Start work on code to transform OPF2 to OPF3

src/calibre/ebooks/metadata/opf_2_to_3.py

@@ -0,0 +1,70 @@
+#!/usr/bin/env python2
+# vim:fileencoding=utf-8
+# License: GPLv3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>
+
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from lxml import etree
+
+from calibre.ebooks.metadata.opf3 import (
+    OPF, XPath, read_prefixes, read_refines, refdef, remove_element, set_refines
+)
+from calibre.ebooks.metadata.utils import parse_opf, pretty_print_opf
+
+
+class Data(object):
+    pass
+
+
+def upgrade_identifiers(root, data):
+    for ident in XPath('./opf:metadata/dc:identifier')(root):
+        val = (ident.text or '').strip()
+        lval = val.lower()
+        scheme = ident.attrib.pop(OPF('scheme'), None)
+        if lval.startswith('urn:'):
+            prefix, rest = val[4:].partition(':')[::2]
+            if prefix and rest:
+                scheme, val = prefix, rest
+        if scheme and val:
+            ident.text = '{}:{}'.format(scheme, val)
+        for attr in tuple(ident.attrib):
+            if attr != 'id':
+                del ident.attrib[attr]
+
+
+def upgrade_title(root, data):
+    first_title = None
+    for title in XPath('./opf:metadata/dc:title')(root):
+        if not title.text or not title.text.strip():
+            remove_element(title, data.refines)
+            continue
+        if first_title is None:
+            first_title = title
+
+    title_sort = None
+    for m in XPath('./opf:metadata/opf:meta[@name="calibre:title_sort"]')(root):
+        ans = m.get('content')
+        if ans:
+            title_sort = ans
+        remove_element(m, data.refines)
+
+    if first_title is not None:
+        ts = [refdef('file-as', title_sort)] if title_sort else ()
+        set_refines(first_title, data.refines, refdef('title-type', 'main'), *ts)
+
+
+def upgrade_metadata(root):
+    data = Data()
+    data.prefixes = read_prefixes(root)
+    data.refines = read_refines(root)
+
+    upgrade_identifiers(root, data)
+    upgrade_title(root, data)
+    pretty_print_opf(root)
+
+
+if __name__ == '__main__':
+    import sys
+    root = parse_opf(open(sys.argv[-1], 'rb'))
+    upgrade_metadata(root)
+    print(etree.tostring(root))