This file isn't comprehensive, and is only quick overview. It's probably only useful in conjunction with skimming the appropriate headers (application/ChatProtocol.h, application/ChatProtocolMessages.h) and one of the included add-ons.

This file's mostly here mostly here to clear up some behaviors that might not be immediately clear.

Add-on structure

An add-on should export a few functions, and offer at least one class inheriting ChatProtocol.

Each add-on must export the following functions;

ChatProtocol* protocol_at(int32 i)
int32 protocol_count()
const char* signature()
const char* friendly_signature()
uint32 version()

A single add-on can support multiple protocols (the Purple add-on being the only current example of this)― but generally returning a "1" from protocol_count() and only returning a protocol from protocol_at(0) should be all you need.

For a full description of the ChatProtocol object, look through application/ChatProtocol.h.

Each ChatProtocol can be treated as either an account's instance, or solely for retrieving general metadata from the Icon(), Signature(), etc. methods― so please don't start the connection from the constructor.

Connection details

A ChatProtocol's UpdateSettings() method should be used to receive settings from the program and declare a separate connection thread, but it generally shouldn't actually start the connection nor this thread.

The connection should be started when the user's status is set to STATUS_ONLINE― and correspondingly, the connection should be paused or terminated when it is STATUS_OFFLINE. The user should be able to easily toggle the connection this way without any real consequences. If this is impossible, then the add-on can send IM_PROTOCOL_DISABLE just as the user-status is set to offline.

STATUS_OFFLINE is for a momentary pause, i.e., the server is down or the user toggled the connection. The ChatProtocol will remain existent and active.

If the status is set to offline by the protocol (and not the user!) Chat-O-Matic will automatically attempt a reconnect after some time by trying to set the status to STATUS_ONLINE, which should toggle the connection.

IM_PROTOCOL_DISABLE deletes the ChatProtocol, and should only be sent to the app when an irrecoverable error requiring user intervention has happened, i.e., a configuration error, incorrect password, etc. If possible, it's preferable to send the user a notification (with IM_ERROR) telling them about the problem, just before sending IM_PROTOCOL_DISABLE.

Templates

Each ChatProtocol has to provide UI "templates" for some important dialogues through the SettingsTemplate() method. In order of importance, they are "account", "create_room", "join_room", and "roster".

"account" is used for accounts settings (seen by the user when configuring their account), "create_room"/"join_room" for creating or joining a room respectively, and "roster" for adding/editing a contact on the roster.

Here's a shorter version of the XMPP add-on's "account" settings:

BMessage('IMst') {
        setting[0] = BMessage(0x0) {
                name = string("username")
                description = string("Jabber identifier:")
                error = string("You can't log into an account without a username.")
                type = int32(0x43535452 or 1129534546)
        }
        setting[1] = BMessage(0x0) {
                name = string("password")
                description = string("Password:")
                error = string("You can't log into an account without a password.")
                type = int32(0x43535452 or 1129534546)
                is_secret = bool(true)
        }
        setting[2] = BMessage(0x0) {
                name = string("server")
                description = string("Server:")
                error = string("You can't add an account without a server.")
                type = int32(0x43535452 or 1129534546)
        }
}

The template is a BMessage with sub-messages named "setting", each with, at least, an internal "name" (the slot used by Chat-O-Matic in the message parameter of UpdateSettings()), a user-friendly label ("description"), and the slot type in "type"― currently B_INT32_TYPE,B_STRING_TYPE, and B_BOOL_TYPE are accepted.

By default, slots are not required, and it's accepted for the user to skip them. To make a slot required, put an error message into "error", warning the user to change their ways.

Also optionally accepted are "is_secret" to determine if entered text is visible and "default" for a default value.

The internal names of "settings" in these templates determine the values you should expect to receive for some messages from the app, like IM_JOIN_ROOM.

Dealing with messages

For documentation of each API message, look through application/ChatProtocolMessages.h. For an example add-on, take a look at protocols/xmpp/― though it might not be simple, it is feature-complete.

When messages are received from or to the app, it will generally be a message of IM_MESSAGE with an int32 named "im_what" containing the value.

"im_what" values (along with comprehensive descriptions of their meanings) can be found in application/ChatProtocolMessages.h.

Slots

Here are standard message slots that are frequently used or required, along with their meanings:

* chat_id   Unique identifier for a chatroom. (e.g., room address)
* chat_name Display-name for a chatroom. Uniqueness not required.
* user_id   Unique identifier for a user. (e.g., JID, Matrix username)
* user_name Nick-name or display name for a user. Uniqueness not required.
* body      Used for message-text, or explanation of an action (inviting or banning a user, etc)

user_names and chat_names can be changed at will (through IM_CONTACT_INFO/IM_USER_SET_NAME/IM_ROOM_PARTICIPANTS and IM_ROOM_DATA/IM_ROOM_NAME_SET respectively), but user_ids and chat_ids cannot be changed.

If you have to, you can "change" a chat or user's ID, by faking the user leaving and re-joining the room. This should be avoided if possible, since it breaks continuity a bit.

Joining a room

The basic structure for joining a room should be like this, with each line being a subsequent response to the previous message:

* App (`IM_JOIN_ROOM`/`IM_CREATE_CHAT`) → Protocol
* Protocol (`IM_ROOM_JOINED`/`IM_CHAT_CREATED`) → App
* App (`IM_GET_ROOM_METADATA` & `IM_GET_ROOM_PARTICIPANTS`) → Protocol
* Protocol (`IM_ROOM_METADATA` & `IM_ROOM_PARTICIPANTS`) → App

Preferably, IM_ROOM_METADATA and IM_ROOM_PARTICIPANTS should only be used as above (in response to a request from Chat-O-Matic) since they are silent and don't explicitly tell the user what's happened― whereas messages like IM_ROOM_PARTICIPANT_JOINED and IM_ROOM_SUBJECT_SET will inform the user of the change.

You can send IM_ROOM_PARTICIPANTS multiple times in a row― users not mentioned in subsequent mentions are not implicitly removed from the user-list, you must send a separate IM_ROOM_PARTICIPANT_LEFT for each parting user.

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