Development: Fix duplicate server calls for messages when selecting a conversation

[PaRangger]

Checklist

General

• I tested all changes and their related features with all corresponding user types on a test server.
• This is a small issue that I tested locally and was confirmed by another developer on a test server.
• Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• I chose a title conforming to the naming conventions for pull requests.

Client

• Important: I implemented the changes with a very good performance, prevented too many (unnecessary) REST calls and made sure the UI is responsive, even with large data (e.g. using paging).
• I strictly followed the client coding and design guidelines.

Motivation and Context

Addresses #9496

When selecting a channel the /course/id/messages api is called twice. This is inefficient and also creates a flashing ui effect of the messages appearing shortly, dissapearing and appearing again.

Description

I added a check that compares the current active conversation with the one the metis service provides. DistinctUntilChanged did not seem to work in this scenario, so i compared the id's of the conversations.

Steps for Testing

Prerequisites:

• 1 Student
• 1 Course with communication enabled
• Open the "Network" Tab in the Browser Debug Window

1. Log in to Artemis
2. Navigate to course
3. Navigate to the communication tab
4. Select channels and verify if the messages api is called once per channel

Testserver States

Note

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Review Progress

Performance Review

Code Review

• Code Review 1
• Code Review 2

Manual Tests

• Test 1
• Test 2

Test Coverage

Summary by CodeRabbit

• Bug Fixes
  • Improved efficiency in handling active conversations by preventing unnecessary updates when the conversation has not changed.

[coderabbitai]

Walkthrough

The changes in this pull request focus on the ConversationMessagesComponent class, specifically enhancing the subscribeToActiveConversation method. A conditional check is introduced to prevent unnecessary updates when the active conversation remains unchanged. This optimization improves the efficiency of active conversation handling without altering the overall structure or functionality of the component.

Changes

File	Change Summary
src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts	Added a conditional check in subscribeToActiveConversation to exit early if the active conversation has not changed.

Possibly related PRs

• Communication: Fix user interface reload on channel selection #9464: This PR modifies the CourseConversationsComponent and the conversation-messages.component.html, which are directly related to the ConversationMessagesComponent class and its handling of conversation messages, enhancing the loading state management and visual feedback during data fetching.
• Communication: Fix an issue where the client does not keep track of the posts on screen #8990: This PR also involves changes to the conversation-messages.component.html, updating the logic for displaying messages based on the presence of posts, which is closely related to the functionality of the subscribeToActiveConversation method in the main PR.

Suggested labels

tests, bugfix, ready for review, component:Communication

Suggested reviewers

• krusche
• SimonEntholzer
• edkaya
• florian-glombik

---

📜 Recent review details

Configuration used: .coderabbit.yaml
Review profile: CHILL

📥 Commits

Files that changed from the base of the PR and between a3b7022 and 3bf8bf5.

📒 Files selected for processing (1)

• src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts

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[coderabbitai]

Actionable comments posted: 0

🧹 Outside diff range and nitpick comments (2)

src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts (2)

Line range hint 1-276: Consider breaking down the component for better maintainability.

While the current changes are effective, the component handles multiple responsibilities. Consider the following architectural improvements:

1. Extract search functionality into a dedicated search service
2. Move post management logic to a separate service
3. Create a custom directive for scroll handling

This would improve:

• Testability: Smaller, focused units are easier to test
• Maintainability: Separation of concerns makes the code easier to maintain
• Reusability: Services can be reused across components

Would you like me to provide a detailed refactoring plan for any of these suggestions?

---

Line range hint 52-52: Consider a more descriptive name for the search Subject.

The search$ Subject could be renamed to better indicate its purpose, e.g., searchTerms$ or searchQuery$, following Angular naming conventions for Observables.

-    private readonly search$ = new Subject<string>();
+    private readonly searchTerms$ = new Subject<string>();

📜 Review details

Configuration used: .coderabbit.yaml
Review profile: CHILL

📥 Commits

Files that changed from the base of the PR and between 6e1c562 and a3b7022.

📒 Files selected for processing (1)

• src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts (1 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts (1)

Pattern src/main/webapp/**/*.ts: angular_style:https://angular.io/guide/styleguide;methods_in_html:false;lazy_loading:true;code_reuse:true;tests:meaningful;types:PascalCase;enums:PascalCase;funcs:camelCase;props:camelCase;no_priv_prefix:true;strings:single_quotes;localize:true;btns:functionality;links:navigation;icons_text:newline;labels:associate;code_style:arrow_funcs,curly_braces,open_braces_same_line,indent_4;memory_leak_prevention:true;routes:naming_schema;chart_framework:ngx-charts;responsive_layout:true

🔇 Additional comments (1)

src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts (1)

110-112: LGTM! Effective solution to prevent duplicate API calls.

The implementation efficiently prevents duplicate processing when the conversation hasn't changed, directly addressing the issue of duplicate API calls. The use of optional chaining ensures null safety.

Let's verify the fix prevents duplicate API calls:

✅ Verification successful

Based on the results from our verification scripts, I can now provide a final response:

Verified: The duplicate API call prevention is correctly implemented

The implementation is sound because:

• The subscribeToActiveConversation method is used consistently across components (header, messages, and parent)
• Each component properly implements unsubscribe patterns with takeUntil
• The ID comparison check in the messages component (if (this._activeConversation?.id === conversation.id)) is the only place where message loading is triggered via onActiveConversationChange()
• The change only affects the messages component's subscription, leaving other components' behavior intact

🏁 Scripts executed

The following scripts were executed for the analysis:

Script:

#!/bin/bash
# Description: Verify that the messages API endpoint is only called once per conversation change
# Look for other potential duplicate API call patterns in the codebase

# Test 1: Check for other subscriptions to activeConversation$ that might trigger duplicate calls
rg -l "activeConversation\$.*subscribe" 

# Test 2: Verify proper unsubscribe handling in components using activeConversation$
ast-grep --pattern 'takeUntil.*activeConversation\$'

Length of output: 219

---

Script:

#!/bin/bash
# Let's try a different approach to verify the subscription patterns

# Check for activeConversation usage patterns
rg -A 5 "activeConversation\$" --type ts

# Look for message API endpoint calls
rg -A 5 "/course/.*/messages" --type ts

# Check for subscription patterns in the component
rg -A 10 "subscribeToActiveConversation" --type ts

Length of output: 9811

---

Script:

#!/bin/bash
# Let's examine the message loading implementation to verify the fix

# Look for message loading implementation
rg -A 10 "onActiveConversationChange" --type ts

# Check for message API endpoint calls in the service
rg -A 5 "getMessages" --type ts

# Look for the message service implementation
rg -A 10 "class.*MessageService" --type ts

Length of output: 4697

[HawKhiem]

Tested on TS4. Click through multiple channels, each time the message api is called once.