move validation outside librarian

[librarian.git] / librarian / formats / cover / evens / __init__.py

diff --git a/librarian/formats/cover/evens/__init__.py b/librarian/formats/cover/evens/__init__.py
index a4b721c..003807d 100644 (file)
--- a/librarian/formats/cover/evens/__init__.py
+++ b/librarian/formats/cover/evens/__init__.py
@@ -19,15 +19,20 @@ class EvensCover(Cover):
     logo_bottom = 100
 
     def set_images(self, ctx):
-        cover_url = self.doc.meta.get(DCNS('relation.coverimage.url'))[0]
-        if not cover_url:
-            raise BuildError('No cover specified')
-        if cover_url.startswith('file://'):
-            cover_url = ctx.files_path + urllib.quote(cover_url[7:])
         try:
-            self.background_img = urlopen(cover_url)
-        except URLError:
-            raise BuildError('Cannot open the cover image: %s' % cover_url)
+            cover_url = self.doc.meta.get(DCNS('relation.coverimage.url'))[0]
+        except IndexError:
+            cover_url = False
+        if cover_url:
+            if cover_url.startswith('file://'):
+                cover_url = ctx.files_path + urllib.quote(cover_url[7:])
+            IMG_EXT = ('png', 'jpg', 'jpeg', 'gif')
+            if '.' not in cover_url or cover_url.rsplit('.', 1)[1].lower() not in IMG_EXT:
+                raise BuildError('Wrong cover format, should be PNG, JPG or GIF')
+            try:
+                self.background_img = urlopen(cover_url)
+            except URLError:
+                raise BuildError('Cannot open the cover image: %s' % cover_url)
 
         if getattr(ctx, 'cover_logo', None):
             self.logo_width = 150