updated `/stats` to use new slash command arch (#4146)

6 files changed, 163 insertions, 105 deletions

diff --git a/packages/cli/src/services/CommandService.test.ts b/packages/cli/src/services/CommandService.test.ts
index e780ec5f..bbee13fc 100644
--- a/packages/cli/src/services/CommandService.test.ts
+++ b/packages/cli/src/services/CommandService.test.ts
@@ -12,6 +12,7 @@ import { helpCommand } from '../ui/commands/helpCommand.js';
 import { clearCommand } from '../ui/commands/clearCommand.js';
 import { authCommand } from '../ui/commands/authCommand.js';
 import { themeCommand } from '../ui/commands/themeCommand.js';
+import { statsCommand } from '../ui/commands/statsCommand.js';
 import { privacyCommand } from '../ui/commands/privacyCommand.js';
 import { aboutCommand } from '../ui/commands/aboutCommand.js';
 
@@ -34,6 +35,9 @@ vi.mock('../ui/commands/themeCommand.js', () => ({
 vi.mock('../ui/commands/privacyCommand.js', () => ({
   privacyCommand: { name: 'privacy', description: 'Mock Privacy' },
 }));
+vi.mock('../ui/commands/statsCommand.js', () => ({
+  statsCommand: { name: 'stats', description: 'Mock Stats' },
+}));
 vi.mock('../ui/commands/aboutCommand.js', () => ({
   aboutCommand: { name: 'about', description: 'Mock About' },
 }));
@@ -62,7 +66,7 @@ describe('CommandService', () => {
         const tree = commandService.getCommands();
 
         // Post-condition assertions
-        expect(tree.length).toBe(7);
+        expect(tree.length).toBe(8);
 
         const commandNames = tree.map((cmd) => cmd.name);
         expect(commandNames).toContain('auth');
@@ -70,6 +74,7 @@ describe('CommandService', () => {
         expect(commandNames).toContain('help');
         expect(commandNames).toContain('clear');
         expect(commandNames).toContain('theme');
+        expect(commandNames).toContain('stats');
         expect(commandNames).toContain('privacy');
         expect(commandNames).toContain('about');
       });
@@ -77,14 +82,14 @@ describe('CommandService', () => {
       it('should overwrite any existing commands when called again', async () => {
         // Load once
         await commandService.loadCommands();
-        expect(commandService.getCommands().length).toBe(7);
+        expect(commandService.getCommands().length).toBe(8);
 
         // Load again
         await commandService.loadCommands();
         const tree = commandService.getCommands();
 
         // Should not append, but overwrite
-        expect(tree.length).toBe(7);
+        expect(tree.length).toBe(8);
       });
     });
 
@@ -96,7 +101,7 @@ describe('CommandService', () => {
         await commandService.loadCommands();
 
         const loadedTree = commandService.getCommands();
-        expect(loadedTree.length).toBe(7);
+        expect(loadedTree.length).toBe(8);
         expect(loadedTree).toEqual([
           aboutCommand,
           authCommand,
@@ -104,6 +109,7 @@ describe('CommandService', () => {
           helpCommand,
           memoryCommand,
           privacyCommand,
+          statsCommand,
           themeCommand,
         ]);
       });
diff --git a/packages/cli/src/services/CommandService.ts b/packages/cli/src/services/CommandService.ts
index ef31952d..cc7b4e62 100644
--- a/packages/cli/src/services/CommandService.ts
+++ b/packages/cli/src/services/CommandService.ts
@@ -10,6 +10,7 @@ import { helpCommand } from '../ui/commands/helpCommand.js';
 import { clearCommand } from '../ui/commands/clearCommand.js';
 import { authCommand } from '../ui/commands/authCommand.js';
 import { themeCommand } from '../ui/commands/themeCommand.js';
+import { statsCommand } from '../ui/commands/statsCommand.js';
 import { privacyCommand } from '../ui/commands/privacyCommand.js';
 import { aboutCommand } from '../ui/commands/aboutCommand.js';
 
@@ -20,6 +21,7 @@ const loadBuiltInCommands = async (): Promise<SlashCommand[]> => [
   helpCommand,
   memoryCommand,
   privacyCommand,
+  statsCommand,
   themeCommand,
 ];
 
diff --git a/packages/cli/src/ui/commands/statsCommand.test.ts b/packages/cli/src/ui/commands/statsCommand.test.ts
new file mode 100644
index 00000000..485fcf69
--- /dev/null
+++ b/packages/cli/src/ui/commands/statsCommand.test.ts
@@ -0,0 +1,78 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { vi, describe, it, expect, beforeEach } from 'vitest';
+import { statsCommand } from './statsCommand.js';
+import { type CommandContext } from './types.js';
+import { createMockCommandContext } from '../../test-utils/mockCommandContext.js';
+import { MessageType } from '../types.js';
+import { formatDuration } from '../utils/formatters.js';
+
+describe('statsCommand', () => {
+  let mockContext: CommandContext;
+  const startTime = new Date('2025-07-14T10:00:00.000Z');
+  const endTime = new Date('2025-07-14T10:00:30.000Z');
+
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.setSystemTime(endTime);
+
+    // 1. Create the mock context with all default values
+    mockContext = createMockCommandContext();
+
+    // 2. Directly set the property on the created mock context
+    mockContext.session.stats.sessionStartTime = startTime;
+  });
+
+  it('should display general session stats when run with no subcommand', () => {
+    if (!statsCommand.action) throw new Error('Command has no action');
+
+    statsCommand.action(mockContext, '');
+
+    const expectedDuration = formatDuration(
+      endTime.getTime() - startTime.getTime(),
+    );
+    expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+      {
+        type: MessageType.STATS,
+        duration: expectedDuration,
+      },
+      expect.any(Number),
+    );
+  });
+
+  it('should display model stats when using the "model" subcommand', () => {
+    const modelSubCommand = statsCommand.subCommands?.find(
+      (sc) => sc.name === 'model',
+    );
+    if (!modelSubCommand?.action) throw new Error('Subcommand has no action');
+
+    modelSubCommand.action(mockContext, '');
+
+    expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+      {
+        type: MessageType.MODEL_STATS,
+      },
+      expect.any(Number),
+    );
+  });
+
+  it('should display tool stats when using the "tools" subcommand', () => {
+    const toolsSubCommand = statsCommand.subCommands?.find(
+      (sc) => sc.name === 'tools',
+    );
+    if (!toolsSubCommand?.action) throw new Error('Subcommand has no action');
+
+    toolsSubCommand.action(mockContext, '');
+
+    expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+      {
+        type: MessageType.TOOL_STATS,
+      },
+      expect.any(Number),
+    );
+  });
+});
diff --git a/packages/cli/src/ui/commands/statsCommand.ts b/packages/cli/src/ui/commands/statsCommand.ts
new file mode 100644
index 00000000..87e902d4
--- /dev/null
+++ b/packages/cli/src/ui/commands/statsCommand.ts
@@ -0,0 +1,63 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { MessageType, HistoryItemStats } from '../types.js';
+import { formatDuration } from '../utils/formatters.js';
+import { type CommandContext, type SlashCommand } from './types.js';
+
+export const statsCommand: SlashCommand = {
+  name: 'stats',
+  altName: 'usage',
+  description: 'check session stats. Usage: /stats [model|tools]',
+  action: (context: CommandContext) => {
+    const now = new Date();
+    const { sessionStartTime } = context.session.stats;
+    if (!sessionStartTime) {
+      context.ui.addItem(
+        {
+          type: MessageType.ERROR,
+          text: 'Session start time is unavailable, cannot calculate stats.',
+        },
+        Date.now(),
+      );
+      return;
+    }
+    const wallDuration = now.getTime() - sessionStartTime.getTime();
+
+    const statsItem: HistoryItemStats = {
+      type: MessageType.STATS,
+      duration: formatDuration(wallDuration),
+    };
+
+    context.ui.addItem(statsItem, Date.now());
+  },
+  subCommands: [
+    {
+      name: 'model',
+      description: 'Show model-specific usage statistics.',
+      action: (context: CommandContext) => {
+        context.ui.addItem(
+          {
+            type: MessageType.MODEL_STATS,
+          },
+          Date.now(),
+        );
+      },
+    },
+    {
+      name: 'tools',
+      description: 'Show tool-specific usage statistics.',
+      action: (context: CommandContext) => {
+        context.ui.addItem(
+          {
+            type: MessageType.TOOL_STATS,
+          },
+          Date.now(),
+        );
+      },
+    },
+  ],
+};
diff --git a/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts b/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
index 6946bde0..f39795c0 100644
--- a/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
+++ b/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
@@ -54,7 +54,16 @@ vi.mock('../../utils/version.js', () => ({
 }));
 
 import { act, renderHook } from '@testing-library/react';
-import { vi, describe, it, expect, beforeEach, afterEach, Mock } from 'vitest';
+import {
+  vi,
+  describe,
+  it,
+  expect,
+  beforeEach,
+  afterEach,
+  beforeAll,
+  Mock,
+} from 'vitest';
 import open from 'open';
 import { useSlashCommandProcessor } from './slashCommandProcessor.js';
 import { MessageType, SlashCommandProcessorResult } from '../types.js';
@@ -207,76 +216,6 @@ describe('useSlashCommandProcessor', () => {
   const getProcessor = (showToolDescriptions: boolean = false) =>
     getProcessorHook(showToolDescriptions).result.current;
 
-  describe('/stats command', () => {
-    it('should show detailed session statistics', async () => {
-      // Arrange
-      mockUseSessionStats.mockReturnValue({
-        stats: {
-          sessionStartTime: new Date('2025-01-01T00:00:00.000Z'),
-        },
-      });
-
-      const { handleSlashCommand } = getProcessor();
-      const mockDate = new Date('2025-01-01T01:02:03.000Z'); // 1h 2m 3s duration
-      vi.setSystemTime(mockDate);
-
-      // Act
-      await act(async () => {
-        handleSlashCommand('/stats');
-      });
-
-      // Assert
-      expect(mockAddItem).toHaveBeenNthCalledWith(
-        2, // Called after the user message
-        expect.objectContaining({
-          type: MessageType.STATS,
-          duration: '1h 2m 3s',
-        }),
-        expect.any(Number),
-      );
-
-      vi.useRealTimers();
-    });
-
-    it('should show model-specific statistics when using /stats model', async () => {
-      // Arrange
-      const { handleSlashCommand } = getProcessor();
-
-      // Act
-      await act(async () => {
-        handleSlashCommand('/stats model');
-      });
-
-      // Assert
-      expect(mockAddItem).toHaveBeenNthCalledWith(
-        2, // Called after the user message
-        expect.objectContaining({
-          type: MessageType.MODEL_STATS,
-        }),
-        expect.any(Number),
-      );
-    });
-
-    it('should show tool-specific statistics when using /stats tools', async () => {
-      // Arrange
-      const { handleSlashCommand } = getProcessor();
-
-      // Act
-      await act(async () => {
-        handleSlashCommand('/stats tools');
-      });
-
-      // Assert
-      expect(mockAddItem).toHaveBeenNthCalledWith(
-        2, // Called after the user message
-        expect.objectContaining({
-          type: MessageType.TOOL_STATS,
-        }),
-        expect.any(Number),
-      );
-    });
-  });
-
   describe('Other commands', () => {
     it('/editor should open editor dialog and return handled', async () => {
       const { handleSlashCommand } = getProcessor();
diff --git a/packages/cli/src/ui/hooks/slashCommandProcessor.ts b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
index e8d773b4..31397af5 100644
--- a/packages/cli/src/ui/hooks/slashCommandProcessor.ts
+++ b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
@@ -248,36 +248,6 @@ export const useSlashCommandProcessor = (
         action: (_mainCommand, _subCommand, _args) => openEditorDialog(),
       },
       {
-        name: 'stats',
-        altName: 'usage',
-        description: 'check session stats. Usage: /stats [model|tools]',
-        action: (_mainCommand, subCommand, _args) => {
-          if (subCommand === 'model') {
-            addMessage({
-              type: MessageType.MODEL_STATS,
-              timestamp: new Date(),
-            });
-            return;
-          } else if (subCommand === 'tools') {
-            addMessage({
-              type: MessageType.TOOL_STATS,
-              timestamp: new Date(),
-            });
-            return;
-          }
-
-          const now = new Date();
-          const { sessionStartTime } = session.stats;
-          const wallDuration = now.getTime() - sessionStartTime.getTime();
-
-          addMessage({
-            type: MessageType.STATS,
-            duration: formatDuration(wallDuration),
-            timestamp: new Date(),
-          });
-        },
-      },
-      {
         name: 'mcp',
         description: 'list configured MCP servers and tools',
         action: async (_mainCommand, _subCommand, _args) => {