akkoma/docs/API/chats.md

# Chats

Chats are a way to represent an IM-style conversation between two actors. They are not the same as direct messages and they are not `Status`es, even though they have a lot in common.

## Why Chats?

There are no 'visibility levels' in ActivityPub, their definition is purely a Mastodon convention. Direct Messaging between users on the fediverse has mostly been modeled by using ActivityPub addressing following Mastodon conventions on normal `Note` objects. In this case, a 'direct message' would be a message that has no followers addressed and also does not address the special public actor, but just the recipients in the `to` field. It would still be a `Note` and is presented with other `Note`s as a `Status` in the API.

This is an awkward setup for a few reasons:

- As DMs generally still follow the usual `Status` conventions, it is easy to accidentally pull somebody into a DM thread by mentioning them. (e.g. "I hate @badguy so much")
- It is possible to go from a publicly addressed `Status` to a DM reply, back to public, then to a 'followers only' reply, and so on. This can be become very confusing, as it is unclear which user can see which part of the conversation.
- The standard `Status` format of implicit addressing also leads to rather ugly results if you try to display the messages as a chat, because all the recipients are always mentioned by name in the message.
- As direct messages are posted with the same api call (and usually same frontend component) as public messages, accidentally making a public message private or vice versa can happen easily. Client bugs can also lead to this, accidentally making private messages public.

As a measure to improve this situation, the `Conversation` concept and related Pleroma extensions were introduced. While it made it possible to work around a few of the issues, many of the problems remained and it didn't see much adoption because it was too complicated to use correctly. 

## Chats explained
For this reasons, Chats are a new and different entity, both in the API as well as in ActivityPub. A quick overview:

- Chats are meant to represent an instant message conversation between two actors. For now these are only 1-on-1 conversations, but the other actor can be a group in the future.
- Chat messages have the ActivityPub type `ChatMessage`. They are not `Note`s. Servers that don't understand them will just drop them.
- The only addressing allowed in `ChatMessage`s is one single ActivityPub actor in the `to` field.
- There's always only one Chat between two actors. If you start chatting with someone and later start a 'new' Chat, the old Chat will be continued.
- `ChatMessage`s are posted with a different api, making it very hard to accidentally send a message to the wrong person.
- `ChatMessage`s don't show up in the existing timelines.
- Chats can never go from private to public. They are always private between the two actors.

## Caveats

- Chats are NOT E2E encrypted (yet). Security is still the same as email.

## API

In general, the way to send a `ChatMessage` is to first create a `Chat`, then post a message to that `Chat`. `Group`s will later be supported by making them a sub-type of `Account`.

This is the overview of using the API. The API is also documented via OpenAPI, so you can view it and play with it by pointing SwaggerUI or a similar OpenAPI tool to `https://yourinstance.tld/api/openapi`.

### Creating or getting a chat.

To create or get an existing Chat for a certain recipient (identified by Account ID)
you can call:

`POST /api/v1/pleroma/chats/by-account-id/{account_id}`

The account id is the normal FlakeId of the user
```
POST /api/v1/pleroma/chats/by-account-id/someflakeid
```

If you already have the id of a chat, you can also use

```
GET /api/v1/pleroma/chats/:id
```

There will only ever be ONE Chat for you and a given recipient, so this call
will return the same Chat if you already have one with that user.

Returned data:

```json
{
  "account": {
    "id": "someflakeid",
    "username": "somenick",
    ...
  },
  "id" : "1",
  "unread" : 2,
  "last_message" : {...} // The last message in that chat
}
```

### Marking a chat as read

To set the `unread` count of a chat to 0, call

`POST /api/v1/pleroma/chats/:id/read`

Returned data:

```json
{
  "account": {
    "id": "someflakeid",
    "username": "somenick",
    ...
  },
  "id" : "1",
  "unread" : 0
}
```


### Getting a list of Chats

`GET /api/v1/pleroma/chats`

This will return a list of chats that you have been involved in, sorted by their
last update (so new chats will be at the top).

Returned data:

```json
[
   {
      "account": {
        "id": "someflakeid",
        "username": "somenick",
        ...
      },
      "id" : "1",
      "unread" : 2,
      "last_message" : {...} // The last message in that chat
   }
]
```

The recipient of messages that are sent to this chat is given by their AP ID.
The usual pagination options are implemented.

### Getting the messages for a Chat

For a given Chat id, you can get the associated messages with

`GET /api/v1/pleroma/chats/{id}/messages`

This will return all messages, sorted by most recent to least recent. The usual
pagination options are implemented.

Returned data:

```json
[
  {
    "account_id": "someflakeid",
    "chat_id": "1",
    "content": "Check this out :firefox:",
    "created_at": "2020-04-21T15:11:46.000Z",
    "emojis": [
      {
        "shortcode": "firefox",
        "static_url": "https://dontbulling.me/emoji/Firefox.gif",
        "url": "https://dontbulling.me/emoji/Firefox.gif",
        "visible_in_picker": false
      }
    ],
    "id": "13"
  },
  {
    "account_id": "someflakeid",
    "chat_id": "1",
    "content": "Whats' up?",
    "created_at": "2020-04-21T15:06:45.000Z",
    "emojis": [],
    "id": "12"
  }
]
```

### Posting a chat message

Posting a chat message for given Chat id works like this:

`POST /api/v1/pleroma/chats/{id}/messages`

Parameters:
- content: The text content of the message
- media_id: The id of an upload that will be attached to the message.

Currently, no formatting beyond basic escaping and emoji is implemented, as well as no
attachments. This will most probably change.

Returned data:

```json
{
  "account_id": "someflakeid",
  "chat_id": "1",
  "content": "Check this out :firefox:",
  "created_at": "2020-04-21T15:11:46.000Z",
  "emojis": [
    {
      "shortcode": "firefox",
      "static_url": "https://dontbulling.me/emoji/Firefox.gif",
      "url": "https://dontbulling.me/emoji/Firefox.gif",
      "visible_in_picker": false
    }
  ],
  "id": "13"
}
```

### Deleting a chat message

Deleting a chat message for given Chat id works like this:

`DELETE /api/v1/pleroma/chats/{chat_id}/messages/{message_id}`

Returned data is the deleted message.

### Notifications

There's a new `pleroma:chat_mention` notification, which has this form:

```json
{
  "id": "someid",
  "type": "pleroma:chat_mention",
  "account": { ... } // User account of the sender,
  "chat_message": {
    "chat_id": "1",
    "id": "10",
    "content": "Hello",
    "account_id": "someflakeid"
  },
  "created_at": "somedate"
}
```