Bugfix: fix some issues with kobo sync

Kobo sync's logic is incorrect, and looks like it pretty much always has
been. This is seen on initial sync of a freshly reset device against c-w
configured to sync all shelves. I have 1500+ books to sync, but c-w syncs
only about 250 or so before saying it's done. That's two full batches of 100,
followed by a partial batch.

The problem is in the way the query performs paging. On the first pass
it discovers all the books that need to be synced. On the second pass it
does pretty well.  Third pass, it does badly. All this is because of the
way it currently detects which books have been modified since last sync.
As it goes through the sync, this query result set gets progressively
smaller, incorrectly.

I've tried to repair the logic, and what I get now works perfectly for
my case. I'm not 100% sure it's exactly right but it's doing a lot
better now for both initial sync and maintenance sync.

Author: xdgc

cps/kobo.py

@@ -146,13 +146,20 @@ def HandleSyncRequest():
     if not current_user.role_download():
         log.info("Users need download permissions for syncing library to Kobo reader")
         return abort(403)
+
     sync_token = SyncToken.SyncToken.from_headers(request.headers)
     log.info("Kobo library sync request received")
     log.debug("SyncToken: {}".format(sync_token))
     log.debug("Download link format {}".format(get_download_url_for_book('[bookid]', '[bookformat]')))
     if not current_app.wsgi_app.is_proxied:
         log.debug('Kobo: Received unproxied request, changed request port to external server port')
 
+    # Produce an equivalent curl command to assist with debugging
+    #curl = f"curl -X{request.method} '{request.url}'"
+    #for key, value in request.headers.items():
+    #    curl += f" -H'{key}: {value}'"
+    #log.debug(f"curl: {curl}")
+
     # if no books synced don't respect sync_token
     if not ub.session.query(ub.KoboSyncedBooks).filter(ub.KoboSyncedBooks.user_id == current_user.id).count():
         sync_token.books_last_modified = datetime.min
@@ -172,6 +179,8 @@ def HandleSyncRequest():
 
     only_kobo_shelves = current_user.kobo_only_shelves_sync
 
+    log.debug("Kobo Sync: books last modified: {}".format(sync_token.books_last_modified))
+
     if only_kobo_shelves:
         changed_entries = calibre_db.session.query(db.Books,
                                                    ub.ArchivedBook.last_modified,
@@ -182,11 +191,14 @@ def HandleSyncRequest():
                                                                           ub.ArchivedBook.user_id == current_user.id))
                            .filter(db.Books.id.notin_(calibre_db.session.query(ub.KoboSyncedBooks.book_id)
                                                       .filter(ub.KoboSyncedBooks.user_id == current_user.id)))
-                           .filter(ub.BookShelf.date_added > sync_token.books_last_modified)
+                           .filter(or_(
+                                ub.BookShelf.date_added > sync_token.books_last_modified,
+                                db.Books.last_modified > sync_token.books_last_modified,
+                           ))
                            .filter(db.Data.format.in_(KOBO_FORMATS))
                            .filter(calibre_db.common_filters(allow_show_archived=True))
+                           .order_by(db.Books.last_modified)
                            .order_by(db.Books.id)
-                           .order_by(ub.ArchivedBook.last_modified)
                            .join(ub.BookShelf, db.Books.id == ub.BookShelf.book_id)
                            .join(ub.Shelf)
                            .filter(ub.Shelf.user_id == current_user.id)
@@ -205,10 +217,11 @@ def HandleSyncRequest():
                            .filter(db.Data.format.in_(KOBO_FORMATS))
                            .order_by(db.Books.last_modified)
                            .order_by(db.Books.id))
+    log.debug("Kobo Sync: changed entries: {}".format(changed_entries.count()))
 
     reading_states_in_new_entitlements = []
     books = changed_entries.limit(SYNC_ITEM_LIMIT)
-    log.debug("Books to Sync: {}".format(len(books.all())))
+    log.debug("Kobo Sync: selected to sync: {}".format(len(books.all())))
     for book in books:
         formats = [data.format for data in book.Books.data]
         if 'KEPUB' not in formats and config.config_kepubifypath and 'EPUB' in formats:
@@ -240,12 +253,6 @@ def HandleSyncRequest():
         new_books_last_modified = max(
             book.Books.last_modified.replace(tzinfo=None), new_books_last_modified
         )
-        try:
-            new_books_last_modified = max(
-                new_books_last_modified, book.date_added
-            )
-        except AttributeError:
-            pass
 
         new_books_last_created = max(ts_created, new_books_last_created)
         kobo_sync_status.add_synced_books(book.Books.id)
@@ -262,20 +269,19 @@ def HandleSyncRequest():
     book_count = changed_entries.count()
     # last entry:
     cont_sync = bool(book_count)
-    log.debug("Remaining books to Sync: {}".format(book_count))
+    log.debug("Kobo Sync: remaining books to sync: {}".format(book_count))
     # generate reading state data
     changed_reading_states = ub.session.query(ub.KoboReadingState)
 
+    log.debug("Kobo Sync: rstate last modified: {}".format(sync_token.reading_state_last_modified))
     if only_kobo_shelves:
         changed_reading_states = changed_reading_states.join(ub.BookShelf,
                                                              ub.KoboReadingState.book_id == ub.BookShelf.book_id)\
             .join(ub.Shelf)\
             .filter(current_user.id == ub.Shelf.user_id)\
             .filter(ub.Shelf.kobo_sync,
-                    or_(
-                        ub.KoboReadingState.last_modified > sync_token.reading_state_last_modified,
-                        func.datetime(ub.BookShelf.date_added) > sync_token.books_last_modified
-                    )).distinct()
+                    ub.KoboReadingState.last_modified > sync_token.reading_state_last_modified)\
+            .distinct()
     else:
         changed_reading_states = changed_reading_states.filter(
             ub.KoboReadingState.last_modified > sync_token.reading_state_last_modified)
@@ -284,6 +290,7 @@ def HandleSyncRequest():
         and_(ub.KoboReadingState.user_id == current_user.id,
              ub.KoboReadingState.book_id.notin_(reading_states_in_new_entitlements)))\
         .order_by(ub.KoboReadingState.last_modified)
+    log.debug("Kobo Sync: changed states: {}".format(changed_reading_states.count()))
     cont_sync |= bool(changed_reading_states.count() > SYNC_ITEM_LIMIT)
     for kobo_reading_state in changed_reading_states.limit(SYNC_ITEM_LIMIT).all():
         book = calibre_db.session.query(db.Books).filter(db.Books.id == kobo_reading_state.book_id).one_or_none()