Advice requested to complete a auto-convert-format import plugin

[anoved]

I usually get ebooks in Mobi format for best results with my Kindle, but I like to maintain ePub versions as well to use with with other apps and devices. I don't add new books to my library so frequently that it's a hassle to do this manually, but I thought it would be a good project to write a plugin to do it for me automatically.

Goal: A plugin that automatically generates ePub versions of imported Mobi files. End state of import is a single book record with two formats, ePub and Mobi. (Eventually, I suppose this could be generalized to any preferred formats.)

Status: Close, but no cigar. The plugin I've written runs when a Mobi file is imported, creates an ePub version, and adds the ePub version to the library before proceeding to import the Mobi as usual. The result, however, is two separate book records, one in ePub format and the other Mobi, with otherwise identical metadata. I had hoped enabling the Automerge option would be sufficient to merge these, but it is not the case. (I suspect the unorthodox sequence of importing one book while ostensibly importing another doesn't give automerge a chance to work.)

Request: Any help figuring out how to implement this last step (merging the ePub version with the Mobi) would be appreciated. Also, since this is my first attempt at a plugin and I'm as yet somewhat unfamiliar with the Calibre code, any advice on canonical/better ways to do things would be great.

from calibre.customize import FileTypePlugin

class AutoCreateEpubFromMobi(FileTypePlugin):

	name = 'AutoCreateEpubFromMobi Plugin'
	description = 'Automatically create ePub versions of imported Mobi files.'
	supported_platforms = ['windows', 'osx', 'linux']
	author = 'Jim DeVona'
	version = (1, 0, 0)
	minimum_calibre_version = (0, 8, 39)
	file_types = set(['mobi'])
	on_import = True
	
	def run(self, path_to_ebook):
		
		# Make an ePub version of the input Mobi file.
		from calibre.ebooks.conversion.plumber import Plumber
		from calibre.utils.logging import Log
		log = Log()
		output_path = self.temporary_file('.epub')
		plumber = Plumber(path_to_ebook, output_path.name, log)
		plumber.run()
		
		# Get the ePub metadata, needed to import it manually.
		from calibre.ebooks.metadata.meta import get_metadata
		mdfile = open(output_path.name, 'r+b')
		mi = get_metadata(mdfile, 'epub')

		# Import the ePub.
		# Ideally, with correct Automerge settings, this format would be merged
		# with the original Mobi file being imported in a single book record.
		from calibre.utils.config import prefs
		from calibre.library.database2 import LibraryDatabase2
		db = LibraryDatabase2(prefs['library_path'])
		epub_id = db.import_book(mi, [output_path.name])
		
		# Get the imported ePub to show up in the browser.
		# (Without this, it doesn't appear in GUI until after restart.)
		# Not sure if there's a better way. Lifted from calibre/library/cli.py
		from calibre.utils.ipc import RC
		import time
		t = RC()
		t.start()
		time.sleep(1)
		if t.done:
			t.conn.send('refreshdb:')
			t.conn.close()		
		
		# Resume importing the original Mobi.
		return path_to_ebook

[kovidgoyal]

A file type plugin is not the right place to do this and you really shouldn't create an extra db instance. Having multiple db objects writing to the same db is a recipe for bad things to happen. In fact on windows, you will get permission denied errors since windows enforces mandatory file locking.

Instead create a replacement for the add books plugin (you can re-use the calibre add books code for the most part) and have that plugin scan newly imported book records for ones that contain only a single format, and launch a convert for them, by calling the convert books plugin.

[anoved]

Thanks for the rapid reply. Thanks also for the architectural advice about how to proceed - I was starting from the simplest plugin example, so writing an on_import action seemed logical given my goal. I will investigate the approach you suggest tomorrow and post any follow-up questions here.

[RobertoOG]

Hi Anoved, have you been able to create that plugin? I was wondering because I want to make almost the same for kepub format, and if you made it and published the source code it would be a lot easier for me

Thank you

[BetterRed]

Originally Posted by RobertoOG

Hi Anoved, have you been able to create that plugin? I was wondering because I want to make almost the same for kepub format, and if you made it and published the source code it would be a lot easier for me

Thank you

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BR