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

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(),
+        );
+      },
+    },
+  ],
+};