I wish to know if it is possible to do the following modifications to the <metadata> section of content.opf through a calibre plug-in, to be run automatically after conversion and/or
polish book -> update metadata in book file
1. retrieve the 'value' (integer) from field #custom_date and
* add it as <dc:date opf:event="creation">'value'</dc:date>
* delete any existing <dc:date>...</dc:date> (no opf:event)
2. for all existing <dc:subject>...</dc:subject>, coming from my calibre tags or already in the original epub:
* if of the form <dc:subject>[item_in_list1]</dc:subject>, change to <dc:source>item_in_list1</dc:source>
* delete the rest if not of the form <dc:subject>item_in_list2</dc:subject> (my genres)
3. delete all <<meta name="calibre:user_ .../>
I am currently doing this through a (personal) sigil plug-in: chiefly a magnified search&replace along the beautiful soup 'meta tag', but I cannot see how to do the same 'at source' in calibre.
The 'mi' object doesn't seem to provide the ability to substitute/delete <tag>...</tag>, and I haven't seen in the documentation any other way likely to work.
Any help would be appreciated--even if it is on the lines 'you cannot do that'.
