[Obs AI Assistant] Chat history details in conversation list (elastic…

…#207426)

Closes elastic#176295

## Summary

Categorizes the chat history based on `lastUpdated` date of the
conversation.

### Checklist

- [x] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

x-pack/platform/packages/shared/kbn-ai-assistant/src/buttons/new_chat_button.tsx

@@ -24,7 +24,7 @@ export function NewChatButton(
     </EuiButton>
   ) : (
     <EuiButtonIcon
-      data-test-subj="observabilityAiAssistantNewChatButtonButton"
+      data-test-subj="observabilityAiAssistantNewChatButton"
       iconType="newChat"
       size="xs"
       {...nextProps}

x-pack/platform/packages/shared/kbn-ai-assistant/src/chat/conversation_list.test.tsx

@@ -0,0 +1,204 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import React from 'react';
+import { i18n } from '@kbn/i18n';
+import { render, screen, fireEvent } from '@testing-library/react';
+import { DATE_CATEGORY_LABELS } from '../i18n';
+import { ConversationList } from './conversation_list';
+import { UseConversationListResult } from '../hooks/use_conversation_list';
+import { useConversationsByDate } from '../hooks/use_conversations_by_date';
+
+jest.mock('../hooks/use_conversations_by_date', () => ({
+  useConversationsByDate: jest.fn(),
+}));
+
+jest.mock('../hooks/use_confirm_modal', () => ({
+  useConfirmModal: jest.fn().mockReturnValue({
+    element: <div data-test-subj="confirmModal" />,
+    confirm: jest.fn(() => Promise.resolve(true)),
+  }),
+}));
+
+const mockConversations: UseConversationListResult['conversations'] = {
+  value: {
+    conversations: [
+      {
+        conversation: {
+          id: '1',
+          title: "Today's Conversation",
+          last_updated: '2025-01-21T10:00:00Z',
+        },
+        '@timestamp': '2025-01-21T10:00:00Z',
+        labels: {},
+        numeric_labels: {},
+        messages: [],
+        namespace: 'namespace-1',
+        public: true,
+      },
+      {
+        conversation: {
+          id: '2',
+          title: "Yesterday's Conversation",
+          last_updated: '2025-01-20T10:00:00Z',
+        },
+        '@timestamp': '2025-01-20T10:00:00Z',
+        labels: {},
+        numeric_labels: {},
+        messages: [],
+        namespace: 'namespace-2',
+        public: true,
+      },
+    ],
+  },
+  error: undefined,
+  loading: false,
+  refresh: jest.fn(),
+};
+
+const mockCategorizedConversations = {
+  TODAY: [
+    {
+      id: '1',
+      label: "Today's Conversation",
+      lastUpdated: '2025-01-21T10:00:00Z',
+      href: '/conversation/1',
+    },
+  ],
+  YESTERDAY: [
+    {
+      id: '2',
+      label: "Yesterday's Conversation",
+      lastUpdated: '2025-01-20T10:00:00Z',
+      href: '/conversation/2',
+    },
+  ],
+  THIS_WEEK: [],
+  LAST_WEEK: [],
+  THIS_MONTH: [],
+  LAST_MONTH: [],
+  THIS_YEAR: [],
+  OLDER: [],
+};
+
+const defaultProps = {
+  conversations: mockConversations,
+  isLoading: false,
+  selectedConversationId: undefined,
+  onConversationSelect: jest.fn(),
+  onConversationDeleteClick: jest.fn(),
+  newConversationHref: '/conversation/new',
+  getConversationHref: (id: string) => `/conversation/${id}`,
+};
+
+describe('ConversationList', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+    (useConversationsByDate as jest.Mock).mockReturnValue(mockCategorizedConversations);
+  });
+
+  it('renders the component without errors', () => {
+    render(<ConversationList {...defaultProps} />);
+
+    const todayCategoryLabel = screen.getByText(/today/i, {
+      selector: 'div.euiText',
+    });
+    expect(todayCategoryLabel).toBeInTheDocument();
+
+    const yesterdayCategoryLabel = screen.getByText(/yesterday/i, {
+      selector: 'div.euiText',
+    });
+    expect(yesterdayCategoryLabel).toBeInTheDocument();
+
+    expect(screen.queryByRole('progressbar')).not.toBeInTheDocument();
+    expect(
+      screen.queryByText(
+        i18n.translate('xpack.aiAssistant.conversationList.errorMessage', {
+          defaultMessage: 'Failed to load',
+        })
+      )
+    ).not.toBeInTheDocument();
+
+    expect(
+      screen.queryByText(
+        i18n.translate('xpack.aiAssistant.conversationList.noConversations', {
+          defaultMessage: 'No conversations',
+        })
+      )
+    ).not.toBeInTheDocument();
+
+    expect(screen.getByTestId('observabilityAiAssistantNewChatButton')).toBeInTheDocument();
+  });
+
+  it('displays loading state', () => {
+    render(<ConversationList {...defaultProps} isLoading={true} />);
+    expect(screen.getByRole('progressbar')).toBeInTheDocument();
+  });
+
+  it('displays error state', () => {
+    const errorProps = {
+      ...defaultProps,
+      conversations: { ...mockConversations, error: new Error('An error occurred') },
+    };
+    render(<ConversationList {...errorProps} />);
+    expect(
+      screen.getByText(
+        i18n.translate('xpack.aiAssistant.conversationList.errorMessage', {
+          defaultMessage: 'Failed to load',
+        })
+      )
+    ).toBeInTheDocument();
+  });
+
+  it('renders categorized conversations', () => {
+    render(<ConversationList {...defaultProps} />);
+    Object.entries(mockCategorizedConversations).forEach(([category, conversationList]) => {
+      if (conversationList.length > 0) {
+        expect(screen.getByText(DATE_CATEGORY_LABELS[category])).toBeInTheDocument();
+        conversationList.forEach((conversation) => {
+          expect(screen.getByText(conversation.label)).toBeInTheDocument();
+        });
+      }
+    });
+  });
+
+  it('calls onConversationSelect when a conversation is clicked', () => {
+    render(<ConversationList {...defaultProps} />);
+    const todayConversation = screen.getByText("Today's Conversation");
+    fireEvent.click(todayConversation);
+    expect(defaultProps.onConversationSelect).toHaveBeenCalledWith('1');
+  });
+
+  it('calls onConversationDeleteClick when delete icon is clicked', async () => {
+    render(<ConversationList {...defaultProps} />);
+    const deleteButtons = screen.getAllByLabelText('Delete');
+    await fireEvent.click(deleteButtons[0]);
+    expect(defaultProps.onConversationDeleteClick).toHaveBeenCalledWith('1');
+  });
+
+  it('renders a new chat button and triggers onConversationSelect when clicked', () => {
+    render(<ConversationList {...defaultProps} />);
+    const newChatButton = screen.getByTestId('observabilityAiAssistantNewChatButton');
+    fireEvent.click(newChatButton);
+    expect(defaultProps.onConversationSelect).toHaveBeenCalledWith(undefined);
+  });
+
+  it('renders "no conversations" message when there are no conversations', () => {
+    const emptyProps = {
+      ...defaultProps,
+      conversations: { ...mockConversations, value: { conversations: [] } },
+    };
+    render(<ConversationList {...emptyProps} />);
+    expect(
+      screen.getByText(
+        i18n.translate('xpack.aiAssistant.conversationList.noConversations', {
+          defaultMessage: 'No conversations',
+        })
+      )
+    ).toBeInTheDocument();
+  });
+});