From 7a082c971e2ab130a722135f085af23b6e49413f Mon Sep 17 00:00:00 2001
From: Ryan Pitts <ryan.a.pitts@gmail.com>
Date: Sun, 28 Oct 2012 11:21:29 -0700
Subject: [PATCH] article feeds handle tag intersection queries

---
 source/base/feeds.py | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/source/base/feeds.py b/source/base/feeds.py
index ad4977d..225e97a 100644
--- a/source/base/feeds.py
+++ b/source/base/feeds.py
@@ -11,9 +11,13 @@ class ArticleFeed(Feed):
     def get_object(self, request, *args, **kwargs):
         self.section = kwargs.get('section', None)
         self.category = kwargs.get('category', None)
-        self.tag_slug = kwargs.get('tag_slug', None)
-        if self.tag_slug:
-            self.tag = get_object_or_404(Tag, slug=self.tag_slug)
+        self.tags = None
+        self.tag_slugs = kwargs.get('tag_slugs', None)
+        self.tag_slug_list = []
+        if self.tag_slugs:
+            self.tag_slug_list = self.tag_slugs.split('+')
+            # need to fail if any item in slug list references nonexistent tag
+            self.tags = [get_object_or_404(Tag, slug=tag_slug) for tag_slug in self.tag_slug_list]
         return ''
 
     def title(self, obj):
@@ -21,8 +25,8 @@ def title(self, obj):
             return "Source: %s" % SECTION_MAP[self.section]['name']
         elif self.category:
             return "Source: Articles in the category %s" % CATEGORY_MAP[self.category]['name']
-        elif self.tag_slug:
-            return "Source: Articles tagged with '%s'" % self.tag.name
+        elif self.tag_slugs:
+            return "Source: Articles tagged with '%s'" % "+".join([tag.name for tag in self.tags])
         return "Source"
 
     def link(self, obj):
@@ -30,8 +34,8 @@ def link(self, obj):
             return reverse('article_list_by_section', kwargs={'section': self.section})
         elif self.category:
             return reverse('article_list_by_category', kwargs={'category': self.category})
-        elif self.tag_slug:
-            return reverse('article_list_by_tag', kwargs={'tag_slug': self.tag_slug})
+        elif self.tag_slugs:
+            return reverse('article_list_by_tag', kwargs={'tag_slugs': self.tag_slugs})
         return reverse('homepage')
 
     def description(self, obj):
@@ -40,8 +44,8 @@ def description(self, obj):
             identifier = "in the %s section" % SECTION_MAP[self.section]['name']
         elif self.category:
             identifier = "in the %s category" % CATEGORY_MAP[self.category]['name']
-        elif self.tag_slug:
-            identifier = "tagged with '%s'" % self.tag.name
+        elif self.tag_slugs:
+            identifier = "tagged with '%s'" % "+".join([tag.name for tag in self.tags])
         return "Recent articles %s" % identifier
 
     def item_title(self, item):
@@ -56,8 +60,9 @@ def items(self, obj):
             queryset = queryset.filter(article_type__in=SECTION_MAP[self.section]['article_types'])
         elif self.category:
             queryset = queryset.filter(article_type=self.category)
-        elif self.tag_slug:
-            queryset = queryset.filter(tags__slug=self.tag_slug)
+        elif self.tag_slugs:
+            for tag_slug in self.tag_slug_list:
+                queryset = queryset.filter(tags__slug=tag_slug)
         return queryset[:20]
 
 class CodeFeed(Feed):