Support NIP-30 custom emoji in messages and reactions

crates/chat/src/message.rs

@@ -22,6 +22,8 @@ pub struct Message {
     pub created_at: Timestamp,
     /// List of mentioned public keys in the message
     pub mentions: Vec<Mention>,
+    /// Custom emoji (NIP-30) declared by this message's `emoji` tags
+    pub emojis: Vec<(String, Url)>,
     /// List of event of the message this message is a reply to
     pub replies_to: Vec<EventId>,
     /// Encrypted file attachment
@@ -85,6 +87,7 @@ fn from_parts(
     let has_file = file.is_some();
 
     let replies_to = extract_reply_ids(tags);
+    let emojis = Message::emojis_from_tags(tags);
 
     // For file messages `.content` is the encrypted blob URL, not text or media
     let mentions = if has_file {
@@ -106,6 +109,7 @@ fn from_parts(
         media,
         created_at,
         mentions,
+        emojis,
         replies_to,
         file,
     }
@@ -146,6 +150,35 @@ impl Message {
 
         self.content.clone().into()
     }
+
+    /// Custom emoji (NIP-30) declared by `emoji` tags, first per shortcode wins
+    pub fn emojis_from_tags(tags: &Tags) -> Vec<(String, Url)> {
+        let mut emojis: Vec<(String, Url)> = Vec::new();
+
+        for tag in tags.iter() {
+            let Ok(Nip30Tag::Emoji {
+                shortcode,
+                image_url,
+                ..
+            }) = Nip30Tag::try_from(tag)
+            else {
+                continue;
+            };
+
+            if !emojis.iter().any(|(existing, _)| *existing == shortcode) {
+                emojis.push((shortcode, image_url));
+            }
+        }
+
+        emojis
+    }
+
+    /// Image URL of a `:shortcode:` reaction, if the shortcode is declared
+    pub fn reaction_image(content: &str, emojis: &[(String, Url)]) -> Option<Url> {
+        let shortcode = content.strip_prefix(':')?.strip_suffix(':')?;
+        let (_, url) = emojis.iter().find(|(name, _)| name == shortcode)?;
+        Some(url.clone())
+    }
 }
 
 /// New message.
@@ -226,3 +259,68 @@ fn extract_reply_ids(inner: &Tags) -> Vec<EventId> {
 
     replies_to
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn rumor(kind: Kind, content: &str, tags: Tags) -> UnsignedEvent {
+        let sender = Keys::generate();
+
+        let mut rumor = EventBuilder::new(kind, content)
+            .tags(tags)
+            .finalize_unsigned(sender.public_key());
+        rumor.ensure_id();
+        rumor
+    }
+
+    fn emoji_tag(shortcode: &str, url: &str) -> Tag {
+        Tag::parse(vec!["emoji", shortcode, url]).expect("valid emoji tag")
+    }
+
+    #[test]
+    fn emojis_from_tags_parses_and_deduplicates() {
+        let tags = Tags::from_list(vec![
+            emoji_tag("soapbox", "https://example.com/soapbox.png"),
+            emoji_tag("soapbox", "https://example.com/other.png"),
+            emoji_tag("bad shortcode", "https://example.com/bad.png"),
+        ]);
+
+        let emojis = Message::emojis_from_tags(&tags);
+
+        assert_eq!(emojis.len(), 1);
+        assert_eq!(emojis[0].0, "soapbox");
+        assert_eq!(
+            emojis[0].1,
+            Url::parse("https://example.com/soapbox.png").unwrap()
+        );
+    }
+
+    #[test]
+    fn message_parses_emoji_tags() {
+        let tags = Tags::from_list(vec![emoji_tag(
+            "soapbox",
+            "https://example.com/soapbox.png",
+        )]);
+
+        let message = Message::from(&rumor(Kind::PrivateDirectMessage, "hi :soapbox:", tags));
+
+        assert_eq!(message.emojis.len(), 1);
+        assert_eq!(message.emojis[0].0, "soapbox");
+    }
+
+    #[test]
+    fn reaction_image_matches_declared_shortcode() {
+        let emojis = vec![(
+            String::from("soapbox"),
+            Url::parse("https://example.com/soapbox.png").unwrap(),
+        )];
+
+        assert_eq!(
+            Message::reaction_image(":soapbox:", &emojis),
+            Some(Url::parse("https://example.com/soapbox.png").unwrap())
+        );
+        assert_eq!(Message::reaction_image("😂", &emojis), None);
+        assert_eq!(Message::reaction_image(":unknown:", &emojis), None);
+    }
+}