Refactor cover detection

obsolate hardcode %cover_id%= ‘cover’ in <pkg:item name=%cover_id% href=%coverfile%>
now  %cover_id% retrieve from <meta name=“cover” content=%cover_id%>

cps/epub.py

@@ -72,26 +72,22 @@ def get_epub_info(tmp_file_path, original_file_name, original_file_extension):
     if len(coversection) > 0:
         coverfile = extractCover(zip, coversection[0], coverpath, tmp_file_path)
     else:
-        coversection = tree.xpath("/pkg:package/pkg:manifest/pkg:item[@id='cover']/@href", namespaces=ns)
-        if len(coversection) > 0:
-            filetype = coversection[0].rsplit('.',1)[-1]
-            if filetype == "xhtml" or filetype == "html": #if cover is (x)html format
-                markup = zip.read(os.path.join(coverpath,coversection[0]))
-                markupTree = etree.fromstring(markup)
-                #no matter xhtml or html with no namespace
-                imgsrc = markupTree.xpath("//*[local-name() = 'img']/@src")
-                #imgsrc maybe startwith "../"" so fullpath join then relpath to cwd
-                filename = os.path.relpath(os.path.join(os.path.dirname(os.path.join(coverpath, coversection[0])), imgsrc[0]))
-                coverfile = extractCover(zip, filename, "", tmp_file_path)
-            else:
-                coverfile = extractCover(zip, coversection[0], coverpath, tmp_file_path)
-        else:
-            meta_cover = tree.xpath("/pkg:package/pkg:metadata/pkg:meta[@name='cover']/@content", namespaces=ns)
-            if len(meta_cover) > 0:
-                meta_cover_content = tree.xpath("/pkg:package/pkg:manifest/pkg:item[@id='"+meta_cover[0]+"']/@href", namespaces=ns)
-                if len(meta_cover_content) > 0:
-                    coverfile = extractCover(zip, meta_cover_content[0], coverpath, tmp_file_path)
-
+        meta_cover = tree.xpath("/pkg:package/pkg:metadata/pkg:meta[@name='cover']/@content", namespaces=ns)
+        if len(meta_cover) > 0:
+            coversection = tree.xpath("/pkg:package/pkg:manifest/pkg:item[@id='"+meta_cover[0]+"']/@href", namespaces=ns)
+            if len(coversection) > 0:
+                filetype = coversection[0].rsplit('.',1)[-1]
+                if filetype == "xhtml" or filetype == "html": #if cover is (x)html format
+                    markup = zip.read(os.path.join(coverpath,coversection[0]))
+                    markupTree = etree.fromstring(markup)
+                    #no matter xhtml or html with no namespace
+                    imgsrc = markupTree.xpath("//*[local-name() = 'img']/@src")
+                    #imgsrc maybe startwith "../"" so fullpath join then relpath to cwd
+                    filename = os.path.relpath(os.path.join(os.path.dirname(os.path.join(coverpath, coversection[0])), imgsrc[0]))
+                    coverfile = extractCover(zip, filename, "", tmp_file_path)
+                else:
+                    coverfile = extractCover(zip, coversection[0], coverpath, tmp_file_path)
+            
     if epub_metadata['title'] is None:
         title = original_file_name
     else: