string $id, string $ip): void
    {
        $statement = $this->connection->prepare(
            'UPDATE sessions
             SET access = :access,
                 ip_address = :ip_address
             WHERE id = :id'
        );
        $statement->bindValue(':access', time(), PDO::PARAM_INT);
        $statement->bindValue(':ip_address', $ip, PDO::PARAM_STR);
        $statement->bindValue(':id', $id, PDO::PARAM_STR);
        $statement->execute();
    }
}

$handler = new MySqlSessionHandler();
session_set_save_handler($handler, true);
session_start();

// Only enforce IP mismatch for authenticated sessions (user_id present)
if (!empty($_SESSION['user_id']) && $handler->hasIpMismatch()) {
    session_unset();
    session_destroy();
    setcookie(session_name(), '', time() - 42000, '/');
    header('Location: /index.php');
    exit;
}