expose invoke-go-api to renderer process

client/electron/go_helpers.ts

@@ -19,7 +19,6 @@
  */
 
 import {pathToEmbeddedTun2socksBinary} from './app_paths';
-import {invokeGoApi} from './go_plugin';
 import {ChildProcessHelper} from './process';
 import {TransportConfigJson} from '../src/www/app/outline_server_repository/vpn';
 
@@ -58,13 +57,3 @@ export async function checkUDPConnectivity(
   }
   return true;
 }
-
-/**
- * Fetches a resource from the given URL.
- *
- * @param url The URL of the resource to fetch.
- * @returns A Promise that resolves to the fetched content as a string.
- */
-export function fetchResource(url: string): Promise<string> {
-  return invokeGoApi('FetchResource', url);
-}

client/electron/go_plugin.ts

@@ -20,6 +20,8 @@ import {pathToBackendLibrary} from './app_paths';
 
 let invokeGoAPIFunc: Function | undefined;
 
+export type GoApiName = 'FetchResource';
+
 /**
  * Calls a Go function by invoking the `InvokeGoAPI` function in the native backend library.
  *
@@ -33,7 +35,7 @@ let invokeGoAPIFunc: Function | undefined;
  * in `./client/go/outline/electron/go_plugin.go`.
  */
 export async function invokeGoApi(
-  api: 'FetchResource',
+  api: GoApiName,
   input: string
 ): Promise<string> {
   if (!invokeGoAPIFunc) {

client/electron/index.ts

@@ -34,7 +34,7 @@ import {
 import {autoUpdater} from 'electron-updater';
 
 import {lookupIp} from './connectivity';
-import {fetchResource} from './go_helpers';
+import {GoApiName, invokeGoApi} from './go_plugin';
 import {GoVpnTunnel} from './go_vpn_tunnel';
 import {installRoutingServices, RoutingDaemon} from './routing_service';
 import {TunnelStore} from './tunnel_store';
@@ -501,10 +501,19 @@ function main() {
     mainWindow?.webContents.send('outline-ipc-push-clipboard');
   });
 
-  // Fetches a resource (usually the dynamic key config) from a remote URL.
+  // This IPC handler allows the renderer process to call Go API functions exposed by the backend.
+  // It takes two arguments:
+  //   - api: The name of the Go API function to call.
+  //   - input: A string representing the input data to the Go function.
+  //
+  // The handler returns the output string from the Go function if successful.
+  // Both the input string and output string need to be interpreted by the renderer process according
+  // to the specific API being called.
+  // If Go function encounters an error, it throws an Error that can be parsed by the `PlatformError`.
   ipcMain.handle(
-    'outline-ipc-fetch-resource',
-    (_, url: string): Promise<string> => fetchResource(url)
+    'outline-ipc-invoke-go-api',
+    (_, api: GoApiName, input: string): Promise<string> =>
+      invokeGoApi(api, input)
   );
 
   // Connects to a proxy server specified by a config.

client/go/outline/electron/go_plugin.go

@@ -20,7 +20,7 @@ package main
 // InvokeGoAPIResult is a struct used to pass result from Go to TypeScript boundary.
 typedef struct InvokeGoAPIResult_t
 {
-  // A string representing the result of the Go function call.
+	// A string representing the result of the Go function call.
 	// This may be a raw string or a JSON string depending on the API call.
 	const char *Output;
 
@@ -50,7 +50,7 @@ const (
 	FetchResourceAPI = "FetchResource"
 )
 
-// InvokeGoFunc is the unified entry point for TypeScript to invoke various Go functions.
+// InvokeGoAPI is the unified entry point for TypeScript to invoke various Go functions.
 //
 // The input and output are all defined as string, but they may represent either a raw string,
 // or a JSON string depending on the API call.
@@ -81,6 +81,9 @@ func InvokeGoAPI(api *C.char, input *C.char) C.InvokeGoAPIResult {
 // newCGoString allocates memory for a C string based on the given Go string.
 // It should be paired with [FreeCGoString] to avoid memory leaks.
 func newCGoString(s string) *C.char {
+	if s == "" {
+		return nil
+	}
 	res := C.CString(s)
 	slog.Debug("malloc CGoString", "addr", res)
 	return res
@@ -91,8 +94,10 @@ func newCGoString(s string) *C.char {
 //
 //export FreeCGoString
 func FreeCGoString(s *C.char) {
-	slog.Debug("free CGoString", "addr", s)
-	C.free(unsafe.Pointer(s))
+	if s != nil {
+		slog.Debug("free CGoString", "addr", s)
+		C.free(unsafe.Pointer(s))
+	}
 }
 
 // marshalCGoErrorJson marshals a PlatformError to a C style JSON string.

client/src/www/app/resource_fetcher.electron.ts

@@ -21,7 +21,11 @@ import {PlatformError} from '../model/platform_error';
 export class ElectronResourceFetcher implements ResourceFetcher {
   async fetch(url: string): Promise<string> {
     try {
-      return await window.electron.methodChannel.invoke('fetch-resource', url);
+      return await window.electron.methodChannel.invoke(
+        'invoke-go-api',
+        'FetchResource',
+        url
+      );
     } catch (e) {
       throw PlatformError.parseFrom(e);
     }