nips/25.md

NIP-25
======

Reactions
---------

`draft` `optional` `author:jb55`

A reaction is a `kind 7` event that is used to react to other events.

The generic reaction, represented by the `content` set to a `+` string, SHOULD
be interpreted as a "like" or "upvote".

A reaction with `content` set to `-` SHOULD be interpreted as a "dislike" or
"downvote". It SHOULD NOT be counted as a "like", and MAY be displayed as a
downvote or dislike on a post. A client MAY also choose to tally likes against
dislikes in a reddit-like system of upvotes and downvotes, or display them as
separate tallies.

The `content` MAY be an emoji, or [NIP-30](30.md) custom emoji in this case it MAY be interpreted as a "like" or "dislike",
or the client MAY display this emoji reaction on the post. If the `content` is an empty string then the client should
consider it a "+".

Tags
----

The reaction event SHOULD include `e` and `p` tags from the note the user is
reacting to. This allows users to be notified of reactions to posts they were
mentioned in. Including the `e` tags enables clients to pull all the reactions
associated with individual posts or all the posts in a thread.

The last `e` tag MUST be the `id` of the note that is being reacted to. 

The last `p` tag MUST be the `pubkey` of the event being reacted to.

The reaction event MAY include a `k` tag with the stringified kind number
of the reacted event as its value.

Example code

```swift
func make_like_event(pubkey: String, privkey: String, liked: NostrEvent) -> NostrEvent {
    var tags: [[String]] = liked.tags.filter { 
    	tag in tag.count >= 2 && (tag[0] == "e" || tag[0] == "p") 
    }
    tags.append(["e", liked.id])
    tags.append(["p", liked.pubkey])
    tags.append(["k", liked.kind])
    let ev = NostrEvent(content: "+", pubkey: pubkey, kind: 7, tags: tags)
    ev.calculate_id()
    ev.sign(privkey: privkey)
    return ev
}
```

Custom Emoji Reaction
---------------------

The client may specify a custom emoji ([NIP-30](30.md)) `:shortcode:` in the
reaction content. The client should refer to the emoji tag and render the
content as an emoji if shortcode is specified.

```json
{
  "kind": 7,
  "content": ":soapbox:",
  "tags": [
    ["emoji", "soapbox", "https://gleasonator.com/emoji/Gleasonator/soapbox.png"]
  ],
  "pubkey": "79c2cae114ea28a981e7559b4fe7854a473521a8d22a66bbab9fa248eb820ff6",
  "created_at": 1682790000
}
```

The content can be set only one `:shortcode:`. And emoji tag should be one.

Reaction Suggestions
--------------------

A client may specify suggested reactions in the tags of any event. These may be
emojis, or emoji shortcodes, with definitions included in tags as described above.
Clients MAY prompt users to use these suggestions to react.
```json
{
  "kind": 1,
  "content": "Why did the chicken cross the road?",
  "tags": [
    ["reaction", ":joy:"],
    ["reaction", ":man-shrugging:"],
    ["reaction", "bananas"],
    ["emoji", "bananas", "https://example.com/emoji/bananas.png"]
  ],
  "pubkey": "79c2cae114ea28a981e7559b4fe7854a473521a8d22a66bbab9fa248eb820ff6",
  "created_at": 1682790000
}
```