Extract domain parsing into testable function (#18)

* Initial plan

* Extract domain parsing logic into testable parseDomains function

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

Author: Copilot

src/cli.test.ts

@@ -1,60 +1,36 @@
 import { Command } from 'commander';
+import { parseDomains } from './cli';
 
 describe('cli', () => {
   describe('domain parsing', () => {
     it('should split comma-separated domains correctly', () => {
-      const allowDomainsInput = 'github.com, api.github.com, npmjs.org';
+      const result = parseDomains('github.com, api.github.com, npmjs.org');
 
-      const domains = allowDomainsInput
-        .split(',')
-        .map(d => d.trim())
-        .filter(d => d.length > 0);
-
-      expect(domains).toEqual(['github.com', 'api.github.com', 'npmjs.org']);
+      expect(result).toEqual(['github.com', 'api.github.com', 'npmjs.org']);
     });
 
     it('should handle domains without spaces', () => {
-      const allowDomainsInput = 'github.com,api.github.com,npmjs.org';
-
-      const domains = allowDomainsInput
-        .split(',')
-        .map(d => d.trim())
-        .filter(d => d.length > 0);
+      const result = parseDomains('github.com,api.github.com,npmjs.org');
 
-      expect(domains).toEqual(['github.com', 'api.github.com', 'npmjs.org']);
+      expect(result).toEqual(['github.com', 'api.github.com', 'npmjs.org']);
     });
 
     it('should filter out empty domains', () => {
-      const allowDomainsInput = 'github.com,,, api.github.com,  ,npmjs.org';
-
-      const domains = allowDomainsInput
-        .split(',')
-        .map(d => d.trim())
-        .filter(d => d.length > 0);
+      const result = parseDomains('github.com,,, api.github.com,  ,npmjs.org');
 
-      expect(domains).toEqual(['github.com', 'api.github.com', 'npmjs.org']);
+      expect(result).toEqual(['github.com', 'api.github.com', 'npmjs.org']);
     });
 
     it('should return empty array for whitespace-only input', () => {
-      const allowDomainsInput = '  ,  ,  ';
+      const result = parseDomains('  ,  ,  ');
 
-      const domains = allowDomainsInput
-        .split(',')
-        .map(d => d.trim())
-        .filter(d => d.length > 0);
-
-      expect(domains).toEqual([]);
+      expect(result).toEqual([]);
     });
 
     it('should handle single domain', () => {
-      const allowDomainsInput = 'github.com';
-
-      const domains = allowDomainsInput
-        .split(',')
-        .map(d => d.trim())
-        .filter(d => d.length > 0);
+      const result = parseDomains('github.com');
 
-      expect(domains).toEqual(['github.com']);
+      expect(result).toEqual(['github.com']);
     });
   });
 

src/cli.ts

@@ -20,6 +20,18 @@ import {
   cleanupFirewallNetwork,
 } from './host-iptables';
 
+/**
+ * Parses a comma-separated list of domains into an array of trimmed, non-empty domain strings
+ * @param input - Comma-separated domain string (e.g., "github.com, api.github.com, npmjs.org")
+ * @returns Array of trimmed domain strings with empty entries filtered out
+ */
+export function parseDomains(input: string): string[] {
+  return input
+    .split(',')
+    .map(d => d.trim())
+    .filter(d => d.length > 0);
+}
+
 /**
  * Redacts sensitive information from command strings
  */
@@ -97,10 +109,7 @@ program
 
     logger.setLevel(logLevel);
 
-    const allowedDomains = options.allowDomains
-      .split(',')
-      .map((d: string) => d.trim())
-      .filter((d: string) => d.length > 0);
+    const allowedDomains = parseDomains(options.allowDomains);
 
     if (allowedDomains.length === 0) {
       logger.error('At least one domain must be specified with --allow-domains');
@@ -224,4 +233,7 @@ program
     }
   });
 
-program.parse();
+// Only parse arguments if this file is run directly (not imported as a module)
+if (require.main === module) {
+  program.parse();
+}