[ide-mode] Write port to file in ide-server (#5811)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/core/src/ide/process-utils.ts

@@ -0,0 +1,62 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { exec } from 'child_process';
+import { promisify } from 'util';
+import os from 'os';
+
+const execAsync = promisify(exec);
+
+/**
+ * Traverses up the process tree from the current process to find the top-level ancestor process ID.
+ * This is useful for identifying the main application process that spawned the current script,
+ * such as the main VS Code window process.
+ *
+ * @returns A promise that resolves to the numeric PID of the top-level process.
+ * @throws Will throw an error if the underlying shell commands fail unexpectedly.
+ */
+export async function getIdeProcessId(): Promise<number> {
+  const platform = os.platform();
+  let currentPid = process.pid;
+
+  // Loop upwards through the process tree, with a depth limit to prevent infinite loops.
+  const MAX_TRAVERSAL_DEPTH = 32;
+  for (let i = 0; i < MAX_TRAVERSAL_DEPTH; i++) {
+    let parentPid: number;
+
+    try {
+      // Use wmic for Windows
+      if (platform === 'win32') {
+        const command = `wmic process where "ProcessId=${currentPid}" get ParentProcessId /value`;
+        const { stdout } = await execAsync(command);
+        const match = stdout.match(/ParentProcessId=(\d+)/);
+        parentPid = match ? parseInt(match[1], 10) : 0; // Top of the tree is 0
+      }
+      // Use ps for macOS, Linux, and other Unix-like systems
+      else {
+        const command = `ps -o ppid= -p ${currentPid}`;
+        const { stdout } = await execAsync(command);
+        const ppid = parseInt(stdout.trim(), 10);
+        parentPid = isNaN(ppid) ? 1 : ppid; // Top of the tree is 1
+      }
+    } catch (_) {
+      // This can happen if a process in the chain dies during execution.
+      // We'll break the loop and return the last valid PID we found.
+      break;
+    }
+
+    // Define the root PID for the current OS
+    const rootPid = platform === 'win32' ? 0 : 1;
+
+    // If the parent is the root process or invalid, we've found our target.
+    if (parentPid === rootPid || parentPid <= 0) {
+      break;
+    }
+    // Move one level up the tree for the next iteration.
+    currentPid = parentPid;
+  }
+  return currentPid;
+}