feat: Introduce session context and add session duration stat for /stats command (#854)

packages/cli/src/ui/hooks/slashCommandProcessor.ts

@@ -11,6 +11,7 @@ import process from 'node:process';
 import { UseHistoryManagerReturn } from './useHistoryManager.js';
 import { Config, MCPServerStatus, getMCPServerStatus } from '@gemini-cli/core';
 import { Message, MessageType, HistoryItemWithoutId } from '../types.js';
+import { useSession } from '../contexts/SessionContext.js';
 import { createShowMemoryAction } from './useShowMemoryCommand.js';
 import { GIT_COMMIT_INFO } from '../../generated/git-commit.js';
 import { formatMemoryUsage } from '../utils/formatters.js';
@@ -49,6 +50,8 @@ export const useSlashCommandProcessor = (
   toggleCorgiMode: () => void,
   showToolDescriptions: boolean = false,
 ) => {
+  const session = useSession();
+
   const addMessage = useCallback(
     (message: Message) => {
       // Convert Message to HistoryItemWithoutId
@@ -138,6 +141,33 @@ export const useSlashCommandProcessor = (
           openThemeDialog();
         },
       },
+      {
+        name: 'stats',
+        altName: 'usage',
+        description: 'check session stats',
+        action: (_mainCommand, _subCommand, _args) => {
+          const now = new Date();
+          const duration = now.getTime() - session.startTime.getTime();
+          const durationInSeconds = Math.floor(duration / 1000);
+          const hours = Math.floor(durationInSeconds / 3600);
+          const minutes = Math.floor((durationInSeconds % 3600) / 60);
+          const seconds = durationInSeconds % 60;
+
+          const durationString = [
+            hours > 0 ? `${hours}h` : '',
+            minutes > 0 ? `${minutes}m` : '',
+            `${seconds}s`,
+          ]
+            .filter(Boolean)
+            .join(' ');
+
+          addMessage({
+            type: MessageType.INFO,
+            content: `Session duration: ${durationString}`,
+            timestamp: new Date(),
+          });
+        },
+      },
       {
         name: 'mcp',
         description: 'list configured MCP servers and tools',
@@ -447,6 +477,7 @@ Add any other context about the problem here.
       toggleCorgiMode,
       config,
       showToolDescriptions,
+      session.startTime,
     ],
   );