Minor code refactorisation of epub.py

- Reduce the amount of nested indentation
- Use proper functions instead of fragile manual parsing

cps/epub.py

@@ -28,7 +28,7 @@ from .constants import BookMeta
 def _extract_cover(zip_file, cover_file, cover_path, tmp_file_name):
     if cover_file is None:
         return None
-    else:
+
     cf = extension = None
     zip_cover_path = os.path.join(cover_path, cover_file).replace('\\', '/')
 
@@ -87,11 +87,7 @@ def get_epub_info(tmp_file_path, original_file_name, original_file_extension):
         epub_metadata['date'] = ''
 
     if epub_metadata['description'] == u'Unknown':
-        description = tree.xpath("//*[local-name() = 'description']/text()")
-        if len(description) > 0:
-            epub_metadata['description'] = description
-        else:
-            epub_metadata['description'] = ""
+        epub_metadata['description'] = tree.xpath("//*[local-name() = 'description']/text()")
 
     lang = epub_metadata['language'].split('-', 1)[0].lower()
     epub_metadata['language'] = isoLanguages.get_lang3(lang)
@@ -131,13 +127,11 @@ def get_epub_info(tmp_file_path, original_file_name, original_file_extension):
 
 def parse_epub_cover(ns, tree, epub_zip, cover_path, tmp_file_path):
     cover_section = tree.xpath("/pkg:package/pkg:manifest/pkg:item[@id='cover-image']/@href", namespaces=ns)
-    cover_file = None
-    # if len(cover_section) > 0:
     for cs in cover_section:
         cover_file = _extract_cover(epub_zip, cs, cover_path, tmp_file_path)
         if cover_file:
-            break
-    if not cover_file:
+            return cover_file
+
     meta_cover = tree.xpath("/pkg:package/pkg:metadata/pkg:meta[@name='cover']/@content", namespaces=ns)
     if len(meta_cover) > 0:
         cover_section = tree.xpath(
@@ -147,9 +141,10 @@ def parse_epub_cover(ns, tree, epub_zip, cover_path, tmp_file_path):
                 "/pkg:package/pkg:manifest/pkg:item[@properties='" + meta_cover[0] + "']/@href", namespaces=ns)
     else:
         cover_section = tree.xpath("/pkg:package/pkg:guide/pkg:reference/@href", namespaces=ns)
+
+    cover_file = None
     for cs in cover_section:
-            filetype = cs.rsplit('.', 1)[-1]
-            if filetype == "xhtml" or filetype == "html":  # if cover is (x)html format
+        if cs.endswith('.xhtml') or s.endswith('.html'):
             markup = epub_zip.read(os.path.join(cover_path, cs))
             markup_tree = etree.fromstring(markup)
             # no matter xhtml or html with no namespace
@@ -164,7 +159,7 @@ def parse_epub_cover(ns, tree, epub_zip, cover_path, tmp_file_path):
                 cover_file = _extract_cover(epub_zip, filename, "", tmp_file_path)
         else:
             cover_file = _extract_cover(epub_zip, cs, cover_path, tmp_file_path)
-            if cover_file: break
+        if cover_file:
             return cover_file