<?php
/**
 * API: Live-Sessions (Lehrer schaut Schüler:innen live beim Spielen zu)
 *
 * POST /api/live  {action:'heartbeat', module_id, state}  → Schüler-Sim, alle 3-5s
 * GET  /api/live?class_id=X                               → Lehrer: alle aktiven Sessions der Klasse
 * GET  /api/live?student_id=X                             → Lehrer: state eines Schülers für Spectator-View
 *
 * "Aktiv" = letzter Heartbeat liegt höchstens 30 s zurück.
 *
 * Bootstrap: idempotent, falls die Datei direkt (nicht über index.php) angesprochen wird.
 */
require_once __DIR__ . '/../config/app.php';
require_once __DIR__ . '/../lib/Database.php';
require_once __DIR__ . '/../lib/Session.php';
require_once __DIR__ . '/../lib/Response.php';

$method = $_SERVER['REQUEST_METHOD'];
$db = Database::get();

const LIVE_ACTIVE_WINDOW_SEC = 30;

if ($method === 'POST') {
    $sessionId = Session::requireStudent();
    $body = json_decode(file_get_contents('php://input'), true);
    $action = $body['action'] ?? 'heartbeat';

    if ($action === 'heartbeat') {
        $moduleId = (string)($body['module_id'] ?? $body['moduleId'] ?? '');
        if ($moduleId === '' || strlen($moduleId) > 32) Response::error('module_id erforderlich');
        $state = $body['state'] ?? null;
        $stateJson = is_string($state) ? $state : json_encode($state, JSON_UNESCAPED_UNICODE);
        if ($stateJson !== null && strlen($stateJson) > 50000) {
            // Überlange States kappen (Sicherheitsnetz; State sollte schlank gehalten werden)
            $stateJson = substr($stateJson, 0, 50000);
        }

        $session = $db->fetchOne('SELECT class_id, display_name FROM student_sessions WHERE id = ?', [$sessionId]);
        if (!$session || !$session['class_id']) Response::ok(['ok' => false, 'reason' => 'no-class']);
        $student = $db->fetchOne('SELECT id FROM students WHERE class_id = ? AND display_name = ?', [$session['class_id'], $session['display_name']]);
        if (!$student) Response::ok(['ok' => false, 'reason' => 'no-student']);

        $studentId = (int)$student['id'];
        $classId = (int)$session['class_id'];

        // started_at frisch setzen, wenn (a) anderes Modul oder (b) länger als 30s
        // kein Heartbeat kam (Sim wurde geschlossen und neu gestartet).
        $db->execute(
            'INSERT INTO live_sessions (student_id, class_id, module_id, state_json, started_at, last_seen)
             VALUES (?, ?, ?, ?, NOW(), NOW())
             ON DUPLICATE KEY UPDATE
               class_id   = VALUES(class_id),
               module_id  = VALUES(module_id),
               state_json = VALUES(state_json),
               started_at = IF(module_id <> VALUES(module_id) OR last_seen < NOW() - INTERVAL 30 SECOND, NOW(), started_at),
               last_seen  = NOW()',
            [$studentId, $classId, $moduleId, $stateJson]
        );
        Response::ok(['ok' => true]);
    }

    if ($action === 'end') {
        $session = $db->fetchOne('SELECT display_name, class_id FROM student_sessions WHERE id = ?', [$sessionId]);
        $student = $session ? $db->fetchOne('SELECT id FROM students WHERE class_id = ? AND display_name = ?', [$session['class_id'], $session['display_name']]) : null;
        if ($student) $db->execute('DELETE FROM live_sessions WHERE student_id = ?', [(int)$student['id']]);
        Response::ok();
    }

    Response::error('Unbekannte Aktion');
}

if ($method === 'GET') {
    $teacherId = Session::requireTeacher();

    // Spectator: state eines Schülers
    if (isset($_GET['student_id'])) {
        $studentId = (int)$_GET['student_id'];
        $row = $db->fetchOne(
            'SELECT ls.*, s.display_name, s.username, s.emoji_avatar, c.id AS owner_class_id
               FROM live_sessions ls
               JOIN students s ON s.id = ls.student_id
               JOIN classes  c ON c.id = ls.class_id
              WHERE ls.student_id = ? AND c.teacher_id = ?',
            [$studentId, $teacherId]
        );
        if (!$row) Response::ok(['active' => false]);
        $stale = (strtotime($row['last_seen']) < time() - LIVE_ACTIVE_WINDOW_SEC);
        Response::ok([
            'active'      => !$stale,
            'student_id'  => (int)$row['student_id'],
            'username'    => $row['username'],
            'displayName' => $row['display_name'] ?: $row['username'],
            'emoji'       => $row['emoji_avatar'] ?: '🧑‍🎓',
            'module_id'   => $row['module_id'],
            'state'       => $row['state_json'] ? json_decode($row['state_json'], true) : null,
            'started_at'  => $row['started_at'],
            'last_seen'   => $row['last_seen'],
        ]);
    }

    // Klassen-Liste: alle aktiven Sessions
    $classId = (int)($_GET['class_id'] ?? 0);
    if (!$classId) Response::error('class_id erforderlich');
    $class = $db->fetchOne('SELECT id FROM classes WHERE id = ? AND teacher_id = ?', [$classId, $teacherId]);
    if (!$class) Response::error('Klasse nicht gefunden', 404);

    $rows = $db->fetchAll(
        'SELECT ls.student_id, ls.module_id, ls.state_json, ls.started_at, ls.last_seen,
                s.username, s.display_name, s.emoji_avatar,
                mi.title AS module_name, mi.icon AS module_icon, mi.play_url AS play_url
           FROM live_sessions ls
           JOIN students s ON s.id = ls.student_id
           LEFT JOIN module_info mi ON mi.module_id = ls.module_id
          WHERE ls.class_id = ?
            AND ls.last_seen > NOW() - INTERVAL ? SECOND
          ORDER BY ls.last_seen DESC',
        [$classId, LIVE_ACTIVE_WINDOW_SEC]
    );
    $list = array_map(function($r) {
        return [
            'student_id'  => (int)$r['student_id'],
            'username'    => $r['username'],
            'displayName' => $r['display_name'] ?: $r['username'],
            'emoji'       => $r['emoji_avatar'] ?: '🧑‍🎓',
            'module_id'   => $r['module_id'],
            'moduleName'  => $r['module_name'] ?: $r['module_id'],
            'moduleIcon'  => $r['module_icon'] ?: '📚',
            'playUrl'     => $r['play_url'] ?: $r['module_id'],
            'state'       => $r['state_json'] ? json_decode($r['state_json'], true) : null,
            'started_at'  => $r['started_at'],
            'last_seen'   => $r['last_seen'],
        ];
    }, $rows);
    Response::ok($list);
}

Response::error('Methode nicht erlaubt', 405);