Angular Diagnostic Message Display

In modern web applications, providing clear and actionable feedback to users is crucial for a good user experience. This challenge focuses on implementing a system for displaying diagnostic messages within an Angular application, allowing for various types of messages (e.g., success, warning, error) and clear visual distinction.

Problem Description

Your task is to create a reusable Angular component and service that can be used to display diagnostic messages throughout an application. The system should allow different message types to be defined and styled accordingly. Messages should be dismissible by the user.

Key Requirements:

• MessageService: Create an Angular service that manages the display of diagnostic messages. It should have methods to:
  • Add a new message.
  • Remove a specific message.
  • Clear all messages.
  • Provide a way for components to subscribe to message updates.
• MessageComponent: Create a reusable Angular component that will be responsible for rendering the diagnostic messages. This component should:
  • Listen for changes from the MessageService.
  • Display messages in a list.
  • Each message should have a distinct visual style based on its type (e.g., a specific color, icon).
  • Each message should have a "close" button to dismiss it individually.
  • The component should be able to contain multiple messages simultaneously.
• Message Types: Support at least three distinct message types: success, warning, and error.
• Dismissibility: Users must be able to click a close button to remove an individual message.

Expected Behavior:

When a message is added via the MessageService, the MessageComponent should display it. If multiple messages are added, they should all be visible. Clicking the close button on a message should remove it from the display.

Edge Cases:

• What happens if the MessageService is empty? The MessageComponent should display nothing.
• How are messages ordered if added in quick succession? The order should be predictable (e.g., by addition time).

Examples

Example 1: Adding and Displaying Messages

Assume the MessageService is injected into another component (e.g., AppComponent or a feature component).

• Input (Action within another component):

  // In another component
  constructor(private messageService: MessageService) {}
  
  showSuccess() {
    this.messageService.add({ type: 'success', text: 'Operation completed successfully!' });
  }
  
  showError() {
    this.messageService.add({ type: 'error', text: 'An error occurred while processing your request.' });
  }
  

• Output (Rendered by MessageComponent): A visual representation of two messages, one styled as 'success' and the other as 'error', each with a close button.

• Explanation: The MessageService is used to add two messages. The MessageComponent, which subscribes to the service, receives these messages and renders them with appropriate styling and dismiss buttons.

Example 2: Dismissing a Message

• Input (Action within MessageComponent): The user clicks the "close" button next to the 'success' message from Example 1.

• Output (Rendered by MessageComponent): Only the 'error' message remains displayed.

• Explanation: Clicking the close button associated with a specific message triggers the MessageService to remove that message, and the MessageComponent updates its display accordingly.

Example 3: Clearing All Messages

• Input (Action within another component):

  // In another component
  constructor(private messageService: MessageService) {}
  
  clearAll() {
    this.messageService.clearAll();
  }
  

• Output (Rendered by MessageComponent): No diagnostic messages are displayed.

• Explanation: The clearAll method on the MessageService is called, which signals the MessageComponent to remove all currently displayed messages.

Constraints

• The MessageService and MessageComponent should be designed as standalone features, meaning they can be imported and used independently in different parts of the application.
• The styling for message types should be implemented using CSS (or SCSS/LESS if preferred for the project) within the MessageComponent.
• Performance: The system should be efficient enough to handle a reasonable number of messages (e.g., up to 10-20) without noticeable degradation.
• Angular Version: Target Angular version 14 or later.

Notes

• Consider using an observable (like BehaviorSubject) within the MessageService to broadcast message changes to any listening components.
• Think about how to uniquely identify each message for removal. A simple ID or reference might be necessary.
• The MessageComponent should ideally be placed at a high level in your application's component tree (e.g., in AppComponent) so that messages are always visible regardless of the current route.
• The structure of a message object could be an interface like { type: 'success' | 'warning' | 'error'; text: string; id?: string; }.