feat: mentions and following tickets

Mention project members in comments with @, follow and unfollow tickets,
and get told when something changes on the tickets you follow. Commenting
on a ticket starts following it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/tracker/domain/src/index.ts

@@ -3,3 +3,4 @@ export * from './lib/models/models';
 export * from './lib/models/inputs';
 export * from './lib/models/workflow';
 export * from './lib/ports/gateways';
+export * from './lib/models/mentions';

libs/web/tracker/domain/src/lib/models/mentions.spec.ts

@@ -0,0 +1,30 @@
+import {
+  insertMention,
+  matches,
+  mentionQuery,
+  mentionSegments,
+} from './mentions';
+
+describe('mentions', () => {
+  it('splits a text into words and mentions', () => {
+    expect(mentionSegments('Hola @[Ana](u1), ¿lo miras?')).toEqual([
+      { text: 'Hola ' },
+      { mention: 'Ana', userId: 'u1' },
+      { text: ', ¿lo miras?' },
+    ]);
+  });
+
+  it('notices an @ being typed and completes it', () => {
+    expect(mentionQuery('Pregunta a @an')).toBe('an');
+    expect(mentionQuery('Pregunta a @')).toBe('');
+    expect(mentionQuery('correo@dominio')).toBeNull();
+    expect(
+      insertMention('Pregunta a @an', { id: 'u1', name: 'Ana García' }),
+    ).toBe('Pregunta a @[Ana García](u1) ');
+  });
+
+  it('finds people ignoring accents and case', () => {
+    expect(matches('José Pérez', 'jose pe')).toBe(true);
+    expect(matches('Ana', 'bob')).toBe(false);
+  });
+});

libs/web/tracker/domain/src/lib/models/mentions.ts

@@ -0,0 +1,52 @@
+/**
+ * Mentions are stored as `@[Ana García](<user id>)` — the API reads the id to
+ * tell that person; people see `@Ana García`.
+ */
+const MENTION = /@\[([^\]\n]{1,80})\]\(([\w-]{1,64})\)/g;
+
+export type TextSegment =
+  | { text: string }
+  | { mention: string; userId: string };
+
+/** The text in pieces, to show mentions highlighted. */
+export function mentionSegments(text: string): TextSegment[] {
+  const segments: TextSegment[] = [];
+  let last = 0;
+  for (const match of text.matchAll(MENTION)) {
+    const at = match.index ?? 0;
+    if (at > last) segments.push({ text: text.slice(last, at) });
+    segments.push({ mention: match[1], userId: match[2] });
+    last = at + match[0].length;
+  }
+  if (last < text.length) segments.push({ text: text.slice(last) });
+  return segments;
+}
+
+const TYPING = /(^|\s)@([^\s@[\]()]{0,30})$/u;
+
+/** What is being typed after an `@` at the end of the text, or null. */
+export function mentionQuery(text: string): string | null {
+  return TYPING.exec(text)?.[2] ?? null;
+}
+
+/** Replaces the `@what-was-typed` at the end with the mention. */
+export function insertMention(
+  text: string,
+  user: { id: string; name: string },
+): string {
+  const name = user.name.replace(/[[\]()\n]/g, ' ').trim();
+  return text.replace(
+    TYPING,
+    (_, before: string) => `${before}@[${name}](${user.id}) `,
+  );
+}
+
+/** Case- and accent-insensitive "contains". */
+export function matches(name: string, query: string): boolean {
+  const fold = (s: string) =>
+    s
+      .normalize('NFD')
+      .replace(/\p{Diacritic}/gu, '')
+      .toLowerCase();
+  return fold(name).includes(fold(query));
+}

libs/web/tracker/domain/src/lib/models/models.ts

@@ -86,6 +86,8 @@ export interface Issue extends IssueSummary {
   dueDate: string | null;
   links: IssueLink[];
   attachments: Attachment[];
+  /** People following the ticket. */
+  watchers: UserRef[];
   allowedTransitions: string[];
   createdAt: string;
 }

libs/web/tracker/domain/src/lib/ports/gateways.ts

@@ -87,6 +87,8 @@ export abstract class IssuesGateway {
     issueId: string,
     releaseId: string | null,
   ): Observable<CommandResult>;
+  /** The signed-in person follows (or stops following) the ticket. */
+  abstract watch(issueId: string, watching: boolean): Observable<CommandResult>;
 }
 
 export abstract class CommentsGateway {