function getConversation($userId, $otherUserId) {
    $messages = readDB(DATA_PATH . '/direct_messages.json');
    $conversationMessages = [];
    
    foreach ($messages as $message) {
        if (($message['sender_id'] === $userId && $message['receiver_id'] === $otherUserId) ||
            ($message['sender_id'] === $otherUserId && $message['receiver_id'] === $userId)) {
            $conversationMessages[] = $message;
        }
    }
    
    // Sort by time
    usort($conversationMessages, fn($a, $b) => $a['created_at'] <=> $b['created_at']);
    
    return $conversationMessages;
}

function markAsRead($messageId, $userId) {
    $messages = readDB(DATA_PATH . '/direct_messages.json');
    
    foreach ($messages as &$message) {
        if ($message['id'] === $messageId && $message['receiver_id'] === $userId) {
            $message['is_read'] = true;
            $message['read_at'] = time();
        }
    }
    
    writeDB(DATA_PATH . '/direct_messages.json', $messages);
}

function markConversationAsRead($userId, $otherUserId) {
    $messages = readDB(DATA_PATH . '/direct_messages.json');
    
    foreach ($messages as &$message) {
        if ($message['sender_id'] === $otherUserId && 
            $message['receiver_id'] === $userId && 
            !($message['is_read'] ?? false)) {
            $message['is_read'] = true;
            $message['read_at'] = time();
        }
    }
    
    writeDB(DATA_PATH . '/direct_messages.json', $messages);
}

function getUnreadCount($userId) {
    $messages = readDB(DATA_PATH . '/direct_messages.json');
    $unreadCount = 0;
    
    foreach ($messages as $message) {
        if ($message['receiver_id'] === $userId && !($message['is_read'] ?? false)) {
            $unreadCount++;
        }
    }
    
    return $unreadCount;
}

function deleteMessage($messageId, $userId) {
    $messages = readDB(DATA_PATH . '/direct_messages.json');
    
    $messages = array_filter($messages, function($msg) use ($messageId, $userId) {
        return !($msg['id'] === $messageId && 
                ($msg['sender_id'] === $userId || $msg['receiver_id'] === $userId));
    });
    
    writeDB(DATA_PATH . '/direct_messages.json', array_values($messages));
}

function createNotification($userId, $type, $fromUserId, $relatedId = null) {
    $notifications = readDB(DATA_PATH . '/notifications.json');
    
    $notification = [
        'id' => uniqid('notif_'),
        'user_id' => $userId,
        'type' => $type, // message, like, comment, follow, mention
        'from_user_id' => $fromUserId,
        'related_id' => $relatedId,
        'is_read' => false,
        'created_at' => time()
    ];
    
    $notifications[] = $notification;
    writeDB(DATA_PATH . '/notifications.json', $notifications);
    
    return $notification;
}

function getUnreadNotificationCount($userId) {
    $notifications = getNotifications($userId, true);
    return count($notifications);
}

function initDirectMessages() {
    if (!file_exists(DATA_PATH . '/direct_messages.json') || filesize(DATA_PATH . '/direct_messages.json') < 2) {
        writeDB(DATA_PATH . '/direct_messages.json', []);
    }
    if (!file_exists(DATA_PATH . '/notifications.json') || filesize(DATA_PATH . '/notifications.json') < 2) {
        writeDB(DATA_PATH . '/notifications.json', []);
    }
}

function updateOnlineStatus($userId) {
    $statuses = readDB(DATA_PATH . '/online_status.json');
    
    $found = false;
    foreach ($statuses as &$status) {
        if ($status['user_id'] === $userId) {
            $status['last_seen'] = time();
            $found = true;
            break;
        }
    }
    
    if (!$found) {
        $statuses[] = [
            'user_id' => $userId,
            'last_seen' => time()
        ];
    }
    
    writeDB(DATA_PATH . '/online_status.json', $statuses);
}

function isUserOnline($userId) {
    $statuses = readDB(DATA_PATH . '/online_status.json');
    
    foreach ($statuses as $status) {
        if ($status['user_id'] === $userId) {
            // Online if last seen within 5 minutes
            return (time() - $status['last_seen']) < 300;
        }
    }
    
    return false;
}

function getLastSeen($userId) {
    $statuses = readDB(DATA_PATH . '/online_status.json');
    
    foreach ($statuses as $status) {
        if ($status['user_id'] === $userId) {
            return $status['last_seen'];
        }
    }
    
    return null;
}

function formatLastSeen($timestamp) {
    if (!$timestamp) return 'Mai visto';
    
    $diff = time() - $timestamp;
    
    if ($diff < 60) return 'Online';
    if ($diff < 3600) return floor($diff / 60) . ' min fa';
    if ($diff < 86400) return floor($diff / 3600) . ' ore fa';
    if ($diff < 604800) return floor($diff / 86400) . ' giorni fa';
    
    return date('d/m/Y', $timestamp);
}