[Thread] Thread-aware Actions + Optimistic UI Update

[dab246]

Related

• ADR-0072

Description

When a user performs an action (mark read, star, move, delete, etc.) on one or more threads in the email list, the system must:

1. Expand ThreadId to List<EmailInThreadDetailInfo>
2. Execute the action on all emails in the thread
3. Update UI immediately before server response (optimistic UI)
4. Handle rollback on failure

Tasks

Thread Expansion Service

• Create ThreadExpansionService with in-memory cache, parallel execution, and error isolation
• Create ThreadExpansionResult data model (emailThreadInfos + errors)
• Implement expandThreads() reusing ThreadDetailRepository.getThreadById

Thread-aware Interactors

• Create ThreadActionResult model (success, actionErrors, expansionErrors)
• Create MarkAsThreadReadInteractor — expand threads, then delegate to existing email interactor
• Create MoveThreadInteractor — expand threads, then delegate to existing move logic
• Create other thread-aware interactors (star, delete, etc.) following the same pattern

Optimistic UI

• Call updateEmailFlagByEmailIds() before interactor execution (optimistic update)
• On failure: rollback via inverse operation (e.g., markAsRead to markAsUnread)
• On partial success: rollback only failed email IDs
• Sync thread detail UI via dispatchThreadDetailUIAction(UpdatedEmailKeywordsAction(...))

Cache Invalidation

• Clear ThreadExpansionService cache in:
  • ThreadController.refreshAllEmail()
  • ThreadController.refreshChangeEmail()
  • collapseThreads toggle handler
  • After thread action completes

Acceptance Criteria

• Action on a thread applies to all emails within that thread
• UI updates instantly without waiting for server response
• On failure: UI rolls back to previous state
• On partial success: only failed emails are rolled back
• One thread expansion failure does not block other threads

[coderabbitai]

🔗 Related PRs

#4316 - TF-4314 Fix unread emails disappear blink [merged]
#4372 - TF-4368 Fix cannot scroll in email list [merged]
#4377 - TF-4373 Fix deletion is not working on thread [merged]

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