refactor: implement safe download method for url app window

src/main/modules/app-window/i-url-app-window.d.ts

@@ -2,5 +2,7 @@ import { LoadURLOptions } from 'electron';
 import { IAppWindow } from './i-app-window';
 
 export interface IUrlAppWindow extends IAppWindow {
+  downloadUrlSafe(url: string, savePath: string, options?: LoadURLOptions): Promise<void>;
+
   loadUrlSafe(url: string, options?: LoadURLOptions): Promise<void>;
 }

src/main/modules/app-window/url-app-window.ts

@@ -28,6 +28,33 @@ export abstract class UrlAppWindow extends AppWindow implements IUrlAppWindow {
     this.loadOptions = loadOptions;
   }
 
+  public downloadUrlSafe(url: string, savePath: string, options?: LoadURLOptions): Promise<void> {
+    return new Promise<void>((resolve, reject) => {
+      if (!this._window) {
+        throw new WindowClosedError();
+      }
+      this._window.webContents.session.once('will-download', (event, item) => {
+        item.setSavePath(savePath);
+        item.once('done', (doneEvent, state) => {
+          switch (state) {
+            case 'completed':
+              resolve();
+              break;
+            case 'cancelled':
+            case 'interrupted':
+            default:
+              reject(new Error(state));
+              break;
+          }
+        });
+        item.on('updated', () => {
+          item.resume();
+        });
+      });
+      void this.loadUrlSafe(url, options);
+    });
+  }
+
   public async loadUrlSafe(url: string, options?: LoadURLOptions): Promise<void> {
     if (!this._window) {
       throw new WindowClosedError();

src/main/modules/nhentai/nhentai-app-window.ts

@@ -190,30 +190,7 @@ export class NhentaiAppWindow extends UrlAppWindow implements INhentaiAppWindow
     const downloadLink: string = (await this._window.webContents.executeJavaScript(
       `document.getElementById('${downloadLinkId}').href`
     )) as string;
-    await new Promise<void>((resolve, reject) => {
+    await this.downloadUrlSafe(downloadLink, filePath);
-      if (!this._window) {
-        throw new WindowClosedError();
-      }
-      this._window.webContents.session.once('will-download', (event, item) => {
-        item.setSavePath(filePath);
-        item.once('done', (doneEvent, state) => {
-          switch (state) {
-            case 'completed':
-              resolve();
-              break;
-            case 'cancelled':
-            case 'interrupted':
-            default:
-              reject(new Error(state));
-              break;
-          }
-        });
-        item.on('updated', () => {
-          item.resume();
-        });
-      });
-      void this.loadUrlSafe(downloadLink);
-    });
 
     const readable = createReadStream(filePath, { emitClose: true });