feat: add support for exporting pdf and png (#2588)

This closes #2583.

apps/electron/layers/main/src/export/pdf.ts

@@ -0,0 +1,61 @@
+import { BrowserWindow, dialog, shell } from 'electron';
+import fs from 'fs-extra';
+
+import { logger } from '../logger';
+import type { ErrorMessage } from './utils';
+import { getFakedResult } from './utils';
+
+interface SavePDFFileResult {
+  filePath?: string;
+  canceled?: boolean;
+  error?: ErrorMessage;
+}
+
+/**
+ * This function is called when the user clicks the "Export to PDF" button in the electron.
+ *
+ * It will just copy the file to the given path
+ */
+export async function savePDFFileAs(
+  pageTitle: string
+): Promise<SavePDFFileResult> {
+  try {
+    const ret =
+      getFakedResult() ??
+      (await dialog.showSaveDialog({
+        properties: ['showOverwriteConfirmation'],
+        title: 'Save PDF',
+        showsTagField: false,
+        buttonLabel: 'Save',
+        defaultPath: `${pageTitle}.pdf`,
+        message: 'Save Page as a PDF file',
+      }));
+    const filePath = ret.filePath;
+    if (ret.canceled || !filePath) {
+      return {
+        canceled: true,
+      };
+    }
+
+    await BrowserWindow.getFocusedWindow()
+      ?.webContents.printToPDF({
+        pageSize: 'A4',
+        printBackground: true,
+        landscape: false,
+      })
+      .then(data => {
+        fs.writeFile(filePath, data, error => {
+          if (error) throw error;
+          logger.log(`Wrote PDF successfully to ${filePath}`);
+        });
+      });
+
+    shell.openPath(filePath);
+    return { filePath };
+  } catch (err) {
+    logger.error('savePDFFileAs', err);
+    return {
+      error: 'UNKNOWN_ERROR',
+    };
+  }
+}