Introduce mentions comments chip

Find the mention of the currently logged in user in unresolved
threads to show in the mention summary chip.

Google-bug-id: b/236921879
Screenshot: https://imgur.com/a/sWkt6to
Release-Notes: skip
Change-Id: I05157fb58e3e5e7b57207aa169ce3947584a34d2

polygerrit-ui/app/utils/comment-util.ts

diff --git a/polygerrit-ui/app/utils/comment-util.ts b/polygerrit-ui/app/utils/comment-util.ts
index ec9ea19..911c821 100644
--- a/polygerrit-ui/app/utils/comment-util.ts
+++ b/polygerrit-ui/app/utils/comment-util.ts
@@ -30,6 +30,7 @@
 import {DiffInfo} from '../types/diff';
 import {LineNumber} from '../api/diff';
 import {FormattedReviewerUpdateInfo} from '../types/types';
+import {extractMentionedUsers} from './account-util';
 
 export interface DraftCommentProps {
   // This must be true for all drafts. Drafts received from the backend will be
@@ -556,3 +557,19 @@
     },
   ];
 }
+
+function getMentionedUsers(thread: CommentThread) {
+  return thread.comments.map(c => extractMentionedUsers(c.message)).flat();
+}
+
+export function getMentionedThreads(
+  threads: CommentThread[],
+  account: AccountInfo
+) {
+  if (!account.email) return [];
+  return threads.filter(t =>
+    getMentionedUsers(t)
+      .map(v => v.email)
+      .includes(account.email)
+  );
+}

polygerrit-ui/app/utils/comment-util_test.ts

diff --git a/polygerrit-ui/app/utils/comment-util_test.ts b/polygerrit-ui/app/utils/comment-util_test.ts
index 2cad710..4310396 100644
--- a/polygerrit-ui/app/utils/comment-util_test.ts
+++ b/polygerrit-ui/app/utils/comment-util_test.ts
@@ -15,8 +15,13 @@
   getContentInCommentRange,
   createUserFixSuggestion,
   PROVIDED_FIX_ID,
+  getMentionedThreads,
 } from './comment-util';
-import {createComment, createCommentThread} from '../test/test-data-generators';
+import {
+  createAccountWithEmail,
+  createComment,
+  createCommentThread,
+} from '../test/test-data-generators';
 import {CommentSide} from '../constants/constants';
 import {
   PARENT,
@@ -83,6 +88,43 @@
     });
   });
 
+  test('getMentionedThreads', () => {
+    const account = createAccountWithEmail('abcd@def.com');
+    const threads = [
+      createCommentThread([
+        {
+          ...createComment(),
+          message: 'random text with no emails',
+        },
+      ]),
+      createCommentThread([
+        {
+          ...createComment(),
+          message: '@abcd@def.com please take a look',
+        },
+        {
+          ...createComment(),
+          message: '@abcd@def.com please take a look again at this',
+        },
+      ]),
+      createCommentThread([
+        {
+          ...createComment(),
+          message: '@abcd@def.com this is important',
+        },
+      ]),
+    ];
+    assert.deepEqual(getMentionedThreads(threads, account), [
+      threads[1],
+      threads[2],
+    ]);
+
+    assert.deepEqual(
+      getMentionedThreads(threads, createAccountWithEmail('xyz@def.com')),
+      []
+    );
+  });
+
   test('comments sorting', () => {
     const comments = [
       {