<?php
/**
 * GeoGraSim — Session Management
 * Schueler: UUID-Cookie (anonym, kein Login)
 * Lehrkraefte: PHP-Session mit teacher_id
 */

class Session {
    const COOKIE_NAME = 'ggs_session';
    const COOKIE_TTL  = 86400 * 30; // 30 Tage

    public static function start(): void {
        if (session_status() === PHP_SESSION_NONE) {
            session_start();
        }
    }

    /** Schueler-Session-ID aus Cookie */
    public static function studentId(): ?string {
        return $_COOKIE[self::COOKIE_NAME] ?? null;
    }

    /** Neue Schueler-Session erstellen. student_id wird direkt gesetzt (per FK
     *  statt fragilem display_name-Join) — falls nicht übergeben, aus
     *  (class_id, display_name) aufgelöst. */
    public static function createStudent(int $classId, string $displayName = '', ?int $studentId = null): string {
        $uuid = sprintf('%s-%s-%s-%s-%s',
            bin2hex(random_bytes(4)),
            bin2hex(random_bytes(2)),
            bin2hex(random_bytes(2)),
            bin2hex(random_bytes(2)),
            bin2hex(random_bytes(6))
        );

        $db = Database::get();
        if ($studentId === null && $displayName !== '') {
            $row = $db->fetchOne(
                'SELECT id FROM students WHERE class_id = ? AND display_name = ? AND deleted_at IS NULL',
                [$classId, $displayName]
            );
            if ($row) $studentId = (int)$row['id'];
        }
        $db->execute(
            'INSERT INTO student_sessions (id, class_id, display_name, student_id) VALUES (?, ?, ?, ?)',
            [$uuid, $classId, $displayName, $studentId]
        );

        setcookie(self::COOKIE_NAME, $uuid, [
            'expires'  => time() + self::COOKIE_TTL,
            'path'     => BASE_PATH . '/',
            'samesite' => 'Lax',
            'secure'   => IS_PRODUCTION,
            'httponly'  => true,
        ]);

        return $uuid;
    }

    /** API-Guard: 401 wenn keine Session */
    public static function requireStudent(): string {
        $id = self::studentId();
        if (!$id) {
            http_response_code(401);
            echo json_encode(['error' => 'Keine Session']);
            exit;
        }
        return $id;
    }

    /** Lehrer eingeloggt? */
    public static function teacherId(): ?int {
        return $_SESSION['teacher_id'] ?? null;
    }

    /** Lehrer-Login */
    public static function loginTeacher(int $teacherId): void {
        self::start();
        $_SESSION['teacher_id'] = $teacherId;
    }

    /** Lehrer-Guard: 401 wenn nicht eingeloggt */
    public static function requireTeacher(): int {
        $id = self::teacherId();
        if (!$id) {
            http_response_code(401);
            echo json_encode(['error' => 'Nicht eingeloggt']);
            exit;
        }
        return $id;
    }

    public static function logout(): void {
        self::start();
        session_destroy();
        setcookie(self::COOKIE_NAME, '', [
            'expires'  => 1,
            'path'     => BASE_PATH . '/',
            'samesite' => 'Lax',
            'secure'   => IS_PRODUCTION,
            'httponly'  => true,
        ]);
    }
}