Make mentions more permissive

src/nick.rs

@@ -53,13 +53,6 @@ pub fn hue(emoji: &Emoji, nick: &str) -> u8 {
     hue_without_removing_emoji(&emoji.remove(nick))
 }
 
-fn delimits_mention(c: char) -> bool {
-    match c {
-        ',' | '.' | '!' | '?' | ';' | '&' | '<' | '>' | '\'' | '"' => true,
-        _ => c.is_whitespace(),
-    }
-}
-
 /// Normalize a nick to a form that can be compared against other nicks.
 ///
 /// This normalization is less aggressive than the nick hue normalization. It is
@@ -73,11 +66,7 @@ fn delimits_mention(c: char) -> bool {
 ///
 /// The steps performed are as follows:
 ///
-/// 1. Remove all whitespace characters as well as the characters
-///    `,`, `.`, `!`, `?`, `;`, `&`, `<`, `>`, `'`, `"`.
-///    All of these are used by the [frontend to delimit mentions][0].
-///    The `>` character was confirmed to delimit mentions via experimentation.
-///
+/// 1. Apply [`mention`]
 /// 2. Convert to NFKC
 /// 3. Case fold
 ///
@@ -87,13 +76,19 @@ fn delimits_mention(c: char) -> bool {
 ///
 /// [0]: https://github.com/euphoria-io/heim/blob/978c921063e6b06012fc8d16d9fbf1b3a0be1191/client/lib/stores/chat.js#L14
 pub fn normalize(nick: &str) -> String {
-    nick.chars()
-        .filter(|c| !delimits_mention(*c)) // Step 1
+    mention(nick) // Step 1
         .nfkc() // Step 2
         .default_case_fold() // Step 3
         .collect()
 }
 
+fn is_non_whitespace_delimiter(c: char) -> bool {
+    matches!(
+        c,
+        ',' | '.' | '!' | '?' | ';' | '&' | '<' | '>' | '\'' | '"'
+    )
+}
+
 /// Compute a mentionable version of a nick while remaining as close to the
 /// original as possible.
 ///
@@ -101,7 +96,20 @@ pub fn normalize(nick: &str) -> String {
 /// highlight as a mention in the official euphoria client. It should ping any
 /// people using the original nick. It might also ping other people.
 ///
-/// This function performs step 1 of [`normalize`].
+/// In the official euphoria client, mentions are non-whitespace characters
+/// delimited by whitespace and any of the following characters:
+///
+/// `,`, `.`, `!`, `?`, `;`, `&`, `<`, `>`, `'`, `"`.
+///
+/// The first character of a mention may be a delimiting character.
 pub fn mention(nick: &str) -> String {
-    nick.replace(delimits_mention, "")
+    let mut nick = nick.chars().filter(|c| !c.is_whitespace());
+    let mut result = String::new();
+    if let Some(c) = nick.next() {
+        result.push(c);
+    }
+    for c in nick.filter(|c| !is_non_whitespace_delimiter(*c)) {
+        result.push(c);
+    }
+    result
 }