Improve conversation message search responsiveness [WPB-26110]

[MohamadJaara]

WPB-26110 Very slow searching in a conversation

Summary

Improves in-conversation message search responsiveness in the browser.

The search input now debounces queries, avoids stacking multiple expensive searches while the user is still typing, and keeps the browser responsive while scanning large local conversation histories.

Why It Was Slow

Conversation message search was doing more work than it looked like from the UI:

• Every query loaded all text/link-ish events for the conversation from local storage.
• The app scanned those events in JavaScript on the browser main thread.
• Each event extracted searchable text from multiple message shapes before matching.
• The previous search helper rebuilt the same search regex for every single message.
• If the user kept typing while a search was still running, more full scans could queue up behind the active one.

That means searching a large conversation was not just N string checks. It could become repeated local storage reads, repeated message-text extraction, repeated regex compilation, and repeated main-thread scans.

Fixes

• Increased full message search debounce to 500ms.
• Coalesced in-flight searches so only one search runs at a time.
• Kept only the latest pending query while a search is already running.
• Ignored stale search results when the input has moved on.
• Batched local event scanning and yielded between batches so the browser can keep rendering/responding.
• Compiled the search regex once per query instead of once per message.
• Reset the reused global regex before each event match to avoid skipping consecutive results.

Tests

• Added coverage for debounce timing and in-flight search coalescing.
• Added coverage for reused regex matching consecutive events without skipping results.

Verification

• yarn nx test webapp --testFile=apps/webapp/src/script/page/MainContent/panels/Collection/Collection.test.tsx --runInBand
• yarn nx test webapp --testFile=apps/webapp/src/script/repositories/conversation/ConversationService.test.ts --runInBand
• yarn nx run webapp:type-check

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud