feat: Added /copy command for copying output to clipboard with new Command Service approach (#3706)

Co-authored-by: Abhi <43648792+abhipatel12@users.noreply.github.com>
Co-authored-by: N. Taylor Mullen <ntaylormullen@google.com>

packages/cli/src/ui/utils/commandUtils.ts

@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import { spawn } from 'child_process';
+
 /**
  * Checks if a query string potentially represents an '@' command.
  * It triggers if the query starts with '@' or contains '@' preceded by whitespace
@@ -24,3 +26,57 @@ export const isAtCommand = (query: string): boolean =>
  * @returns True if the query looks like an '/' command, false otherwise.
  */
 export const isSlashCommand = (query: string): boolean => query.startsWith('/');
+
+//Copies a string snippet to the clipboard for different platforms
+export const copyToClipboard = async (text: string): Promise<void> => {
+  const run = (cmd: string, args: string[]) =>
+    new Promise<void>((resolve, reject) => {
+      const child = spawn(cmd, args);
+      let stderr = '';
+      child.stderr.on('data', (chunk) => (stderr += chunk.toString()));
+      child.on('error', reject);
+      child.on('close', (code) => {
+        if (code === 0) return resolve();
+        const errorMsg = stderr.trim();
+        reject(
+          new Error(
+            `'${cmd}' exited with code ${code}${errorMsg ? `: ${errorMsg}` : ''}`,
+          ),
+        );
+      });
+      child.stdin.on('error', reject);
+      child.stdin.write(text);
+      child.stdin.end();
+    });
+
+  switch (process.platform) {
+    case 'win32':
+      return run('clip', []);
+    case 'darwin':
+      return run('pbcopy', []);
+    case 'linux':
+      try {
+        await run('xclip', ['-selection', 'clipboard']);
+      } catch (primaryError) {
+        try {
+          // If xclip fails for any reason, try xsel as a fallback.
+          await run('xsel', ['--clipboard', '--input']);
+        } catch (fallbackError) {
+          const primaryMsg =
+            primaryError instanceof Error
+              ? primaryError.message
+              : String(primaryError);
+          const fallbackMsg =
+            fallbackError instanceof Error
+              ? fallbackError.message
+              : String(fallbackError);
+          throw new Error(
+            `All copy commands failed. xclip: "${primaryMsg}", xsel: "${fallbackMsg}". Please ensure xclip or xsel is installed and configured.`,
+          );
+        }
+      }
+      return;
+    default:
+      throw new Error(`Unsupported platform: ${process.platform}`);
+  }
+};