Adapt zip_gallery logic to a dedicated plugin like suggested by @saimn

* ZIP generation logic is now self contained in a plugin
* '.nozip_gallery' file logic is now contained in the same plugin that
  managed the zip generation

sigal/gallery.py

@@ -31,7 +31,6 @@ import os
 import pickle
 import random
 import sys
-import zipfile
 
 from click import progressbar, get_terminal_size
 from collections import defaultdict
@@ -267,7 +266,6 @@ class Album:
         self.settings = settings
         self.subdirs = dirnames
         self.output_file = settings['output_filename']
-        self.disable_zip_gallery = False
         self._thumbnail = None
 
         if path == '.':
@@ -522,43 +520,10 @@ class Album:
 
     @cached_property
     def zip(self):
-        """Make a ZIP archive with all media files and return its path.
-
-        If the ``zip_gallery`` setting is set,it contains the location of a zip
-        archive with all original images of the corresponding directory.
-
+        """Placeholder ZIP method.
+        The ZIP logic is controlled by the zip_gallery plugin
         """
-
-        if self.disable_zip_gallery:
-            # ZIP file generation has been explicitly disabled
-            # by a .nozip_gallery file for instance
-            return
-
-        zip_gallery = self.settings['zip_gallery']
-
-        if zip_gallery and len(self) > 0:
-            zip_gallery = zip_gallery.format(album=self)
-            archive_path = join(self.dst_path, zip_gallery)
-            if (self.settings.get('zip_skip_if_exists', False) and
-                    isfile(archive_path)):
-                self.logger.debug("Archive %s already created, passing",
-                                  archive_path)
-                return zip_gallery
-
-            archive = zipfile.ZipFile(archive_path, 'w', allowZip64=True)
-            attr = ('src_path' if self.settings['zip_media_format'] == 'orig'
-                    else 'dst_path')
-
-            for p in self:
-                path = getattr(p, attr)
-                try:
-                    archive.write(path, os.path.split(path)[1])
-                except OSError as e:
-                    self.logger.warn('Failed to add %s to the ZIP: %s', p, e)
-
-            archive.close()
-            self.logger.debug('Created ZIP archive %s', archive_path)
-            return zip_gallery
+        return None
 
 
 class Gallery(object):

sigal/plugins/zip_gallery.py

@@ -18,8 +18,7 @@
 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 # IN THE SOFTWARE.
 
-""" This plugin offers the ability to disable ZIP gallery generation on a per album
-granularity.
+""" This plugin controls the generation of a ZIP archive for a gallery
 
 To ignore a ZIP gallery generation for a particular album, put a ``.nozip_gallery`` file next to it in its parent
 folder. Only the existence of this ``.nozip_gallery`` file is tested.
@@ -27,19 +26,65 @@ folder. Only the existence of this ``.nozip_gallery`` file is tested.
 
 import logging
 import os
+from os.path import isfile, join, splitext
 from sigal import signals
+from sigal.gallery import Album
+from sigal.utils import cached_property
+import zipfile
 
 logger = logging.getLogger(__name__)
 
+def noop_zip_method(album):
+    """A zip method that does nothing at all"""
+    return False
+
+def generate_album_zip_method(album):
+    """Make a ZIP archive with all media files and return its path.
+
+    If the ``zip_gallery`` setting is set,it contains the location of a zip
+    archive with all original images of the corresponding directory.
+
+    """
+
+    zip_gallery = album.settings['zip_gallery']
+
+    if zip_gallery and len(album) > 0:
+        zip_gallery = zip_gallery.format(album=album)
+        archive_path = join(album.dst_path, zip_gallery)
+        if (album.settings.get('zip_skip_if_exists', False) and
+                isfile(archive_path)):
+            album.logger.debug("Archive %s already created, passing",
+                              archive_path)
+            return zip_gallery
+
+        archive = zipfile.ZipFile(archive_path, 'w', allowZip64=True)
+        attr = ('src_path' if album.settings['zip_media_format'] == 'orig'
+                else 'dst_path')
+
+        for p in album:
+            path = getattr(p, attr)
+            try:
+                archive.write(path, os.path.split(path)[1])
+            except OSError as e:
+                album.logger.warn('Failed to add %s to the ZIP: %s', p, e)
+
+        archive.close()
+        album.logger.debug('Created ZIP archive %s', archive_path)
+        return zip_gallery
+
+
 def nozip_galery_file(album, settings=None):
     """Filesystem based switch to disable ZIP generation for an Album"""
     nozipgallerypath = os.path.join(album.src_path, ".nozip_gallery")
 
+    zip_method = generate_album_zip_method
+
     if os.path.isfile(nozipgallerypath):
         logger.info("Ignoring ZIP gallery generation for album '%s' because of present "
                     ".nozip_gallery file", album.name)
+        zip_method = noop_zip_method
 
-        album.disable_zip_gallery = True
+    album.__class__.zip = cached_property(zip_method)
 
 def register(settings):
     signals.album_initialized.connect(nozip_galery_file)