NIP-28
======

Public Chat
-----------

`draft` `optional`

This NIP defines new event kinds for public chat channels, channel messages, and basic client-side moderation.

It reserves five event kinds (40-44) for immediate use:

- `40 - channel create`
- `41 - channel metadata`
- `42 - channel message`
- `43 - hide message`
- `44 - mute user`

Client-centric moderation gives client developers discretion over what types of content they want included in their apps, while imposing no additional requirements on relays.

## Kind 40: Create channel

Create a public chat channel.

In the channel creation `content` field, Client SHOULD include basic channel metadata (`name`, `about`, `picture` and `relays` as specified in kind 41).

```jsonc
{
  "content": "{\"name\": \"Demo Channel\", \"about\": \"A test channel.\", \"picture\": \"https://placekitten.com/200/200\", \"relays\": [\"wss://nos.lol\", \"wss://nostr.mom\"]}",
 // other fields...
}
```


## Kind 41: Set channel metadata

Update a channel's public metadata.

Kind 41 is used to update the metadata without modifying the event id for the channel. Only the most recent kind 41 per `e` tag value MAY be available.

Clients SHOULD ignore kind 41s from pubkeys other than the kind 40 pubkey.

Clients SHOULD support basic metadata fields:

- `name` - string - Channel name
- `about` - string - Channel description
- `picture` - string - URL of channel picture
- `relays` - array - List of relays to download and broadcast events to

Clients MAY add additional metadata fields.

Clients SHOULD use [NIP-10](10.md) marked "e" tags to recommend a relay.

```jsonc
{
  "content": "{\"name\": \"Updated Demo Channel\", \"about\": \"Updating a test channel.\", \"picture\": \"https://placekitten.com/201/201\", \"relays\": [\"wss://nos.lol\", \"wss://nostr.mom\"]}",
  "tags": [["e", <channel_create_event_id>, <relay-url>]],
  // other fields...
}
```


## Kind 42: Create channel message

Send a text message to a channel.

Clients SHOULD use [NIP-10](10.md) marked "e" tags to recommend a relay and specify whether it is a reply or root message.

Clients SHOULD append [NIP-10](10.md) "p" tags to replies.

Root message:

```jsonc
{
  "content": <string>,
  "tags": [["e", <kind_40_event_id>, <relay-url>, "root"]],
  // other fields...
}
```

Reply to another message:

```jsonc
{
  "content": <string>,
  "tags": [
      ["e", <kind_40_event_id>, <relay-url>, "root"],
      ["e", <kind_42_event_id>, <relay-url>, "reply"],
      ["p", <pubkey>, <relay-url>],
      // rest of tags...
  ],
  // other fields...
}
```


## Kind 43: Hide message

User no longer wants to see a certain message.

The `content` may optionally include metadata such as a `reason`.

Clients SHOULD hide event 42s shown to a given user, if there is an event 43 from that user matching the event 42 `id`.

Clients MAY hide event 42s for other users other than the user who sent the event 43.

(For example, if three users 'hide' an event giving a reason that includes the word 'pornography', a Nostr client that is an iOS app may choose to hide that message for all iOS clients.)

```jsonc
{
  "content": "{\"reason\": \"Dick pic\"}",
  "tags": [["e", <kind_42_event_id>]],
  // other fields...
}
```

## Kind 44: Mute user

User no longer wants to see messages from another user.

The `content` may optionally include metadata such as a `reason`.

Clients SHOULD hide event 42s shown to a given user, if there is an event 44 from that user matching the event 42 `pubkey`.

Clients MAY hide event 42s for users other than the user who sent the event 44.

```jsonc
{
  "content": "{\"reason\": \"Posting dick pics\"}",
  "tags": [["p", <pubkey>]],
  // other fields...
}
```

## Relay recommendations

Clients SHOULD use the relay URLs of the metadata events. 

Clients MAY use any relay URL. For example, if a relay hosting the original kind 40 event for a channel goes offline, clients could instead fetch channel data from a backup relay, or a relay that clients trust more than the original relay.

Motivation
----------
If we're solving censorship-resistant communication for social media, we may as well solve it also for Telegram-style messaging.

We can bring the global conversation out from walled gardens into a true public square open to all.


Additional info
---------------

- [Chat demo PR with fiatjaf+jb55 comments](https://github.com/ArcadeCity/arcade/pull/28)
- [Conversation about NIP16](https://t.me/nostr_protocol/29566)