implement backup export

src/Model/Global/fileTransferModel.ts

@@ -139,7 +139,7 @@ export default class FileTransferModel {
     readonly generateBackup = async (
         directoryPaths: IteratorObject<string[]>,
         passphrase: string,
-    ): Promise<string> => {
+    ): Promise<Blob> => {
         const files: string[] = [];
         for (const directoryPath of directoryPaths) {
             this.storageModel.recurse(directoryPath, (filePath: string[]) => {
@@ -149,7 +149,9 @@ export default class FileTransferModel {
             });
         }
         const rawBackup = stringify(files);
-        return await encryptString(rawBackup, passphrase);
+        const encrypted = await encryptString(rawBackup, passphrase);
+	const blob = new Blob([encrypted], {type: "text/plain"});
+	return blob;
     };
 
     readonly prepareFileForSending = (filePath: string[]): string => {

src/View/Modals/dataTransferModal.tsx

@@ -750,7 +750,7 @@ function ExportModal(
 		    </button>
 		    <button
 			class="primary flex"
-			on:click={fileTransferViewModel}
+			on:click={fileTransferViewModel.downloadFile}
 			toggle:disabled={
 			    fileTransferViewModel.cannotExport
 			}

src/ViewModel/Global/fileTransferViewModel.ts

@@ -120,6 +120,16 @@ export default class FileTransferViewModel extends Context {
         this.transferKey.value = transferData.key;
     };
 
+    downloadFile = async (): Promise<void> => {
+	const date = new Date().toISOString().split("T")[0];
+
+	const backup: Blob = await this.coreViewModel.fileTransferModel.generateBackup(this.selectedPaths.value.values(), this.exportKey.value);
+	const anchor = document.createElement("a");
+	anchor.href = window.URL.createObjectURL(backup); 
+	anchor.download = `comms-${date}.bak`;
+	anchor.click();
+    }
+
     // view
     showDirectionSelectionModal = (): void => {
         this.coreViewModel.context = this;