ASFUR PROTOCOL SPECIFICATION

All packets follow this structure:
    [u16 size][u8 type][data...]

    size: total length of the packet (including header)
    type: packet type identifier
    data: payload bytes (format depends on type)

================================================================================
PACKET TYPES
================================================================================

Client -> Server:
    PACKET_REGISTER      = 1
    PACKET_AUTHENTICATE  = 2
    PACKET_JOIN          = 3
    PACKET_TEXT          = 4
    PACKET_LEAVE         = 5
    PACKET_DM_OPEN       = 7
    PACKET_CREATE_ROOM   = 9
    PACKET_DELETE_ROOM   = 10
    PACKET_LIST_ROOMS    = 12

Server -> Client:
    PACKET_ERROR         = 0
    PACKET_OK            = 6
    PACKET_DM_ROOM       = 8
    PACKET_ROOM_CREATED  = 11
    PACKET_ROOM_LIST     = 13

Bidirectional:
    PACKET_TEXT          = 4   (client sends, server broadcasts)

================================================================================
PACKET DATA LAYOUTS
================================================================================

PACKET_ERROR (0)
    Server response indicating an error occurred.
    [u8 code]

    Error codes:
        0  = ERR_UNKNOWN             (unknown error)
        1  = ERR_INVALID_PACKET      (malformed packet)
        2  = ERR_NOT_AUTHENTICATED   (action requires authentication)
        3  = ERR_ALREADY_REGISTERED  (username already taken)
        4  = ERR_INVALID_CREDENTIALS (wrong username/password)
        5  = ERR_REGISTRATION_DISABLED (server disabled registration)
        6  = ERR_DATABASE            (internal database error)
        7  = ERR_USER_NOT_FOUND      (target user does not exist)
        8  = ERR_ACCESS_DENIED       (not allowed to access resource)
        9  = ERR_ROOM_NOT_FOUND      (room does not exist)
        10 = ERR_ROOM_NAME_TAKEN     (room name already in use)
        11 = ERR_NOT_ROOM_OWNER      (action requires room ownership)

PACKET_REGISTER (1)
    Register a new user account.
    [char username[20]][char password[100]]

    Response: PACKET_OK or PACKET_ERROR

PACKET_AUTHENTICATE (2)
    Authenticate with existing credentials.
    [char username[20]][char password[100]]

    Response: PACKET_OK or PACKET_ERROR

PACKET_JOIN (3)
    Join a room (public or DM).
    [u64 room_id]

    Response: PACKET_OK or PACKET_ERROR
    Requires: authentication

PACKET_TEXT (4)
    Send a message to a room (client -> server).
    [u64 room_id][char message[...]]

    message is variable length (packet size - header - 8 bytes)
    Client must have joined the room first.
    Requires: authentication, joined room

    Broadcast format (server -> client):
    [u64 room_id][char username[32]][char message[...]]

    Server broadcasts to all authenticated clients in the room.

PACKET_LEAVE (5)
    Leave a room.
    [u64 room_id]

    Response: PACKET_OK or PACKET_ERROR
    Requires: authentication

PACKET_OK (6)
    Server response indicating success.
    (no data)

PACKET_DM_OPEN (7)
    Open or get existing DM room with another user.
    [char username[20]]

    Response: PACKET_DM_ROOM or PACKET_ERROR
    Requires: authentication

PACKET_DM_ROOM (8)
    Server response with DM room ID.
    [u64 room_id]

    The room_id can be used with PACKET_JOIN.

PACKET_CREATE_ROOM (9)
    Create a new public room.
    [char name[32]]

    Response: PACKET_ROOM_CREATED or PACKET_ERROR
    Requires: authentication

PACKET_DELETE_ROOM (10)
    Delete a public room.
    [u64 room_id]

    Response: PACKET_OK or PACKET_ERROR
    Requires: authentication, room ownership

PACKET_ROOM_CREATED (11)
    Server response after successful room creation.
    [u64 room_id][char name[32]]

PACKET_LIST_ROOMS (12)
    Request list of all public rooms.
    (no data)

    Response: PACKET_ROOM_LIST or PACKET_ERROR
    Requires: authentication

PACKET_ROOM_LIST (13)
    Server response with list of public rooms.
    [u32 count][room_entry[count]]

    room_entry format:
        [u64 room_id][char name[32]][char owner[20]]

================================================================================
TYPICAL FLOWS
================================================================================

Registration:
    Client: PACKET_REGISTER(username, password)
    Server: PACKET_OK or PACKET_ERROR(ERR_ALREADY_REGISTERED)

Authentication:
    Client: PACKET_AUTHENTICATE(username, password)
    Server: PACKET_OK or PACKET_ERROR(ERR_INVALID_CREDENTIALS)

Join public room:
    Client: PACKET_LIST_ROOMS
    Server: PACKET_ROOM_LIST(rooms)
    Client: PACKET_JOIN(room_id)
    Server: PACKET_OK

Send message:
    Client: PACKET_TEXT(room_id, "hello")
    Server: PACKET_TEXT(room_id, sender_username, "hello") -> all clients in room

Direct message:
    Client: PACKET_DM_OPEN(target_username)
    Server: PACKET_DM_ROOM(room_id)
    Client: PACKET_JOIN(room_id)
    Server: PACKET_OK
    Client: PACKET_TEXT(room_id, "private message")

Create room:
    Client: PACKET_CREATE_ROOM("my-room")
    Server: PACKET_ROOM_CREATED(room_id, "my-room")