Allow subtracting subreddits from /r/mod.

r2/r2/controllers/reddit_base.py

@@ -93,6 +93,8 @@ from r2.models import (
     Frontpage,
     LabeledMulti,
     Link,
+    Mod,
+    ModMinus,
     MultiReddit,
     NotFound,
     Random,
@@ -371,14 +373,24 @@ def set_subreddit():
                 c.site = MultiReddit(multi_path, srs)
     elif '-' in sr_name:
         sr_names = sr_name.split('-')
-        if not sr_names[0].lower() == All.name.lower():
-            redirect_to("/subreddits/search?q=%s" % sr_name)
-        srs = Subreddit._by_name(sr_names[1:], stale=can_stale).values()
-        srs = [sr for sr in srs if not isinstance(sr, FakeSubreddit)]
-        if not srs:
-            c.site = All
+        base_sr_name, exclude_sr_names = sr_names[0], sr_names[1:]
+        srs = Subreddit._by_name(sr_names, stale=can_stale)
+        base_sr = srs.pop(base_sr_name)
+        exclude_srs = [sr for sr in srs.itervalues()
+                          if not isinstance(sr, FakeSubreddit)]
+
+        if base_sr == All:
+            if exclude_srs:
+                c.site = AllMinus(exclude_srs)
+            else:
+                c.site = All
+        elif base_sr == Mod:
+            if exclude_srs:
+                c.site = ModMinus(exclude_srs)
+            else:
+                c.site = Mod
         else:
-            c.site = AllMinus(srs)
+            redirect_to("/subreddits/search?q=%s" % sr_name)
     else:
         try:
             c.site = Subreddit._by_name(sr_name, stale=can_stale)

r2/r2/models/subreddit.py

@@ -1529,6 +1529,32 @@ class ModSR(ModContribSR):
     def is_moderator(self, user):
         return FakeSRMember(ModeratorPermissionSet)
 
+
+class ModMinus(ModSR):
+    def __init__(self, exclude_srs):
+        ModSR.__init__(self)
+        self.exclude_srs = exclude_srs
+        self.exclude_sr_ids = [sr._id for sr in exclude_srs]
+
+    @property
+    def sr_ids(self):
+        sr_ids = super(ModMinus, self).sr_ids
+        return [sr_id for sr_id in sr_ids if not sr_id in self.exclude_sr_ids]
+
+    @property
+    def name(self):
+        exclude_text = ', '.join(sr.name for sr in self.exclude_srs)
+        return 'subreddits you moderate except ' + exclude_text
+
+    @property
+    def title(self):
+        return self.name
+
+    @property
+    def path(self):
+        return '/r/mod-' + '-'.join(sr.name for sr in self.srs)
+
+
 class ContribSR(ModContribSR):
     name  = "contrib"
     title = "communities you're approved on"