Use handlers approach in server child process

src/lib/site-server-process-child.ts

@@ -4,6 +4,9 @@ import { WPNowOptions } from '../../vendor/wp-now/src/config';
 import { setupLogging } from '../logging';
 import type { MessageName } from './site-server-process';
 
+type Handler = ( message: string, messageId: number, data: unknown ) => void;
+type Handlers = { [ K in MessageName ]: Handler };
+
 // Setup logging for the forked process
 if ( process.env.STUDIO_APP_LOGS_PATH ) {
 	setupLogging( {
@@ -16,57 +19,69 @@ if ( process.env.STUDIO_APP_LOGS_PATH ) {
 const options = JSON.parse( process.argv[ 2 ] ) as WPNowOptions;
 let server: WPNowServer;
 
-async function start( message: string, messageId: number ) {
+const handlers: Handlers = {
+	'start-server': createHandler( start ),
+	'stop-server': createHandler( stop ),
+	'run-php': createHandler( runPhp ),
+};
+
+async function start() {
 	server = await startServer( options );
-	process.parentPort.postMessage( {
-		message,
-		messageId,
-		data: {
-			php: {
-				documentRoot: server.php.documentRoot,
-			},
+	return {
+		php: {
+			documentRoot: server.php.documentRoot,
 		},
-	} );
+	};
 }
 
-async function stop( message: string, messageId: number ) {
+async function stop() {
 	await server.stopServer();
-	process.parentPort.postMessage( {
-		message,
-		messageId,
-	} );
 }
 
-async function runPhp( message: string, messageId: number, data: PHPRunOptions ) {
-	const response = await server.php.run( data );
-	process.parentPort.postMessage( { message, messageId, data: response.text } );
+async function runPhp( data: unknown ) {
+	const request = data as PHPRunOptions;
+	if ( ! request ) {
+		throw Error( 'PHP request is not valid' );
+	}
+	const response = await server.php.run( request );
+	return response.text;
+}
+
+function createHandler< T >( handler: ( data: unknown ) => T ) {
+	return async ( message: string, messageId: number, data: unknown ) => {
+		try {
+			const response = await handler( data );
+			process.parentPort.postMessage( {
+				message,
+				messageId,
+				data: response,
+			} );
+		} catch ( error ) {
+			const errorObj = error as Error;
+			if ( ! errorObj ) {
+				process.parentPort.postMessage( { message, messageId, error: Error( 'Unknown Error' ) } );
+				return;
+			}
+			process.parentPort.postMessage( {
+				message,
+				messageId,
+				error: errorObj,
+			} );
+		}
+	};
 }
 
 process.parentPort.on( 'message', async ( { data: messagePayload } ) => {
 	const { message, messageId, data }: { message: MessageName; messageId: number; data: unknown } =
 		messagePayload;
-	try {
-		switch ( message ) {
-			case 'start-server':
-				await start( message, messageId );
-				break;
-			case 'stop-server':
-				await stop( message, messageId );
-				break;
-			case 'run-php':
-				await runPhp( message, messageId, data as PHPRunOptions );
-				break;
-		}
-	} catch ( error ) {
-		const errorObj = error as Error;
-		if ( ! errorObj ) {
-			process.parentPort.postMessage( { message, messageId, error: Error( 'Unknown Error' ) } );
-			return;
-		}
+	const handler = handlers[ message ];
+	if ( ! handler ) {
 		process.parentPort.postMessage( {
 			message,
 			messageId,
-			error: errorObj,
+			error: Error( `No handler defined for message '${ message }'` ),
 		} );
+		return;
 	}
+	await handler( message, messageId, data );
 } );