Start work on kepubify

src/calibre/ebooks/oeb/polish/kepubify.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python
+# License: GPLv3 Copyright: 2025, Kovid Goyal <kovid at kovidgoyal.net>
+
+# Add/remove the markup needed for Kobo's custom EPUB renderer. It's
+# mostly completely unnecessary junk added to the HTML because Kobo
+# doesn't know how to render EPUB without needing such hacks. The list of
+# changes:
+#     * Add Kobo style tweaks
+#     * Add body div wrappers (used to apply pagination styles)
+#     * Add spans around sentences. Apparently Kobo cannot implement
+#       highlighting and bookmarking without this, they should be using CFI for this, sigh.
+#     * Cover marking in the OPF
+#     * Markup cleanup (remove various things that trip up the Kobo renderer)
+
+from calibre.ebooks.oeb.base import XHTML, XPath
+from calibre.ebooks.oeb.parse_utils import merge_multiple_html_heads_and_bodies
+from calibre.ebooks.oeb.polish.utils import extract, insert_self_closing
+
+KOBO_STYLE_HACKS = 'kobostylehacks'
+OUTER_DIV_ID = 'book-columns'
+INNER_DIV_ID = 'book-inner'
+
+
+def add_style(root, css='div#book-inner { margin-top: 0; margin-bottom: 0;}', cls=KOBO_STYLE_HACKS) -> bool:
+
+    def add(parent):
+        e = parent.makeelement(XHTML('style'), type='text/css')
+        e.text = css
+        e.set('class', cls)
+        insert_self_closing(parent, e)
+
+    if heads := XPath('./h:head')(root):
+        add(heads[-1])
+        return True
+    if bodies := XPath('./h:body')(root):
+        add(bodies[-1])
+        return True
+    return False
+
+
+def remove_kobo_styles(root):
+    for x in XPath(f'//h:style[@type="text/css" and @class="{KOBO_STYLE_HACKS}"]')(root):
+        extract(x)
+
+
+def wrap_body_contents(body):
+    # To match official KEPUBs. Kobo wraps the body with two div tags,
+    # div#book-columns > div#book-inner to provide a target for applying
+    # pagination styles.
+    for elem in XPath(f'//*[@id="{OUTER_DIV_ID}" or @id={INNER_DIV_ID}]')(body):
+        elem.attrib.pop('id')
+    outer = body.makeelement(XHTML('div'), id=OUTER_DIV_ID)
+    inner = body.makeelement(XHTML('div'), id=INNER_DIV_ID)
+    outer.append(inner)
+    inner.text = body.text
+    body.text = None
+    for child in body:
+        inner.append(child)
+    del body[:]
+    body.append(outer)
+
+
+def unwrap_body_contents(body):
+    children = []
+    text = ''
+    for inner in XPath(f'./h:div[@id="{OUTER_DIV_ID}"]/h:div[@id="{INNER_DIV_ID}"]')(body):
+        children.extend(inner)
+        if inner.text:
+            text += inner.text
+        extract(inner.getparent())
+    body.extend(children)
+    body.text = text
+
+
+def add_kobo_markup_to_html(root):
+    add_style(root)
+    for body in XPath('./h:body')(root):
+        wrap_body_contents(body)
+
+
+def remove_kobo_markup_from_html(root):
+    remove_kobo_styles(root)
+    for body in XPath('./h:body')(root):
+        unwrap_body_contents(body)
+
+
+def kepubify_html(root):
+    remove_kobo_markup_from_html(root)
+    merge_multiple_html_heads_and_bodies(root)
+    add_kobo_markup_to_html(root)