Provide option to automatically download files upon import

[tobiasdiez]

Is your suggestion for improvement related to a problem? Please describe.
Usually, when importing entries using the browser extension, they include urls to PDFs etc. After the import, one has to go to the general tab and then download these files manually.

Describe the solution you'd like
Add an option in the import dialog (checkbox), that allows to automatically download all linked files and rename /move them to the default file location.

[joelostblom]

This would be a convenient feature! Minor potential addition: remembering the last checked status as the default for the next import dialog, or with the option in the preferences menu of setting the default status.

[LyzardKing]

@tobiasdiez Does the jabref cli have an option to import a pdf?
I'd like to try adding this option

[tobiasdiez]

@LyzardKing Awesome that you want to have a look at this.
No, the cli only allows to import bib entries / databases. But I would integrate this functionality at a later stage anyway. Namely, add a checkbox at the bottom of the import dialog (https://github.com/JabRef/jabref/blob/master/src/main/java/org/jabref/gui/importer/ImportEntriesDialog.java) "Download linked online files" and then reuse this code for the actual download of the contained files:

jabref/src/main/java/org/jabref/gui/fieldeditors/LinkedFileViewModel.java

Lines 395 to 418 in eb988b6

	public void download() {
	if (!linkedFile.isOnlineLink()) {
	throw new UnsupportedOperationException("In order to download the file it has to be an online link");
	}
	try {
	Optional<Path> targetDirectory = databaseContext.getFirstExistingFileDir(filePreferences);
	if (targetDirectory.isEmpty()) {
	dialogService.showErrorDialogAndWait(Localization.lang("Download file"), Localization.lang("File directory is not set or does not exist!"));
	return;
	}
	URLDownload urlDownload = new URLDownload(linkedFile.getLink());
	BackgroundTask<Path> downloadTask = prepareDownloadTask(targetDirectory.get(), urlDownload);
	downloadTask.onSuccess(destination -> {
	LinkedFile newLinkedFile = LinkedFilesEditorViewModel.fromFile(destination, databaseContext.getFileDirectoriesAsPaths(filePreferences), externalFileTypes);
	linkedFile.setLink(newLinkedFile.getLink());
	linkedFile.setFileType(newLinkedFile.getFileType());
	});
	downloadProgress.bind(downloadTask.workDonePercentageProperty());
	taskExecutor.execute(downloadTask);
	} catch (MalformedURLException exception) {
	dialogService.showErrorDialogAndWait(Localization.lang("Invalid URL"), exception);
	}
	}

[LyzardKing]

Ok, so integrate it directly in the jabref dialog!
Sounds good..
I'll try and cook up something :)

[btut]

I implemented the basic functionality. There is no persistence yet though. I think it would be better to have this as a setting rather than remembering if the box was checked the last time or not. Don't know how to do that though as this is my first contribution here.

[LyzardKing]

Great job! I haven't had time to look at this, and you managed to do it better than I could have :)

[ilippert]

ref #1456

[Siedlerchr]

Thanks to @btut this issue should now be fixed in the latest master (should be ready in roughly hafl an hour